Corrosion processes of steel in concrete characterized by means of electrochemical noise

In this paper, the time evolution of corrosion processes of steel in concrete was studied. Two different methods were used: electrochemical noise (EN) and measurements with electrical resistance probes (ER). In order to evaluate the influence of specific parameters on the corrosion processes, both the techniques were used on concrete specimens during successive wetting and drying cycles. The results of the measurements were compared with the results of corrosion assessments of the steel after the specimens were disintegrated. It was established that both techniques are effective for measuring the corrosion of steel embedded in concrete, and to some degree compatible. The electrical resistance probes measure cumulative corrosion damage, whereas the electrochemical noise technique can follow the high corrosion dynamics in concrete. The measured signals contained certain fluctuations, which indicate that the process of corrosion initiation is not a smooth one, but consists of a sequence of several events. The results of the measurements also revealed that the distribution of anodic and cathodic sites may change during wetting and drying of concrete. (C) 2004 Elsevier Ltd. All rights reserved.