Corrosion behaviors of super 13Cr martensitic stainless steel under CO₂ and H₂S/CO₂ environment

The corrosion behaviors of super 13Cr martensitic stainless steel were studied with high temperature and high pressure CO₂ and H₂S/CO₂ test as well as electrochemical measurement at the simulated oilfield corrosion environment.The results show that with increasing temperature the uniform corrosion rate of super 13Cr martensitic stainless steel increases subsequently under CO₂ corrosion environment,and the pitting is very slight.Under H₂S/CO₂ corrosion environment,the uniform corrosion rate of super 13Cr martensitic stainless steel changes little,but the pitting becomes severe.When the Cl^- mass concentration is 160 g·L^-1,the max pitting depth comes to 28 μm.The pitting potential of super 13Cr martensitic stainless steel is bigger than that of common 13Cr,and it decreases with increasing temperature and Cl^- mass concentration as well as the presence of H₂S,while it changes slightly in CO₂ corrosion environment.The recovery potential of super 13Cr martensitic stainless steel is in the passivation zone under N₂ and CO₂ corrosion environment,and the higher recovery potential indicates that super 13Cr martensitic stainless steel possesses the superior re-passivation ability.At the same time,the presence of H₂S makes the recovery potential and pitting potential decrease remarkably.