Influência do ácido aspártico no processo de eletrodeposição de ligas de Cu-Sn-Ni. Avaliação da morfologia, composição, estrutura, adesão e resistência à corrosão dos filmes

Abstract

This research work presents the main results on the development of electrolytic baths with no cyanides for the production of Cu-Sn and Cu-Sn-Ni alloys and also the morphological, chemical and structural characterization of the coatings and also the assessment adhesion and corrosion resistance of the deposits. From the eletrolytic solutions, it was found that for the production of films on both substrate steel or Pt, the pH should be low enough, i.e. 1.20, to avoid Sn hydrolysis and also maintain the additive fully protonated. Electroanalytical studies were conducted looking for the best deposition conditions for obtaining high quality films both on Pt and steel substrates. The influence of the deposition potential or current and the charge deposition and the effect of the additive on the characteristics of the films were analyzed. The voltammetric curves indicated that the Hasp do not influence significantly the thermodynamics of the deposition process regardless the substrate. Only, the presence of the additive led to lower Ni content in the coatings. In general, the films were dendritic and spongy, regardless of the type of deposition, substrate or the presence of Hasp. The electrodeposits phase composition is influenced by the Hasp only on Pt substrate. The phase composition for those produced on steel, without or with the additive exhibited different phases in comparision wiht those produced on Pt. In relation to the Cu-Sn-Ni deposits adherence on steel substrate, in general, they had regular grip, except deposits A_05, B_05 e A_35 which were more adherent than others. The corrosion studies showed that the performance of Cu-Sn and Cu-Sn-Ni coatings were similar. The corrosion potentials were in the range of - 661 ± 27 mV and -777 ± 73 mV, which were less negative than the Ecor of steel substrate (-759 ± 12). Furthermore, Rp values of deposits were also higher than for steel substrate and thus it can be inferred that the films produced provide good corrosion resistance. The alkaline Cu-Ni-Sn solutions were not stable and produce some metal compounds as precipitates, which were washed, dried, homogenized and characterized. It was found the possibility to use them for powder metallurgy for Cu-Sn-Ni alloys.