Chloride induced reinforcement corrosion: Rate limiting step of early pitting corrosion |
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Authors: | Ueli Angst Bernhard Elsener Claus K Larsen Øystein Vennesland |
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Affiliation: | aNTNU Norwegian University of Science and Technology, Department of Structural Engineering, Richard Birkelandsvei 1A, N-7491 Trondheim, Norway;bETH Zurich, Institute for Building Materials (IfB), ETH Hönggerberg, CH-8093 Zurich, Switzerland;cUniversity of Cagliari, Department of Inorganic and Analytical Chemistry, I-09142 Monserrato, Cagliari, Italy;dNorwegian Public Roads Administration, N-0033 Oslo, Norway |
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Abstract: | Transition from passive state to stable localised corrosion of reinforcement steel in concrete owing to chloride ingress takes place over a period of time rather than being a one-step-occurrence. The depassivation process was characterised by frequent measurements of corrosion potential, polarisation resistance, and macro-cell currents when short-circuiting the working electrode with additional cathode surface. In addition, the concrete resistivity was continuously monitored and cathodic and anodic polarisation curves were measured. The results are consistent and imply that the localised corrosion process is in the initial phase of pit growth under mixed anodic/ohmic control. With time, the anodic reaction kinetics become more limited and the corrosion rate gets almost entirely determined by anodic control. The observed relationship between achieved maximum corrosion current and concrete resistivity indicates that the extent to which the anodic reaction kinetics are restricted is determined by the concrete microstructure and its ability to retain ionic movement. |
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Keywords: | Reinforced concrete Chloride-induced corrosion Pitting corrosion |
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