Absorption of hydrogen generated by corrosion of steel in wet hydrogen sulfide (H2S) can have several effects, depending upon the properties of the steel, the characteristics of the environment, and other variables. One adverse effect observed in pipeline steels is the development of cracks along the rolling direction of the steel. Cracks on one plane tend to !ink up with cracks on adjacent planes to form "steps" across the thickness. The cracks can reduce the effective wall thickness until the pipe is overstressed and ruptures. Cracking is sometimes accompanied by surface blistering. Several service failures attributed to such cracking have been reported. The terms "hydrogen-induced cracking" (HIC), "hydrogen pressure cracking", "blister cracking", and "hydrogen-induced stepwise cracking" are used to describe cracking of this type in pipeline steels. The term "stepwise cracking" is used in this standard to 'distinguish the phenomenon that has been observed in pipeline steels from other types of hydrogen-induced cracking.

 1.1 This test method describes procedures for evaluating the resistance of pipeline steels to stepwise cracking induced by hydrogen absorption from aqueous sulfide corrosion. The test is applicable to line pipe with wall thicknessess of 5 to 30 mm.

1.2 The test procedure consists of exposing unstressed coupons to a solution of synthetic seawater saturated with hydrogen sulfide at ambient temperature and pressure at a pH in the range of 4.8 to 5.4. After a specified time the coupons are removed and evaluated.

Historical Document 1987