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Black electroplated finishing with low nickel release


Black electroplated finishing with low nickel release


M. Gajo, G. Gajo
Elsy Research s.n.c., V. Mons. Zoppas, 20 - 31020 Scomigo di Conegliano (Treviso)
I. Del Pace
Valmet srl via Senese 12 - 50124 Firenze
A. Zingales, G. Quartarone, T.Bellomi
Università di Venezia - Dipartimento di Chimica 
G. Paolucci
Università di Padova - Dipartimento di Ingegneria Meccanica


Black colour on galvanic treatments are normally obtained using baths containing high concentration of nickel (black Ni-Sn, black gold) or chromium. Black ruthenium is also used successfully, but new researches to find cheap treatments are suitable. An interesting solution is represented by the bath of Black palladium-nickel. That bath was realized modifying an existing white Pd-Ni already used in production that gives very bright coating even at high thickness  with only 5% of nickel in the alloy. The contain of nickel is very important because of the well known problem of allergies created by nickel in contact with the human body.  For that reason the coated samples with white colour were tested in an artificial sweat solution, using the European nr. 1811 test method to determinate the nickel release, so that it was possible to know the highest contain of nickel allowed in the alloy. Even with a concentration of 10% of nickel the release was lower than 0.5 mg/cm2/week in accordance with the law proposed by the European Committee for Standardisation (CEN). For that reason the target was to modify the bath of white Pd-Ni to obtain a bright black colour with a max 15-20% of nickel contain. The research had been successfully: a very deep and bright black colour had been obtained and the bath seemed to be very easy to use. The alloy had been tested with a SEM to verify the concentration of nickel and the result was 20%.