Reinforcement corrosion in chloride environment of different concentrations

Abstract

Steel reinforcement remains passive until a certain amount of chlorides entry in contact with them. The corrosion develops in local areas and extends around depending on the level of chloride concentration. The further evolution of the corrosion depends on the total amount of chlorides although there is a maximum in the expected values of the corrosion rate. In present paper results are given on several tests that have been performed to establish the corrosion rates in chloride environments of different concentrations. First, the chloride threshold for depassivation will be commented on and its dependence of the $Cl^{-}/OH^{-}$ ratio as well as on the electrical potential exhibited by the reinforcement will be discussed. The depassivation occurs for $Cl^{-}$ amounts between $0.2$ and $1\%$ by cement weight for corrosion potentials more noble positive than $-200$ mVsce. Concerning the values of the corrosion rate, they increase when increasing the chloride concentration until around 1M NaCl, but above this concentration, the corrosion rate does not increase more likely due the decreasing oxygen content in the pore solution. Certain unexpected results are presented to illustrate that the corrosion rate is the result of some counterbalance phenomena, not always taken into account.