Estudo do comportamento da resistência à corrosão da liga NI-W obtida pelo processo de eletrodeposição sobre aços API 5l x70.

Abstract

Corrosion failures are the main cause of leakage in the industry, especially in oil. For this reason, the use of new materials with better resistance to this phenomenon has been studied. This study aimed to obtain Ni-W alloys by the electrodeposition technique and to evaluate the corrosion resistance of coatings on API 5L X70 steels. For the optimization of the electrodeposition process of the alloy, a complete factorial design 2³ + star configuration was performed, quantitatively evaluating the influence of the input variables (pH, Bath Temperature and Current Density) to obtain the optimal conditions to obtain this alloy, characterizing to the alloy composition, microhardness, morphology and corrosion resistance. After the optimization of the process, the effect of the heat treatment on corrosion resistance was evaluated. The results showed that the optimal values of corrosion resistance and hardness for the Ni-W alloy obtained with increasing tungsten in the alloy. The coatings presented amorphous characteristics and the presence of spherical nodules on the surface. The optimum parameters obtained for corrosion potential and polarization resistance were pH of 6.5, bath temperature of 55 ° C and current density 55 mA / cm² with a Rp value of 12.91 KΩ cm2. Obtained for corrosion potential and polarization resistance are statistically significant as they are also valid for predictive purposes. The heat treatment carried out in the optimized sample showed that with increasing temperature, the corrosion resistance and the hardness and modification of the coating morphology increased.