research article corrosion inhibiting mechanism ... - hindawi

Research ArticleCorrosion Inhibiting Mechanism of Nitrite Ion onthe Passivation of Carbon Steel and Ductile Cast Ironfor Nuclear Power Plants

K T Kim1 H W Kim1 H Y Chang2 B T Lim2 H B Park2 and Y S Kim1

1Materials Research Centre for Energy and Clean Technology School of Materials Science and EngineeringAndong National University 1375 Gyeongdongro Andong 760-749 Republic of Korea2Power Engineering Research Institute KEPCO Engineering amp Construction Company 8 Gumiro Bundang SeongnamGyeonggi 463-870 Republic of Korea

Correspondence should be addressed to Y S Kim yikimanuackr

Received 1 July 2015 Accepted 27 September 2015

Academic Editor Randhir Singh

Copyright copy 2015 K T Kim et alThis is an open access article distributed under theCreative CommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

While NaNO2addition can greatly inhibit the corrosion of carbon steel and ductile cast iron in order to improve the similar

corrosion resistance ca 100 times more NaNO2addition is needed for ductile cast iron compared to carbon steel A corrosion and

inhibition mechanism is proposed whereby NO2

minus ion is added to oxidize The NO2

minus ion can be reduced to nitrogen compoundsand these compounds may be absorbed on the surface of graphiteTherefore since nitrite ion needs to oxidize the surface of matrixand needs to passivate the galvanic corroded area and since it is absorbed on the surface of graphite a greater amount of corrosioninhibitor needs to be added to ductile cast iron compared to carbon steel The passive film of carbon steel and ductile cast ironformed by NaNO

2addition showed N-type semiconductive properties and its resistance is increased the passive current density is

thus decreased and the corrosion rate is then lowered In addition the film is mainly composed of iron oxide due to the oxidationby NO

2

minus ion however regardless of the alloys nitrogen compounds (not nitrite) were detected at the outermost surface but werenot incorporated in the inner oxide

1 Introduction

Since the operation period of nuclear power plants aroundthe world increases each year the degradations in buriedpipes have become an important issue in the nuclear powerindustry Many reports have been carried out on the degra-dation of buried pipes such as the lining damage of buriedpipe for a component cooling seawater system at Hanul 1unit (Korea) 1998 [1] the leakage of buried pipe for a fireprotection system at Hanbit 4 unit (Korea) 2006 [2] andthe cooling water leakage (ca 227m3) at Indian Point 2unit (USA) 2009 [3] In the case of buried pipe its corrosionenvironment differs from that of air-exposure pipe Whilethe interior of the pipe becomes corroded by fluids theoutside undergoes mechanical and chemical damage fromthe soil Also even though leakage occurs in the buried

pipe it is very difficult to determine the reason for theleakage and to fix it timely because of a lack of accessibilityVarious pipes of ca 30sim40 km per unit of nuclear powerplant have been buried and operated and depending on theapplication system and water chemistry they are separatelymaintained as the large diameter pipes and the other pipesLarge diameter pipes are installed to convey the primarycooling seawater system the secondary cooling seawatersystem and the circulating system the cooling water ofwhich is seawater [4 5] About 70 of pipes are PrestressedConcrete steel Cylinder Pipe (PCCP) and Prestressed Con-crete Pipe (PCP) Another pipework has been installed forconveying water for the fire-fighting system which was madeof carbon steel or cast iron [6] The types of damage thatcan occur in buried pipe include leakage fracture blockageand deformation by mechanical impact Secondary damage

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2015 Article ID 408138 16 pageshttpdxdoiorg1011552015408138

2 Advances in Materials Science and Engineering

Table 1 Chemical compositions of experimental alloys

Alloys Chemical compositions wtC Mn P S Si Cr Cu Mo Ni V Fe

CS 026 086 0014 0005 023 004 0057 0033 0029 0008 balDCI 401 017 0022 0026 153 mdash 0023 0028 0059 0016 balCS carbon steel ASME SA106 GrB DCI ductile cast iron KS D4311

then occurs including general corrosion pitting microbialinduced corrosion scale buildupmultiplication ofmicrobialand fatigue Therefore several corrosion control methodssuch as painting and coating electrical protection and theuse of corrosion inhibitors have been applied [7ndash9] Carbonsteel and cast iron used in a closed cooling system may becorroded In order to control this type of corrosion problemcorrosion inhibitors such as nitrite silicate molybdate andhydrazine have been used among them nitrite is widely usedbecause of its excellent performance

Many reports have been presented on corrosion inhi-bition by nitrite including Fe

2O3formation on steel by

nitrite addition [10] adherent protective oxide on steel [11]correlation of oxygen and nitrite on steel corrosion [12]comparative study of nitrite including various inhibitors onsteel [13ndash15] and inhibition effect of nitrite on steel withtime [16 17] Nitrite as an anodic inhibitor has a tendencyto increase anodic polarization and thus increase corrosionpotential to a noble direction and decrease the corrosioncurrent Since nitrite contains a strong oxidizing power itoxidizes the surface and forms Fe

2O3[18] Formation rate of

protective film due to nitrite is very fast and thus among theseveral corrosion inhibitors nitrite shows good performance[19]

On the other hand ductile cast iron has a very differentmicrostructure to that of carbon steel Spheroidized graphiteforms in the matrix and galvanic corrosion occurs betweenthe matrix and graphite Also cast iron does not have highcorrosion resistance to various corrosion environments andit should be protected by a coating As described abovemany reports have been presented on the corrosion inhibitionof carbon steel but there are few reports on cast ironTherefore in this work corrosion inhibition effects of nitriteon carbon steel and ductile cast iron for nuclear powerplant pipework using chemical and electrochemical methodswere evaluated This work attempts to clarify the corrosioninhibition mechanism between steel and iron by NaNO

2

addition

2 Experimental Procedure

21 Materials and Corrosion Environments Commercial car-bon steel (ASME SA106 GrB) [20] and ductile cast iron (KSD4311) [21] were used in this work and Table 1 shows thechemical composition of the experimental alloys

The test solution was simulated primary cooling waterused in the nuclear power plant The standard solution was16 ppm NaCl and its pH was modified with 1N NaOHsolution and the range of pH 9 plusmn 02 was controlled NaNO

2

as a corrosion inhibitor was added as a ppm order

22 Corrosion Tests

221 Immersion Corrosion Test A specimen was cut to a sizeof 20times 20times 5mmand each surfacewas groundusing 120 SiCpaper Immersion tests were carried out in a stagnant solutioncondition (500mL glass flask) and in a circulating solutionin which test chamber has a dimension of 50 times 100 times 50 cmand the flow rate was 5 Lmin After the immersion tests eachspecimen was cleaned with acetone and alcohol and was thendried the corrosion rate was then determined

222 Electrochemical Tests Specimens were cut to a sizeof 20 times 20mm and after electrical connection they wereepoxy-mounted and the surface was ground using 600SiC paper and coated with epoxy resin except an area of1 cm2 A polarization test was performed using a potentiostat(Gamry DC105) and the reference electrode was a saturatedcalomel electrode and the counter electrode was Pt wire Thetest solution was deaerated using nitrogen gas at the rateof 100mLmin for 30 minutes and the scanning rate was033mVsec In order to measure the AC impedance thespecimens were ground using 2000 SiC paper and thenpolished using a diamond paste (3120583m)The test solution wasthe same as that of the polarization test AC impedance mea-surement was performed using an electrochemical analyzer(Gamry EIS 300) Before measuring passivation was treatedat +400mV(SCE) for carbon steel and 0mV(SCE) for ductilecast iron for 30 minutes AC impedance was measured ata passivation potential from 10 kHz to 001Hz and the ACvoltage amplitude was 10mV Also a Mott-Schottky plot wasprepared to determine the semiconductive properties of thepassive film The specimen preparation was the same as thatfor AC impedance measurement and the DC amplitude was10mV (peak-to-peak) at 1580Hz of the AC frequency [22]The capacitance was measured at the scan rate of 50mVsecfrom +1V(SCE) to minus15 V(SCE)

