Corrosion behavior of Inconel 625 alloy in high-temperature and high-pressure CO2 environment

Abstract

In this study, the microstructural evolution and corrosion product layer characteristics of Inconel 625 alloy subjected to different solution treatment temperatures in a simulated oilfield environment were investigated, and their influence on corrosion resistance was analysed. The results indicate that after solution treatment in the range of 950–1100 °C, the Mo-rich M₆C carbides and Cr-rich M₂₃C₆ carbides gradually dissolve into the γ matrix, weakening the grain-boundary pinning effect of the carbides and promoting grain growth. Electrochemical measurements revealed that the corrosion current density and charge carrier density of Inconel 625 first decreased but then increased with increasing grain size. In the high temperature and high pressure CO₂ environment, the alloy treated at 1050 °C has better corrosion resistance, which is attributed to the dissolution of M₆C and M₂₃C₆ carbides into the matrix, resulting in an increase in the content of dense Cr₂O₃-based oxides. It effectively inhibits the penetration of Cl⁻ and enhances the pitting corrosion resistance.