cocate - corrosion of pipe steelco2pipehaz.eu/main_download/events/workshop_pdfs_22... · cocate -...

02/05/2012

COCATE - Corrosion of pipe steel

Autoclave tests for pipe steels and coatingsand coatingsX. Zhang, J. Zevenbergen, M. Spruijt

2-5-2012Cocate meeting in Copenhagen/Titel van de presentatie

1

Content

1. Introduction2. Objective3. Approach methods4 Results4. Results

Corrosion of steelsCoatings on carbon steelgImpedance measurementsCross section analysis Pull-off testCoatings with artificial scratches

5. Conclusions5. Conclusions6. Future work


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1. IntroductionFlue gases contain CO2, O2, SOx, NOx, H2O etc. Pipe materials: carbon steel, stainless steel?Questions: corrosion rate, possible solution?

Pool A

Pipes

Pool CLe Havre Rotterdam

p

Pool B

Pipelines/ships

Pipes


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2. Objective

Obtain corrosion data for steels in CO2 flue gas conditionsSearch for solutions (e.g. coatings)


4

Why does CO2 cause corrosion?

Dry CO2 does not cause corrosion. Wet CO2 does.CO2 + H2O → H2CO3

Fe + CO2 + H2O → FeCO3 + H2

Cathodic reactions:2H2CO3 + 2e- → H2 + 2HCO3

-2 3 2 3

2HCO3- + 2e- → H2 + CO3

2-

2H+ + 2e- → H2

Anodic reaction:Fe → Fe2+ + 2e-Fe → Fe 2e


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3. Approach methodsSimulation: to get parameters and estimate corrosion rates

Experimental investigation: autoclave testsSet 1 (measuring the pH value and corrosion rate for metals):

1 Stream CTPbp (CO2+ NO2 O2 N2 + H2O) (1 65 bar 65 C )1. Stream CTPbp (CO2+ NO2, O2, N2 + H2O) (1.65 bar, 65 C )

2. Stream 7Bp (CO2 + NO2, O2, N2, SO2 + H2O) (1.2 bar, 49 C)

3. CO2 + H2O (100 bar, 60 C)( )

Set 2 (Testing coating performance):

Media: CO2 + 3.5% NaCl

Temperature in corrosive media Tc = 60 C

Pressure in autoclave P = 100 barPressure in autoclave P 100 bar


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4. Results

4.1 Calculation using NORSOK Model 506Empirical corrosion rate (CRt) model for carbon steel in water containing CO2 at different temperatures

and wall shear stresses (S)and wall shear stresses (S).

t: 20 - 150 C

CRt = Kt fCO2 0.62 (S/19) 0.146 + 0.0324 log(fCO2) f(pH)t (mm/year)

t: 15 C

CRt = Kt fCO2 0.36 (S/19) 0.146 + 0.0324 log(fCO2) f(pH)t

t 5 Ct: 5 C

CRt = Kt fCO2 0.36 f(pH)t

fCO2: the fugacity of CO2 in bar,

f(pH)t : pH factor at temperature t.


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Calculation using NORSOK M-506 model

Pool 2_ stream CTPbpPressure = 1.643 bar, Shear stress = 1 Pa, CO2 = 11.32 mole%

Molar fraction

Vapour phase

Aqueous phase

2

2.5

3

3.5

te /

(mm

/yea

r)

pH=4 pH=5

mole frac CO2 0.109004 0.113150 0.000044

mole frac H2O 0.183007 0.151925 0.999943

mole frac NO2 0.000060 0.000062 0.000002

mole frac SO2 0.000000 0.000000 0.000000

0

0.5

1

1.5

0 50 100 150 200

Cor

rosi

on ra

pH 5 pH=6 mole frac N2O 0.000000 0.000000 0.000000

mole frac CO 0.000002 0.000002 0.000000

mole frac CH4 0.000000 0.000000 0.000000

l f O2 0 019001 0 019724 0 000000Temperature / (°C) mole frac O2 0.019001 0.019724 0.000000

mole frac N2 0.688926 0.715138 0.000010

Pipe inner diameter (mm) 212 7

pH: 4.4Pipe inner diameter (mm) 212.7

Pipe thickness (mm) 3.2

Temperature © 64.72

Pressure (bar) 1.643

Corrosion rate: 2.7 mm/year(Impurities are not considered in the calculation.)