223 Surface Analysis X-ray photoelectron spectroscopy(XPS K-alpha (Thermo VG UK) Al-K

120572(14866 eV 12 kV

3mA)) was analyzed to determine the chemical state ofseveral species of the passive film The specimen was cutto a size of 20 times 20 times 5mm and then ground with 2000SiC paper and polished with a 3 120583m diamond paste thespecimenwas finally cleaned with alcohol using an ultrasoniccleaner Carbon steel and ductile cast iron were passivatedby immersion for 24 hours in 1000 ppm and 100000 ppmNaNO

2 respectively The depth profile was obtained every

5 seconds by Ar-sputtering Also an Electron Probe MicroAnalyzer (EPMA EPMA-1600 15 KV) was used to identifythe elemental distribution of the passivated surface Optical

Advances in Materials Science and Engineering 3

023

0060 0 0

048

0 0 0 00

02

04

06

08

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0 10 100 1000 10000

Cor

rosio

n ra

te (m

my

r)

Stagnant solutionCirculating solution

NaNO2 (ppm)

(a)


047

009004 002 0 0 0

084

041

014008 007

001 00

02

04

06

08

1

0 10 100 1000 10000 50000 100000

Cor

rosio

n ra

te (m

my

r)

NaNO2 (ppm)

(b)

Figure 1 Effect of NaNO2addition on corrosion rate in circulating and stagnant simulated cooling water at 25∘C (a) carbon steel and (b)

ductile cast iron

Microscope (OM Zeiss Axiotech 100HD) and SEM-EDS(Tescan Vega II LMU) and a 3Dmicroscope (Zeiss KH-7700)were used

224 Corrosion Simulation In order to determine the differ-ence in galvanic corrosion between the matrix and spheroid-ized graphite of the ductile cast iron computer simulationwas performed using COMSOL Multiphysics software Tafelslopes of anodic and cathodic reactions were used and therate controlling equation applied in this modeling was thesecondary corrosion condition

3 Results and Discussion

31 Effect of Nitrite Concentration Figure 1 shows the effectof NaNO

2addition on corrosion rate in circulating and

stagnant simulated coolingwater in the air at 25∘C In the caseof carbon steel increasing NaNO

2concentration reduced

significantly the corrosion rate of carbon steel When theinhibitor was absent the rates of stagnant and circulatingsolutions were 023 and 048mmyear respectively Also theeffect of nitrite ion was stronger in the circulating solutionthan in the stagnant solution However in the case of ductilecast iron the effect of nitrite addition was similar to that ofcarbon steel but the similar corrosion inhibition of ductilecast iron needs a significant addition of NaNO

2 When the

inhibitor was absent the rates of stagnant and circulatingsolutions were 047 and 084mmyear respectively Eventhough the NaNO

2addition was increased the corrosion

rate of ductile cast iron showed relatively higher values thanthose of carbon steel The corrosion of carbon steel can beinhibited at near 100 ppmNaNO

2addition but the corrosion

of ductile cast iron can be inhibited by an addition of morethan 10000 ppm NaNO

2 Moreover while the corrosion of

carbon steel can be inhibited more readily by the circulation

of the solution the circulation facilitated the corrosion ofductile cast iron

The open circuit potential with immersion time byNaNO

2addition in circulating (solid symbol) and stagnant

(open symbol) simulated cooling water in the air at 25∘Cwas shown in Figure 2 Regardless of the alloys used and thecirculation of solution the open circuit potential of the spec-imen without NaNO

2addition decreased with immersion

time However the open circuit potential of the specimenwith NaNO

2addition increased and its tendency depends

on the alloys In the case of carbon steel an addition of100 ppm NaNO

2increased the open circuit potential and the

circulation stimulated its rate Also in the case of ductile castiron a greater concentration (about 100 times) of NaNO

2is

needed for a similar effect of NaNO2addition

The effect of NaNO2addition on the polarization behav-

ior in deaerated simulated cooling water at 25∘Cwas revealedin Figure 3 the scanning rate was 033mVsWhenNaNO

2is

not added carbon steel and ductile cast iron dissolved readilywithout the passivation by anodic polarization With 10and 100 ppm NaNO

2additions carbon steel revealed active-

passive transition but the passive current density was highand transpassive behavior occurred Ductile cast iron did notshow an active-passive transition until a 10000 ppm NaNO

2

addition From a 1000 ppm NaNO2addition carbon steel

showed excellent passivation behavior but the ductile castiron revealed the best passivation curve from 100000 ppmNaNO

2addition This tendency is coincident with the result

of the immersion test shown in Figure 1Figure 4 shows the corrosion rate due to the NaNO

2

addition obtained from the immersion test (circulationcondition) shown in Figure 1 and the current density wasobtained at +400mV(SCE) as shown in Figure 3 Regardlessof the chemical or electrochemical tests the corrosion ofcarbon steel can be inhibited by a small NaNO

2addition


E (m

V(S

CE))

0ppm100ppm1000 ppm10000 ppm

0ppm100ppm1000 ppm10000 ppmCirculating solution Stagnant solution

Time (hour)

minus100

minus200

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100

806040200 100

0

0ppm1000 ppm50000 ppm100000 ppm

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(b)

Figure 2 Open circuit potential with immersion time by nitrite addition in circulating (solid symbol) and stagnant (open symbol) simulatedcooling water at 25∘C (a) carbon steel and (b) ductile cast iron

minus10 minus8 minus6 minus4 minus2 0minus1000

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CE))

minus10 minus8 minus6 minus4 minus2 0log i (Acm2)

100000ppm10000ppm

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10000ppm

1000ppm

100ppm 0ppm

(b)

Figure 3 Effect of NaNO2addition on polarization behavior in deaerated simulated cooling water at 25∘C (scanning rate 033mVs) (a)

carbon steel and (b) ductile cast iron

(ca 1000 ppm) but the corrosion of ductile cast iron couldbe only inhibited by a significant NaNO

2addition (ca

100000 ppm)That is it was demonstrated that the differencein the NaNO

2addition needed between carbon steel and

ductile cast iron was about 100 times

In order to determine the resistance of the passive filmformed on the surface of carbon steel and ductile cast iron byNaNO

2addition the AC impedance was measured Figure 5

shows the effect of NaNO2addition in Nyquist plot obtained

from AC impedance measurement at +400mV(SCE) for


0

1

2

3

4

0 1 2 3 4 5 6

log

corr

osio

n ra

te (120583

my

r)

CSDCI

log C (ppm NaNO2)

(a)

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minus7

minus6

minus5

minus4

minus3

minus2

minus1

0 1 2 3 4 5 6

logi

(Ac

m2)

log C (ppm NaNO2)

(b)

Figure 4 Comparison of (a) corrosion rate (circulation condition) from Figure 1 and (b) current density obtained at +400mV (SCE) ofFigure 3 by NaNO

2addition to simulated cooling water

0

50

100

150

200

250

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1000ppm100ppm10ppm

Real impedance Zr (kΩ)

