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The 2nd International Conference on Materials and Metallurgical Technology 2015 (ICOMMET 2015)

The 7th International Conference on Sensors ASIASENSE 2015

Surabaya, 4-6 October 2015

CORROSION AND FAILURE ANALYSIS


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CODE: CF

Modification of carbon paste electrode with Schiff base for the detection of lead, cadmium and zinc ions

Kisan Koirala, Jose H. Santos, Ai L. Tan, Mohammad A. Ali, Aminul H. Mirza

Department of Chemistry, University Brunei Darussalam, Tungku Link, Gadong BE1410, Brunei Darussalam

Abstract: A sensor was constructed by modifying carbon paste electrode for the determination of lead, cadmium andzinc ions using square wave anodic stripping voltammetry. The modified electrode was prepared by insertinghomogeneous mixture of 2-hydroxy-acetophenonethiosemicarbazone, graphite powder and mineral oil. A comparison

between the modified and unmodified electrodes is presented. Various important parameters controlling the performance of the sensor were investigated and optimized. Electrochemical behavior of modified electrode wascharacterized by cyclic voltammetry. The sensor exhibited linear behavior in the range of 0.25-12.5 mg L -1 for lead andcadmium and 0.50-10.0 mg L-1 for zinc at accumulation time of 70 s. The limit of detection was calculated as 11.23 μgL-1, 13.27 μg L-1 and 16.38 μg L-1 for lead, cadmium and zinc, respectively. It is inexpensive, portable andenvironmentally friendly and was successfully used for the determination of trace amount of lead, cadmium and zinc inlab waste samples. The results obtained were compared with inductively coupled plasma atomic emission spectroscopy.

Keywords: Chemically modified electrodes; anodic stripping voltammetry; Schiff base; heavy metals; electrochemicalsensor

Corresponding author: Kisan Koirala, E-mail: [email protected], Tel. +673-246-3001 Ext. 2620, Fax. +673-2461502

1. Introduction Lead (Pb), cadmium (Cd), and zinc (Zn) are toxic and hazardous pollutants in the environment due to their non-

biodegradability and persistence. They enter the environment through industrial waste, automobiles, atmosphericdeposition (both dry and wet), landfill runoff, and acid mine drainage. Pb causes health problems, such as digestive,neurological, cardiac, and mental troubles [1, 2]. Cd causes nausea, vomiting, diarrhea, and cramps and long term

exposures cause high blood pressure and destruction of red blood cells [3, 4]. Likewise, Zn causes dizziness, chest pain,trouble breathing, fever, chills and jaundice [5, 6].Due to these severe effects in human health, researchers are focused to develop highly sensitive methods for the

detection of heavy metals. Several analytical techniques such as atomic fluorescence spectrometry (AFS) [7], atomicabsorption spectrometry (AAS) [8, 9], inductively coupled plasma optical emission spectroscopy (ICP-OES) [10],neutron activation analysis (NAA) [5] and inductively coupled plasma mass spectrometry (ICP-MS) [11] are in practicefor detecting heavy metals. But these sophisticated instruments are expensive to operate and maintain with limited lifespan. Moreover, these techniques require time-consuming manipulation steps, skilled manpower and are unsuitable forin situ measurements.

Anodic stripping voltammetry (ASV) is the most widely used form of stripping analysis for trace metalconcentration [12-26] as it has shown various advantages such as rapid, accuracy, good selectivity and sensitivity. Thistechnique provides accurate measurements at the parts per billion (ppb) concentration levels and does not requirecomplex and expensive instrumentation. In addition, square wave anodic stripping voltammetry (SWASV) allows

minimizing the interference due to dissolved oxygen, and its use therefore eliminates the need for the time-consumingsample de-aeration [12].Over the past few decades, carbon pastes electrodes (CPE) are used for the fabrication of various electrometric

sensors for analytical purposes. They are prepared by homogenous mixing of carbonaceous material and liquid binder.Recently, to improve the sensitivity, selectivity, detection limit and other features of CPE, chemically modified CPEhave been introduced. CPE are modified by various materials such as appropriate ligands, ion exchangers,functionalized nanoparticles [27-30]. Selectivity and sensitivity of these modified CPE depends on the properties of themodifier materials used.

Previously, we have synthesized and characterized 2-hydroxyl-acetophenonethiosemicarbazone (Fig. 1) which isnewly synthesized Schiff base capable to form complexes with target ions [31]. The binding of metal with Schiff basecontains a number of passive accumulating processes, which may include adsorption, ion exchange, coordination,complexation, chelation and micro-precipitation [32]. Schiff base may be used as a modifier in the electrodes for the

preconcentration of metal ions [33].

In this study, we have modified CPE with 2-hydroxy-acetophenonethiosemicarbazone and applied for thedetermination of Pb2+, Cd2+ and Zn2+ ions using SWASV.


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Fig. 1 Chemical structure of 2-hydroxy-acetophenonethiosemicarbazone

2. Materials and Methods

2.1. Chemicals and reagentsPb, Cd, Zn and potassium nitrate were purchased from Merck. Potassium dihydrogen phosphate (Fluka), potassium

hydrogen phosphate (Fluka), sodium hydroxide (GCE) and hydrochloric acid (Sigma-Aldrich) were purchased asanalytical grade and used without further purification. The CPE was prepared using graphite powder (< 20 μm, Sigma-Aldrich) and mineral oil (Sigma-Aldrich). The phosphate buffer solution (PBS) was prepared from a mixture of

potassium dihydrogen phosphate and potassium hydrogen phosphate and adjusting to the required pH value withhydrochloric acid (0.1 M) or sodium hydroxide (0.1 M). Stock standard solutions of all metal ions (100 mg L-1) were

prepared and preserved at 4 °C when not in use. All the aqueous solutions were prepared by double distilled water atroom temperature.

2.2. Preparations of modified and unmodified electrodesThe modifier, 2-hydroxy-acetophenonethiosemicarbazone, was prepared in accordance to the method described in

the literature [31]. Briefly, 2-hydroxyacetophenonethiosemicarbazone was prepared by dissolving thiosemicarbazide(1.22 g) in a 1:1 mixture of boiling absolute ethanol (10 mL) and dicholoromethane (10 mL). The resulting colorlesssolution turned yellow when a solution of 2-hydroxyacetophenone (1.2 mL) in hot methanol (24 mL) was added. After

the addition of a few drops of 10% HCl, the reaction mixture was heated under reflux for 3 h to obtain a yellow solutionwhich was left to cool at room temperature.Modified carbon paste electrode was prepared by homogenously mixing 2.25 gm (75%, w/w) of graphite powder

with 0.45 gm (15%, w/w) of modifier in a Petri dish for 5 min. Subsequently, 0.3 gm (10%, w/w) of mineral oil wasadded and hand mixed for 10 min to obtain a fine paste. The homogenized paste was inserted into the carbon rod having3 mm diameter and 7.3 cm length. The electrical connection was provided by a copper wire connected to the paste inthe inner hole of the rod. The prepared modified CPE was dried overnight at room temperature before use. The surfaceof the sensing end was smoothed on a glass surface and rinsed carefully with double distilled water. Prior to theelectrochemical measurement, cyclic voltammetry was run for electrochemical activation of the electrode in the rangeof -1.0 V to +1.5 V using scan rate of 100 mV s -1. Unmodified CPE was prepared by following the same procedure butwithout modifier.

2.3. Cyclic voltammetry (CV)

All electrochemical measurements were performed in voltammetrical analyzer using eDAQ system consisting of anED-401 potentiostat connected to an e-corder and the graphs were plotted in eChem version 2.1.5. Measurements were performed at room temperature in a conventional three-electrode cell comprising of silver/silver chloride as referenceelectrode, platinum wire as counter electrode and the modified electrode as the working electrode. The volume of thevoltammetric cell for CV was approximately 10 mL. All the CV measurements were measured at the potential rangefrom -1.0 V to +1.5 V at a scan rate of 100 mV s-1.

2.4. Anodic stripping voltammetry (ASV)ASV is one of the most sensitive electrochemical techniques applied for measuring trace metals. In this study,

SWASV was applied for analyzing Pb2+, Cd2+ and Zn2+ ions using the following steps: (a) preconcentration step, wheremetals were preconcentrated by various deposition potential for 70 sec in a magnetic stirred solution and (b) strippingstep, where accumulated metals are stripped back to solution and SWASV were recorded. Nitrogen gas was purged into the system for 5 minutes before starting the experiment. One of the main features of SWASV is electrochemical

cleaning of electrodes and surface regeneration. A fixed potential of +0.8 V for 60 sec was applied to clean theelectrode surface for Pb2+ and Cd2+ ions and +1.2 V for 60 sec was applied to clean electrode surface for Zn 2+ ions.Blank tests were performed after each measurement of samples to remove any potential for carryover between samples.

OH

H

CH3

NNH NH2

S


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2.5. Analysis of real samplesIn order to demonstrate the applicability and reliability of the proposed sensor, lab waste samples from inorganic

laboratory were collected and diluted twice. Those samples contain unknown concentration of metal ions and they wereevaluated by standard calibration curves. Inductively coupled plasma atomic emission spectroscopy (ICP-AES, iCap6000) was used to measure the concentration of metal ions in real samples. The results obtained from ICP-AES werecompared with those obtained from modified CPE.

3. Results and discussion 3.1. Cyclic voltammetry

CV measurement was performed to characterize the electrode-electrolyte system in the presence and absence ofmodifier. CV for modified and unmodified electrodes in 0.1 M HCl solution is shown in Fig 2. Unmodified CPEshowed flat surface whereas modified CPE showed small anodic current and cathodic current at -0.2 V and -0.5 V,respectively.

