Corrosion inhibitors in reinforced concrete structures - Part 1: Preventative technique

The corrosion of reinforcing bars (rebars) is the main cause of premature failure of reinforced concrete structures. The ingress of chlorides and the carbonation process that leads to the neutralisation of the alkaline pore solution are among the key phenomena promoting such corrosion. This paper deals with the effectiveness of commercial corrosion inhibitors to prevent the corrosion of reinforcement in concrete. Three organic inhibitors and, for comparison, a calcium nitrite based product, were added to fresh concrete in the dosages suggested by producers. Experimental tests were carried out both in chloride contaminated concrete ( produced by adding chlorides directly to the mixture or by penetrating hardened concrete using ponding cycles) and in carbonated concrete. In order to study the effectiveness of the inhibitors on the initiation of corrosion, measurements were made over two years of two electrochemical parameters, the free corrosion potential and the polarisation resistance. These are discussed and compared with results obtained for concrete specimens without inhibitors. One of the organic corrosion inhibitors and the nitrite based product both delayed the initiation of corrosion.