Imag

inar

y im

peda

nceZi

(kΩ

)

(a)

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100

120

140

160

180

0 100 200 300 400

100000ppm50000ppm


Imag

inar

y im

peda

nceZi

(kΩ

)

(b)

Figure 5 Effect of NaNO2addition on Nyquist plot obtained from AC impedance measurement in deaerated simulated cooling water at

25∘C (a) carbon steel at +400mV (SCE) and (b) ductile cast iron at 0V (SCE)

carbon steel and 0V(SCE) for ductile cast iron in deaeratedsimulated cooling water at 25∘C In the case of carbon steel astable passive film could not be formedwith a 10 ppmNaNO

2

addition and very small impedance (156 kohm) was thusshownA 100 ppmNaNO

2addition formed a passive film but

its polarization resistancewas small (1946 kohm)However astable passive film (4425 kohm)was formedwith a 1000 ppmNaNO

2addition In the case of ductile cast iron a stable

passive film (3337 kohm) was formed with a 100000 ppmNaNO

2addition As shown in Figures 1 and 4 the difference

of corrosion inhibition between carbon steel and ductile castiron due to the NaNO

2addition was closely related to the

formation of a stable passive film on the surface

32 Corrosion Inhibition Mechanism of Carbon Steel andDuctile Cast Iron by Nitrite Ion It was revealed that thedifference in the effect of corrosion inhibition due to NaNO

2

addition between carbon steel and ductile cast iron was about100 times through the immersion test and electrochemicaltests as described above As shown in Table 1 the significant


50120583m

(a)

50120583m

(b)

(c) (d)

Figure 6 Optical microstructures (a b) and SEM images (c d) (a c) carbon steel and (b d) ductile cast iron

difference in the composition between the two alloys iscarbon content Figure 6 shows optical microstructures andSEM images for carbon steel and ductile cast iron In the caseof carbon steel ferrite and pearlite phases can be observedHowever in the case of ductile cast iron spheroidized phaseswere formed in the ferrite matrix and the spheroidizedphase was shown to be graphite by SEM-EDS analysis Thesepictures show the typical microstructures of carbon steel andductile cast iron

In order to determine the effect of NaNO2addition

on the corrosion morphologies of ductile cast iron afterimmersion the corroded surface was observed The effect ofNaNO

2addition on the surface appearance of ductile cast

iron after the immersion test in simulated cooling water for 3hours at 25∘C was presented in Figure 7 Figure 7(a) showsthe addition of 0 ppm NaNO

2and Figure 7(b) shows the

addition of 10000 ppmNaNO2When noNaNO

2was added

the ductile cast iron was generally corroded on the entiresurface However when 10000 ppm NaNO

2was added (this

addition of which is not sufficient to inhibit corrosion ofductile cast iron as shown in Figures 1 and 3) the iron wascorroded locally near the spheroidized graphite and the cor-roded areas were agglomerated Figure 8 shows the corrosionmorphologies of ductile cast iron in which ductile cast iron

was corroded for 3 hours in stagnant simulated cooling water(10000 ppm NaNO

2) at 25∘C Figure 8(a) shows the surface

contour using a 3D microscope and local corrosion near thespheroidized graphite was confirmed Figure 8(b) shows anSEM image of the corroded area showing that it was corrodedspherically near the graphite and thenfinally the graphite hadchipped off Also corrosion products and even cracks wereobserved near the chipped-off graphite These figures showthat galvanic corrosion took place in the ductile cast iron Itis well known that graphite is nobler than matrix iron [23]

The galvanic corrosion between graphite and matrixiron was simulated using a COMSOLMultiphysics programAnodic and cathodic Tafel slopes (+108mV and minus206mVresp) were applied to calculate the corrosion behavior of thecorroding and noncorroding areas Figure 9 shows computer3D simulation results of the corrosion propagation of ductilecast iron occurring in stagnant simulated cooling water(10000 ppm NaNO

2) at 25∘C At the initial stage (0 hour)

the potential difference between graphite (the center) andmatrix (left and right) is shown by the blue and red colorsrespectively By increasing the immersion time the matrixnear the graphite corroded and the corrosion depth wasincreased its depth was greater near the graphite (Thisis the distance effect observed in galvanic corrosion) This


50120583m

(a)

50120583m

(b)

Figure 7 Effect of NaNO2addition on surface appearance of ductile cast iron after the immersion test in simulated cooling water for 3 hours

at 25∘C (a) 0 ppm NaNO2and (b) 10000 ppm NaNO

2

12584

10067

7550

5034

2517

0000

(120583m

)

111858120583m107115 120583m

Height 10835120583m

Max 12584120583m

Width 1Width 2

(a) (b)

Figure 8 Corrosion morphologies of ductile cast iron corroded in stagnant simulated cooling water (10000 ppm NaNO2) for 3 hours at

25∘C (a) 3D microscope and (b) SEM image

simulation result differs from that shown in Figure 8(b) Thisdifference could be due to the characteristics of the graphite(However it should be noted that the COMSOLMultiphysicsprogram does not simulate the mechanical damage in gal-vanic corrosion)The crystal structure of graphite is covalentbonded with neighboring atoms in the same layer althoughlayers are van der Waals bonded together [24 25] and thusthe bonding force of graphite is very weak Therefore it isconsidered that the matrix is corroded galvanically and thatthe graphite is protruded and then graphite is peeled off layerby layer because of the weak bonding force of graphite

Figure 10 shows the elemental distribution analyzed usingEPMA on the surface of ductile cast iron passivated in

simulated cooling water (100000 ppm NaNO2) at 25∘C for

72 hours The SEM image clearly shows the microstructureof ductile cast iron Fe was depleted in the graphite area andcarbon was concentrated as spheroidized shapes Also whileoxygen was detected on the entire surface it was particularlyconcentrated on the graphite area and dim spots of nitrogenwere detected Figure 11 shows the elemental distributionanalyzed using EPMA on the surface of ductile cast ironcorroded in simulated cooling water (10000 ppm NaNO

2)

at 25∘C for 72 hours The SEM image shows the locallycorroded morphology as seen in Figure 7(b) Fe was notuniform and this is related to local corrosion However thecarbon distribution was very different to the fully passivated


10 0 minus100

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zx

y

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(120583m)

(120583m

)

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)

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)

(e)

Figure 9 Surface electrolyte potential (V(SCE) the right vertical color bar) obtained by computer 3D simulation (the unit of 119909- 119910- and119911-axes 120583m) using COSOL Multiphysics on corrosion propagation with immersion time of ductile cast iron occurred in stagnant simulatedcooling water (10000 ppm NaNO

2) at 25∘C (a) 0 hour (b) 24 hours (c) 48 hours (d) 72 hours and (e) 144 hours

surface as shown in Figure 10(c)While spheroidized graphitewas not observed destroyed graphite and its location wereidentified this result provides the evidence that graphite canbe peeled off layer by layer as discussed above Oxygen wasdetected more on the Fe-depleted areas and dim spots ofnitrogenwere detectedThis oxygen comes from the sufficientNaNO

2 It will be discussed below

The depth profile on the passivated surface was obtainedusing XPS to determine the role of nitrite ion on thepassivation of steel and iron Figure 12 shows the depth profileusing XPS on the passive film of carbon steel passivated for24 hours in simulated cooling water (1000 ppm NaNO

