Half-cell potential testing is a method used for determining the corrosion activity of reinforcing steel in hardened concrete. The standard test procedure is presented in ASTM C 876, “Half-Cell Potentials for Uncoated Reinforcing Steel in Concrete.”
The test method is based on the principal that during the electrochemical corrosion reaction an electric potential difference is generated in the reinforcing steel. The potential difference between the reinforcing steel (anode) and a copper sulfate half cell (cathode) gives an indication of the presence or absence of corrosion activity in uncoated reinforcing steel in concrete.