3.2. Sensor responsePreliminary experiments were performed to study the behavior of modified CPE on metal ions. Fig 3 shows

SWASV in a solution containing 5 mg L-1 concentration of Pb2+, Cd2+ and Zn2+ ions in unmodified and modified CPE.Modified CPE showed three distinct peaks at -0.50, -0.76 and -1.02 V vs silver/silver chloride corresponding to theoxidation of Pb2+, Cd2+ and Zn2+ ions at the electrode surface, respectively. Metals ions were accumulated by reductionat the electrode surface at deposition potential of -1.5 V. The reduced metal ions were then oxidized in the stripping stepand SWASV peaks were recorded. The response of the CPE in absence of ligand does not show any well defined peaks.The modified CPE exhibited good repeatability, with relative standard deviations (RSD) of 1.85%, 5.37% and 5.53%for Pb2+, Cd2+ and Zn2+ ions, respectively for three successive runs.

3.3. Effects of pHThe influence of pH on electrochemical responses of Pb2+, Cd2+ and Zn2+ ions were studied in PBS at pH range from

1 to 5 is shown in Fig 4. All solutions contained fixed concentration of standard at 10 mg L -1 Pb2+, Cd2+ and Zn2+ ions.The highest peak currents for all the metal ions under study were observed at pH 1. Therefore, pH 1 was used in furtherstudies. Reduction of peak current as the pH became more basic was probably due to the formation of lead hydroxide,cadmium hydroxide or zinc hydroxide, which depleted the cations existence as free ions, and thus less free cations wereavailable at the binding sites of the modifier of CPE [34].

3.4. Effect of deposition timeThe dependence of the anodic peak current on the deposition time was studied. Fig 5 shows the effect of varying

deposition time vs peak current in a solution containing 10 mg L-1 of Pb2+, Cd2+ and Zn2+ ions in the range of 5-80 sec.The stripping peak current increases linearly with increasing deposition time suggesting more metal ions deposition onthe modified electrode surface. However, when the deposition time was beyond 70 s, the stripping current becamealmost constant, indicating that the amount to metal ions on the electrode surface achieves saturation or equilibrium.Hence, 70 s was used for further studies.

3.5. Determination of Pb2+, Cd2+ and Zn2+ The analytical performance of the modified electrode was investigated by individual analysis of Pb 2+, Cd2+ and Zn2+

ions under optimized experimental conditions. The peak current increased with increasing metal ions concentration. Fig

6 shows SWASV response of the modified electrode towards various concentrations of standard solutions in the rangeof 0.25 mg L-1 to 12.5 mg L-1 for Pb2+ and Cd2+ ions, and 0.50 mg L-1 to 10.0 mg L-1 for Zn2+ at accumulation time of 70 s.

The limit of detection (LOD) is defined as 3σ/m, where σ is standard deviation of lowest analyte concentrationsignals and m is slope of the calibration graph. Standard deviation was estimated by six replicate determinations of theleast concentration signals. LOD was calculated as 11.23 μg L-1, 13.27 μg L-1 and 16.38 μg L-1 for Pb2+, Cd2+ and Zn2+ ions, respectively.

3.6. Sample analysisThe analytical performance of the developed sensor was evaluated by measuring Pb 2+, Cd2+ and Zn2+ ions in lab

wastes samples. The results obtained from modified CPE were compared with inductively coupled plasma atomicemission spectroscopy (ICP-AES). The results of these measurements are shown in Table 1.


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Fig. 2 CV of carbon paste electrode with and without modifier in 0.1 M HCl as supporting electrolyte (100mV s-1 scanrate).

Fig. 3 SWASV of 5 mg L-1 of Pb2+, Cd2+ and Zn2+ ions with and without modifier. Conditions: potential applied -1.5 V,0.1 M HCl supporting electrolyte, deposition time 70 s, scan rate 75 mV s-1, square wave frequency 15 Hz, step

potential 5 mV, square wave amplitude 25 mV and resting time 10 s.

-20

0

20

40

60

-1.5 -1 -0.5 0 0.5 1 1.5 2

I / µ A

E / V

Unmodified CPE

Modified CPE

0

20

40

60

80

100

120

-1.2 -1 -0.8 -0.6 -0.4

I /

µ A

E / V

Unmodified CPE

Modified CPE

Zn2+

Cd2+

Pb2+


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Fig. 4 Effects of pH on stripping current for 10 mg L-1

Pb2+

, Cd2+

and Zn2+

ions. Conditions: potential applied -0.9 V forCd2+, Pb2+ ions and -1.5 V and Zn2+ ions, deposition time 70 s, scanrate 75 mV s-1, square wave frequency 15 Hz, step potential 5 mV, square wave amplitude 25 mV and resting time 10 s.

Fig. 5 SWASV peaks for 10 mg L-1 of Pb2+, Cd2+ and Zn2+ ions at various depositions time. Conditions: potentialapplied -0.9 V for Pb2+ and Cd2+ ions whereas -1.5 V for Zn2+ ions, PBS at pH 1 as supporting electrolyte, deposition

time 70 s, scan-rate 75 mV s-1, square-wave frequency 15 Hz, step potential 5 mV, square wave amplitude 25 mV andresting time 10 s.

0

50

100

150

200

250

300

0 1 2 3 4 5 6

I / µ A

pH

lead

Cadmium

Zinc

0

50

100

150200

250

300

350

0 20 40 60 80 100

C u r r e n t

( µ A )

Deposition time (sec)

Lead

Cadmium

Zinc


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(a) Lead (b) Cadmium

Fig. 6 Calibration curve for (a) lead, (b) cadmium and (c) zinc at pH 1 at modified CPE. Condition applied: potentialfrom -0.9 V to +0.3 V, deposition time 70 sec, scan rate 75 mV s-1, square-wave frequency 15 Hz, step potential 5 mV,

square-wave amplitude 25 mV and rest time 10 s.

Table 1. Comparison of results obtained from modified CPE and ICP-AES methods (n = 3).Sample Metal of detection Modified-CPE (mg L-1) ICP-AES (mg L-1)

Lab waste 1

Pb2+ 2.69 ± 0.54 2.52 ± 0.46

Cd2+ 7.08 ± 1.09 6.45 ± 0.88Zn2+ 2.01 ± 0.88 1.34 ± 0.49

Lab waste 2Pb2+ 3.72 ± 0.95 3.56 ± 0.57Cd2+ 4.76 ± 0.38 5.00 ± 0.45Zn2+ 3.46 ± 0.52 3.27 ± 0.32

*ICP-AES: Inductively coupled plasma atomic emission spectroscopy

4. Conclusions A chemically modified CPE with Schiff base was constructed for the determination of Pb 2+, Cd2+ and Zn2+ ions

using SWASV. The sensor response was influenced by measurement conditions such as pH and deposition time.Contamination on the electrode surface can be removed by electrochemical cleaning. The sensor was successfully usedfor the determination of metal ions content in lab waste samples. This sensor has a simple design, uses inexpensivematerials and requires a short measurement time for analysis of metal ions in aqueous solutions.

0

50

100

150

200

250

300

350

-1.2 -1 -0.8 -0.6 -0.4 -0.2 0

I / µ A

E / V

y = 27.122x -23.081

R² = 0.9871

0

100

200

300

400

0 5 10 15

C u r r e n t ,

I / µ A

Lead conc. / mg L-1

0

50

100

150

200

250

300

-1 -0.8 -0.6 -0.4 -0.2 0

I / µ A

E / V

y = 21.85x -10.89

R² = 0.980

0

100

200

300

0 5 10 15

C u r r e n

t ,

I / µ A

Cadmium conc. / mg L-1

(c) Zinc

0

40

80

120

160

200

-1.2 -1 -0.8 -0.6 -0.4

I / µ A

E / V

y = 14.598x -1.3413

R² = 0.9938

0

50

100

150

200

0 2 4 6 8 10 12

C u r r e n t ,

I / µ A

Zinc conc. / mg L-1


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[23] S. Abbasi, A. Bahiraei and F. Abbasai, A highly sensitive method for simultaneous determination of ultra tracelevels of copper and cadmium in food and water samples with luminol as a chelating agent by adsorptive strippingvoltammetry, Food Chemistry, 129(2011), No.3.

[24] E. S. Almeida, E. M. Richter and R. A. A. Munoz, On-site fuel electroanalysis: Determination of lead, copper andmercury in fuel bioethanol by anodic stripping voltammetry using screen-printed gold electrodes, AnalyticaChimica Acta, 837(2014), No.0.

[25] H. Li, J. Li, Z. Yang, Q. Xu, C. Hou, J. Peng and X. Hu, Simultaneous determination of ultratrace lead andcadmium by square wave stripping voltammetry with in situ depositing bismuth at Nafion-medical stone dopeddisposable electrode, Journal of Hazardous Materials, 191(2011), No.1-3.

[26] A. Afkhami, H. Bagheri, H. Khoshsafar, M. Saber-Tehrani, M. Tabatabaee and A. Shirzadmehr, Simultaneoustrace-levels determination of Hg(II) and Pb(II) ions in various samples using a modified carbon paste electrode

based on multi-walled carbon nanotubes and a new synthesized Schiff base, Analytica Chimica Acta, 746(2012), No.0.

