Corrosion Behavior of Alloy 22 According to Hydrogen Sulfide, Chloride, and pH in an Anaerobic Environment

The corrosion behavior of Alloy 22 (UNS N06022) according to the hydrogen sulfide, chloride, and pH in an anaerobic environment was investigated through electrochemical tests, surface analyses, and response surface methodology (RSM). Complex corrosion behavior model according to the HS⁻ ion and Cl⁻ ion concentrations and pH was obtained through RSM. The Cl⁻ ion and pH had minimal effects on the corrosion behavior of Alloy 22. Meanwhile, the corrosion behavior of Alloy 22 changed significantly with increased HS⁻ ion concentration. As the HS⁻ ion concentration increases, sulfide ions are adsorbed on the metal surface, increasing the anodic dissolution of metal and suppressing the formation of Cr₂O₃ passive film, thereby deteriorating the passive properties of Alloy 22. Simultaneously, Mo in Alloy 22 forms MoS₂, which acts as a pseudo-passive film to alleviate the corrosion resistance deterioration caused by HS⁻ ions.