EFFECT OF PROTECTIVE OXIDE SCALES IN THE MACROGALVANIC BEHAVIOR OF CONCRETE REINFORCEMENTS

The influence of macrocell activity on the corrosion of steel in concr ete is studied using concrete beams exposed to the atmosphere for six years. In these beams, the corroding areas (embedded in chloride conta ining concrete) behave as anodes with respect to the segments embedded in the chloride-free concrete. However, after six years of ageing in the laboratory (dry atmosphere), the segments in contact with chloride s reach a kind of passivation state that allows them to act as cathode s when the macrocell is connected. This behaviour is interpreted in te rms of the activity of a Fe2+/Fe3+ redox process, the amount of rust a ccumulated in those sites and the electrical conductivity of this rust , as well as the oxygen availability. (C) 1998 Elsevier Science Ltd. A ll rights reserved.