The Electrochemistry of Steel Corrosion in Concrete Compared to Its Response in Pore Solution

Corrosion control of steel reinforcement relies on the maintenance of the high alkalinity of the hydrated cement especially in the presence of chloride ions. The present paper also indicates the adverse effect that chloride contamination of the initial mix can have on the permeability of the matrix to oxygen diffusion.

Data obtained on steel specimens embedded in ordinary portland cement paste prepared with varying additions of sodium chloride are presented. Potentiodynamic polarization curves obtained after 400-days exposure in a controlled humidity environment are compared to curves from steel immersed in extracted pore solutions. Pore solution measurements are shown to provide analogous information to embedded steel samples on the anodic and passivation processes. However, pore solution experiments do not simulate the influence of the matrix in controlling diffusion and resistivity, which influence the long-term durability and macro-cell development.