Effect of Microstructure on the Corrosion Performance of 5% Cr Steel in a CO₂ Environment

In this study, the CO₂ corrosion behavior of 5% Cr martensite and ferrite-pearlite steels has been investigated by analyzing their corrosion products, surface morphologies, cross-sectional morphologies, and elemental distributions. The results of electrochemical studies demonstrated that 5% Cr steels with different microstructures exhibited pre-passivation characteristics, which decreased their corrosion rates. The produced passivating surface layers consisted of Cr-rich compounds, which significantly affected steel corrosion properties, while the correlation between the observed Volta potential drops and depletion of Cr contents at the grain boundaries, and the corrosion behavior of 5% Cr steel was determined via scanning Kelvin probe force microscopy.