[27] M. H. Mashhadizadeh, A. Mostafavi, H. Allah-Abadi and I. Sheikhshoai, New Schiff base modified carbon pasteand coated wire PVC membrane electrode for silver ion, Sensors and Actuators B: Chemical, Special Issue - Inhonour of Professor Karl Cammann, 113(2006), No.2.

[28] M. R. Nabid, R. Sedghi, A. Bagheri, M. Behbahani, M. Taghizadeh, H. Abdi Oskooie and M. M. Heravi,Preparation and application of poly(2-amino thiophenol)/MWCNTs nanocomposite for adsorption and separationof cadmium and lead ions via solid phase extraction, Journal of Hazardous Materials, 203-204(2012), No.0.

[29] C. s. R. T. Tarley, V. S. Santos, B. E. L. Baeta, A. C. s. Pereira and L. T. Kubota, Simultaneous determination ofzinc, cadmium and lead in environmental water samples by potentiometric stripping analysis (PSA) usingmultiwalled carbon nanotube electrode, Journal of Hazardous Materials, 169(2009), No.1-3.

[30] F. Li, J. Li, Y. Feng, L. Yang and Z. Du, Electrochemical behavior of graphene doped carbon paste electrode andits application for sensitive determination of ascorbic acid, Sensors and Actuators B: Chemical , 157(2011), No.1.

[31] A. L. T. Mohammad Akbar Ali, Aminul Huq Mirza, Jose H. Santos, Aimi Hanisah Bte Hj Abdullah, Synthesis,structural characterization and electrochemical studies of nickel(II), copper(II) and cobalt(III) complexes of someONS donor ligands derived from thiosemicarbazide and S-alkyl/aryl dithiocarbazates, Transition Met Chem,37(2012).

[32] G. Donmez, Z. Aksu, A. Ozturk and T. Kutsal, A comparative study on heavy metal biosorption characteristics ofsome algae, Process Biochemistry, 34(1999), No.9.

[33] A. Afkhami, H. Ghaedi, T. Madrakian and M. Rezaeivala, Highly sensitive simultaneous electrochemicaldetermination of trace amounts of Pb(II) and Cd(II) using a carbon paste electrode modified with multi-walledcarbon nanotubes and a newly synthesized Schiff base, Electrochimica Acta, 89(2013), No.0.

[34] M. R. R. Kooh, J. H. Santos and M. K. Dahri, Preparation and Evaluation of Acetabularia-Modified Carbon PasteElectrode in Anodic Stripping Voltammetry of Copper and Lead Ions, Journal of Chemistry, 2013(2013).


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CODE: CF

Failure Analysis of Secondary Superheater Inlet Boiler Tube of Fossil Power Plant in Indonesia

Cukup Mulyana1) , Sulthoni Akbar

2) , Bambang Soegijono

2) , Tri Wibowo

3) , M Rizka Putra B

4)

1Electrical Engineering Study Programme, Padjadjaran University, Jatinangor 45363,Indonesia2Material Science, Faculty of Mathematics and Natural Sciences, University of Indonesia, Salemba 10430,Indonesia3Balai Besar Teknologi Kekuatan Struktur, Badan Pengkajian dan Penerapan Teknologi, Serpong 10340,Indonesia4Physics Study Programme, Padjadjaran University, Jatinangor 45363,Indonesia

Abstract. There has been a premature failure of secondary super heater inlet tube boiler of the steam power plant inIndonesia, this caused the plant stop operating. The damage is in the boiler tube number 47, crack propagated quicklystopped in thicker welded connection. The tube originally was straight and become totally bent in 90° after failure. Thestudy of failure analysis has been conducted. Plant operational and pipes data, chronological record before accident has

been collected. Further observation and serial test the chemical composition, high temperature tensile, hardness, SEM –EDX, and metallographic test have been completed. From the spectrometer analysis the chemical composition ofmaterial is low carbon steel SA 213 T22. From visual observation the ruptured tube is the edge thinning, fish mouth andshaped knifelike. The mechanism of failure start with bulging, wall tube thinning following with the increasing of hoopstress exceeding the plastic limits, finally bursting. Circumferential hoop stress caused crack in radial direction followed

by longitudinal stress caused crack along the axis, thermal compression stress bent the tube 90°.From the data analysisthe boiler pipes failed premature in the form of short term overheating at temperature> 890°C. From the fault treeanalysis fire impingement and the flow fluid pattern is not following procedure are the most possible event. The fireimpingement because of abnormal burning process (excess fuel or oxygen) and other undefined process parameters.

Keyword : Boiler tube; short-term overheat; violent rupture; Fault Tree Analysis

Corresponding author: Cukup Mulyana, E-mail: [email protected], Tel. +62-81573208420

1. IntroductionBoiler is main facility for generating steam and rotates turbine converting mechanical energy to electrical energy

in power plant. The fluid is flown in a great number of tubes. The heat from combustion process in the burner isradiated and convected to the tube change the water into super heated steam.

The failure is in tube number 47 swelling and bursting. The crack propagate rapidly and it stop at the weld joint of athicker tube. The tube geometry change from horizontal bent tube 90°.

From the historical data this tube is failed in 2005 and replace with the new one, and fail again in 2014, consideringthe time life of the tube it is classified as premature failure. The specification of tube material is low carbon steel SA-213 T22. This material has relatively high thermal resistance and corrosion. The operation temperature of tube is 505 °C

Initial observation start after the all system is shutdown, the rupture sample was cut to be observed in laboratory.

The chronological data and the temperature change per minute during failure process is taken from site and controlroom. From the first observation the failure is predicted because of local heating and short term overheat.Finding the root cause of the failure the sample ruptured is observed and serial tested is conducted in laboratory.The objective of the research are determining the mechanism of ruptured tube, the root cause of tube failure number

47 in superheater inlet boiler, finding other contributed factors of the failure and giving recommendation to avoid thesimilar failure in the future through inspection procedure, maintenance, and operation procedure.

2. Method and ExperimentFirst the observation were focused on the operational data of boiler, the historical data of failure tube, the

chronology of failure process and the record of temperature fluctuation, all data are taken from the control room. Thedata of ruptured tube is observed directly from the field, the foto macro of the ruptured tube is taken. The mechanical

properties of material strenght, hardness is tested in laboratory, the chemical composition is also tested by spectrometer,while the microstructure of material is observed by optical mycroscope. The fracture mode, and deposit of corrosion in

the failure tube is observed by SEM /EDX. All the data were analyzed, from the the all the facts it try to find therelation of all evident and classified the major or the minor cause that afect the tube ruptured. Finally the root cause ofthe filler was constructed by fault tree analysis. The recommendation is given to the company in order to avoid thesimilar failure in the future.


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The 2nd International Conference o

The 7th International Conference on


3. Result and DiscussionThe damage occur in tube number 4

Fig.

Materials and Metallurgical Technology 2015 (I

Sensors ASIASENSE 2015

7 in superheater inlet which the position is shown in F

1. Superheater tube scheme inside the boiler.

(a)

(b)

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ig. 1.


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Fig. 2.The rupture tube condition (a) Before cutting (b) After cutting (c) Crack propagation.

From Figure 2 (a) it can be shown originally the tube is a straight line, after ruptured the tube bent 90° and push farfrom it position. After the ruptured tube is cut, from the photo macro the profile of ruptured tube is thin lips or fishmouth shape, it indicated that there is local heating in a short periods, or short term overheating. In the bent position thewall tube become thinner drastically, the tube is bulging, swelling finally bursting. The stress on the wall tube increasedmore than its plastic limit rapidly, this caused the tube ruptured. Mechanism of crack is indicated in Figure 2(c).Starting from the thinnest part of the failure tube, because of the increasing of the hoop stress the crack propagatehorizontally, indicated by arrow 1, and 2.After that, the crack propagate along the tube axis to the right arrow 3 and tothe left arrow 4 and stop at the joint weld of at thicker tube, and turn to the right arrow 5.

3.1. Chemical Composition TestUsing spectrometer the Chemical composition of the ruptured tube is in table 1. Specimen A is for the thin tube,

and specimen C is for the thick one.

TABLE 1. Chemical composition test result

Refer to standard, the specimen A and C is ferritic low carbon steel SA-213 T22.

3.2. Mechanism of CrackStress equation (1) explained the crack mechanism of the ruptured tube:

σ = σ + σ + σ (1)

σ = + + ∝ E∆T

Where P is internal pressure inside the tube, D is Outer Diameter, t is tube thickness, α is linear thermal coefficientof expansion, E is Young Modulus and ΔT is difference of temperature. Theσ ishoop stress work in circumferentialdirection of the tube because of internal pressure. Due to the bulging process, the thickness of wall tube decreased, thehoop stress exceed Yield Strength (YS) of material that cause fracture in the tube as the direction is shown by arrownumber 1 and 2. σis longitudinal stress which is stress along the axis, and it is thermal stress caused by extremetemperature increase in short term. Thermal stress is compressive stress it cause the tube bend to 90° angle.

1 2 3 4 5 6 7 8 9

C Si S P Mn Ni Cr Mo Fe

Specimen A 0.09682 0.28996 0.003 0.0088 0.48196 0.02595 2.02072 0.94014 96.0519

Specimen C 0.09878 0.28622 0.0019 0.0066 0.47604 0.0251 1.99294 0.96575 96.0473

SA 213 T22

standart 0.15 max 0.5 max 0.025 max 0.025 max 0.3 - 0.6 - 1.9 - 2.6 0.87 - 1.13 -

The Contain

of Atom (%)

Atom

Number

(c)

5

1

2

3

4


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Metallography test is conducted inwhich is undergo depletion and themetallography test is shown by Fig. 3 (

Fig. 3.Metallography test sample spot (

Titik A

Titik B

Titik C



3 points, such as the edge of un-deformed thin tube,edge of deformed thick tube as shown in Fig. 2(), (b), (c). In the figure 3 (a), grain boundaries is circ

a) The edge of thin tube (b) The edge of fracture tube

(a)

(b)

(c)

Titik B

(a)

(b)

COMMET 2015)

the edge of fractured tube), (b), (c). The result oflar symmetry-formed.

