Abstract: The effect of calcium ions on the corrosion behavior of 3Cr low-alloy steel in CO₂-containing sodium chloride solution was investigated by immersion test and electrochemical measurements. It is found that with the addition of Ca²⁺ to CO²-containing solution, the crazing level of the corrosion scale on the specimen is much slighter than that of the specimen immersed in solution without Ca²⁺. The pitting on the surface of the specimens immersed in the solution with Ca²⁺ is relatively small and distributes uniformly all over the surface. The significant change in the anodic polarization curve is attributed to the deposition of the CaCO₃. CaCO₃ deposits on the specimen surface and gives a protection to the metal substrate. And with the anodic proceeding, the concentration of H⁺ in the solution increases. The CaCO₃ deposition dissolves in the low pH solution and the protection effect disappears.

Key words: Steel, Corrosion, Corrosion scale, Polarization, EIS, SEM