Effect of the frequency of high-angle grain boundaries on the corrosion performance of 5wt%Cr steel in a CO₂ aqueous environment

The corrosion behavior of 5wt%Cr steel tempered at different temperatures was investigated by immersion testing and electrochemical testing in a CO₂ aqueous environment. When the tempering temperature exceeded 500℃, the corrosion rate increased. The corrosion layers consisted of Cr-rich compounds, which affected the corrosion behaviors of the steels immersed in the corrosive solution. The results of electrochemical experiments demonstrated that 5wt%Cr steels with different microstructures exhibited pre-passivation characteristics that decreased their corrosion rate. Analysis by electron back-scattered diffraction showed that the frequency of high-angle grain boundaries (HAGBs) and the corrosion rate were well-correlated in specimens tempered at different temperatures. The corrosion rate increased with increasing HAGB frequency.