Estudo experimental e simulado de eletrodeposição da Liga Ni-W.

Abstract

Protective coatings are an important prevention corrosion, and electrodeposition is an important technique used in obtaining coatings to metal surfaces in order to inhibit corrosion. One of the most commonly used coatings in electroplating is hard chromium coating, due to its excellent properties of hardness, low coefficient of friction and large corrosion resistance, but their industrial applications are having environmental aspects of the process of chromium plating thanks to its toxicity, is necessary to study acceptable alternatives for the substitution of electrodeposition of chromium. Among the possible alternatives to electrodeposition of alloys containing tungsten seems to be an interesting and safe choice because tungsten is located in the same group as the periodic table (group VI) and is expected to have chromium-like chemical properties. With the computational techniques and the incredible progress of computers themselves, numerical simulation has become an important tool for scientific research. The purpose of this study was to develop metallic alloys Ni-W corrosion resistant and use a numerical simulation to predict behavior of the electrodeposition process. The electrochemical bath used in the electrodeposition of the Ni-W alloy was made up of the following reagents: boron, nickel sulfate, sodium tungstate, ammonium citrate, and 1-dodecylsulfate of sodium. The pH of the bath was adjusted by adding ammonia hydroxide or sulfuric. The Ni-W alloys were electrodeposited on a copper substrate. At optimum conditions for bath composition in relation to deposition efficiency for Ni-W alloy were obtained using the concentrations of 0.093M for the sodium tungstate and 0.111M for nickel sulphate, obtaining an efficiency of approximately 61%. For the evaluation and simulation, a reaction and the Butler-Volmer equation was applied with the intention of obtaining the exchange current to calculate the mass deposited. From the results it was possible to carry out a study comparing them with the experimental results and thus analyzing the behavior of the model.