Structural and mechanical characterization of nano-structured CuAg bimetallic coatings developed from a novel thiourea-based electroplating bath

The present study elucidates the electrodeposition of an Ag Cu bimetallic composite coating on a copper substrate from a thiourea-based (TU, CH 4 N 2 S) electroplating bath by pulse galvanostatic electrodeposition route. Electrochemical studies (LSV and EIS) demonstrate the metal-complex interactions and reduction mechanism of the bimetallic complexes occurring during the electrodeposition process. The pulse current transients provide insight into the deposition mechanism of the bi-metallic coating. X-ray diffraction studies of the electrodeposited coatings confirm the existence of both Ag and Cu without any solid solution phases. The SEM micrographs show that at higher current density there is a globular morphology of the deposits. Additionally, the proposed growth mechanism suggests the growth of higher index planes at the surface of the coating as the lower index planes gradually vanish. The coatings deposited at 1 and 5 mA/cm 2 demonstrate a hardness of 382 ± 7.5 and 174 ± 5 VHN, respectively. Additionally, the coating also exhibits good adhesion to the substrate, examined by the pull-out test. The electrical resistivity studies show that the resistivity value of coatings is similar to that of bulk Ag. • A novel thiourea (TU)-based electroplating bath is used. • LSV and EIS provide an insight into the metal-complex interactions. • Lower index planes vanish and higher index planes are stable on the coating surface. • The pulse galvanostatic route produces Ag Cu bimetallic coatings.