Analytical Characterisation and Antibacterial Properties of Novel Cyanide‐Free Electrodeposited White Bronze Coatings

ABSTRACT

Different bronze‐based coatings were investigated as sustainable alternatives to conventional chromium plating, incorporating antibacterial properties for decorative and high‐contact applications. A conventional white bronze was compared with two newly developed cyanide‐free acidic bronze alloys: a CuSn and a novel CuSnAg formulation, in which Ag replaces Zn to maintain the bright white aesthetic typical of chrome finishes while introducing potentially improved antibacterial functionality. A comprehensive analytical characterisation included colorimetric analysis, surface spectroscopy (XPS) for elemental and chemical speciation, ion release quantification, electrochemical and accelerated corrosion testing and antibacterial activity assays against E. coli and S. aureus following ISO 22196. Unlike conventional white bronze, the CuSnAg alloy exhibited effective antibacterial activity (R = 1.0) together with high brightness (1530 gloss), as well as good corrosion resistance and colour stability in neutral salt spray tests, fulfilling both functional and decorative requirements. XPS analyses revealed that the antibacterial performance is governed by the surface content of Cu and Ag species, rather than the bulk alloy composition. This study introduces a novel cyanide‐free white bronze formulation that combines aesthetic quality, durability, and antimicrobial protection, addressing the health and environmental issues associated with Ni‐ and Cr‐based coatings. The primary novelty of this work lies in successfully codepositing a cyanide‐free Cu‐Sn‐Ag white bronze that fulfills both decorative brightness and antimicrobial requirements without toxic bath additives. The new CuSnAg finish represents a promising, sustainable alternative to chromium plating for applications such as faucets, jewellery and door handles, where both hygiene and appearance are critical.