(c) The edge of thick tube.


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Fig. 4.Metallography test result (a)

From the result of metallography tefailure do not exist as well. However tthe spot which is far from ruptured spo

from ruptured spot). In the ruptured spo phase and followed by rapid cooling rferrite and pearlite alloy.

Hardness level gradation which is re

Fig. 5. Hardness

From Brinell test, hardness level ch by Fig. 6



he edge of thin tube (b) The edge of fracture tube (c)

t above, the micro voids do not exist, which means tere are significant differences in the microstructureas shown in the figure 3 (B and C is ruptured spot,

t there are martensite and bainite alloy which indicateate. While at the spot which is far from ruptured sp

lated with several tube spot could be seen in Fig. 5.

test specimen for sample A, B, C as function of dista

ange as function of distance for each the hardness of

(c)

Sample A

Sample B

Sample C

COMMET 2015)

The edge of thick tube.

e creep phenomena in this between ruptured spot and

hile A is spot which is far

the heating up to austenitet the only exist phase are

ce.

specimen is further shown


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Fig. 7. Isothermal Cooling Curv

microstructure and hardness3.3. Fault Tree analysis

The failure root and other contribu“AND” and “OR” all possible evident i

Fig. 8. Fault Tree Analysis (FTA)

The“AND” logic gate FTA in Figsimultaneously happened, while the “Omore preceding event are happened. Fin the boiler and the pressurized tub

mechanism is swelling and bulging, tmartensite, and bainite indicate austeniis because of short term overheat. Thercorrosion, fire impingement and the



for medium carbon steel. The cooling rate difference

alue from Martensite (M), bainite (B), ferrite (F), pea

tive factor is determined by fault tree analysis (FTevaluated.

for determining the root cause of the ruptured super h

ure 8 express one event only can exist if two orR” logic gate express one event only can exist if at lom first investigation the ruptured tube exist becausee exceed the operation pressure. The possible pr

ere is no indication of corrosion. From metallogr e temperature is exceeded,the possible evident of theare three possible event preceding the short term ov

flow fluid pattern that is not following procedure.

COMMET 2015)

will result different

rlite (P) structure

), using binary logic gate

eater inlet boiler tube.

more preceding event areast one event from two orof the damage mechanism

eceding event of damage

phic test the existence of bulging and bursting tuber heat, the blockage due torom the data analysis fire


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impingement and the flow fluid pattern is not following procedure are the most possible event. From further analysis thefire impingement can be exist if there is uncontrollable burning process or the excessive heat occur because of excessivefuel and oxygen and other undefined process parameters. To determine the failure root precisely, it still need moreinformation data tube investigated.

4. ConclusionThe failure cause of tube number 47 in superheater inlet boiler is short term overheat. with the temperature > 890

°C. Failure mechanism started with bulging, wall-tube thinning, the increasing of hoop stress exceed plastic limit finally bursting. The crack propagation started in radial direction because of hoop stress, following in the axial direction because of longitudinal stress. Bending process cause by thermal stress compression due to the extreme temperature inshort period of time. From FTA fire impingement and the flow fluid pattern is not following procedure are the most

possible event. The fire impingement because of abnormal burning process (excess fuel or oxygen) and other undefined process parameters.

AcknowledgementsWe would like to say thank to PT. Indonesia Power which allow us to investigate the root cause of the ruptured

tube number 47 in super heater inlet boiler unit 2 Suralaya Indonesia,and to BPPT that helped us in laboratory sampletest during the investigation. With their contribution, this research can be finished.

References[1] ASM Handbook Volume 11: Failure Analysis and Prevention; 2002 [2] Viswanathan, Ramaswamy. 1989. Damage Mechanism and Life Assessment of High-Temperature Components.

USA: ASM International[3] Dieter, E. George. 1988. Mechanical Metallurgy, SI Metric ed. Singapore: McGraw Hill Book Co[4] French, N “Metallurgical Failures in Fossil Fired Boiler”, John Wiley and Sons. Inc[5] Purwono, Sari. 2010. Data Operasional Boiler Unit 2 Juni 2010 –limited. PT. Indonesia Power UBP Suralaya


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CODE: CF

Investigation of Corrosion Protection of Rebar Steel using Organic Inhibitor in Simulated Pore Solution

Arini Nikitasari1)

, Efendi Mabruri1)

1Research Center for Metallurgy and Material, Indonesian Institute of Sciences, Serpong 15313, Indonesia

Abstract: Rebar steel embedded in concrete is naturally protected against corrosion by passive layer formed on thesteel surface by the high alkalinity of the concrete. Corrosion in concrete rebar steel can initiate only when passive layeris destroyed due to the ingress of chloride or carbonation of concrete. Aim of this paper is to investigate on the

performance of organic inhibitor dimethylethaneamine (DMEA) in protecting rebar steel from carbonates and chloridesinduced corrosion in concrete. Rebar steel specimen immersed in three kinds of solution : simulated pore solutionmixed with seawater, simulated pore solution mixed with sodium chloride as the sources of chloride, simulated poresolution mixed with seawater, sodium chloride, sodium carbonate, and bicarbonate as the source of carbonate to corrodethe rebar steel. DMEA was added in the solution with various concentration (0,1 M; 0,3 M; 0,6 M). The performance ofthe organic inhibitor was evaluated by corrosion measurement system for 20 days. The results give information about

corrosion rate and corrosion prevention ability of the analysed organic inhibitor.Keywords: Simulated concrete pore solution, rebar steel; organic inhibitor; DMEA; carbonation; corrosionmeasurement system.

Corresponding author: Arini Nikitasari, E-mail : [email protected], Tel. 085286244363

1. Introduction Reinforced concrete is widely used for building materials and plays a significant role in economic development.

However, the premature degradation of reinforced concrete structures due to the reinforcing steel corrosion has becomea serious problem in modern society, which results in a huge economic loss [1]. Steel reinforcement embedded inconcrete is naturally protected against corrosion by a thin iron oxide layer that is formed on the steel surface by the highalkalinity of the concrete [2]. Corrosion can initiate only when passivity is destroyed. This occurs in two ways:carbonation of concrete, the reaction of atmospheric CO2 with cement paste, that lowers pH and causes generalcorrosion; the presence of chlorides at the steel surface in concentration higher than a critical threshold, generallyconsidered in the range of 0.4-1% by cement weight. Chlorides may be added to concrete in the mix water or in theaggregates, even if nowadays it is restricted by standards; chlorides can also penetrate from outside, in highwayviaducts where de-icing salts are used, or in marine structures [3].

When steel in concrete corrodes, the cross section of the reinforcing bar becomes smaller, thus reducing the loadcarrying capacity of the reinforced concrete member. The volume of corrosion products exerts pressure on the concreteresulting in spalling of the concrete cover and directly exposing the steel to the corrosive agents. This lead to the loss ofa structure’s load carrying capacity and to the need for repairs [4]. In an attempt to minimize the effect of rebarcorrosion, various procedures are frequently employed, such as cathodic protection, the use of inhibitors, and theapplication of coatings to the external concrete surface or to the reinforcing steel bars [5]. Among available methods,corrosion inhibitors seem to be attractive because of their low cost and easy handling, compared with other preventivemethods [6].

Corrosion inhibitors is a chemical compound which when added in adequate amounts to concrete can preventcorrosion of embedded steel and has no adverse effect on the properties of concrete. Nowadays corrosion inhibitor presents an easily implemented solution to the growing problem of corrosion of reinforcing steel in concrete. However,to be considered viable, these additives should not only prevent or delay the onset of corrosion they must not have anydetrimental effect on the properties of concrete itself such as strength, setting time, workability and durability. It must

be clarified that corrosion inhibitors do not totally stop corrosion but rather increase the time to the onset of corrosionand reduce its eventual rate [7]. The effect of organic corrosion inhibitor, N,N’ dimethylaminoethanol (DMEA) on thecorrosion of steel due to chloride ingress and carbonation was experimentally investigated in this paper.

The long time necessary for chlorides and carbonate to penetrate the concrete cover can be avoided by testing thesteel in simulated pore solution, which is mainly consistes of saturated calcium hydroxide, sodium hydroxide, and

potassium hydroxide with the pH ~13.5 [8]. This paper illustrates the results of 20 days investigation on the inhibitiveeffectiveness of organic commercial corrosion inhibitors in preventing carbonation and chlorides induced corrosion.Corrosion was monitored by rebar potential and corrosion rate measurements. Visual observation at the end of exposure

was carried out. Results are discussed in terms of ability of the corrosion inhibitors to prevent corrosion occurence or todecrease corrosion rate, once corrosion started.


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2. Experimental 2.1. Materials

Corrugated steel bars with the composition is given in Table 1 were used for the experiments. Prior to theexperiment the reinforcing steel electrodes were cleaned in HCl : H2O (1:1) with hexamethylentetramine solutions anddegreased in acetone. Rebar steel as specimen cut to size 1 cm and mounted with resin so the exposed area of thereinforcing steel electrodes was 1.23 cm2. The mounted rebar steel then abraded with abrasive paper from 80 cw till1000 cw. The specimen immersed in the test solution for 20 days.

