Introduction
To meet special applications for sour service, JST has developed a series of sour service line pipes made from hot-rolled coiled skelps. Our PSL-2 pipelines present high resistance to HIC (hydrogen induced cracking) and SSCC (sulfide stress corrosion cracking). HIC is also known as SWC (step wise cracking), which is one of the most common chemical damages suffered by line pipes.
HIC Resistance
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Cause of HIC
HIC arises because of both metallurgical and environmental factors about line pipe steels. The metallurgical factors are alloy elements, microstructure, strength, non-metallic inclusions, etc. The environmental factors are partial pressures of H2S and CO2, temperature, medium PH, active ions (like chloride), etc. Our sour service line pipes are also improved on the basis of these factors. -
Research on HIC Resistance
To solve this problem, producers, users and research organizations have done great efforts to study HIC mechanism. Then, a special test method is developed to identify and quantify susceptibility to HIC. Accordingly, steel with high HIC resistance is developed. To make steel qualified in applications, NACE MR0175 has developed TM-02-84 for tests for line pipe steels. -
Test for HIC Resistance
It is available for sour service line pipes in thickness of 5 mm to 30 mm. In the test, expose coupons to synthetic seawater which is saturated with H2S. This seawater is at PH 4.8 to PH 5.4. Besides, test is conducted at room temperature and standard atmospheric pressure. Then, coupons are sectioned, polished and etched so that cracks are distinct. Next, calculate CSR (crack sensitivity ratio), CLR (crack length ratio) and CTR (crack thickness ratio) of each section. At last, HIC resistance is determined by these values.
