Hydrogen Induced Cracking (HIC) can be a major issue for line pipe exposed to sour environments. Most commonly, solution A in NACE TM0284 (5.0 wt% NaCl and 0.5 wt% CH3COOH) is used under 1 bar H2S to evaluate HIC susceptibility of steel plates and pipe products. High Strength Line Pipe (HLP) Committee of The Iron and Steel Institute of Japan (ISIJ)(1) has investigated Fitness for Purpose (FFP) HIC evaluations and proposed 5%NaCl + 0.93N (CH3COOH+CH3COONa) solution. It was reported that the 0.93N acetate solution provided excellent pH stability during HIC test in comparison with conventional EFC(2)16 solution (0.05N CH3COONa) in our previous papers.
In this study, influence of the test solutions on HIC evaluation was investigated from the view point of corrosion. Electrochemical measurements were employed to compare corrosion behavior of line pipe steels between the 0.93N acetate buffer solution and the conventional 0.05N acetate solution. In addition, corroded surface was investigated since hydrogen entry into steel strongly depends on corrosion morphology. Applicability of the proposed 0.93N acetate solution will be also discussed based on results obtained from this study.
Key words: downloadable, HIC, sour environment, H2S, line pipes, fit-for-purpose, pH, buffer solution, HLP