Microstructure and corrosion behaviour of deformed pearlitic and brass-coated pearlitic steels in sodium chloride solution

The microstructure and corrosion behaviour in 0.1 M NaCl of the brass coating and solid brass are first determined. Obtained results indicate that their microstructure plays a significant role in dezincification and in the kinetics of the oxygen reduction. The results suggest that the coating is significantly affected by plastic deformation (microstructure, thickness). The corrosion behaviour of the pearlitic steel and the brass-coated pearlitic steel is then investigated after plastic deformation. The coating breakdown happens at a critical concentration of vacancies generated by dezincification in the ultra-thin parts of the coating. The substrate is then exposed to the solution. Hydrolysis of Fe2+ induces a pH decrease, which can promote dezincification and then dissolution of the coating. Plastic deformation increases sharply the corrosion susceptibility of the pearlitic steel.