Table 1 . Chemical Composition of Rebar SteelKomposisi Kimia (%)

C Si Mn P S Fe0,37 0,23 0,54 0,03 0,04 Bal

2.2. Solution testThere are three kinds of solution test used in this experiment : simulated pore solution mixed with seawater;

simulated pore solution mixed with 3.5 %wt sodium chloride; simulated pore solution mixed with seawater, sodiumchloride, sodium carbonate, and bicarbonate. Table 2 shows the chemical composition of simulated pore solution.

DMEA was added with various concentration (0.1 M, 0.3 M, 0.6 M) into solution test. A series of solution test is givenin Table 3.

Table 2 . Chemical Composition of Simulated Pore Solution [8]

Unsur Mol/literNaOHKOHCa(OH)2 CaSO4.H2O

0,10,30,030,02

Table 3 . Series of Solution TestNo Solution Test DMEA123456789101112

Simulated Pore Solution + SeawaterSimulated Pore Solution + SeawaterSimulated Pore Solution + SeawaterSimulated Pore Solution + SeawaterSimulated Pore Solution + Seawater + 0.3 M NaHCO3 + 0.015 Na2CO3Simulated Pore Solution + Seawater + 0.3 M NaHCO3 + 0.015 Na2CO3Simulated Pore Solution + Seawater + 0.3 M NaHCO3 + 0.015 Na2CO3Simulated Pore Solution + Seawater + 0.3 M NaHCO3 + 0.015 Na2CO3Simulated Pore Solution + NaCl 3.5 % + 0.3 M NaHCO3 + 0.015 Na2CO3Simulated Pore Solution + NaCl 3.5 % + 0.3 M NaHCO3 + 0.015 Na2CO3Simulated Pore Solution + NaCl 3.5 % + 0.3 M NaHCO3 + 0.015 Na2CO3Simulated Pore Solution + NaCl 3.5 % + 0.3 M NaHCO3 + 0.015 Na2CO3

-0.1 M0.3 M0.6 M-0.1 M0.3 M0.6 M-0.1 M0.3 M0.6 M

2.3. Measurement TechniqueCorrosion potential and corrosion rate measurement in this experiment based on ASTM G-5 standard.

Measurement was done everyday for 20 days using Gamry Instruments G750 Series. Measurement techniques ofcorrosion potential and corrosion rate using Tafel polarization in potential range -200 mV to 200 mV from OCP (OpenCircuit Potential) with 1.5 mV/s scan rate.There are three kinds of electrodes used for this measurement techniques suchas Fig.1, counter electrode was grafit, reference electrode was SCE (Saturated Calomel Electrode), and workingelectrode was mounted rebar steel specimen.


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Fig. 1 . Three Electrodes Scheme [9]

3. Results and discussion3.1. Corrosion behaviour

Corrosion behaviour of rebar steel in three kinds of test solution (simulated pore solution (SPS) mixed withseawater, SPS mixed with seawater and carbonate, and SPS mixed with sodium chloride and carbonate) has beeninvestigated by polarization study. The evolution of corrosion potential (Ecorr ) and corrosion current density (Icorr ) withtime for simulated pore solution (SPS) mixed with seawater with different concentration of inhibitor is given in Fig.2.Based on Fig. 2, it can be observed that the addition of DMEA results in a reduction of the corrosion current density. Onthe other hand, the presence of DMEA produces a shift of E corr towards more negatif values with respect to the solutionwithout DMEA. Fig. 3 shows the evolution of corrosion rate (i corr ) with time of rebar steel in simulated pore solutionmixed with seawater at different DMEA concentration. It can be observed that the increase of DMEA concentration

produces a reduction of the corrosion rate, supporting the registered reduction of the corrosion current density. FromFig.3, corrosion rate in solution without inhibitor rises drastically from 4 mpy at 1st day to 20 mpy at approximately 20days of experiment time. Corrosion rate with inhibitor also rises but lower than without inhibitor, so DMEA is effectiveto inhibit corrosion of rebar steel in seawater environment and the best performance for inhibiting corrosion is DMEAwith concentration 0.6 M. Corrosion rate for DMEA concentration 0.1 M increases dramatically at last day

measurement, this is suggest that DMEA 0.1 M has been depleted in the 20th day, so for better performance DMEAshould use in higher concentration than 0.1 M.

In Fig. 4, the evolution with time of Ecorr and Icorr of steels submerged in simulated pore solution mixed withseawater and carbonate without DMEA and with 0.1 M, 0.3 M, and 0.6 M of DMEA is presented. The trend of Ecorr with 0.3 M and 0.6 M DMEA is more positif while 0.1 M of DMEA is more negatif value than without DMEA. Basedon Fig. 4, DMEA with concentration 0.6 M produces a slight decrease in the corrosion current density, the addition ofDMEA in lower concentration (0.1 M and 0.3 M) results in a higher corrosion current density.

Fig. 5 shows the evolution corrosion rate with time of rebar steel in simulated pore solution mixed with seawaterand carbonate at different DMEA concentration. The trend of corrosion rate in accordance with corrosion currentdensity trend. Only DMEA with concentration 0.6 M can slightly reduce corrosion rate compared with without DMEA.The addition of DMEA with concentration 0.1 M and 0.3 M does not reduce the corrosion rate. DMEA withconcentration 0.1 M and 0.3 M can inhibit corrosion in seawater and carbonate environment only untill 5 th day. Thisresult indicate that DMEA with concentration 0.1M-0.6 M is not effective to retard the corrosion on rebar steel of

concrete in seawater and carbonate environtment.Fig. 6 shows the evolution of Ecorr and Icorr with time for simulated pore solution mixed with sodium chloride and

carbonate with different DMEA concentration. It is appreciated again that the addition of DMEA decrease Ecorr and Icorr .


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Fig. 2 . Evolution of Ecorr and Icorr vs. time in simulated pore solution mixed with seawater with differentDMEA concentration.

Fig. 3 . Evolution of icorr vs. time in simulated pore solution mixed with seawater with different DMEAconcentration.


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Fig. 4. Evolution of Ecorr and Icorr vs. time in simulated pore solution mixed with seawater and carbonate withdifferent DMEA concentration.

Fig. 5. Evolution of icorr vs. time in simulated pore solution mixed with seawater and carbonate with differentDMEA concentration.


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Fig. 6. Evolution of Ecorr and Icorr vs. time in simulated pore solution mixed with sodium chloride andcarbonate with different DMEA concentration.

Fig. 7. Evolution of icorr vs. time in simulated pore solution mixed with sodium chloride and carbonate with differentDMEA concentration.

In Fig. 7, the evolution of corrosion rate with time of rebar steel submerged in simulated pore solution mixed withsodium chloride and carbonate of different DMEA concentration is plotted. As can be seen in Fig.7, the higher DMEA

concentration the lower corrosion rate and the lowest corrosion rate is DMEA 0.6M. It is clearly observed how thecoorosion level is reduced in solution incorporating DMEA.Based on the evolution of icorr in Fig. 3, Fig. 5, and Fig. 7,the most corrosive environtment is seawater.


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3.2. Inhibitor efficiencyInhibitor efficiency is effectiveness percentage of inhibitor to inhibit corrosion process. Inhibitor efficiency

calculated based on Eq.1. Inhibitor efficiency calculation based on average 20 days corrosion rate measurement, shownin Table.4. As can be seen in Table.4, the best inhibitor efficiency for all test solution is DMEA with concentration0.6M. For seawater and carbonate environtment, the addition of DMEA even increases the corrosion rate, so DMEAshould not use in this environment. The highest inhibitor efficiency of DMEA (61%) is corrosion rate of rebar steel insodium chloride and carbonate environment with 0.6 M DMEA concentration. Inhibitor efficiency in sodium chlorideand carbonate environtment increases with increasing DMEA concentration. It is evident that DMEA effective to inhibitcorrosion process by forming a stable interfacial layer on steel surface which is able to keep the interface in a passivestate.

Inhibitor Efficiency (%) = Corrosion Rate without inhibitor-Corrosion Inhibitor with inhibitor Corrosion rate without inhibitor

x 100 (1)

Tabel 4. Inhibitor efficiency DMEA in all variation solution test

DMEA

SPS + Seawater SPS + Seawater + Carbonate SPS + NaCl + Carbonate

Concentration Corrosion Rate Inhibitor Corrosion Rate Inhibitor Corrosion Rate InhibitorEfficiency Efficiency Efficiency

- 12.13 - 4.45 - 6.07 - 0,1 M 6.53 46% 6.72 -51% 5.54 9%

0,3 M 7.42 39% 5.22 -17% 4.16 31%

0,6 M 4.94 59% 3.76 16% 2.33 62%

3.3. Visual observationsFig.8 shows visual observation of rebar steel in the test solution without DMEA and with 0.6 M DMEA

concentration. It can be observed that without DMEA in seawater solution test, the corrosion product clearly visible andmore dense than corrosion product with DMEA. With DMEA 0.6 M, the largest corrosion product exists on

thespecimen in seawater test solution. This visual obsevation appropriate with corrosion rate measurement that the mostaggressive environtment is seawater.

(a) (b) (c) (d)

Fig. 8. Photographs of specimen after 20 days in simulated pore solution mixed with (a) seawater wihout DMEA (b)seawater with 0.6 M DMEA (c) seawater and carbonate with 0.6 M DMEA (d) sodium chloride and carbonate with 0.6

M DMEA.

