Electrochemical Treatment and Protection: Lessons Learnedby Jack Bennett, ELTECH Research Corp, Fairport Harbor, United States,
Abstract: Corrosion is recognized today as one of the major contributors to the deterioration of steel reinforced concrete structures. Two electrochemical techniques, chloride removal and cathodic protection, have been demonstrated to be effective for mitigating corrosion in chloride contaminated concrete. The principal objective of chloride removal is to migrate chloride ions toward the anode and out of the concrete structure in a period of 2-6 weeks. The current efficiency of this process is about 10-20%, resulting in the removal of typically 40-60% of the chloride originally present. An important additional benefit of the treatment is the generation of excess alkalinity in the concrete around the reinforcing bars. This treatment has been found to be a highly effective means of arresting corrosion. Cathodic protection is a process in which corrosion of the steel is mitigated by shifting the potential of the steel in the cathodic direction using a permanently embedded anode. An important benefit of this process, like chloride removal, is the depletion of chloride ions and generation of alkalinity near the surface of the steel. A mathematical model was developed to predict the movement of ions through concrete and the development of chloride and hydroxide concentration profiles which develop. The corrosion rate of steel was determined in a simulated concrete environment at various conditions of chloride concentration, pH, temperature and applied current. Cathodic protection current was found to be a highly effective technique for arresting corrosion in concrete. Two improved and simplified criteria were also developed for use with cathodic protection systems.
Subject Headings: Reinforced concrete | Chloride | Cathodic protection | Steel | Electrokinetics | Heat treatment
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