Measuring the Rate of Corrosion of Steel in Concrete

Abstract

A study on the relationship of pH, chloride concentration, and oxygen concentration shows that a drying cycle, which locally concentrates chloride and oxygen, initiates the corrosion of steel in concrete. Once corrosion is initiated, the pH at the anodic areas decreases allowing corrosion to proceed more easily. Oxygen controls the rate of corrosion, but chloride affects the number of sites where corrosion initiates. Using a small portable computer system that applied the technique of polarization resistance with current interruption for elimination of iR error, the voltage measurement error generated when current flows through a resistive media, the corrosion of steel in concrete was measured in the laboratory. The portable system was then used to perform preliminary rate of corrosion measurements on reinforcing steel in three bridge decks in Frederick County, Maryland.