Tailoring α/β-Brass coating on steel via one-bath co-deposition: Influence of current density and electrolyte composition in pyrophosphate system

Abstract

Brass electroplating on steel wire is widely employed in the radial tire industry. However, controlling the formation of α/β-brass coating during the co-deposition of Cu-Zn remains challenging. This study investigates the influence of current density, Cu2+/Zn2+ ratio, and pyrophosphate concentration on phase formation using a cyanide-free process. Quantifications of Cu/Zn content and α/β phase ratio in brass coatings were accomplished using EDS and XRD techniques. α-rich brass was favored at moderate current density (5 A/dm2) and an optimal Cu2+/Zn2+ ratio of 1.5:1, while higher currents favored the β-phase regardless of the Cu2+/Zn2+ ratio. An optimal pyrophosphate concentration of 1.0 M yielded α-rich brass, with higher concentrations promoting unalloyed deposits and β-phase formation. α-rich brass coatings exhibited 13–17 % greater adhesion strength to rubber compared to β-rich coatings.