Efeito dos parâmetros operacionais na eletrodeposição da liga Ni-Mo-P.

Abstract

In this work, the effect of variation of the operating parameters of current density, temperature and pH of the electrolytic bath on the electrodeposition of Ni-Mo-P using sodium citrate as a complexing agent due to the corrosion behavior of the same, the chemical composition was studied microstructure and morphology of the coatings. The characterization of the layers was done by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). The corrosion tests were performed at room temperature in 0.1 M NaCl by linear potentiodynamic polarization techniques (PPL) and electrochemical impedance spectroscopy (EIS). As an optimization tool, a complete 23 factorial design associated with response surface methodology (RSM) was used. The corrosion properties and chemical composition of the coatings of Ni-Mo-P showed to be dependent on the current density, temperature and pH of the electrolytic bath. The corrosion resistance increased with increasing current density and decreasing temperature to pH 9.0. Since the morphology of the obtained layers and the phase structure was dependent on the contents of phosphorus and molybdenum, which found the formation of an amorphous structure to a higher percentage mass of phosphorus in the alloy coating and a crystalline structure to a higher percentage by mass molybdenum. The absence of cracks was observed for coatings with a low content of molybdenum and proved to be a necessary requirement for obtaining good properties with electrodeposited corrosion resistance. The results revealed that the coating had the best corrosion resistance was obtained at current density of 100 mA cm-1 at 40 ° C and pH 9.0 with composition of 87 wt.% Ni, 6 wt. 7% Mo and wt.% P and nodular morphology.