Study of the influence of bath alkalinity on the nickel electrodeposition process in the presence of aspartic acid

Ni coatings are widely industrially applied due to their excellent properties like resistance to corrosion and wear, increasing the durability of coated surfaces. Ni electrodeposits on steel were produced from an alternative bath to the traditional Watts type, using aspartic acid as a complexing agent at pH = 5 and 11. Scanning Electron Microscopy micrographs revealed that all deposits obtained from the acid and alkaline baths showed smooth morphology with fine grains and no cracks. The smoothest deposits were obtained at deposition current of − 2.05 mA cm⁻² for both baths. The X-ray diffraction patterns of Nickel deposits obtained at pH = 5 and 11 indicated phases of pure Ni with the following reflections Ni(200), Ni (220), Ni (311), and a lower crystallinity for the deposits obtained at pH = 11 compared to that obtained at pH = 5. Adherence tests showed that the Ni coatings produced adhered well to the steel substrate, irrespective of the pH and deposition current density. By open circuit potential and linear polarizations, it was observed that Ni deposits presented a lower corrosion current and more positive corrosion potential than that of steel, indicating protection against corrosion, with those produced with j_dep = -2.05 mA cm⁻² responsible for the best protection and j_dep = -5.00 mA cm⁻² (pH = 11) the lowest protection.