Hydrogen-Induced Cracking of Line Pipe Steels Used in Sour Service

Laboratory studies on a sour-service grade of line pipe steel showed the steel to be highly resistant to hydrogen-induced cracking even at a pH of 1.1, as evidenced by ultrasonic C-scan patterns obtained before and after exposure to acidic solution saturated with hydrogen sulfide. H concentration at the inside surface of the pipe increased with decreasing pH of the medium. The activation energy for H diffusion into the line pipe steel was 21 kJ/mol.