Novel pulse potentiostatic electrodeposition route for obtaining pure intermetallic Cu5Zn8-CuZn composite coating using glycerol-NaOH based electrolyte with advanced scratch resistance and anti-corrosive properties

Abstract In this present study, a Cu 5 Zn 8 -CuZn intermetallic composite coating is deposited on mild steel from a non-cyanide glycerol-NaOH based electrolyte by pulse potentiostatic deposition route. Linear sweep voltammetry and electrochemical impedance spectroscopy studies demonstrate the reduction mechanism of copper and zinc complexes, the behavior of the electrolyte and the metal-complex interactions occurring during the electrodeposition process. The pulse current transients and cyclic voltammetry studies provide insight into the mechanism of intermetallic formation. X-ray diffractogram and corresponding Rietveld refinement of the electrodeposited coatings confirm the existence of Cu 5 Zn 8 and CuZn intermetallics without any unwanted solid solution phases. The coating demonstrates a high hardness value of 337 ± 17 HV. Additionally, the coating also exhibits excellent adhesion to the substrate and commendable scratch resistance under both progressive and constant loads as high as 10,000 mN. Corrosion study in 3.5 wt% NaCl solution reveals a corrosion current density of 12.6 μA/cm 2 which is anodic with respect to mild steel.