Controlled modulation of coating morphology, mechanical properties and anti-tarnishing response of nanocrystalline Au-Cu alloy coatings electrodeposited from a thiourea (TU)-based non-toxic cyanide-free bath: Effect of current density variation

Abstract

In the present work, Au-Cu alloy coatings are prepared by pulse galvanostatic electrodeposition from a novel thiourea (TU)-based bath by varying the current density from 5 to 25 mA/cm2. The effect of the applied current density on the surface morphology, mechanical properties, and anti-tarnishing performance of the developed Au-Cu coatings is investigated. Linear sweep voltammetry (LSV) experiments from different bath compositions are carried out to explore the electroanalytical behaviour of Au and Cu in the system. The SEM and EDS investigations show a wide variation in the surface morphology and Cu content of the deposited coatings as the applied current density changes from 5 to 25 mA/cm2. As the current density increases, the hardness of the coatings escalates from 173 to 279 VHN. The electrochemical impedance spectroscopy (EIS) studies suggest that the severity of tarnishing decreases with the increase in the current density.