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51313-02455-Study on the Growth of Corrosion Scales on X65 Steel in CO2 Top-of-Line Corrosion Environment

Product Number: 51313-02455-SG
ISBN: 02455 2013 CP
Author: Lining Xu
Publication Date: 2013
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$20.00
$20.00

For subsea wet gas transportation pipelines top-of-line corrosion (TLC) is a big problem. TLC is a phenomenon encountered under condensation conditions and water in liquid form is greatly corrosive to carbon steel as it is saturated with acid gases e.g. CO2 H2S HAc etc. In addition TLC is hard to mitigate by inhibitor and usually cause localized attack. Due to the poor CO2 corrosion resistance carbon steels are very susceptible to TLC causing severe damages to pipelines for wet gas transportation. Extensive work focused on the analysis of corrosion scales formed in wet gas environment as the protectiveness of corrosion scales would greatly influence the CO2 corrosion resistance. But till now the growth mechanism of corrosion scales on carbon steel is not well understood under wet gas environment. And the localized corrosion caused by TLC has not been thoroughly revealed. Therefore it is in urgent need of purposeful laboratory test.
In this paper corrosion behavior of X65 pipeline steel was studied in a high temperature and high pressure condensation autoclave simulating the CO2 TLC environment. The corrosion rate was measured by weight loss method. Scanning Electron Microscope (SEM) was employed to analyze the surface and cross-section morphology of corrosion scales. A series of experiments were carried out at the test duration of 15d 30d and 45d. Under different test duration the thickness compactness and crystalline state of corrosion scales were compared and the growth mechanism of corrosion scales in wet gas environment is analyzed. The results indicated that the corrosion scales thickened gradually with the increasing test duration and the corrosion scales exhibited layered structure. The corrosion scales of X65 steel after corroded for 45 days exhibited a three-layer structure: amorphous layer layer composed of small crystal and layer composed of large crystal. The severity level of localized corrosion changed under different test duration. It was deduced that the localized corrosion occurred under TLC environment was related to the characteristic of corrosion scales.

Keywords: Top of line corrosion (TLC) corrosion scales growth mechanism localized corrosion
 

For subsea wet gas transportation pipelines top-of-line corrosion (TLC) is a big problem. TLC is a phenomenon encountered under condensation conditions and water in liquid form is greatly corrosive to carbon steel as it is saturated with acid gases e.g. CO2 H2S HAc etc. In addition TLC is hard to mitigate by inhibitor and usually cause localized attack. Due to the poor CO2 corrosion resistance carbon steels are very susceptible to TLC causing severe damages to pipelines for wet gas transportation. Extensive work focused on the analysis of corrosion scales formed in wet gas environment as the protectiveness of corrosion scales would greatly influence the CO2 corrosion resistance. But till now the growth mechanism of corrosion scales on carbon steel is not well understood under wet gas environment. And the localized corrosion caused by TLC has not been thoroughly revealed. Therefore it is in urgent need of purposeful laboratory test.
In this paper corrosion behavior of X65 pipeline steel was studied in a high temperature and high pressure condensation autoclave simulating the CO2 TLC environment. The corrosion rate was measured by weight loss method. Scanning Electron Microscope (SEM) was employed to analyze the surface and cross-section morphology of corrosion scales. A series of experiments were carried out at the test duration of 15d 30d and 45d. Under different test duration the thickness compactness and crystalline state of corrosion scales were compared and the growth mechanism of corrosion scales in wet gas environment is analyzed. The results indicated that the corrosion scales thickened gradually with the increasing test duration and the corrosion scales exhibited layered structure. The corrosion scales of X65 steel after corroded for 45 days exhibited a three-layer structure: amorphous layer layer composed of small crystal and layer composed of large crystal. The severity level of localized corrosion changed under different test duration. It was deduced that the localized corrosion occurred under TLC environment was related to the characteristic of corrosion scales.

Keywords: Top of line corrosion (TLC) corrosion scales growth mechanism localized corrosion
 

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