The role of thiourea as an organic additive in the nucleation and growth mechanism was studied for copper deposition and its application in the decorative electroplating and fashion accessory industries. The bath was designed to reduce the environmental and ecological impacts using methanesulfonic acid as electrolyte as an alternative to alkaline cyanide baths. We evaluated the nucleation and growth mechanism of copper exploiting voltametric and chronoamperometric measurements with a brightener concentration ranging from 0 to 90 ppm. We used the Scharifker–Hills model to estimate the type of nucleation mechanism after progressive addition of thiourea. Scanning electron microscope was employed for surface analysis and morphological characterisation of the nuclei. We verified that progressive nucleation is a key step in the obtainment of a shiny and homogeneous copper film, but an excess of thiourea could cause parasitic adsorption reactions on the surface of the substrate. X-ray fluorescence spectroscopy was used for the thickness determination of the copper deposits and the electrodeposition efficiency correlated to thiourea concentration. Finally, the optimal concentration of thiourea was assessed to be 60 ppm for the used formulation of copper plating.

The interest in scientific research within the metal finishing sector is growing. The demand for durable metals and adaptable manufacturing processes are increasing across a wide range of applications, from aerospace and automotive to machinery and jewelry. An essential step in the production line is the surface engineering of metals, as this determines the final appearance and functionality of a product. Therein electroplating is recognized as a mature technology allowing the low cost fabrication of defined surfaces with extensive property profile. Galvanic electrodeposition accounts today for almost 40% of the global market value share with North America and Western Europe leading the scenery. Although technological and processing advancements occurred in the past forty years, industrial firms are still struggling to provide solutions to corrosion protection as well as reduction of toxic wastes. Specifically, large-scale industrialization of electroplating techniques will continue to be limited by strict environmental regulations. Due to adverse ecological impacts, the adoption of plating processes involving toxic metals such as lead or cadmium is prohibited. Moreover, price volatility of the highly demanding electroplated materials gold, copper and nickel is expected to impact the market share for more than 60% by 2026. In that respect, alloy plating offers better answers in terms of economic growth and environmental sustainability due to fine tuning composition, morphology and crystallinity [1]. Here, current trends on alloy electrodeposition research are reviewed highlighting open challenges and process innovations from an industrial perspective. The main categories of alloy compounds are presented and the most important properties for the manufacturing process discussed. Particular attention is devoted to advances in industrial quality control and viable solutions for the reduction of precious metal content in electroplated accessories as well as replacement of cyanide and nickel baths with non-toxic compounds. The present study funded by the PRIN Project (“Progetti di Ricerca di Rilevante Interesse Nazionale”), “Novel Multilayered and Micro-Machined Electrode Nano-Architectures for Electrocatalytic Applications (Fuel Cells and Electrolyzers)”, grant number 2017YH9MRK. References [1] W. Giurlani, M. Innocenti et all. , Review, Coatings 2018, 8(8), 260.