Velocity (m/s) 19.44


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Stream Pool 4-7Bp

Pressure = 1.15 bar, Shear stress = 1 Pa, CO2 = 8.566 mole%

2.5

)

mole frac CO2 0.084238 0.085662 0.000029

Molar fraction

Vapour phase

Aqueous phase

1

1.5

2

on ra

te /

(mm

/yea

r)

pH=4 pH=5 pH=6

mole frac H2O 0.116490 0.101548 0.999952

mole frac NO2 0.000164 0.000167 0.000008

mole frac SO2 0.000114 0.000116 0.000002

mole frac N2O 0.000000 0.000000 0.000000

0

0.5

0 50 100 150 200

Temperature / (°C)

Cor

rosi

o pH 6 mole frac N2O 0.000000 0.000000 0.000000

mole frac CO 0.000000 0.000000 0.000000

mole frac CH4 0.000000 0.000000 0.000000

mole frac O2 0.087870 0.089356 0.000001

l f N2 0 711124 0 723150 0 000008Temperature / ( C) mole frac N2 0.711124 0.723150 0.000008

Pipe inner diameter (mm) 901.6

Pipe thickness (mm) 6.4pH: 4.5Temperature © 48.83

Pressure (bar) 1.15

Velocity (m/s) 21.02Corrosion rate: 1.7 mm/year(Impurities are not considered in the calculation.)


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4. Results

4.1 Calculation using NORSOK Model 5064.2 Experimental results

4.2.1 Corrosion of steels


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Experimental set-up

Gas mixture container

Heating system Stirring controller Autoclave

Sample mounting


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2. Corrosion of Carbon steel

S355 in flue 7Bp (1.2 bar, 49 C)pH 5.5Day 6: Corr rate: 0.2 mm/y

Corrosion rate analysisCorrosion rate analysis

-4

-3

Log(

Cur

rent

/A)

-5

4

Potential -0.9 -0.8 -0.7 -0.6 -0.5

V

-6


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2. Corrosion of steelsS335 steel in the CO2 CTP gas flue solution

(1.65 bar, 65°C, pH during CO2 charging: 4.7-5.3)

Corrosion current density in CTP flue

3 0E-05

3.5E-05

4.0E-05

1.0E-05

1.5E-05

2.0E-05

2.5E-05

3.0E-05

i (A

/cm

^2) CS1

CS2

CS3

Time(day) CS1 CS2 CS3 Average (mm/y)

0.0E+00

5.0E-06

2 3 4 5 6 7 8

Time (day)Corrosion rate ( y) g ( y)3 0.23 0.14 0.11 0.16 4 0.29 0.20 0.11 0.20 5 0.37 0.23 0.23 0.28 6 0.41 0.29 0.19 0.30 7 0.41 0.29 0.20 0.30


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Corrosion for carbon steel

CO2 + H2O (600ml)100 bar 60 CDay 6, Corrosion rate: 0.02 mm/y

Corrosion rate analysis

-5

-4

Log(

Cur

rent

/A)

-7

-6

Potential -60 -40 -20 0

mV

-8


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Corrosion of stainless steel 316S

in flue 7Bp (1.2 bar, 49 C)pH 5.5Corr rate: 0.00005 mm/y

Corrosion rate analysis

-5

-4

og(C

urre

nt /A

)

