Obtenção e caracterização da liga Ni-Co-P obtida por eletrodeposição.

Abstract

The corrosive process tends to degrade the metallic materials causing them to lose their mechanical properties and become unsuitable for their initial purpose. One of the corrosion prevention techniques is the use of metallic coatings, which can be obtained by electrodeposition, which is a technique that produces coatings of high quality metal alloys with good mechanical properties and economically, improving the initial properties of the material that if desired. The purpose of this study was to optimize the input variables (current density and pH) and to obtain corrosion resistant Ni-Co-P alloy, characterizing it as morphology, cathodic current efficiency, alloy composition, microhardness and resistance to corrosion. For the optimization of the alloy electrodeposition process, a central composite 2² factorial design was performed. The influence of the input variables, as well as their interactions with the minimum number of experiments, were quantitatively evaluated. The electrodeposition process of Ni-Co-P alloy on A1020 steel was studied using a bath containing nickel sulfate, cobalt sulfate, sodium hypophosphite and sodium citrate. All the experiments were carried out under a temperature of 70 ° C, the optimum values found by linear potentiodynamic polarization were: cathode current density of 30 mA/cm2 and pH 9; with these parameters it was possible to achieve a corrosion potential of -0.649 V, a polarization resistance of 19.749 KΩ and a corrosion current of 3.806 μA. The electrochemical impedance assays confirmed the results obtained by the linear potentiodynamic polarization tests. The average composition of this deposit was 61 wt% Ni, 15 wt% Co and 24 wt. % P. These alloys may be of great utility in various applications in the chemical, mechanical, electronics, petroleum, petrochemical and civil construction industries due to some special characteristics such as high corrosion and wear resistance, magnetic and tribological properties of Ni-Co-P alloy.