Relationships between anodic polarisation and corrosion of steel in concrete

Corrosion of reinforcement in concrete is a topic of concern mainly because of the high cost of repair and rehabilitation of concrete structural elements. There is as yet no method of assessment that would enable the rapid and accurate prediction of the extent of corrosion of reinforcing steel in concrete on site. Half cell potential techniques commonly used in situ give only probabilistic information on corrosion activity. Research effort is thus needed in both investigating and developing methods to assess more accurately the corrosion characteristics of steel in concrete with an ultimate view of site application. Long-term investigations on chloride induced corrosion of steel reinforcement have been conducted on a series of concrete slab specimens to establish relationships between electrochemical data and chloride induced corrosion of steel reinforcement. Potentiodynamic anodic polarisation procedures were used to monitor corrosion of steel reinforcement in concrete slab specimens over a period of four years. A statistically significant relationship between the area under the corrosion current and time relationship and the weight loss of steel reinforcement was established. Assessments of corrosion rates of steel in the concretes studied were thus verified. Reinforcement corrosion was found to be localised under the high chloride conditions occurring mainly in an area adjacent to the chloride source.