8

-7

-6

Potential

Lo

0.0 0.2 0.4 0.6

V

-9

-8


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4. Results


4.2.1 Corrosion of steels4 2 2 Coatings on carbon steel4.2.2 Coatings on carbon steel


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4.2.2 Coatings on carbon steel

A hitA: white, ~ 360 µm

B: off-white, ~1060 µm

C: grey, ~ 1150 µm


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4. Results


4.2.1 Corrosion of steels4 2 2 Coatings on carbon steel4.2.2 Coatings on carbon steel4.2.3 Impedance measurements4.2.4 Cross section analysis y4.2.5 Pull-off test4.2.6 Coatings with artificial scratches


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4.2.3 Impedance measurements

Impedance plots for three coatings in the CO2 plus 3.5% NaCl at 60ºC and 100 bar.


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After autoclave test (for 60 days)(white) (off-white) (grey)

In 3.5% NaCl solution charged with CO2 to 100 bar atIn 3.5% NaCl solution charged with CO2 to 100 bar at 60 C


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4. Results


4.2.1 Corrosion of steels4 2 2 Coatings on carbon steel4.2.2 Coatings on carbon steel4.2.3 Impedance measurements4.2.4 Cross section analysis y


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Cross section analysis: coating AdelaminationColour: white

Thickness: ~ 360 µm

After exposure for 60 daysBefore the test

The white coating showed delamination at the coating/metal interface after the test.


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Cross section analysis: coating B

Colour: off-white; Thickness: ~1060 µm

Off-white coating did not show delamination after the test



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Cross section analysis: coating CColour: grey; Thickness: ~ 1150 µm

Blisters are found in the coating, but not at the coating/metal interface


ste s a e ou d t e coat g, but ot at t e coat g/ eta te ace


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4. Results


4.2.1 Corrosion of steels4 2 2 Coatings on carbon steel4.2.2 Coatings on carbon steel4.2.3 Impedance measurements4.2.4 Cross section analysis y4.2.5 Pull-off test


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Pull-off test before and after the autoclave test

White coating

A3 before exposure, (break in the coating)

A2 after exposure, (break at the coating/metal

interface)


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Pull-off test

B3 before exposure, (break in the coating)

B2 after exposure, (break at the coating/metal

interface)


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Pull-off test

C3 b f C2 ftC3 before exposure, (break in the coating)

C2 after exposure, (break partly it the coating)


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Pull-off strength test

Sample Before exposure

(MPa)

After exposure

(MPa)

Breaking place

(MPa) (MPa)

Coating A 22.4 4.5 coating/metal

interfaceinterface

Coating B 20.1 8.4 40% coating

Coating C 10.4 9.0 In coating


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4. Results


4.2.1 Corrosion of steels4 2 2 Coatings on carbon steel4.2.2 Coatings on carbon steel4.2.3 Impedance measurements4.2.4 Cross section analysis y4.2.5 Pull-off test4.2.6 Coatings with artificial scratches


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Coating with an artificial scratch

Coating A Coating B Coating C

After test in autoclave at 100bar and 60°CAfter test in autoclave at 100bar and 60 C.


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5. ConclusionsThe corrosion rates calculated using NORSOK M-506 model are higher than

that measured from experiments.

The measured corrosion rate for carbon steel S355 in the flue gas environment

is higher (about 0.3 mm/y) than in CO2 saturated water at 100 bar and 60 C

(about 0 02mm/y) within 6 days(about 0.02mm/y) within 6 days.

The stainless steel has a very low general corrosion rate in the flue gas

environment.

The off-white coating (B) performs better than the other two, which can be a

good candidate for the application in the pipes to against the CO2 corrosion.


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6. Future work

Mass loss test for carbon steel in the gas flue 7BpSurface analysis to check localized corrosionAutoclave tests for coating B in different thicknessAutoclave tests for coatings on CS/SS welds to simulate the coatingsAutoclave tests for coatings on CS/SS welds to simulate the coatings at joints of different materials.


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Thank you!Thank you!

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