A simultaneous screening of the corrosion resistance of Ni–W thin film alloys

Abstract

A range of Ni–W thin film alloys have been synthesised by evaporation from atomic sources to produce a compositional gradient across the substrate, and characterised by X-ray diffraction (phase identification and crystallite size) and EDX (composition). The corrosion resistance of 100 discrete alloy compositions has been measured simultaneously in identical environments using a high-throughput screening protocol based on cyclic voltammetry. The corrosion resistances and potentials are extracted from potentiodynamic data by both the linear polarisation resistance (LPR) and Tafel extrapolation methods; results from these are shown to be self-consistent. The high-throughput approach allows, for the first time, a direct correlation to be made between the bulk crystalline phases and morphology, and the corrosion behaviour of Ni–W alloys. The incorporation of W in the Ni–W solid solution at low W compositions results in a continuous reduction in crystallite size, a small cathodic shift in corrosion potential, and a small reduction in corrosion resistance. A large cathodic shift in corrosion potential together with a significant increase in the corrosion resistance is observed for alloy compositions greater than 24%at.W. This composition range coincides with the formation of the amorphous phase.