4. ConclusionsThe evolution of corrosion current density and corrosion rate for 20 days measurement decrease with increasing

DMEA concentration. The best performance of DMEA concentration is 0.6 M for all three kinds of test solution.DMEA is more effective used in seawater and combination of sodium chloride and carbonate environtment, forcombination of seawater and carbonate environtment DMEA with concentration 0.1M-0.6 M is not effective. The higestinhibitor efficiency is DMEA 0.6 M in sodium chloride and carbonate environtment.

Acknowledgements This work was supported by Resesarch Center for Metallurgy and Materials, Indonesian Institute of Sciences. Theauthors are thankful to the earth science deputy of Indonesian Institute of Sciences for financial support for this research

by 2015 excellence programme.


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References [1] M. Pandiarajan, P. Prabhakar, S. Rajendran. Corrosion behaviour of mild steel in simulated concrete pore solution

prepared in rain water, well water and sea water. Eur. Chem. Bull , 1(2012) No.7,p. 238-240.[2] Linhua Jiang, Guohong huang, Jinxia Xu, Yeran Zhu, Lili Mo. Influence of chloride salt type on threshold level of

reinforcement corrosion in simulated concrete pore solutions. Construction and Building Materials, 30(2012),p.516-521.

[3] M. Ormellese, M. Berra, F. Bolzoni, T. Pastore. Corrosion inhibitors for chlorides induced corrosion in reinforcedconcrete structures. Cement and Concrete Research, 36 (2005), p. 536-547.

[4] I.L. Kondratova, P. Montes, T.W. Bremner. Natural marine exposure results for reinforced concrete slabs withcorrosion inhibitors. Cement and Concrete Composite, 25 (2003) p. 483-490.

[5] M. B. Valcarce, C. Lopez, and M. Vazquez. The role of chloride, nitrite and carbonate ions on carbon steel passivity studied in simulating concrete pore solutions. Journal of The Electrochemical Society, 159(2012) , No.5, p.244-251.

[6] B. Elsener. Corrosion inhibitors for steel in concrete. State of the Art Report , EFC Publications, vol 35, (2001).[7] E. Rakanta, Th. Zafeiropoulou, G. Batis. Corrosion protection of steel with dmea-based organic inhibitor.

Construction and Building Materials, 44 (2013), p. 507-513.[8] Amir Poursaee. Corrosion of steel bars in saturated ca(oh)2 and concrete pore solution. Concrete Research

Letters,1 (2010), No.3.[9] P. Garces, P. Saura, E. Zornoza, C. Andrade. Influence of ph on the nitrite corrosion inhibition of reinforcing steel

in simulated concrete pore solution. Corrosion Science,53 (2011), p. 3991-4000.


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CODE: CF

Synergistic Effect of Triazine and Potassium Iodide as Corrosion Inhibitors for Carbon Steel in 0.5M HClAqueous Solution

Andi Rustandi1), Freddy Valensky1), Johny Wahyuadi Soedarsono1), M. Akbar Barrinaya1)

1 Departemen Teknik Metalurgi dan Material, Universitas Indonesia, Depok, 16424, Indonesia

Abstract . The effects of Triazine (C6H15 N3) and its synergistic effect with Potassium Iodide (KI) on the corrosion ofmild steel in 0.5 M HCl was investigated using polarization and electrochemical impedance (EIS) methods at 301 o K. .The effect of KI addition on Triazine inhibitors can increase the efficiency 88.72% become 94.23%. The synergisticeffect of different concentrations of Triazine and KI was determined by calculating the synergism parameters, whichshowed that a cooperative mechanism exists between the iodide anion and Triazine cations. The inhibitors act as mixedtype with predominant cathodic effect. The inhibitors were adsorbed on the mild steel surface according to theLangmuir adsorption isotherm. The Triazine characterization was verified by using FTIR.

Keywords: HCl; Corrosion inhibitors; Adsorption; Triazine; Potassium Iodide.

Corresponding author : Andi Rustandi, E-mail: [email protected] or [email protected], Tel. +62-812-9742-7324.

1. Introduction Numerous systems in the petroleum industry have corrosion problems. One of them is Acidizing of oil and gas

wells[1]. Acidizing is an oil reservoir stimulation technique for increasing well productivity. M.A. Migahed et al.[3]have studied the using of triazine for corrosion inhibition of Tubing steel during acidization of oil and gas wells. Thetype of triazine used was 6-methyl-5-[m-nitro styryl]-3-mercapto-1,2,4-triazine with resulting 86.7% efficiency byusing 300 ppm of the inhibitor. Synergistic inhibition is an effective means to improve the inhibitive force of theinhibitor, to decrease the amount of usage and to diversify the application of the inhibitor in acidic media. Manyinvestigations in regard to synergistic inhibition have been carried out and are being investigated. Orubite Okorosaye etal. have studied the synergistic Inhibition effect of iodide ions and extract of nypa fruticans on the corrosion of mildsteel iron in 0.1 and 0.5M HCl solution. The inhibition efficiency was enhanced by the addition of iodide ions becauseof synergistic effects [4]. The use of organic compounds containing oxygen, sulfur and nitrogen synergized with KI toreduce corrosion attack on steel has been studied [5–10].

The aim of this work is to investigate and report the influence of the new synthesized compound namely hexahydro-1,3.5-trimethyl-1,3,5-triazine synergized with addition of KI (iodide ions) as the corrosion inhibitor for mild steel in0.5M HCl solution by using electrochemical techniques such as polarization measurement and ElectrochemicalImpedance Spectroscopy (EIS).

2. Experimental workThe solution (0.5M HCl) was prepared by dilution of analytical grade 32% HCl with double distilled water. The

working electrode was mild steel in a rectangular shape. The working solution was 0.5M HCl. A mild steel with thesame chemical composition was mounted in Teflon with an exposed surface area of 1 cm2 was used in allelectrochemical measurements. The specimens were cleaned according to ASTM standard G1-03. Measurements wereundertaken in stagnant non-aerated 0.5M HCl acid solutions in the presence and absence of triazine 300 ppm and KI

ppm alone and concentrations of different triazine (100–300 ppm) in combination with 75 ppm KI at 301 K.

3. Results and discussionElectrochemical measurements were conducted by using Metrohm Autolab Instruments Poten-tiostat/Galvanostat

PGSTAT302N with NOVA 1.10 software. The cell contained three electrodes; the mild steel as working, carbon ascounter electrode and Ag/AgCl reference electrodes. Fig.1 shows that the addition of triazine reduces anodic dissolutionand also reduce the hydrogen evolution reaction, which indicates that triazine is a mixed-type inhibitor and controls

both the anodic and cathodic reactions.


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Fig. 1. Polarizatio

The decrease in icorr with increasingtriazine does not shift the Ecorr valuescathodic type inhibitor only can be hap

The Nyquist plots for mild steel incombination with KI are shown in Fig.2

Fig. 2. Nquist Pl

In 0.5 M HCl solution with theconcentration of triazin and KI then theaddition would enhance its inhibition p

Adsorption isotherm has been calinhibition in the presence of 75 ppm Kassumption that the adsorption of triaziLangmuir adsorption isotherm.

Fig. 3. Adsorption is



n Curve of Carbon Steel in 0. M HCl at Various Con

concentration shows the efficiency of the corrosion

significantly, suggesting that they behave as mixedened if Ecorr.inh is shifted more than 85 mV againts Eco

the presence and absence of different concentration.

ot of HCl 0.5M Solution at Various Inhibitor Conce

presence of triazine and its combination with KIimpedance values increased significantly. This revearformance on carbon steel.ulated on the mild steel surface to investigate th

I. The plot of C/θ against C in Fig.3 yields a straightne in the present of KI on a mild steel surface in 0.5

otherms for mild steel in 1.0 M HCl in different conc

COMMET 2015)

entrations.

inhibitor is enhanced. Thetype inhibitors. Anodic orr.uninh.s of Triazine alone and in

trations.

showed that with higherled that with triazin and KI

mechanism of corrosionline, and this supports theM HCl solution obeys the

ntrations.


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Values of ∆G up to -20 kJ molmolecules and the charged metal surfawith chemisorption, which involves c

bond[5]. The calculated ∆G values iand chemisorption[10].3.1. Synergistic inhibition effect of io

Halide ions facilitate the adsorption positively charged inhibitor moleculesto increase in the order of I- > Br - >compared to solutions without KI. This0,5M HCl solution, this can be explaadsorbed by columbic attraction (electrStabilization of the adsorbed iodide iinhibition [5]. The synergism parameteHackerman [5, 6]. Generally, values of

adsorption, whereas S 1 > 1 indicates ametal surface by a adsorption mechanilarger than one, a cooperative mechaniKI enhances the inhibition performancmeasurements.

3.2. Triazine characterization by FTFig. 4 shows the FTIR spectra of th

the C-H bond, 2139 cm-1 correspond bond.

4. Conclusions

Triazine performs inhibition of tstudies showed that the triazine is a miefficiency from 88.72% up to 94.23%.surface in 0.5M HCl obeys the Langmof the inhibitor molecules on the mild ssuggests that triazine in the presence omechanism between the iodide anion an

References[1] Allen, T.O, Robert, A.P, “Produc[2] Doherty, Henry L., “Acidizing Fu[3] M.A.Migahed and I.F.Nassar.,”C

Electrochimica Acta 53 (2008) 28[4] Orubite Okorosaye K, Jack I.R, O Mild Steel in HCl Medium by Ext

27 – 31.



