Half-Cell Potential Test | Advance Testing Lab in Delhi
The half-cell potential test is the best corrosion monitoring technique tested as per ASTM C876 – 15: Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete.
It is used to determine the probability of corrosion within the rebar in reinforced concrete structures. Corrosion, which is an electrochemical process, occurs in concrete when oxygen and moisture are present. The actual corrosion is an exchange of energy within different sections of the uncoated reinforcing steel.
The relative energy levels can be determined in relation to a reference electrode with a stable electrochemical potential.
By connecting a high impedance voltmeter between the reinforcing steel and a reference electrode placed on the concrete surface, a measurement can be made for the half cell potential at the location of the reference cell. This is a measurement of the probability of corrosion activity in the steel in the vicinity of the reference cell.
This is used to locate corroding steel reinforcement. The reference half-cell potential test is copper in a copper sulphate solution. By taking half cell potential measurements a fixed distance apart, a grid of half cell potentials can be quickly made and thus, areas delineated with a high probability of corrosion of the reinforcing steel.
For example, the following guide is listed in ASTM C 876 using a copper-copper sulphate half-cell potential test:
Table 1: Relationship between the potential values and corrosion probability
(adapted from ASTM C876)
|Measured Potential(mV CSE)||Probability of steel corrosion activity|
|>-200||Less than 10%|
|-200 to -350||Uncertain|
|<-350||More than 90%|