Understanding the intrinsic effect of fly ash on passivity and chloride-induced corrosion of carbon steel and stainless steel in cement extract solutions

Abstract

Compared with the ordinary Portland cement extract solution (OPC solution), the passivation capability and chloride-induced corrosion behavior of carbon steel (Q235) and 316 stainless steel (316ss) in fly ash modified cement extract solution (FA solution) were intensively investigated in this study. The composition and electrochemical properties of steel passive films were studied using XPS technique and a series of electrochemical measurements including M − S, EIS and CPP. Moreover, FT-IR, AFM and SEM/EDS were employed to analyze the corrosion products and morphology on the steel surface. After 10 d of passivation, the film resistance of Q235 in OPC solution was 1.42 times that in FA solution, but an opposite result was observed for 316ss, which is consistent with the subsequent chloride-induced corrosion behavior. Steel passive films of different thicknesses and protective characteristics for Q235 and 316ss formed in alkaline solutions were confirmed to be the dominating reason for the distinct passivity and corrosion resistance to chloride attack. Accordingly, the intrinsic impact mechanisms of fly ash on passivation capability and chloride-induced corrosion of Q235 and 316ss in extract solutions were proposed.