2) at

25∘COxygen and nitrogenwere enriched at the outer surfaceand Fe drastically increased with etch time Figures 12(b)and 12(c) show that iron oxide was enriched at the outersurfaceNitrogenwas only detected before sputtering andwasnot detected at any sputtered depths This provides evidencethat nitrogen is present only on the outermost surface evenwith the NaNO

2addition to the solution Figure 13 shows

the depth profile using XPS on the passive film of ductilecast iron passivated for 24 hours in simulated cooling water(100000 ppm NaNO

2) at 25∘C Oxygen and nitrogen were

enriched at the outer surface and Fe is drastically increasedwith etch time Figures 13(b) and 13(c) show that iron oxide


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(e)

Figure 10 Elemental distribution analyzed by EPMA on the surface of ductile cast iron passivated in simulated cooling water (100000 ppmNaNO

2) at 25∘C for 72 hours (a) SEM image (b) Fe (c) C (d) O and (e) N


32880

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Figure 11 Elemental distribution analyzed by EPMA on the surface of ductile cast iron corroded in simulated cooling water (10000 ppmNaNO



0

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tent

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)

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CO

FeN

(a)

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704706708710712714716

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nts

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nsity

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0 s5 s20 s40 s

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(d)

Figure 12 Depth profile by XPS on passive film of carbon steel passivated for 24 hours in simulated cooling water (1000 ppm NaNO2) at

25∘C (a) depth profile (b) Fe2p detail scan (c) O1s detail scan and (d) N

1s detail scan

was enriched at the outer surface Nitrogen was only detectedbefore sputtering and at 10 secondsrsquo etch time and was notdetected at any sputtered depths This provides evidencethat nitrogen is present only on the outermost surfaceeven with the NaNO

2addition to the solution However

nitrogen of passivated ductile cast iron was detected at aslightly deeper depth than that of the passivated carbonsteel This behavior seems to be related to the corrosion andpassivation between graphite and matrix in ductile cast iron

Figure 14 shows the deconvolution of the chemical speciesdetermined by XPS on the surface of (a b c) carbon steelpassivated in 1000 ppm NaNO

2and (a1015840 b1015840 c1015840) ductile cast

iron passivated in 100000 ppm NaNO2 Regardless of the

alloys and sputtering time (0 sec and 10 sec) the passivefilms formed by NaNO

2addition were composed of iron

oxides (Fe2+ and Fe3+) Also nitrogen before sputtering existsas nitrogen compounds including NOminus (4004 3992 eV)NH4

+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

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ity (c

ps)

Binding energy (eV)

100 s

0 s

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405 404 403 402 401 400 399 398 397 396

(d)

Figure 13 Depth profile by XPS on passive film of ductile cast iron passivated for 24 hours in simulated cooling water (100000 ppmNaNO2)

at 25∘C (a) depth profile (b) Fe2p detail scan (c) O1s detail scan and (d) N

1s detail scan

[26 27] However it should be noted that the chemical statesof nitrogen on the passivated surface are not easy to identifyby XPS

Therefore as discussed above corrosion and its inhibitionmodel can be proposed as follows Figure 15 shows the corro-sion and inhibition steps of ductile cast iron with nitrite addi-tion When no corrosion inhibitor is used general corrosionand galvanic corrosion occur simultaneously and thus thesurfacemay show relatively uniform corrosion (Figure 15(a))Also when the amount of corrosion inhibitor is insufficient

(eg 10000 NaNO2) some area may be passivated (red

line) and galvanic corrosion can occur finally the iron thenreveals localized corrosion (Figure 15(b)) However whena sufficient corrosion inhibitor (eg 100000 ppm NaNO

2

in Figure 15(c)) is used (even though galvanic corrosionbetween graphite andmatrix has occurred) the entire surfacecan be passivated and thus corrosion can be inhibited Alsoit should be noted that NO

2

minus ion is used to oxidize thematrixand can itself be reduced to nitric oxide this compound canbe absorbed on the surface of graphite and thus the enriched


0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)

Figure 14 Deconvolution of the chemical species determined by XPS on the surface of (a a1015840 c) carbon steel passivated in 1000 ppmNaNO2

and (b b1015840 c1015840) ductile cast iron passivated in 100000 ppm NaNO2 (a) and (a1015840) Fe 2p (b) and (b1015840) Fe 2p and (c) and (c1015840) N 1s


G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)

Figure 15 Corrosion and inhibition steps with nitrite addition of ductile cast iron (a) without corrosion inhibitor (b) with insufficientcorrosion inhibitor (10000 ppmNaNO

2) and with sufficient corrosion inhibitor (100000 ppmNaNO

2) (G graphite red line metallic oxide

dot line nitrogen compound)

0

50

100

150

200

minus15 minus1 minus05 0 05 1E (V(SCE))

1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150

minus15 minus1 minus05 0 05 1

100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)

Figure 16 Effect of NaNO2addition on Mott-Schottky plot for the passive film formed in deaerated simulated cooling water at 25∘C (a)

carbon steel at +400mV (SCE) and (b) ductile cast iron at 0mV (SCE)

nitrogen compounds could be detected in the EPMA andXPS results Therefore since nitrite ion needs to oxidize thesurface of the matrix and needs to passivate the galvaniccorroded area and since it is absorbed on the surface ofgraphite a larger amount of corrosion inhibitor is needed forductile cast iron than for carbon steel

On the other hand passivated film of various alloysexhibits semiconductive properties [28ndash30] Acquisition ofMott-Schottky plots is a usual way for semiconductor mate-rials electrochemical characterization Mott-Schottky plot(inverse square of space charge layer capacitance 119862sc

minus2versus semiconductor electrode potential 119864) gives dopingdensity by slope of the straight line and flat band potential byintercept [31] A positive slope in the plot indicates theN-typesemiconductive properties Figure 16 shows a Mott-Schottky

plot of the effect of NaNO2addition for the passive film

formed in deaerated simulated coolingwater at 25∘C Regard-less of the alloys the increasing inhibitor concentrationstrengthened the N-type properties Also these plots revealedthe N-type semiconductive properties of the passivated sur-face film due to nitrite addition

4 Conclusions

(1) While NaNO2addition can greatly inhibit the corro-

sion of carbon steel and ductile cast iron in orderto improve the similar corrosion resistance ca 100timesmore NaNO

2addition is needed for ductile cast

iron than for carbon steel A corrosion and inhibitionmechanism is proposed whereby NO

2

minus ion is added


to oxidize The NO2

minus ion can be reduced to nitrogencompound and this compound may be absorbed onthe surface of graphite Therefore since nitrite ionneeds to oxidize the surface of matrix and needs topassivate the galvanic corroded area and since it isabsorbed on the surface of graphite a greater amountof corrosion inhibitor needs to be added to ductilecast iron than to carbon steel

(2) The passive film of carbon steel and ductile cast ironformed by NaNO

2addition showed N-type semi-

conductive properties and its resistance is increasedthe passive current density is thus decreased and thecorrosion rate is then lowered In addition the filmis mainly composed of iron oxide due to the oxida-tion by NO

2

minus ion however regardless of the alloysnitrogen compounds (not nitrite) were detected at theoutermost surface but were not incorporated in theinner oxide

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

This work was supported by the Nuclear Power CoreTechnology Development Program of the Korea Instituteof Energy Technology Evaluation and Planning (KETEP)granted financial resource from theMinistry of Trade Indus-try amp Energy Republic of Korea (no 20131520000100)

References

[1] Plant Shutdown Caused by the Crack of the Essential ServiceWater System Concrete Pipe Incident Report 7285 Hanul 1Republic of Korea 1998