-1 are consistent with the electrostatic interactionce (physisorption), whereas those around 40 kJ mol

arge sharing or transfer from organic molecules

dicated that the adsorption mechanisms were a co

dide ionsof organic inhibitors in acidic media by forming intnd the metal surface[10]. The synergistic effect of tCl-. As can be seen from the η% for solutions witreflects that KI has a synergistic effect on the corrosi

ined that the inhibitor molecules which had beenostatics) to the metal surface which have been negations with the inhibitor leads to greater surface covs (S 1) value is 1,78 were calculated using the relationS 1 < 1 imply that antagonistic behavior prevails, whi

synergistic effect. The iodide ions enhance the stabism, which may be either be competitive or cooperasm existed between the iodide anion and triazine cati

of the triazine in 0,5M HCl solution, as confirmed

IRe synthesized triazine. The absorption bands appearto the C≡N bond and the peak at 1635 cm-1 is assig

ig. 4. FTIR of the synthesized Triazine.

e corrosion of mild steel in 0.5M HCl solution. Poed-type inhibitor. The effect of KI addition KI on triaThe adsorption of triazine with the presence and a

ir adsorption isotherm. A combination of both physiteel surface was proposed based on the ∆G0ads valueKI would inhibit the corrosion of mild steel in HCl,

d triazine cation.

ion Operations, Well Completion, Workover and stim

damentals”, Society of Petroleum Engineering, Newrrosion Inhibition of Tubing Steel During Acidizati

77–2882.chei M, Akaranta O., Synergistic of Potassium Iodideract of Nypa Fruticans’ Wurmb, J. Appl. Sci. Enviro

COMMET 2015)

etween charged inhibitor-1 or lower are associatedto form a coordinate-type

bination of physisorption

ermediate bridges betweene halide ions was reportedKI exhibit higher values

on process of mild steel inrotonated by H+ are thenely charged by iodide ion.

erage and thereby greatership given by Aramaki andh may lead to competitive

lity of the inhibitor on thetive. The values of S1 areons, where the addition ofearlier by electrochemical

t 3338 cm-1 correspond toed to the bending of C=N

entiodynamic polarizationzine inhibitors increase thesence of KI on the metalorption and chemisorption. The synergism parameterand there is a cooperative

ulation”.1979York, 1979.n of Oil and Gas Wells”,

on Corrosion Inhibition of

n. Manage Vol. 11 (2007)


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CODE: CF

Sarang Semut (Myrmecodia Pendans) extract as a green corrosion inhibitor for material API 5L Grade B in 1 MH2SO4 solution

Atria Pradityana1) , Sulistijono2) , Abdullah Shahab1)

1Department of Mechanical Engineering, Institut Tekonologi Sepuluh Nopember, Surabaya 60111, Indonesia2Department of Materials and Metallurgical Engineering, Institut Tekonologi Sepuluh Nopember, Surabaya 60111,Indonesia

Abstract. Corrosion is a change process of material’s characteristic due to the influence of or the reaction with thesurrounding environment. One way of corrosion control is by adding the corrosion inhibitor. The purpose of this studyis to analyze the influence of Sarang Semut plant extract (Myrmecodia pendans) as the organic inhibitor of acidsolution. This study uses the material of API 5L Grade B while the used corrosive media is the solution of 1 M H2SO4.The concentration of Sarang Semut extract which is used in this study ranges to 0 until 5000 mg/L (the multiple of 1000mg/L). From the result of the experiment, the optimal inhibition efficiency occurs if there is a concentration addition asmuch as 5000 mg/L. The mechanism of adsorption in this system follows the Freundlich adsorption.

Keywords: sarang semut; inhibitor; H2SO4; Freundlich

Corresponding author: Atria Pradityana, E-mail: [email protected], Tel. +62-821-41080460

1. Introduction One way to prevent the occurrence of corrosion is by adding the inhibitor. Corrosion inhibitor is a compound in the

small numbers but it can be able to inhibit the metal corrosion reaction with the environment. It can be said that theinhibitor build a protective layer on the metal surface with the reaction between the solution and the corroded metalsurface. With the addition of inhibitor in the environment, the corrosion rate will be reduced.

The use of plants as the corrosion inhibitor can be proven by the contained phytochemical molecule in which thestructures of the electrochemistry and the molecular are similar to the inhibitor molecule of the conventional organic[1]. The basic mechanism of inhibitor is actually done by adsorbing the ions or molecules on the surface of the metal inwhich the inhibitor is able to control the electrochemical reaction (anodic and cathodic) and to create a thin layer (filmforming) to inhibit the corrosion process.

Sarang Semut (Myrmecodia pendans) is one kind of plant which content has been well-known [2] to be used as theinhibitor by several researchers [3]. These plant can be applied as an organic inhibitor for the pipe material which usescarbon steel API 5L Grade B with the inhibitor concentration of 0-500 mg/L in the acid media. This has been proven

by the previous research conducted by Atria [4]. The result of that research shows that the inhibition efficiency is stillfewer than 50% so that the produced efficiency can be said as not maximum.

In this study, it is conducted in environment of 1M H2SO4. The material used is API 5L Grade B. However, therange of the inhibitor concentration is higher than the previous research which is 0-5000 mg/L (the multiple of 1000mg/L). It is expected that by increasing the inhibitor concentration, the efficiency of inhibition that is occurred willincrease as well.

2. Experimental 2.1. The specimen preparationThe weight loss experiment. This experiment uses the steel of API 5L Grade B which is trimmed into the

dimension of 2 x 2 x 3 mm for one each specimen. The specimens are sanded so that the corrosion products are gonethen the top of the specimens are drill. The drill result will be used as the place of the yarn winding so that specimenscan be hung on the dyeing process. Before the specimen experiment is done, the initial weight should be calculated.

2.2. The solution preparationThe used solution is H2SO4 98%. The process of making H2SO4 1M is done by mixing the solution of H2SO4 98%

as much as 54.64 ml with the aquades until volume reaches to 1000 mL.

2.3. The inhibitor preparationSarang Semut is extracted by using maceration method. The process of maceration uses ethanol 80%. This is

followed with a process of evaporation by using a rotary evaporator. This process aims to separate the solution with itsextract. The remaceration of the Sarang Semut dreg will be done as if the needed targeted amount of extract is still notfulfilled yet.


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2.4. The Weight Loss ExperimentThe method of weight loss is also known as the method of losing weight. The method of corrosion measurement is

the method that often used because the method is easy to be done and the used tool is also simple. The metal experimentwill be placed in a particular environment for a certain time so that it can be corroded. The metal experiment iscommonly called as coupons. Coupon is a metal plate that is placed in the system and made to be corroded to determinethe rate of corrosion through the weight reduction. In this study, it is used the concentration addition of 1000, 2000,3000, 4000, 5000 mg/L with the immersion process for 72 hours. After the immersion process is complete, the next stepis pickling process which is done by using 5M HCL for cleaning the corrosion then it is washed by using the soapywater.

2.5. The Method of Electrochemical Impedance SpectroscopyElectrochemical Impedance Spectroscopy is a method which is used to analyze the response of a corroded

electrode to a potential signal of AC as the frequency function. This method is used to determine the mechanism ofinhibition. The wave of AC at the low amplitude of 10 in the frequency range of 0,01 Hz to 1000 Hz. Principally, theEIS is used to determine the electrochemical kinetic parameters which relate to the electric elements such as theresistance, R, capacitance, C, and inductance, L.

2.6. The FTIR experiment

FTIR experiment is conducted to determine the mechanism of inhibition that occurs in the steel of API 5L GradeB after being added with the inhibitor. By doing FTIR experiment, the peak or curve wave will be resulted with thevarious intensities and the functional groups contained in a material. In this study, FTIR experiment is done in thespecimen weight loss with the concentration of 5000 ppm (the highest efficiency) and without inhibitor.

3. Results and discussion3.1. The Weight Loss

From the Table 1, it can be seen that the concentration increases by the time the more inhibitor is mixed into thesolution. Besides, the more increasing the inhibitor concentration, the more decreasing the corrosion rate and the moreincreasing the inhibition efficiency will be. The lowest corrosion rate occurs when there is an addition of inhibitorconcentration of 5000 mg/L, ie 647.676 mpy with the inhibition efficiency of 56.56%.

Table 1. The rate of corrosion occurs during being added by the inhibitor of Sarang Semut.Concentration of inhibitor (mg/L) Corrosion rate (mpy) Efficiency of inhibition (%)

0 1702,634 -1000 1527,695 10,272000 1192,390 29,973000 1066,409 37,374000 944,718 44,515000 869,747 48,92

3.2. The Electrochemical Impedance Spectroscopy (EIS)This experiment is used to determine the mechanism of inhibition through the parameter of equivalent circuit

electrochemical. The equivalent circuit is obtained by fitting the graph of EIS. From the Figure 1, it can be seen that theyield curve of fitting is similar to the actual electrochemical curve. The samples which are conducted by EIS only the

ones that have the highest inhibition efficiency. So, concentration used is 0 and 5000 mg/L.Based on the circuit in Figure 2, at the beginning of the series there is existed a resistance of solution (Rs). Rshappens at the beginning of the series due to the fact that EIS can detect any resistances formed between the electrolytesolution and the samples of steel. The Table 2 shows the results of the parameters that are formed such as the values ofRs, Rp, Rct, and Cdl. The value of y Rct at concentration of 0 mg/L is as much as 10,66 Ω while the concentration of5000 mg/L generates a value of 15,75 Ω. This shows that if the inhibitor is added to the solution, the value of Rct willincrease. The Rct value is associated with the move of electron in which if the electron moves faster, the resistance willdecrease and the corrosion rate will increase. On the other hand, if the electron moves slower, the resistance will begreater and the corrosion rate will decrease. The high rate of Rct at 5000 mg/L indicates that the resistance is greaterthan the resistance at 0 mg/L. Thus, the thin layers on the metal-solution interface froms as the protection. These layerscause the movement of ions from the electrolyte to the metal become inhibited. The more the passive layers formed, themore rate of the Rct value and the fewer the value of the CPE will be.


