Stress corrosion cracking behavior of 16Mn steel and heat-affected zone in alkaline sulfide with different concentrations

This research aims to study the stress corrosion cracking (SCC) behavior and its mechanism of 16Mn steel and heat-affected zone in alkaline (pH=11.7) sulfide solution with different concentrations using electrochemical technology and U-bent specimen immersing test. Original structure, coarse grain structure (air cooling structure) and hardening structure (quenching structure) turned into the state of passivation in alkaline sulfide solution, and the current density of passivation decreased gradually. The current density of hydrogen evolution of hardening organization was higher and corrosion rate was slower. And the corrosion near the fusion line part was deeper and the residual tensile stress area was exposed after long-term service, which caused stress corrosion cracking. The sensitivity of SCC lowered gradually when hardening organization, open grain structure and original structure of HAZ were in alkaline sulfide environment. Hardening structure exhibited high susceptibility to SCC. Coarse grain structure and original structure exhibited low susceptibility to SCC. The susceptibility increased by increasing the concentration of H₂S. The SCC mechanism of 16Mn steel was anodic dissolution (AD) and was intergranular fracturing when it was in the solution of alkaline sulfide.