Otimização da composição do banho para eletrodeposição das ligas de Co-W e Ni-Co-W e avaliação da sua resistência à corrosão.

Abstract

The problems caused for the corrosion occur in more diverse activities, as for example, in chemical, petroliferous, petrochemical, naval the industries, civil, automobile construction and others, being able in such a way to cause serious accidents for the man how much for the half-environment. Therefore, to become necessary the development of advanced materials that can fight or brighten up the effect of the corrosion. The considered study it had as purpose to optimize the components of the bath for electroplating of the alloys Co-W and Ni-Co-W in function of the deposition efficiency. The used electrochemical bath in the electroplating of the league of Co-W was constituted of the following reagents: sulphate of cobalto, tungstate of sodium, sodium citrate, fosfato of boron and 1-dodecilsulfato of sodium, for the Ni-Co-W league the bath was constituted of the following reagents: sulphate of cobalto, sodium tungstate, nickel sulphate, fosfato of boron, sodium citrate and 1 - dodecilsulfato of sodium. The values of pH had been adjusted adding itself hidroxidos of sulfuric acid ammonium or. The leagues Co-W and Ni-Co-W had been electroplated on a copper substratum. Anodo consisted of a cylindrical platinum mesh. The optimizaption of the concentrations of the components of the banns was carried through aiming at to get the best efficiency of deposition of the deposits. The excellent conditions of the composition of the bath in relation to the efficiency of deposition for Co-W alloys were gotten using concentrations of: 0,100M of sulphate of cobalto, 0,150M of sodium tungstate and 0.250M of sodium citrate getting a eficiecia of deposition of approximately 25% and for league of Ni-Co-W 0,050M of sulphate of cobalto, 0,030M of sodium tungstate and 0,06M of nickel sulphate, getting an efficiency of approximately 52%. The Ni-Co-W alloy showed to properties anticorrosive superior when comparative the alloy of Co-W.