Avaliação do efeito das variáveis densidade de corrente e PH do banho eletrolítico na liga NI-CO-FE obtida por eletrodeposição.

Abstract

The Ni-Co-Fe alloys have generated great interest because of their mechanical properties such as ductility, corrosion resistance and wear resistance. This study aimed to obtain Ni-Co-Fe coatings and optimize the operating parameters (current density and pH Electrolytic bath) by Electrodeposition process, in order to obtain corrosion-resistant alloys. The electrochemical bath used for the electroplating of NiCo-Fe coatings consisted of the following chemical reagents: nickel sulfate, cobalt sulfate, iron sulfate, sodium citrate and boric acid. For the optimization of the parameters employed a Outlining Central Composite Rotational complete 22 with two central points. The bath temperature was kept constant at 70 ± 2 ° C. The coatings were electrodeposited on a copper substrate with a surface area of 8cm2 . To characterize the coatings obtained were used the Energy Dispersive Spectroscopy techniques of X-ray (EDX), current efficiency (CE), scanning electron microscopy (SEM), hardness, diffraction X-ray (XRD), linear potentiodynamic polarization (PPL) and electrochemical impedance spectroscopy (EIS). The coating had the best corrosion resistance was achieved with low current density (30 mA / cm2 ) and pH 8.5, obtaining a polarization resistance (Rp) of 37715 Ohms. The presence of the nanonodules cauliflower shape and needle as the pH was changed was observed. The deposited coatings were bright and adherent to the copper substrate. On the surface of the coatings that obtained the best performance against corrosion, the morphology obtained was in needle form. According to the results obtained in basic pH and high current density, nickel is preferentially deposited. The highest cathode efficiency and the highest value of hardness in coatings coincided with the best corrosion resistant result. According to the analysis-ray diffraction (XRD), it was observed that the coatings obtained had different crystallographic behavior.