Process control of reinforcement corrosion in concrete. Part 1: Effect of corrosion products

•FeOOH can replace oxygen to be a new cathodic depolarizer once the corrosion begins.•Total corrosion current is sum of corrosion currents from oxygen and FeOOH depolarization.•The maximum of Icorr appears where concrete is saturated.•The control type of corrosion process of rebar in concrete is mixed control.•Oxygen is one of the key factors influencing rebar corrosion but not the controlling factor. The effect of degree of pore saturation (PS) in concrete on corrosion current is investigated in this paper. Results showed that the maximum of corrosion current appeared in the saturated concrete and it decreased in dried concrete. After the corrosion products were enough, FeOOH in corrosion layer could act as a depolarizer instead of oxygen. As a result, the corrosion rate remained high even when the concrete was completely water saturated. Therefore, oxygen is not the factor controlling corrosion process of steel rebar in concrete, although it is one of the key factors. When the concrete drying process stars from water saturation, there is little difference between the control degree of cathodic reaction and the control degree of anodic reaction on corrosion process; the control type of corrosion reaction is mixed control. Part I of this article presents experimental results obtained from the thermostatic drying tests and the effect of corrosion products on process control of reinforcement corrosion in concrete. The time-dependent dominating factors of rebar corrosion process under different environmental conditions will be discussed in Part 2.