Abstract
When the steel, containing scrap elements like copper, is used as reinforcing steel bars for concrete, the steel is exposed to alkaline environments. In this study, AC impedance technique has been applied to the monitoring of corrosion rates of iron and several Fe-Cu (0.4,3,10wt%) alloys in a wet-dry cycle condition. The wet-dry cycle was conducted by exposure to alternate conditions of 1hour-immersion in a simulated pHIO concrete solution ($Ca(OH)_2$ containing 0.01M NaCI and 3hour-drying at 298K and 50%RH. The corrosion rate of the iron is greatly accelerated by the wet-dry cycles. Because the active FeOOH species, which are produced by the oxidation of Fe(lI, III)oxide in air during drying, act as very strong oxidants to the corrosion in the wet condition. As the drying progresses, iron shows a large increase in the corrosion rate and a small shift of the corrosion potential to the positive values. This can be explained by acceleration of oxygen transport through the thin electrolyte layer. In contrast to iron, the Fe-Cu alloys show low corrosion rates and the high corrosion potentials in whole cycles.