[2] Firewater Supply Valve Downstream Buried Piping Leakage ofIntake Area Equipment Failure Report 06-Hanbit 4-1 Hanbit4 Republic of Korea 2006

[3] USNRC ldquoGeneric aging lessons learned (GALL) reportrdquo TechRep NUREG-1801 Rev 2 Division of Regulatory ImprovementPrograms 2010

[4] EPRI ldquoNondestructive evaluation guided wave technologydevelopment and nuclear application assessmentrdquo Tech RepEPRI-1015156 2007

[5] EPRI ldquoCondition assessment of large-diameter buried pipingphase 2-vehicle design and constructionrdquo EPRI 1011829 EPRI2005

[6] NRC Inspection Manual ldquoInspection of structures passivecomponents and civil engineering features at nuclear powerplantsrdquo Inspection Procedure 62002 United States NuclearRegulatory Commission (USNRC) 1996

[7] E McCafferty Introduction to Corrosion Science Springer NewYork NY USA 2009

[8] V S Sastri Corrosion Inhibitors Principles and ApplicationsWiley London UK 1998

[9] K NMohana andAM Badiea ldquoEffect of sodiumnitrite-boraxblend on the corrosion rate of low carbon steel in industrial

watermediumrdquoCorrosion Science vol 50 no 10 pp 2939ndash29472008

[10] M Cohen ldquoInhibition of steel corrosion by sodium nitrite inwaterrdquo Journal of the Electrochemical Society vol 93 no 1 pp26ndash39 1948

[11] R Pyke and M Cohen ldquoRate of breakdown and mechanism ofnitrite inhibition of steel corrosionrdquo Journal of the Electrochem-ical Society vol 93 no 3 pp 63ndash78 1948

[12] M Cohen R Pyke and P Marier ldquoThe effect of oxygen oninhibition of corrosion by nitriterdquo Journal ofTheElectrochemicalSociety vol 96 no 4 pp 254ndash261 1949

[13] S M Matsuda and H H Uhlig ldquoEffect of pH sulfates andchlorides on behavior of sodium chromate and nitrite aspassivators for steelrdquo Journal of the Electrochemical Society vol111 no 2 pp 156ndash161 1964

[14] W D Robertson ldquoMolybdate and tungstate as corrosioninhibitors and the mechanism of inhibitionrdquo Journal of theElectrochemical Society vol 98 no 3 pp 94ndash100 1951

[15] M J Pryor and M Cohen ldquoThe inhibition of the corrosion ofiron by some anodic inhibitorsrdquo Journal of the ElectrochemicalSociety vol 100 no 5 pp 203ndash215 1953

[16] S Karim C M Mustafa Md Assaduzzaman and M IslamldquoEffect of nitrite ion on corrosion inhibition of mild steelin simulated cooling waterrdquo Chemical Engineering ResearchBulletin vol 14 pp 87ndash91 2010

[17] Y T Horng and Y L Tsai ldquoAn investigation of mild steel withnitrogen-containing inhibitor in hydrochloric acidrdquo CorrosionScience and Technology vol 2 no 5 pp 233ndash237 2003

[18] L Abosrra M Youseffi and A F Ashour ldquoEffectiveness ofcalcium nitrite in retarding corrosion of steel in concreterdquoInternational Journal of Concrete Structures and Materials vol5 no 1 pp 65ndash73 2011

[19] R Mehra and A Soni ldquoInhibition of corrosion of mild steelby nitrite hydrogen phosphate and molybdate ions in aqueoussolution of sodium chloriderdquo Indian Journal of Engineering ampMaterials Sciences vol 9 no 2 pp 141ndash146 2002

[20] ASME ASME Boiler amp Pressure Vessel Section IImdashPart AlsquoFerrous Materials Specifications (Beginning to SA-450)rsquo ASME2011

[21] KoreanAgency for Technology and StandardsKSD4311 DuctileIron Pipe Korean Agency for Technology and StandardsGyeonggi-do South Korea 2010

[22] D DMacdonald ldquoThe point defect model for the passive staterdquoJournal of the Electrochemical Society vol 139 no 12 pp 3434ndash3449 1992

[23] Y S Kim S J Park and Y R Yoo ldquoGalvanic corrosion behaviorbetween carbon steel bolted GECM(graphite epoxy compositematerial)Al platesrdquo Corrosion Science and Technology vol 12no 1 pp 19ndash33 2013

[24] P Q Dai Z R He W Q Wu and Z Y Mao ldquoMechanicalbehaviour of graphite in fracture of austempered ductile ironrdquoMaterials Science and Technology vol 18 no 9 pp 1052ndash10562002

[25] J R Davis ASM Specialty Handbook Cast Irons ASM Interna-tional Novelty Ohio USA 1996

[26] C D Wagner W H Riggs L E Davis J F Moulder and GE Muilenberg Handbook of X-Ray Photoelectron SpectroscopyPerkin-Elmer 1979

[27] Y S Kim ldquoSynergistic effect of nitrogen and molybdenum onlocalized corrosion of stainless steelrdquo Corrosion Science andTechnology vol 9 no 1 pp 20ndash28 2010


[28] H J Jang ldquoStudy on the semiconducting properties of thepassive films formed on Ni-Cr alloys in pH 85 buffer solutionrdquoJournal of Advanced Engineering and Technology vol 2 no 2pp 285ndash289 2009

[29] A Di Paola ldquoSemiconducting properties of passive films onstainless steelsrdquo Electrochimica Acta vol 34 no 2 pp 203ndash2101989

[30] C Sunseri S Piazza and F Di Quarto ldquoPhotocurrent spectro-scopic investigations of passive films on chromiumrdquo Journal ofthe Electrochemical Society vol 137 no 8 pp 2411ndash2417 1990

[31] A S Bondarenko and G A Ragoisha ldquoVariable Mott-Schottky plots acquisition by potentiodynamic electrochemicalimpedance spectroscopyrdquo Journal of Solid State Electrochem-istry vol 9 no 12 pp 845ndash849 2005

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


Table 1 Chemical compositions of experimental alloys

Alloys Chemical compositions wtC Mn P S Si Cr Cu Mo Ni V Fe

CS 026 086 0014 0005 023 004 0057 0033 0029 0008 balDCI 401 017 0022 0026 153 mdash 0023 0028 0059 0016 balCS carbon steel ASME SA106 GrB DCI ductile cast iron KS D4311

then occurs including general corrosion pitting microbialinduced corrosion scale buildupmultiplication ofmicrobialand fatigue Therefore several corrosion control methodssuch as painting and coating electrical protection and theuse of corrosion inhibitors have been applied [7ndash9] Carbonsteel and cast iron used in a closed cooling system may becorroded In order to control this type of corrosion problemcorrosion inhibitors such as nitrite silicate molybdate andhydrazine have been used among them nitrite is widely usedbecause of its excellent performance

Many reports have been presented on corrosion inhi-bition by nitrite including Fe

2O3formation on steel by

nitrite addition [10] adherent protective oxide on steel [11]correlation of oxygen and nitrite on steel corrosion [12]comparative study of nitrite including various inhibitors onsteel [13ndash15] and inhibition effect of nitrite on steel withtime [16 17] Nitrite as an anodic inhibitor has a tendencyto increase anodic polarization and thus increase corrosionpotential to a noble direction and decrease the corrosioncurrent Since nitrite contains a strong oxidizing power itoxidizes the surface and forms Fe

2O3[18] Formation rate of

protective film due to nitrite is very fast and thus among theseveral corrosion inhibitors nitrite shows good performance[19]

