Effect of Cr(III) passivation layer on surface modifications of zinc-nickel coatings in chloride solutions

Surface chemical and morphological modifications of as-plated Cr(III)-passivated monophasic zinc-nickel coatings induced by corrosion in chloride solutions are demonstrated. The passivated samples showed slower anodic dissolution, less significant de-alloying, smaller surface dezincification lower coating cracking, as demonstrated Scanning Electron Microscopy Energy Dispersive X-ray Spectroscopy (SEM-EDX) the inductively coupled plasma atomic emission spectroscopy solution analysis. characterization photoelectron (XPS), Raman SEM-EDS indicated simonkolleite main product for both, coatings. In contrast, only coating, which experienced higher new Ni containing phases (metallic NiO) were evidenced. phase transition via selective dissolution zinc is supposed to increase concentration structural defects could explain cracking non-passivated Zn-Ni coating.