Anticorrosive Zn–Ni alloys: An alternative for the treatment of electroplating industry wastewater

Abstract

Substrate protection coatings are widely applied in the industry. Zn–Ni alloys have less potential for corrosion, thus preserving the steel substrate by corroding first. In this sense, this study used nickel-rich electroplating industry wastewater to produce Zn–Ni alloys under different conditions, analyzing the zinc sulfate concentration, electric current density, and rotating cathode in the deposition. The nickel removal kinetics showed a reversible and first-order behavior. The alloys with a composition of 2 wt.% nickel, according to energy-dispersive X-ray spectroscopy analysis, were more anti-corrosive with polarization resistance of 1276.7 Ω cm2, than the alloys containing 5 wt.% nickel. Electrochemical impedance spectroscopy proved that alloys containing 2 wt.% nickel were more resistant to corrosion and indicated the formation of a porous oxide layer. Besides, the micrographs of the alloys containing 2 wt.% nickel showed homogeneity without cracks and nodular grains, unlike the alloys with 5 wt.% nickel, which had cracks and were heterogeneous. The X-ray diffraction diffractograms showed different structures according to the amount of Ni. Thus, the deposition of metals from wastewater is an alternative to conventional treatments and avoids the use of synthetic baths.