The surface alloy RHODUNA Alloy, developed by Umicore Metal Deposition Solutions already in 2010, has now been examined by FRANCÉCLAT (Paris / France), an independent technical committee for economic development serving, among others, the jewelry industry. FRANCÉCLAT confirms the qualitative properties of the electrolyte. The rhodium-ruthenium electrolyte is composed of 75 percent rhodium and 25 percent ruthenium. Similar to pure rhodium, the rhodium-ruthenium alloy can be easily deposited in layer thicknesses between 0.05 micrometers and 0.2 micrometers. The goals set, lower cost with high quality, were achieved and some qualitative properties could actually be improved, proves the independent FRANCÉCLAT test report now published.
The committee used the Turbula abrasion test commonly used in the jewelry industry. Here, the L* values (brightness in the CIELAB color space) of the 0.1 micrometer cover layers were checked in two tests on the substrates palladium and ruthenium. After only two hours, the first signs of dissolution of the pure rhodium layer could be seen from the decreasing L* value, and after five hours the layer had been almost completely removed. The L* value was about 30 points lower and thus almost corresponded to the brightness value of the substrate used in each case. In contrast, the RHODUNA Alloy topcoat in the same test run was still largely intact after 10 hours and showed an L* value loss of only 10 points regardless of the substrate type.