Enhancement of electrical conductivity and corrosion resistance by gold-nickel coating of additively manufactured AlSi10Mg alloy

Abstract

Gold-nickel coatings (Au–Ni) were applied by electrodeposition (ED) and electroless deposition (ELD) on additively manufactured (AM) AlSi10Mg alloy to improve the electrical conductivity and electrochemical behavior. Characterization of the Au–Ni coatings was performed by a scanning electron microscope equipped with energy dispersive X-ray spectroscopy (EDS) and x-ray diffraction to study the tiny features. The surface indentation hardness of the coated alloy was evaluated to study the coating strength. The electrochemical behavior of the as-built part and its counterpart, Au–Ni coated surfaces, were evaluated by conducting potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in a 3.5% NaCl solution.The results revealed that the Au–Ni coatings with layers thickness of ∼2 and 10 μm, respectively, could overcome the surface critical defects, i.e., pores and flaws. The surface hardness of the coated AM alloy has significantly increased six times due to the hard Ni layer. The electrochemical measurements showed a significant decrease in the anodic dissolution rate and increase in pitting corrosion resistance for the Au–Ni coated surfaces compared to the bare AM AlSi10Mg alloy with the as-built and polished surface condition in chloride solution. This was attributed to the stability of the Au–Ni coatings against the anodic overpotential. Moreover, it was observed that the Au–Ni coatings reduce the electrical resistance of the studied AM alloy by 40%. Consequently, the surface electrical conductivity property of the AM AlSi10Mg alloy was enhanced by both Au–Ni coating procedures.