Thickness-dependent pitting corrosion behavior in Ni-Nb thin film metallic glass

Thin film metallic glasses (TFMGs) with a composition of Ni60Nb40 were magnetron sputtered on the substrate of austenitic stainless steel (SS). Potentiodynamic polarization measurements on TFMGs with different thicknesses in NaCl solution were conducted, and better corrosion resistance is achievable by increasing the film thickness. However, a critical film thickness exists, above which anti-pitting property cannot be significantly improved. The film density as a function of thickness has a similar tendency with the corrosion resistance, indicating the correlation of film density and corrosion resistance. Fossettes in the pits were observed in TFMGs deposited on SS rather than the bare SS, since pitting nuclei in TFMG can propagate more rapidly along depth than width due to the stronger pitting susceptibility of SS.