Half-Cell Potential Corrosion Surveying

The corrosion potential survey technique is used to investigate corrosion-related deterioration in structures and infrastructure at all stages of service life. Corrosion potentials, also known as Half-Cell Potencials (HCP), assesses the thermodynamic corrosion tendency of reinforcing steel in concrete. As part of structural condition assessment, Half-Cell Potential surveys of a structure may be used to identify the pattern and extent of corrosion. Survey data obtained can be used to infer the cause and likely extent of future distress before the corrosion results in visible damage to the concrete structure.

Methodology

Typically, a copper-copper sulphate half-cell electrode (CSE) is used, which consists of a copper rod immersed into a saturated copper sulphate solution. The base of the reference cell consists of a porous plug that provides ionic current path between the reinforcing steel and the copper rod when the electrode is placed on the surface of the concrete. By taking readings of half-cell potentials on the concrete surface over a uniformly spaced grid, an evaluation of the corrosion risk of the embedded reinforcing steel (or other metals) over a large area can be made. More positive potentials (in the range -0.1 to -0.2 V vs CSE typically indicate a low risk of corrosion. More negative potentials (in the range -0.4 V vs CSE or more) typicaly signify the risk of corroion at the time of measurement is high. Advanced analysis and contour plotting can provide additional information. This technique is also integral in the evaluation of cathodic protection system performance.

Common Applications

  • Assessment of corrosion potential of concrete structures such as walls, bridge elements and utility structures

  • Assessment of concrete structures in contact with soil, such as foundations, tunnels and retaining walls

  • Provide preliminary indication of corrosion in the absence of visible damage

  • Development of corrosion potential contour maps

  • Evaluation of the effectiveness of cathodic protection systems installed on concrete structures