Corrosion Resistance of 0-15% Ni-Zn Alloy Electroplated Coatings

The corrosion resistance of 0 to 15% Ni-Zn electroplated alloy coatings was examined using salt-spray, cyclic corrosion and electrochemical tests. Our findings support those of previous investigations showing that the single phase (gamma) 11 to 15% Ni-Zn coatings provide the best barrier protection for unpainted applications, while the pure Zn coatings provide the highest level of galvanic protection. However, we have found that dual phase (gamma + eta) 9% Ni-Zn coatings appear to provide the best compromise between galvanic and barrier corrosion protection, and a minimum amount of paint delamination. In addition, we found that deformation, similar to body panel stamping, does not have a significant effect on the corrosion resistance of the pure Zn and low Ni-content coatings. However, deformation does produce cracking and a reduction in corrosion resistance for unpainted samples having higher Ni-content coatings.