| Stress corrosion cracking (SCC) in near-neutral pH solutions of API X-52 and X-80 line pipe steels has been investigated mainly with slow strain rate test (SSRT). The SCC was examined according to the variations of electropotentials, pH values, slow strain rates, the concentration of chloride ions in the solutions and hydrogen pre-charging on specimens before the SSRT. The SCC susceptibility was primarily judged by the ductility loss of the steels in combination with the observations on the side and fracture surfaces of the SSRT specimens under scanning electron microscopy (SEM). Electrochemical polarization tests were also used to study the passivation behaviors of the steels. Stress corrosion cracking growth path was revealed under optical microscope and crack growth rates were estimated. The mechanisms of SCC in the near-neutral pH solutions were proposed based on the analysis of the results from SSRT. |
