Abstract
The corrosion resistance of epoxy coated reinforcing steel from ten different sources was evaluated by 1) 14 day immersion in 80°C distilled water and 3.5% NaCl, 2) longer-term ambient temperature immersion in these same solutions as well as simulated pore water both with and without chlorides and 3) outdoor exposure in concrete slabs with different wet-dry ponding cycles. Coating performance was assessed during the course of the exposures by electrochemical impedance spectroscopy and by defect characterization and at the conclusion of exposure by adhesion testing. Preliminary evaluation of data from the experiments, which are ongoing, indicated a general similarity in the coating degradation process(es) for the three test procedures. An impedance decrease with exposure duration was noted in essentially all experiments. In the case of specimens with initially detectable coating defects this was attributed to progressive corrosion at the defect base. For specimens without initially detectable defects the reduced impedance was attributed to a decrease in coating pore resistance and, in some cases, development of defects during testing. The results are discussed within the context mechanistic aspects of coating degradation and projection of coating performance and recommendations are made regarding quality control methodologies for epoxy coating reinforcing steel.
