Corrosion performance of ZrN/ZrO2 multilayer coatings deposited on 304 stainless steel using multi-arc ion plating

Coatings of single-layer ZrN, bilayer and multilayer ZrN/ZrO2 were deposited onto 304 stainless steel using a multi-arc ion plating technique, and their corrosion properties were tested in various solutions of 3.5 wt% sodium chloride (NaCl), 10 wt% and 20 wt% hydrochloric (HCl) acids, respectively.Results showed that the single-layer ZrN coating resisted the corrosion in the HCl acid with a concentration of 10 wt%, and the multilayer ZrN/ZrO2 coating acted as an effective protective layer in 20 wt% HCl solution. Polarization curve of the bilayer ZrN/ZrO2 coated specimens showed the lowest corrosion current density in 3.5 wt% NaCl and 20 wt% HCl solutions. However after polarization tests, the bilayer coating showed severe delamination after exposed in air, due to the large coating stress and brittleness of oxide ceramic layer. The multilayer ZrN/ZrO2 coating exhibited similar corrosion potentials and corrosion current densities compared with those of the bilayer coating. However, there was hardly any microscopic failure observed on the surfaces of the multilayer coatings after tested in all chloride solutions, which is attributed to the combined effects including improvement in coating toughness due to the multilayer design and ZrN sub-layer, reduced coating stress, and good corrosion resistance from the ZrO2 sub layer.