Structural and corrosion study of uncoated and Zn-Cu coated magnesium-based alloy

Abstract

Zn-Cu alloy was deposited onto AZ63 substrate, and the corrosion behaviour of resulting modified electrodes was investigated in 3 wt % NaCl solution in comparison with uncoated AZ63. Electrochemical, structural, and morphological study of the coating is presented. SEM images reveal that the surface morphology of the films is uniformly small spherical grain distributions. The XRD patterns illustrate polycrystalline structure and the formation of peaks corresponding to hexagonal close-packed ε-phase of Zn-Cu with various crystallographic orientations. Cyclic voltammetry was used to determine the potential ranges where the various redox processes occur. Linear sweep voltammetry results illustrate that longer exposure of uncoated AZ63 in NaCl solution produces a greater corrosion potential shift because of the formation of an oxide layer that did not prevent the progression of corrosion attack. The corrosion resistivity of Zn-Cu coated AZ63 is approximately two orders of magnitude greater than that of uncoated AZ63.