Characterization and corrosion resistance of TiZr coating on SS304 stainless steel using cathodic arc evaporation techniques

In this study, an alternating titanium and zirconium (TiZr) nano-composite layer is deposited on a SS304 stainless steel surface to improve the corrosion resistance of bare SS304 in an acid environment with and without F ions as well as in a NaCl salt solution using cathodic arc evaporation techniques. The microstructures of this TiZr coating are studied and correlated with corrosion resistance. The corrosion resistance of a TiN/ZrN coating, which has an alternating titanium nitride/zirconium nitride (TiN/ZrN) multilayer, is compared with the corrosion resistance of the TiZr coating. The results show that the TiZr coating (layer thickness of 3.66 μm) has a nano-composite structure consisting of alternating Ti and Zr layers with a hexagonal closest-packed (hcp) arrangement. The corrosion rates of SS304 coated with a TiZr layer are much lower than those of uncoated SS304 in H2SO4 with and without F ions as well as in the NaCl salt solution. Additionally, the corrosion resistance of our TiZr coating is better than that of TiN/ZrN, CrN, TiN, TiN/CrN and CrN/Ti coatings and a bulk Ti25Zr75 alloy. The excellent corrosion resistance of the TiZr coating is attributed to the alternating Ti and Zr nano-composite structure with an hcp arrangement, which provides an effective impediment to active corrosive ions during anodic dissolution. Furthermore, the TiZr coating has lower interfacial contact resistance than the SS304, even after corrosion in H2SO4 with F ions, and it offers less surface resistance than the TiN/ZrN coating. This makes the TiZr coating a better protective coating for SS304 bipolar plates.