Field measurement of the corrosion rate of steel in concrete using a microprocessor controlled unit with a monitored guard ring for signal confinement

The principle of corrosion rate measurement by the linear polarisation resistance method is simple. The equipment measures the half cell potential, applies a small current and measures the change in potential. The corrosion rate is proportional to the applied current divided by the potential shift. Using the technique in the field on reinforced concrete structures is complicated because the area of measurement must be defined and readings fluctuate with the weather conditions. This paper describes the use of a corrosion rate device in Europe and the USA on bridges, buildings and other structures. Its application for measuring the effectiveness of chloride removal and other rehabilitation techniques is discussed.