Half-cell Potential

The half-cell potential, E_corr, is the difference in potential between the metal element and a reference electrode.  Equipment required for performing measurement of half-cell potential includes a half-cell, a high impedance voltmeter, and a set of lead wires.  A copper/copper sulfate reference electrode (CSE) is usually used for field measurements involving buried metal elements. Lead wires are attached to the end of the test element and the half-cell.  The lead from the half-cell is connected to the negative terminal of the voltmeter and the test element lead is connected to the positive terminal.  Results from the test can provide a comparison between metallic elements at different locations at the same site, as well as identifying the presence of different metals, e.g., zinc or iron. Half-cell potentials may be correlated with zinc loss and used to monitor the condition of galvanized reinforcements. Coupons or dummy reinforcements assist in interpretation of half-cell potential measurements. Plain steel, galvanized steel and zinc coupons may provide baseline measurements for comparison.