Quantifying Corrosion between Carbon Fibre Reinforced Polymers (CFRP) and Steel Caused by High Temperature Marine Environments

Research into carbon fibre reinforced polymers (CFRP)'s application to steel as a retrofitting technique has shown very promising results for improving mechanical properties. However, the limitation of these materials in a corrosion inducing environment has generally been overlooked. In this study, the interaction of CFRP and steel in extreme weather conditions and the material characteristics in causing localised corrosion (e.g. pitting) were investigated, with the primary aim of quantifying pit depth. Pits are known to initiate fatigue cracks in steels. Steel tiles placed in direct contact with different varieties of CFRP were exposed to 5% NaCl solutions at two temperatures for different durations. The specimens were microscopically examined to find the existence of pits, their depth and density. Steel with prior grinding suffered negligible pitting, whereas the sand-blasting created distinct isolated regions where pitting was more commonly witnessed. However, the most relevant observation was that even after 6 months of exposure to the aggressive NaCl environment, whatever pitting occurred, it was found not to be overly critical in reducing the mechanical strength of the CFRP/steel bonds.