Investigation on the intergranular corrosion resistance of the AISI 316L(N) stainless steel after long time creep testing at 600 °C

The effect of precipitation on the corrosion resistance of AISI 316L(N) stainless steel previously exposed to creep tests at 600 °C for periods of up to 10 years, has been studied. The corrosion resistance was investigated in 2 M H2SO4 + 0.5 M NaCl + 0.01 M KSCN solution at 30 °C by electrochemical methods. The results showed that the susceptibility to intergranular corrosion was highly affected by aging at 600 °C and creep testing time. The intergranular corrosion resistance decreased by more than twenty times when the creep testing time increased from 7500 h to 85,000 h. The tendency to passivation decreased and less protective films were formed on the creep tested samples. All tested samples also showed susceptibility to pitting. Grain boundary M23C6 carbides were not found after long-term exposure at 600 °C and the corrosion behavior of the creep tested samples was attributed to intermetallic phases (mainly sigma phase) precipitation.