Influence of Chloride Ions on Corrosion of Modified Martensitic Stainless Steels at High Temperatures Under a CO2 Environment

The influence of chloride ion concentration on the passivation film and corrosion product film of martensitic stainless steels (SS) (13% Cr, modified 13% Cr-1% Mo, modified 13% Cr-2% Mo, and 15% Cr SS) have been investigated using immersion tests and electrochemical measurements in sweet environments at temperatures of 150°C and 180°C in the presence of carbon dioxide (CO2). The corrosion rate of conventional 13% Cr SS was found to increase with increasing chloride ion concentration at 150°C. However, the corrosion rates of modified 13% Cr SS and 15% Cr SS were independent of the chloride ion concentration at 150°C. The corrosion rates of modified 13% Cr SS increased with increasing chloride ion concentration above 1,000 ppm at 180°C. The corrosion rate of 15% Cr SS slightly increased at high chloride ion concentration at 180°C. Chromium-enriched corrosion product films were produced on all alloys considered, except for 15% Cr SS, at 180°C. A passivation film was maintained for 15% Cr SS at 180°C. In addi...