CORROSION RATE ON REINFORCED CONCRETE STRUCTURES DETERMINED BY ELECTROCHEMICAL METHODS

Quality control, maintainance and planning of the restoration work on reinforced concrete structures need rapid, non-destructive inspection techniques to assess corrosion of the rebars and provide a quantitative measure of instantaneous corro¬sion rate. Different stationary and transient techniques (e.g. galvanostatic pulse measurements GPM) to measure corrosion rates of steel in concrete in the laboratory and on site are discussed. Experimental data from on site measurements are presented showing that on real structures "correct" polarization resistance (and thus corrosion rate) can be obtained only by signal confinement or by mathematical corrections based on the trans¬mission line due to the non uniform current distribution. It is further shown that in the (frequent) case of chloride induced, very localized corrosion attacks the average corrosion rates determined from polarization resistance measurements underestimate the real, local penetration rates by a factor of five to ten. Furtheron the corrosion rates measured are instantaneous, life time predictions can be made only with a better knowledge of the environmental changes and their effects on corrosion rate.