Electrochemical deposition of coloured Ni/Cu2O bilayer films on large area plastic substrates for decorative applications

Abstract

In this study, coloured Ni/Cu2O bilayer films were electrochemically deposited on large area automobile plastic parts (7 x 13 cm) for decorative applications. Such coatings may become an alternative to ubiquitously used Cr coatings for plastics. Purple, dark cyan and gold colours with good homogeneity and high brightness could be produced by tuning the deposition time of the Cu2O layer. Colouration of the bilayer film can be ascribed to interference of light through the metal/dielectric layer, where the thickness of the dielectric layer controls the wavelength of the reflected light. Cu2O film has a compact structure and low roughness, which is essential to obtain uniform colours. Moreover, the Ni/Cu2O bilayer exhibits good adhesion behaviour, environmental stability and enhanced corrosion resistance. This process is industrially viable and enables the large scale production of such decorative coatings.