10297 Environmental Effects on the Susceptibility and Crack Growth of Near Neutral Ph Stress Corrosion Cracking

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Product Number: 51300-10297-SG

ISBN: 10297 2010 CP

Author: Jeffrey Xie, Chris Foy, Bob Worthingham and Mark Piazza

Publication Date: 2010

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The environmental effects on the susceptibility and crack growth of near-neutral pH stress corrosion cracking (SCC) were characterized using mechanical testing, hydrogen permeation and potential drop measurements. The investigated environmental parameters were dissolved CO2, HCO3 -, pH, sulfate and chloride, sulfide and organics (9,10-anthraquinone-2,6-disulfonate (AQDS), Laurentian humic acid (LHA) and Laurentian fulvic acid (LFA)).

Sufficient hydrogen concentration was critical for the susceptibility of near-neutral pH SCC. Hydrogen concentration was directly proportional to the concentration of sulfide (HS-), and the %RAratio decreased linearly with the logarithm of sulfide concentration. Organic compounds, like AQDS, LHA and LFA, had an inhibitive effect on the crack growth rates, and also reduced the hydrogen concentration. Higher CO2 concentrations led to a decrease in solution pH. However the addition of HCO3 - may result in the formation of a ferrous carbonate film that could protect the underlying steel and slow the corrosion process.

Key words: Stress corrosion cracks, pipelines, hydrogen permeation, sulfide, AQDS, LHA, LFA, carbonates, dormancy