Know About the Use of Half Cell Potential Test

The half-cell potential test is conducted to determine and estimate the possibility of corrosion in reinforced concrete structures. Corrosion of the reinforcing steel is considered an electro-chemical process, so the steel's behaviour can be determined by measuring the electrical potential field within the concrete with a reference electrode A more negative potential in concrete that is not oxygen starved generally depicts a higher corrosion risk. The test is usually performed on a grid with varied spacing depending on the type of structure and the concrete properties. High-end equipment and devices are used when measuring both resistivity and half-cell potential, and they typically consist of a reference half-cell electrode, internal voltmeter, connecting wires, and copper/copper sulphate or silver/silver chloride electrode.

Copper-copper sulphate is the preferred electrode in high-end half-cell potential testing metres for easy of serviceability and its use in standards, but certain applications may require a different pair of electrodes, such as silver/silver chloride. Using a half-cell potential metre, you can easily identify potential corrosion of the rebars based on reinforced concrete's electro-chemical properties. Some of the best half cell potential metres come with a standard connection, which can easily be connected to third-party electrodes. That way, you can use others electrodes that are suitable to the type of test you will conduct.

The copper sulphate half-cell is held against the surface of concrete to serve as a battery, rebar as one metal, with the other side being the copper rod (the reference half-cell). The voltage or potential difference is determined by the voltmeter, which is connected to the copper rod and rebar. The reference half-cell is moved from one point to another on the surface of the concrete. As the copper rod's potential is constant, the various voltages measured are considered the difference in potential created by the differences in the bar surfaces' potentials. However, keep in mind that the measurements are only the reflection of the actual bar potentials. Measured values are determined by factors like the cover and concrete resistivity.