Fundamental Study on Depolarization Value and Protection Effects of Steel in Concrete under Cathodic Protection

Abstract

Cathodic protection controls the corrosion current of steel in concrete by polarizing the steel potential in the less noble direction. Furthermore, cathodic protection is accompanied by spin-off reactions such as increase in pH by the generation of OH^- ion and decrease in chloride ion concentration near the steel surface. In this study, a cathodic protection test was conducted to maintain depolarization values of 25 mV, 50 mV, and 100 mV for the steel in concrete specimens with different levels of chloride ion concentration. The protection effect was examined on the basis of the corrosion rate of the steel bars in concrete. The corrosion rate of the steel bars under cathodic protection was observed to decrease to less than 1.0 mA/m², indicating a passive condition. The results also showed that the corrosion rate of steel decreases under cathodic protection even for depolarization values of less than 100 mV, which is the standard value under cathodic protection conditions.