Comparative Corrosion Study of a New Type of “Ni-Free” Alloy for Decorative Applications

Nickel is the primary determinant of contact sensitization, therefore there is now a tendency to take nickel out of goods that could be in contact with human body. However this needs careful evaluation of the corrosion properties of nickel substitution especially in the fashion and jewellery industry where aesthetical defects are not acceptable. This paper analyses the corrosion behaviour of a recently patented Cu-Sn-Zn-In alloy, named “Quatro®”. The alloy is substantially nickel-free and can be obtained as thin coatings by electrodeposition from aqueous solutions. The obtained coatings show mechanical and aesthetical properties similar to the nickel ones constituting a potentially inexpensive alternative to this one. In this paper the corrosion properties of Quatro® coatings, electrochemically deposited on brass substrates, were evaluated by free corrosion tests and analysis of electrochemical parameters such as open circuit potential, corrosion current, breakdown potential and potentiodynamic polarization curves. In NaCl solution the corrosion properties of this alloy result to be similar to the traditional nickel coatings. In view of possible applications of this alloy as “Ni-free” solution for jewellery application, the corrosion properties in artificial sweat were also tested. In this environment, the investigations evidenced higher corrosion activity, assessing this solution not suitable for top finishing goods designed to be in contact with skin.