Synergistic inhibition of molybdate and phytate on chloride-induced corrosion of carbon steel in simulated concrete pore solutions

Improving the corrosion resistance of reinforcing steel is particularly important to prolong the service life of reinforced concrete (RC) structures. This study proposes a novel mixed corrosion inhibitor of sodium molybdate and sodium phytate to enhance the corrosion resistance of Q235 carbon steel in concrete exposed to aggressive environments. Based on the synergistic inhibition of the mixed corrosion inhibitor with an optimal concentration ratio, the passivation and chloride-induced corrosion of steel in simulated concrete pore solutions were investigated using electrochemical measurements, XPS, AFM, SEM/EDS and ATR-FTIR. The results indicated that the mixed corrosion inhibitor could promote the passivation process of steel by increasing the passive film thickness, despite no significantly improved passivation ability was highlighted for steel. Furthermore, due to the formation of a protective and thick passive film with a specific three-layer structure, the mixed corrosion inhibitor markedly improved the pitting corrosion resistance of steel and exhibited a high inhibition efficiency after 30 days of chloride exposure. Accordingly, the corresponding synergistic inhibition mechanism of the mixed corrosion inhibitor was proposed.