Corrosion behaviour of Zn-Co alloy and multilayered metallic coatings: a comparative insight

Zinc layers are widely used for the protection of various classes of steel in atmospheric conditions. An improvement in corrosion performance of these layers may qualify them to be used in harsh marine conditions. In this study, two practical approaches, including alloying Zn with Co at different current densities and electrolyte temperatures, as well as deposition of multilayered Zn-Co films with various numbers of interlayers, were applied to fabricate corrosion barrier coatings on St 37 steel. The surface and cross-sectional morphologies of the coatings were studied using scanning electron microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarisation tests were employed to compare the corrosion resistance of the alloy and multilayered coatings. Results illustrated that the best protection performance is obtained for multilayered coatings with top Co layer showing promise to be used in marine applications.