XPS study on the passivity of coarse-grained polycrystalline and electrodeposited nanocrystalline nickel-iron (NiFe) alloys

[Display omitted] •Using PARXPS, passive films on NiFe alloys of varying grain size were investigated.•Poly- and nanocrystalline NiFe alloys exhibited similar passive film compositions.•Grain size reduction increases the anodic activity of the alloy, affecting passivity.•Current transients suggested increased passivation kinetics for nano NiFe alloys.•Passive currents of poly- and nanocrystalline NiFe were similar (order-of-magnitude). Electrodeposited nanocrystalline NiFe alloys are compared to their polycrystalline, coarse-grained counterparts to understand the effects of grain size reduction on the passivation kinetics and the chemical structure of the passive film. The passive film formed in acidic sulfate environment was characterized using parallel angle-resolved XPS (PARXPS) to obtain non-destructive compositional depth profiles. The composition (Ni:Fe) of the passive film was insensitive to grain size; however, grain size reduction resulted in increased anodic activity producing thicker films that contained increased concentrations of higher oxide species.