On the other hand ductile cast iron has a very differentmicrostructure to that of carbon steel Spheroidized graphiteforms in the matrix and galvanic corrosion occurs betweenthe matrix and graphite Also cast iron does not have highcorrosion resistance to various corrosion environments andit should be protected by a coating As described abovemany reports have been presented on the corrosion inhibitionof carbon steel but there are few reports on cast ironTherefore in this work corrosion inhibition effects of nitriteon carbon steel and ductile cast iron for nuclear powerplant pipework using chemical and electrochemical methodswere evaluated This work attempts to clarify the corrosioninhibition mechanism between steel and iron by NaNO

2

addition

2 Experimental Procedure

21 Materials and Corrosion Environments Commercial car-bon steel (ASME SA106 GrB) [20] and ductile cast iron (KSD4311) [21] were used in this work and Table 1 shows thechemical composition of the experimental alloys

The test solution was simulated primary cooling waterused in the nuclear power plant The standard solution was16 ppm NaCl and its pH was modified with 1N NaOHsolution and the range of pH 9 plusmn 02 was controlled NaNO

2

as a corrosion inhibitor was added as a ppm order

22 Corrosion Tests

221 Immersion Corrosion Test A specimen was cut to a sizeof 20times 20times 5mmand each surfacewas groundusing 120 SiCpaper Immersion tests were carried out in a stagnant solutioncondition (500mL glass flask) and in a circulating solutionin which test chamber has a dimension of 50 times 100 times 50 cmand the flow rate was 5 Lmin After the immersion tests eachspecimen was cleaned with acetone and alcohol and was thendried the corrosion rate was then determined

222 Electrochemical Tests Specimens were cut to a sizeof 20 times 20mm and after electrical connection they wereepoxy-mounted and the surface was ground using 600SiC paper and coated with epoxy resin except an area of1 cm2 A polarization test was performed using a potentiostat(Gamry DC105) and the reference electrode was a saturatedcalomel electrode and the counter electrode was Pt wire Thetest solution was deaerated using nitrogen gas at the rateof 100mLmin for 30 minutes and the scanning rate was033mVsec In order to measure the AC impedance thespecimens were ground using 2000 SiC paper and thenpolished using a diamond paste (3120583m)The test solution wasthe same as that of the polarization test AC impedance mea-surement was performed using an electrochemical analyzer(Gamry EIS 300) Before measuring passivation was treatedat +400mV(SCE) for carbon steel and 0mV(SCE) for ductilecast iron for 30 minutes AC impedance was measured ata passivation potential from 10 kHz to 001Hz and the ACvoltage amplitude was 10mV Also a Mott-Schottky plot wasprepared to determine the semiconductive properties of thepassive film The specimen preparation was the same as thatfor AC impedance measurement and the DC amplitude was10mV (peak-to-peak) at 1580Hz of the AC frequency [22]The capacitance was measured at the scan rate of 50mVsecfrom +1V(SCE) to minus15 V(SCE)

223 Surface Analysis X-ray photoelectron spectroscopy(XPS K-alpha (Thermo VG UK) Al-K

120572(14866 eV 12 kV

3mA)) was analyzed to determine the chemical state ofseveral species of the passive film The specimen was cutto a size of 20 times 20 times 5mm and then ground with 2000SiC paper and polished with a 3 120583m diamond paste thespecimenwas finally cleaned with alcohol using an ultrasoniccleaner Carbon steel and ductile cast iron were passivatedby immersion for 24 hours in 1000 ppm and 100000 ppmNaNO

2 respectively The depth profile was obtained every

5 seconds by Ar-sputtering Also an Electron Probe MicroAnalyzer (EPMA EPMA-1600 15 KV) was used to identifythe elemental distribution of the passivated surface Optical


023

0060 0 0

048

0 0 0 00

02

04

06

08

1

0 10 100 1000 10000

Cor

rosio

n ra

te (m

my

r)


NaNO2 (ppm)

(a)


047

009004 002 0 0 0

084

041

014008 007

001 00

02

04

06

08

1

0 10 100 1000 10000 50000 100000

Cor

rosio

n ra

te (m

my

r)

NaNO2 (ppm)

(b)


ductile cast iron









2 When the


















2is




2is




2





2


2addition


E (m

V(S

CE))



Time (hour)

minus100

minus200

minus300

minus400

minus500

minus600

minus700

minus800

100

806040200 100

0

(a)

E (m

V(S

CE))


Time (hour)

minus100

minus200

minus300

minus400

minus500

minus600

minus700

minus800

100

806040200 100

0

0ppm1000 ppm50000 ppm100000 ppm

0ppm1000 ppm50000 ppm100000 ppm

(b)



minus800

minus600

minus400

minus200

0

200

400

600

800

1000

E (m

V(S

CE))

10000ppm1000ppm

100ppm10ppm0ppm

10000ppm

1000ppm

100ppm

10ppm

0ppm

log i (Acm2)

(a)

minus1000

minus800

minus600

minus400

minus200

0

200

400

600

800

1000

E (m

V(S

CE))


100000ppm10000ppm

1000ppm100ppm0ppm

100000ppm

10000ppm

1000ppm

100ppm 0ppm

(b)




2addition (ca









0

1

2

3

4

0 1 2 3 4 5 6

log

corr

osio

n ra

te (120583

my

r)

CSDCI

log C (ppm NaNO2)

(a)

CSDCI

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0 1 2 3 4 5 6

logi

(Ac

m2)

log C (ppm NaNO2)

(b)



0

50

100

150

200

250

0 100 200 300 400 500

1000ppm100ppm10ppm


Imag

inar

y im

peda

nceZi

(kΩ

)

(a)

0

20

40

60

80

100

120

140

160

180

0 100 200 300 400

100000ppm50000ppm


Imag

inar

y im

peda

nceZi

(kΩ

)

(b)




2











2



50120583m

(a)

50120583m

(b)

(c) (d)









2was added


2was added (this









50120583m

(a)

50120583m

(b)



2

12584

10067

7550

5034

2517

0000

(120583m

)

111858120583m107115 120583m

Height 10835120583m

Max 12584120583m

Width 1Width 2

(a) (b)







2)



10 0 minus100

50

0minus10

10

zx

y

Graphite

055050045040035030(V(SCE))

(120583m)

(120583m

)

(120583m

)

(a)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m

)

(120583m

)

(b)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(c)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m)

(120583m

)

(d)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(e)






2) at







24384

42064

30120583m

(a)

523483443

564

362322282

402

241201161

80400

120

30120583m

(b)

339431332872

3656

235020891828

2611

156613051044

5222610

783

30120583m

(c)

928578

100

645750

71

433629

1581

22

30120583m

(d)

928578

100

645750

71

433629

1581

22

30120583m

(e)




32880

40288

60120583m

(a)

463

431

398

496

333

301

268

366

236

203

171

106

73

41

138

60120583m

(b)

125011541058

1347

865769673

962

577481384

192960

288

60120583m

(c)

315291267

340

219195171

243

14612298

50262

74

60120583m

(d)

928578

100

645750

71

423528

1470

21

60120583m

(e)




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




023

0060 0 0

048

0 0 0 00

02

04

06

08

1

0 10 100 1000 10000

Cor

rosio

n ra

te (m

my

r)


NaNO2 (ppm)

(a)


047

009004 002 0 0 0

084

041

014008 007

001 00

02

04

06

08

1

0 10 100 1000 10000 50000 100000

Cor

rosio

n ra

te (m

my

r)

NaNO2 (ppm)

