Anodic polarisation measurements of corrosion and corrosion inhibition of Steel in concrete

Abstract

Anodic polarisation experiments were carried out on steel in concrete. The effects of surface treatment of the steel, medium of curing, as well as durations of curing were investigated.

Corrosion of steel in concrete due to the presence of the corroding chloride ions, either added to the mixing water or diffusing from the external attacking medium, was also investigated. The chloride ions when present in the mixing water are more effective in destroying the passivation of steel than when present in the outside medium. In the former case a minimum concentration of 1 % is required for this action, while in the latter case 4% is required.

Anodic corrosion inhibitors like nitrite, chromate, phosphate, benzoate and silicate were tried in order to suppress the action of the corrodent. The minimum concentration required of the inhibitor to stifle the corrosion is generally lower in the case when it is added to the mixing water of concrete. Possible mechanisms of corrosion and corrosion inhibition are discussed in the light of the current views on both processes.