CORROSION INHIBITION FOR CARBON STEEL REBARS IN SIMULATED CONCRETE PORE SOLUTIONS

Abstract

In the high pH environment of reinforced concrete, carbon steel rebars are initially protected from corrosion. However, chloride ingress and the carbonation-induced drop in pH value result in increased susceptibility to localised and general corrosion. Corrosion inhibitors represent a simple and economical method for corrosion protection of reinforced concrete structures. In this work, sodium molybdate was tested as an inhibitor for carbon steel in various simulated concrete pore solutions against localised and general corrosion. Results show that molybdate can prevent passivity breakdown under open-circuit conditions. The effect of molybdate at different stages of pitting was investigated. Under certain conditions, a calcium molybdate film is precipitated that reduces the general corrosion rate. The critical concentration of molybdate required is lower than traditional nitrite inhibitors, resulting in near cost parity. It is proposed that molybdate be incorporated into a smart corrosion inhibitor system with targeted release for maximum efficiency.