(b)


ductile cast iron









2 When the


















2is




2is




2





2


2addition


E (m

V(S

CE))



Time (hour)

minus100

minus200

minus300

minus400

minus500

minus600

minus700

minus800

100

806040200 100

0

(a)

E (m

V(S

CE))


Time (hour)

minus100

minus200

minus300

minus400

minus500

minus600

minus700

minus800

100

806040200 100

0

0ppm1000 ppm50000 ppm100000 ppm

0ppm1000 ppm50000 ppm100000 ppm

(b)



minus800

minus600

minus400

minus200

0

200

400

600

800

1000

E (m

V(S

CE))

10000ppm1000ppm

100ppm10ppm0ppm

10000ppm

1000ppm

100ppm

10ppm

0ppm

log i (Acm2)

(a)

minus1000

minus800

minus600

minus400

minus200

0

200

400

600

800

1000

E (m

V(S

CE))


100000ppm10000ppm

1000ppm100ppm0ppm

100000ppm

10000ppm

1000ppm

100ppm 0ppm

(b)




2addition (ca









0

1

2

3

4

0 1 2 3 4 5 6

log

corr

osio

n ra

te (120583

my

r)

CSDCI

log C (ppm NaNO2)

(a)

CSDCI

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0 1 2 3 4 5 6

logi

(Ac

m2)

log C (ppm NaNO2)

(b)



0

50

100

150

200

250

0 100 200 300 400 500

1000ppm100ppm10ppm


Imag

inar

y im

peda

nceZi

(kΩ

)

(a)

0

20

40

60

80

100

120

140

160

180

0 100 200 300 400

100000ppm50000ppm


Imag

inar

y im

peda

nceZi

(kΩ

)

(b)




2











2



50120583m

(a)

50120583m

(b)

(c) (d)









2was added


2was added (this









50120583m

(a)

50120583m

(b)



2

12584

10067

7550

5034

2517

0000

(120583m

)

111858120583m107115 120583m

Height 10835120583m

Max 12584120583m

Width 1Width 2

(a) (b)







2)



10 0 minus100

50

0minus10

10

zx

y

Graphite

055050045040035030(V(SCE))

(120583m)

(120583m

)

(120583m

)

(a)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m

)

(120583m

)

(b)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(c)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m)

(120583m

)

(d)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(e)






2) at







24384

42064

30120583m

(a)

523483443

564

362322282

402

241201161

80400

120

30120583m

(b)

339431332872

3656

235020891828

2611

156613051044

5222610

783

30120583m

(c)

928578

100

645750

71

433629

1581

22

30120583m

(d)

928578

100

645750

71

433629

1581

22

30120583m

(e)




32880

40288

60120583m

(a)

463

431

398

496

333

301

268

366

236

203

171

106

73

41

138

60120583m

(b)

125011541058

1347

865769673

962

577481384

192960

288

60120583m

(c)

315291267

340

219195171

243

14612298

50262

74

60120583m

(d)

928578

100

645750

71

423528

1470

21

60120583m

(e)




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




E (m

V(S

CE))



Time (hour)

minus100

minus200

minus300

minus400

minus500

minus600

minus700

minus800

100

806040200 100

0

(a)

E (m

V(S

CE))


Time (hour)

minus100

minus200

minus300

minus400

minus500

minus600

minus700

minus800

100

806040200 100

0

0ppm1000 ppm50000 ppm100000 ppm

0ppm1000 ppm50000 ppm100000 ppm

(b)



minus800

minus600

minus400

minus200

0

200

400

600

800

1000

E (m

V(S

CE))

10000ppm1000ppm

100ppm10ppm0ppm

10000ppm

1000ppm

100ppm

10ppm

0ppm

log i (Acm2)

(a)

minus1000

minus800

minus600

minus400

minus200

0

200

400

600

800

1000

E (m

V(S

CE))


100000ppm10000ppm

1000ppm100ppm0ppm

100000ppm

10000ppm

1000ppm

100ppm 0ppm

(b)




2addition (ca









0

1

2

3

4

0 1 2 3 4 5 6

log

corr

osio

n ra

te (120583

my

r)

CSDCI

log C (ppm NaNO2)

(a)

CSDCI

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0 1 2 3 4 5 6

logi

(Ac

m2)

log C (ppm NaNO2)

(b)



0

50

100

150

200

250

0 100 200 300 400 500

1000ppm100ppm10ppm


Imag

inar

y im

peda

nceZi

(kΩ

)

(a)

0

20

40

60

80

100

120

140

160

180

0 100 200 300 400

100000ppm50000ppm


Imag

inar

y im

peda

nceZi

(kΩ

)

(b)




2











2



50120583m

(a)

50120583m

(b)

(c) (d)









2was added


2was added (this









50120583m

(a)

50120583m

(b)



2

12584

10067

7550

5034

2517

0000

(120583m

)

111858120583m107115 120583m

Height 10835120583m

Max 12584120583m

Width 1Width 2

(a) (b)







2)



10 0 minus100

50

0minus10

10

zx

y

Graphite

055050045040035030(V(SCE))

(120583m)

(120583m

)

(120583m

)

(a)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m

)

(120583m

)

(b)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(c)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m)

(120583m

)

(d)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(e)






2) at







24384

42064

30120583m

(a)

523483443

564

362322282

402

241201161

80400

120

30120583m

(b)

339431332872

3656

235020891828

2611

156613051044

5222610

783

30120583m

(c)

928578

100

645750

71

433629

1581

22

30120583m

(d)

928578

100

645750

71

433629

1581

22

30120583m

(e)




32880

40288

60120583m

(a)

463

431

398

496

333

301

268

366

236

203

171

106

73

41

138

60120583m

(b)

125011541058

1347

865769673

962

577481384

192960

288

60120583m

(c)

315291267

340

219195171

243

14612298

50262

74

60120583m

(d)

928578

100

645750

71

423528

1470

21

60120583m

(e)




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

1

2

3

4

0 1 2 3 4 5 6

log

corr

osio

n ra

te (120583

my

r)

CSDCI

log C (ppm NaNO2)

(a)

CSDCI

minus7

minus6

minus5

minus4

minus3

minus2

minus1

0 1 2 3 4 5 6

logi

(Ac

m2)

log C (ppm NaNO2)

(b)



0

50

100

150

200

250

0 100 200 300 400 500

1000ppm100ppm10ppm


Imag

inar

y im

peda

nceZi

(kΩ

)

(a)

0

20

40

60

80

100

120

140

160

180

0 100 200 300 400

100000ppm50000ppm


Imag

inar

y im

peda

nceZi

(kΩ

)

(b)




2











2



50120583m

(a)

50120583m

(b)

(c) (d)









2was added


2was added (this









50120583m

(a)

50120583m

(b)



2

12584

10067

7550

5034

2517

0000

(120583m

)

111858120583m107115 120583m

Height 10835120583m

Max 12584120583m

Width 1Width 2

(a) (b)







2)



10 0 minus100

50

0minus10

10

zx

y

Graphite

055050045040035030(V(SCE))

(120583m)

(120583m

)

(120583m

)

(a)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m

)

(120583m

)

(b)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(c)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m)

(120583m

)

(d)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(e)






2) at







24384

42064

30120583m

(a)

523483443

564

362322282

402

241201161

80400

120

30120583m

(b)

339431332872

3656

235020891828

2611

156613051044

5222610

783

30120583m

(c)

928578

100

645750

71

433629

1581

22

30120583m

(d)

928578

100

645750

71

433629

1581

22

30120583m

(e)




