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Md Mayeedul Islam

PhD student

Curtin University

DEVELOPMENT OF ELECTROCHEMICAL

METHOD TO STUDY TOP-OF-THE-LINE CORROSION

Content

• Background of study

• Experimental

• Results

• Conclusions

Top-of-the-line Corrosion

Top-of-the-line corrosion (TLC) is the result of temperature gradient between

inside and outside of the pipeline in stratified flow regime

Background of study

QCMER

probe Weight

lossCold finger

probe

TLC monitoring techniques

Advantages

In-situ, operating on mechanism, no

disturbance to specimen, easy to operate

Electrochemical

technique

Challenges

Low volume and conductivity of the

electrolyte, complicated cell arrangement

Objectives

To incorporate electrochemical method for in-situ monitoring

of TLC

To study the interfacial process under a condensed liquid

droplet

Experimental setup

1. Working electrode connection, 2. Counter/reference connection, 3. Thermocouple, 4. Surface temperature

probe, 5. Gas temperature probe, 6. CO2 inlet, 7. Cooling coil for maintaining surface temperature, 8. Polyethylene

terephthalate lid, 9. TLC probe, 10. Condensate collector, 11. 2-L glass vessel, 12. CO2 outlet, 13. Condensate

reservoir, 14. Milli-Q water, 15. Heater

1

2

3

1

3

30

mm

20 mm

2 m

m

1 = Counter electrode

2 = Resin

3 = Working electrode

Ø

12

3

4

5

6 7

8 9

10 11

14

12

13

15

Test Matrix

Parameters Condition

Gas temperature, °C 55

Surface temperature of the sample, °C 20, 30, 40 an 45

Test duration 5 days, 17 days

Bulk liquid Deionized water

Materials Carbon steel

Non-electrochemical method Weight loss, Fe2+measurement

Electrochemical method EFM, LPR and EIS

TLC rate from non-electrochemical method

Fe2+

measurement

1 2 3 4 50.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

Corr

osio

n r

ate

(m

m y

-1)

Exposure time (d)

20 C

30 C

40 C

0.2

0.4

0.6

0.8

1.0

1.2

0.4

0.6

0.8

1.0

1.2

1.4

20 30 40

Condensation ra

te (

g m

-2s

-1)

Corr

osio

n r

ate

(m

m y

-1)

Surface temperature (°C)

Weight

loss

TLC rate from electrochemical method

1 2 3 4 50.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

Corr

osio

n r

ate

(m

m y

-1)

Exposure time (d)

20 C

30 C

40 C EFM

1 2 3 4 5Exposure time (d)

20 C

30 C

40 C

LPR

TLC rates comparison from different technique

0.0

0.2

0.4

0.6

0.8

1.0

Temperature (°C)

Co

rro

sio

n r

ate

(m

m y

-1)

Wt. loss

Fe2+

EFM

LPR

EIS

20 30 40

Study of the interfacial process

Surface temperature = 45 °C

Gas temperature = 55 °C

Corrosion rate measured by LPR

Active

dissolution

Formation of

porous layer

Formation of

protective layer

Active dissolution (D1-D5)

0 50 100 150 200 250 300

0

50

100

150

200

250

Zim

az (

ohm

.cm

2)

Zreal

(ohm.cm2)

D1

D5

FittedRs R1

Rl

C1

L

Surface image at 3rd day

Formation of porous layer (D6-D13)

0 100 200 300 400 500 600 700 800

0

100

200

300

400

500

600

700

Zim

az (

ohm

.cm

2)

Zreal

(ohm.cm2)

D7

D11

D13

Fitted

Rs

R1

C1

C2

R2

Corrosion product at 6th day

Surface

Cross section

Porous layer

Double layer

Formation of protective layer (D14-D17)

500 1000 1500 2000 2500 3000 3500 4000 4500

0

1000

2000

3000

4000

Zim

az (

oh

m.c

m2)

Zreal

(ohm.cm2)

D14

D15

D16

D17

Fitted

Rs

R2

C2

C3

R3

C1

R1

Surface

Cross section

Corrosion product at 17th day

Outer layer

Inner layer

Double layer

Conclusions

Electrochemical method is successfully applied for online monitoring of

TLC, which gives comparable results with non-electrochemical tests.

Mechanism and growth of corrosion product film can be successfully

explained under a condensing droplet.

The method opens up a new window for investigating the volatile

corrosion inhibitor for mitigating TLC by studying the interfacial process

under condensing condition.

Acknowledgement

• Professor Rolf Gubner

• Dr Thunyaluk Pojtanabuntoeng

• Curtin University for Providing IPRS scholarship

• Curtin Corrosion Centre

THANK YOU FOR YOUR ATTENTION

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