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Fig. 1. The

Fig. 2. the e

Table 2. the daConcentration of inhibitor

(mg/L)

05000

3.3. The Mechanism of Isotherm AdsIsotherm adsorption can provide t

metal when the metal immersed in theorganic inhibitor in the metal surface wthe organic molecules in the solutionassociated with the fraction of the surfthe covered surface is obtained from tvalue of surface coverage (θ) is used iconcentration. The degree of surface co

By using the adsorption isotherm, tθ is used with the common types of adswith the phenomenon of monolayer whof Langmuir (2) and Freundlich (3) adthis equation (4):



esult of fitting nyquist plot by using NOVA software

uivalent circuit of the Nyquist plot in Nova software

a of equivalent circuit result in Steel of API 5L Grad

Rp (Ω) Rs (Ω) Rct (Ω) Cdl (µF)

10.761 35.679 10.66 84.69215.998 35.679 15.75 53.257

orptione information about the interaction between the inhielectrolyte solution which has been mixed with the ith the solution can occur because of the substitutionnd the water molecules on the surface of the metal.ce which is covered by the adsorption of the inhibitohe data of the weight loss method. In determining t

which the value varies according to the addition oerage θ is calculated by using the followings:

θ = IE% / 100

he corrosion adsorption process can be understood. Torption isotherms such as Langmuir and Freundlich.ile Freundlich. Langmuir is associated with multi-laorption isotherm which are used and for calculating

= +

COMMET 2015)

B

Efisiensi inhibisi (%)

-23.32

itor and the surface of thehibitor. The absorption of

bsorption process betweenThe efficiency inhibitor ismolecule. The fraction of

he adsorption process, thethe Sarang Semut extract

(1)

he adjustment of the valuehe Langmuir is associateders. Below is the equationthe value kads is by using

(2)


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= (3)

= , exp∆

(4)

where :C = Concentration of inhibitor (mg/L)kads = Constant of adsorptionT = Temperature (K)R = Constant of ideal gas (8.314 J/mol K)−∆ = Free standart energy adsorption (kJ/mol)

Table 3. The calculation data of surface coverage for adsorption graphConcentration ofinhibitor (mg/L)

Corrosionrate (mpy)

Efficiency ofinhibition (%)

Surfacecoverage (θ)

C/θ Log C Log (θ/1-θ)

0 1702,634 - - - - -1000 1527,695 10,27 0,103 9732,730 3,000 -0,9412000 1192,390 29,97 0,300 6673,806 3,301 -0,3693000 1066,409 37,37 0,374 8028,454 3,477 -0,2244000 944,718 44,51 0,445 8985,868 3,602 -0,0965000 869,747 48,92 0,489 10221,284 3,699 -0,019

Fig. 3. The graph of Langmuir adsorption

y = 0.3289x + 7741.7R² = 0.135

0.000

2000.000

4000.000

6000.000

8000.000

10000.000

12000.000

0 1000 2000 3000 4000 5000 6000

C / θ

C

LangmuirAdsorption

LangmuirAdsorption

Linear (LangmuirAdsorption)


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Fig. 4. The graph of Freundlich adsorption

It can be seen from the figures 3 and 4, the value of R 2 for the Langmuir Adsorption is only 0.135 while the valueof R 2 for the Freundlich Adsorption is 0.960. The value of R 2 in Figure 3 shows that the line obtained by R 2


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[3]. Pradityana. A, Sulistijono, Shahab.A. Effectiveness of Myrmecodia Pendans Extract as Eco-Friendly CorrosionInhibitor for Material API 5L Grade B in 3,5% NaCl Solution. Trans Tech Publications , Switzerland. Advanced

Material Research Vol. 789 pp 484-491. (2013).[4]. Pradityana. A, Sulistijono, Shahab.A. The Influence of Adding Bio Inhibitor Sarang Semut (Myrmecodia

Pendans) to Carbon Steel API 5L Grade B in Solution of HCl 1 M. Trans Tech Publications, Switzerland . Advanced Materials Research Vol. 1123 pp 187-191. (2015).

[5]. Pradityana. A, Sulistijono, Shahab.A. Application of Myrmecodia Pendans Extract as a Green Corrosion Inhibitorfor Mild Steel in 3,5% NaCl. Trans Tech Publications, Switzerland .. Applied Mechanics and Materials Vol. 493pp684-690. (2014)

[6]. Pradityana. A, Sulistijono, Shahab.A. Eco-Friendly Green Inhibitor of Mild Steel in 3,5% NaCl Solution bySarang Semut (Myrmecodia Pendans) Extract. Published by the AIP Publishing. American Institute of Physics1617, 161. (2014).

[7]. Taleb Ibrahim. The Effect of Thyme Leaves Extraction Corrosiob of Mild Steel in HCl. Progress in OrganicCoating 75 (456-462). (2012).


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CODE: CF

Myrmecodia Pendans (Sarang Semut) Extract as Corrosion Inhibitor of Mild Steel in 0,5 M H2SO4 Solution

Atria Pradityana1) , Sulistijono

2) , Abdullah Shahab

1) , Subowo

1)

1Department of Mechanical Engineering, Institut Tekonologi Sepuluh Nopember, Surabaya 60111, Indonesia2Department of Materials and Metallurgical Engineering, Institut Tekonologi Sepuluh Nopember, Surabaya 60111,Indonesia

Abstract. Inhibitor is a substance that is added to the corroded media to inhibit the corrosion rate. The organicinhibitors more develop than the anorganic ones because they are environmentally friendly. The organic compounds can

be adsorbed by the metal surface and block the active surface to reduce the corrosion rate. In this research, the used pipeof API 5L Grade B with 0,5 M H2SO4 solution as the corrosion media. The variation concentration of extract sarangsemut used is 0 - 500 mg/L (multiple of 100 mg/L). The extraction method used is maceration. In this research, severalexperiments are used such as weight loss experiment, EIS, and FTIR. The highest efficiency occurs at the addition of400 mg/L of inhibitor. From the result, it shows that with the addition of sarang semut inhibitor, it is able to reduce thecorrosion rate by forming a thin layer on the metal surface.

Keywords: organic inhibitor; Myrmecodia pendans; acid solutions

Corresponding author: Atria Pradityana, E-mail: [email protected], Tel. +62-821-41080460

1. Introduction Corrosion is a material degradation caused by its chemical reaction with other material and the environment [1].

This process often occurs in the industry of oil and gas. In the industrial field, carbon steel is a type of material that iscommonly used in various applications. One of those types of carbon steel which is often used in the industrial field isAPI 5L steel grade B. The API 5L steel is one of the steels used in the applications of water transport, oil, and naturalgas. One of the problems that often occur in the distribution process of crude oil is the existence of sediment called asthe crust (scale). The crust is the result of mineral precipitation which is derived from the water formation producedalong with the oil and gas [2]. This type of steel is easily to be corroded in acidic solution environment. In fact,corrosion cannot be prevented but its speed can be controlled by the addition of inhibitor. Inhibitor is a substance whichis capable of inhibiting or reducing the rate of metal corrosion with the environment [1]. It can also be said that theinhibitor form a protective layer on the metal surface by the reacting between the solution and the corroded metalsurface [3].

In this case, there are many researches done to find a new source of the corrosion inhibitor which sources are mainlyfrom the natural materials. Natural materials are chosen as the alternative because of their characteristics which are safe,easily available, biodegradable, cheap, and eco-environment [4,5,6].

The organic material used as the inhibitor can prevent the material oxidation reaction of the contained antioxidantelement through a certain mechanism. Antioxidant is defined as a compound that is able to delay, slow down, and

prevent the oxidation process [5]. The antioxidant works by donating the electron to the oxidantcompounds so that theactivity of antioxidant compound can be inhibited. One of the organic materials which contains the antioxidant isSarang Semut plant [7]. The result of Sarang Semut extract has previously been analyzed showing that it contains the

flavonoid as the antioxidant which can be used in the process of green inhibitor making [8-11].It has been previously studied that Sarang Semut (Myrmecodia pendans) can be applied as the organic inhibitor forthe pipe material which is the API 5L carbon steel Grade B with the inhibitor concentration of 0-500 mg/L in acidicmedia of 1M HCl and 1M H2SO4 by doing immersion method [9]. From the previous study, it has not been obtained theoptimum efficiency in the application of Sarang Semut in an acidic environment. In this research, it will be conductedthe experiment of Sarang Semut inhibition for the carbon steel material of API 5L Grade B with the same variation ofinhibitor concentration which is 0-500 mg/L but that the concentration of the electrolyte solution media is diluted into0,5 M H2SO4 by using immersion method. So, it is expected to produce the inhibition efficiency optimum in acidicmedia.

2. Experimental 2.1. The preparation of inhibitor

Myrmecodia Pendans (MP), the epiphytic plant,

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