Electrodeposition of 70-30 Cu-Ni nanocomposite coatings for enhanced mechanical and corrosion properties

Abstract

A copper-nickel alloy (70:30 ratio) was electrochemically deposited and compared to a composite coating incorporating layered silicate platelets to obtain copper-nickel-montmorillonite (MMT). The composite coatings were electrochemically deposited from a citrate bath to investigate the effects of MMT on the corrosion and mechanical properties of the coatings. Incorporation of MMT into the Cu–Ni alloy films was not affected by the deposition parameters such as applied voltage and pH. Scanning electron microscopy and atomic absorption spectroscopy confirmed the successful incorporation of the MMT into the coatings. Longer term stability in the presence of corroding solutions was noted for the copper-nickel composite films. The Tafel calculations showed an increase in polarization resistance, Rp, from 190.7 kΩ·cm2 for pure Cu–Ni to 314.3 kΩ·cm2 for Cu–Ni-0.2% MMT after soaking the coatings in 3.5% NaCl at 25 °C for two weeks, which was consistent with the resistance increase measured by electrochemical impedance spectroscopy. Microhardness test results showed about a 25% increase in the hardness for the copper-nickel coatings incorporated with the layered silicate platelets versus the pure Cu–Ni coating.