Corrosion rates of steel in concrete

This paper critically examines DC and AC electrochemical techniques as used to determine the rate of corrosion of steel in concrete. Experimental evidence is presented to show that film resistance and mass transport can be factors determining the rate of corrosion and rates calculated from DC polarization resistance values can be in error. The values of the Tafel parameters required to estimate the corrosion rate appear to vary widely and estimation of the appropriate values is difficult. The AC technique involving measurement of the impedance over a range of frequencies gives information concerning the corrosion process and the factors controlling the rate.