Fundamentals, mechanisms and reactions in marine reinforcement corrosion

According to conventional wisdom reinforcement corrosion commences when the inward diffusion of chlorides causes a critical concentration at the steel or when the pH of the concrete falls below about 11. These criteria are inconsistent with basic corrosion science and with field observations. A 10 year study showed only negligible corrosion for concretes made with seawater. Compaction was high. It influences contact between reinforcement and concrete. Loss of alkalis is the main cause for corrosion initiation. This is consistent with classical observations that in stagnant conditions, as inside well-made concretes, oxygen rather than chloride is the governing electron acceptor. Mechanisms for alkali loss are described. Although these mechanisms depart from the conventional wisdom, the requirements for durable reinforced concrete structures do, however, agree.