Stress corrosion cracking of 16MnR steel in FCCU regeneration environments

The stress corrosion behavior of the weld seam and base metal of 16MnR steel in solution of HNO₃-H₂SO₄-H₂O, one of the typical environments of FCCU regenerator, was investigated using U-bend specimen immersion test and electrochemical polarization curves. The results show that the weld seam of 16MnR is more sensitive to nitrate stress corrosion cracking than base metal, its mechanism is anodic dissolution. Both the introduction of sulfate and the slightly reduction of pH can destroy the protective film on 16MnR steel, and increase the corrosion susceptibility of its weld seam. However, when the pH of solution is less than 2, the material is in active state, resulting in a serious of uniform corrosion. Besides the effective methods to slow down the stress corrosion of materials in catalytic cracking regenerator are analyzed in this article.