In-depth insight into the role of molybdate in corrosion resistance of reinforcing steel in chloride-contaminated mortars

The purpose of this study is to achieve a better understanding of the inhibition mechanism of molybdate as a potential corrosion inhibitor for reinforcing steel embedded in chloride-contaminated mortars. After adding sodium molybdate, mortars with and without admixed chlorides were exposed to chloride solution for evaluating the inhibition behavior of molybdate using electrochemical measurements and microstructural characterization techniques. In addition, the influence of molybdate on mechanical properties, pore structures and hydration products of mortars was also investigated. Although molybdate could yield a negative impact on mortar properties in terms of reduced strength and electrical resistance due to the increased porosity, the improved corrosion resistance was highlighted for steel in mortars containing molybdate. Based on the interactions between steel corrosion products and mill scale at the steel-mortar interface, the possible inhibition mechanisms of molybdate in chloride-contaminated mortars were proposed.