A comparative study of electrodeposition routes for obtaining silver coatings from a novel and environment-friendly thiosulphate-based cyanide-free electroplating bath

Abstract In the present study, silver coatings are deposited from a novel cyanide-free thiosulphate-based electroplating bath containing cetyltrimethylammonium bromide (CTAB), 1,4-diazabicyclo[2.2.2]octane (DABCO), and pyridine-3-carboxylic acid (Niacin). LSV and EIS are carried out to demonstrate the metal-complex interactions and the reduction mechanism during electroplating. Depositions are carried out by both DC and pulse galvanostatic methods for comparison. XRD and EDS analysis confirmed the presence of elemental silver in the coatings. The SEM analysis and surface profilometry show the morphological variations and changes in surface roughness as a function of the electrodeposition route. Nano-indentation measurements reveal that the samples deposited under pulse conditions have a hardness of 196 ± 6.5 and 227 ± 15.6 VHN at current densities of 0.1 and 0.01 mA/cm2, respectively. By comparing the results obtained via both the deposition routes, it can be concluded that the pulse galvanostatic route can obtain a highly compact and adherent silver coating having a mirror-finish appearance that lasts for a long time under ambient indoor environment. Therefore, the developed bath can be used for producing mirror-bright silver coatings for aesthetic usage via pulse galvanostatic route.