Estudo do efeito da densidade de corrente e da agitação no processo de eletrodeposição da liga Ni-W.

Abstract

Protective coatings and are an important way to prevent metal corrosion, particularly atmospheric, can greatly improve the physicochemical properties of the surfaces, the coatings are the most common of copper, nickel and chromium. Electroplating is a good way to coat the metal surfaces. Protective coatings may be obtained by several methods, the most widely used is that obtained by electrodeposition, this technique involves depositing a thin layer on the surface of a substrate by means of electrolysis. Despite its excellent corrosion resistance and mechanical properties, hard chrome coatings are becoming less popular in industrial applications due to environmental and toxicological problems, because the plating bath are used carcinogenic Cr6+ ions. In recent years the electrodeposition of Ni - W have received considerable attention due to its resistance to wear and corrosion, with high tensile strength and high hardness. Furthermore, the Ni -W alloy can be used as a substrate for superconductors subjected to high temperatures. This paper aims to obtain coatings of Ni - W and evaluate the corrosion resistance of the alloys obtained. In preparing the bath reagents were used with a high degree of analytical grade ammonium sulfate, sodium tungstate, sodium oxalate and nickel sulphate . The pH of the solutions was 7.0 and this was adjusted by adding ammonium hydroxide or sulfuric acid. In optimizing the electrodeposition process of Ni- W, we used a 22 full factorial design with one center point experiments totaling 5 experiments in duplicate. Through the response surface methodology (RSM) was done to study the main and interaction effects on the deposition efficiency of the system, polarization resistance and corrosion potential. Was successfully obtained by electrodeposition of an alloy binary Ni - W. It was observed that the best value of the corrosion potential was -0.276 V that obtained with increasing current density (100 mA/cm2 ) and with decreasing agitation (0).