Estudo da caracterização da liga Cu-Zn-Ni obtida pelo processo da eletrodeposição.

Abstract

The corrosion process is constantly transforming metallic materials, so that their durability and behavior no longer satisfy their goals. One way to minimize corrosion in metallic materials is to coat them with other materials. Electrodeposition is a widely used method in obtaining metallic coatings resistant to corrosion and mechanic wear. Through electrodeposition, it is possible to obtain alloys, which are generally prepared in order to improve the characteristics of their initial constituents. The proposed study has, as a goal, to optimize the input variables (current density and pH), and obtain the Cu-Zn-Ni alloy resistant to corrosion. A 32 experimental design was used to optimize the electrodeposition process. Both the input variable influence, and their possible interactions, performing less experiments as possible, were quantitatively evaluated. The electrodeposition process of the Cu-Zn-Ni on a cathode was studied, using a bath containing copper sulfate, zinc sulfate, nickel sulfate and sodium citrate. All experiments were conducted at room temperature and in triplicate. The best reached values, through linear potentiodynamic polarization, were: cathode current density of 30 mA/cm2 and pH 6.0; with those parameters, it was possible to reach a potential of -0.31949 V, a 948090 Ω polarization resistance, and a 6.4265 nA current density. Electrochemical impedance spectroscopy confirms the linear potentiodynamic polarization results. Its chemical composition, in average, was 56 w.t. % of Cu, 38 w.t.% of Zn, and 6 w.t.% of Ni. Those found alloys showed bright, adherence and good resistance to polarization, and, through X-ray diffraction, it is concluded that the alloy is crystalline. The morphology study pointed out the presence of spherical nodules with different sizes on the alloy surface. The chemical composition of the coatings seems to be the most important factor for the coatings microhardness, since the experiment with the highest zinc content showed the highest microhardness value, which was 571 HV. Those alloys may have great utility in many applications in chemical, oil, petrochemical, naval industries, civil construction and automobile industries, because of some special characteristics, such as high resistance to corrosion and wear, and low overpotential for hydrogen evolution reaction of the Cu-Zn-Ni alloy.