RAULINO, J. L. C; http://lattes.cnpq.br/7914687214624647; RAULINO, José Leonardo Costa.
Résumé:
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.
