Corrosion protection of NiNb metallic glass coatings for 316SS by magnetron sputtering

Abstract Metallic glasses (MGs) appear as promising anti-corrosion coating materials due to their microstructural and physicochemical advantages. Herein, we proposed magnetron sputtered NiNb thin film MG coatings (MGCs) with different structures and compositions for corrosion protection of 316 stainless steel in an aggressive saline environment. The properties of monolayered Ni50Nb50 and Ni60Nb40, as well as the multilayered Ni50Nb50/Ni60Nb40 (at.%) MGCs, were characterized in terms of morphology and microstructural properties, as well as the anticorrosion behavior. All the NiNb MGCs presented compact structure and the monolayered coatings exhibited preferable adhesion properties in comparison with the multilayered coating. The electrochemical tests and XPS results imply that the monolayered Ni50Nb50 MGC with high Nb content resisted corrosion mainly due to the formation of stable passive film that contained abundant Nb2O5 species, whereas the Ni60Nb40 MGC with high Ni content showed week corrosion protection performance during long-term service due to the dissolution of Ni cations and the devastation of the coating structure. Though with bit worse adhesion and more vulnerable Ni60Nb40 layers, the multilayered Ni50Nb50/Ni60Nb40 MGC possessed comparable corrosion resistance with the monolayered Ni50Nb50 MG coating, which remained stable even after 32 days of exposure. Such performance should be ascribed to the combined eff ;ect of the repassivation property for the sub-layers, the hindrance of propagation paths of micro-defects, and the obstruction of corrosive species by interfaces in the multilayered coating.