32880

40288

60120583m

(a)

463

431

398

496

333

301

268

366

236

203

171

106

73

41

138

60120583m

(b)

125011541058

1347

865769673

962

577481384

192960

288

60120583m

(c)

315291267

340

219195171

243

14612298

50262

74

60120583m

(d)

928578

100

645750

71

423528

1470

21

60120583m

(e)




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




50120583m

(a)

50120583m

(b)

(c) (d)









2was added


2was added (this









50120583m

(a)

50120583m

(b)



2

12584

10067

7550

5034

2517

0000

(120583m

)

111858120583m107115 120583m

Height 10835120583m

Max 12584120583m

Width 1Width 2

(a) (b)







2)



10 0 minus100

50

0minus10

10

zx

y

Graphite

055050045040035030(V(SCE))

(120583m)

(120583m

)

(120583m

)

(a)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m

)

(120583m

)

(b)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(c)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m)

(120583m

)

(d)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(e)






2) at







24384

42064

30120583m

(a)

523483443

564

362322282

402

241201161

80400

120

30120583m

(b)

339431332872

3656

235020891828

2611

156613051044

5222610

783

30120583m

(c)

928578

100

645750

71

433629

1581

22

30120583m

(d)

928578

100

645750

71

433629

1581

22

30120583m

(e)




32880

40288

60120583m

(a)

463

431

398

496

333

301

268

366

236

203

171

106

73

41

138

60120583m

(b)

125011541058

1347

865769673

962

577481384

192960

288

60120583m

(c)

315291267

340

219195171

243

14612298

50262

74

60120583m

(d)

928578

100

645750

71

423528

1470

21

60120583m

(e)




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




50120583m

(a)

50120583m

(b)



2

12584

10067

7550

5034

2517

0000

(120583m

)

111858120583m107115 120583m

Height 10835120583m

Max 12584120583m

Width 1Width 2

(a) (b)







2)



10 0 minus100

50

0minus10

10

zx

y

Graphite

055050045040035030(V(SCE))

(120583m)

(120583m

)

(120583m

)

(a)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m

)

(120583m

)

(b)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(c)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m)

(120583m

)

(d)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(e)






2) at







24384

42064

30120583m

(a)

523483443

564

362322282

402

241201161

80400

120

30120583m

(b)

339431332872

3656

235020891828

2611

156613051044

5222610

783

30120583m

(c)

928578

100

645750

71

433629

1581

22

30120583m

(d)

928578

100

645750

71

433629

1581

22

30120583m

(e)




32880

40288

60120583m

(a)

463

431

398

496

333

301

268

366

236

203

171

106

73

41

138

60120583m

(b)

125011541058

1347

865769673

962

577481384

192960

288

60120583m

(c)

315291267

340

219195171

243

14612298

50262

74

60120583m

(d)

928578

100

645750

71

423528

1470

21

60120583m

(e)




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




10 0 minus100

50

0minus10

10

zx

y

Graphite

055050045040035030(V(SCE))

(120583m)

(120583m

)

(120583m

)

(a)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m

)

(120583m

)

(b)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(c)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zx

y

Graphite

(120583m)

(120583m)

(120583m

)

(d)

10 0 minus10

0

50

0minus10

10

055050045040035030(V(SCE))

zxy

Graphite

(120583m)

(120583m

)

(120583m

)

(e)






2) at







24384

42064

30120583m

(a)

523483443

564

362322282

402

241201161

80400

120

30120583m

(b)

339431332872

3656

235020891828

2611

156613051044

5222610

783

30120583m

(c)

928578

100

645750

71

433629

1581

22

30120583m

(d)

928578

100

645750

71

433629

1581

22

30120583m

(e)




32880

40288

60120583m

(a)

463

431

398

496

333

301

268

366

236

203

171

106

73

41

138

60120583m

(b)

125011541058

1347

865769673

962

577481384

192960

288

60120583m

(c)

315291267

340

219195171

243

14612298

50262

74

60120583m

(d)

928578

100

645750

71

423528

1470

21

60120583m

(e)




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




24384

42064

30120583m

(a)

523483443

564

362322282

402

241201161

80400

120

30120583m

(b)

339431332872

3656

235020891828

2611

156613051044

5222610

783

30120583m

(c)

928578

100

645750

71

433629

1581

22

30120583m

(d)

928578

100

645750

71

433629

1581

22

30120583m

(e)




32880

40288

60120583m

(a)

463

431

398

496

333

301

268

366

236

203

171

106

73

41

138

60120583m

(b)

125011541058

1347

865769673

962

577481384

192960

288

60120583m

(c)

315291267

340

219195171

243

14612298

50262

74

60120583m

(d)

928578

100

645750

71

423528

1470

21

60120583m

(e)




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




32880

40288

60120583m

(a)

463

431

398

496

333

301

268

366

236

203

171

106

73

41

138

60120583m

(b)

125011541058

1347

865769673

962

577481384

192960

288

60120583m

(c)

315291267

340

219195171

243

14612298

50262

74

60120583m

(d)

928578

100

645750

71

423528

1470

21

60120583m

(e)




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

Con

tent

s (at

)

Etch time (s)

CO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

0 s

110 s

(b)

5255275295315335355370

500

1000

1500

2000

2500

3000

3500

Cou

nts

s

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s110 s

110 s

0 s

(c)

minus30

minus20

minus10

0

10

20

30

396398400402404

Inte

nsity

(cps

)

Binding energy (eV)

0 s5 s20 s40 s

60 s80 s100 s

0 s

100 s

(d)



1s detail scan










+ (4011 eV) NH3(3986 3998 eV) and NO (3996 eV)


0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

20

40

60

80

100

minus5 0 5 10 15 20 25 30 35 40 45 50

(at

)

Etch time (s)

CSiO

FeN

(a)

0

2000

4000

6000

8000

10000

704706708710712714716

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(b)

0

500

1000

1500

2000

2500

3000

3500

525527529531533535537

Cou

nts

s

Binding energy (eV)

0 s

110 s

0 s5 s20 s40 s

60 s80 s110 s

(c)

minus30

minus20

minus10

0

10

20

30In

tens

ity (c

ps)

Binding energy (eV)

100 s

0 s

0 s5 s20 s40 s

60 s80 s100 s

405 404 403 402 401 400 399 398 397 396

(d)



1s detail scan





2


2



0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+ FeM

10 s

0

100

200

300

400

500

704706708710712714716

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+ Fe2+

FeM

0 s

0

500

1000

1500

2000

2500

704706708710712714

Inte

nsity

(cps

)

Binding energy (eV)

Fe3+

Fe2+ FeM

10 s

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

0

10

20

30

40

397398399400401402

Inte

nsity

(cps

)

Binding energy (eV)

0 s

NOminus

NOminus

NH3

NH3NO

NH4+

(a)

(b)

(c)

(a998400)

(b998400)

(c998400)




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




G G G

G G G

G G G

DCI

DCI

DCI

(a)

DCI

DCI

DCI

G G G

G G G

GG

(b)

DCI

DCI

DCI

G G G

G G G

G G G

(c)





0

50

100

150

200


1000ppm100ppm

Cminus2

()

120583Fminus2cm

4times10

9

(a)

0

50

100

150


100000ppm50000ppm

E (V(SCE))

Cminus2

()

120583Fminus2cm

4times10

9

(b)








4 Conclusions





2

minus ion is added


to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




to oxidize The NO2





2




Acknowledgment


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article corrosion inhibiting mechanism ... - hindawi

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