Eletrodeposição de ligas Zn–Mn a partir de materiais eletrolíticos recuperados de pilhas alcalinas para proteção a corrosão

Abstract

Zinc and manganese metals, from waste alkaline batteries disposed through a recycling process, were used in electroplating processes to form Zn–Mn alloy coatings, to improve resistance against corrosive process. The proposed methodology used acid leaching of alkaline battery components, preparation of electrolytic baths with the bleached solutions and analysis of electrochemical techniques, to obtain optimized parameters for the Zn–Mn alloy electrodeposition and gauging the coatings against the corrosion process. Cyclic voltammetry measurements were performed in the 0 to –1.8 V potential window and it was possible to study the occurrence of reduction and oxidation reactions, with the appearance of cathodic and anodic peaks in the voltammograms. The voltammogram peaks helped to choose the potential values used in the electrodeposition processes, performed at –1.4; –1.6 and –1.75 V. The coatings obtained were characterized by the use of scanning electron microscopy and x–ray scattering spectroscopy. Analyzing the coatings and aiming at a better uniformity of grain growth morphology and a higher amount of Manganese in the Zn–Mn alloy ratio, new electrodeposition processes were performed at –1.6 V potential with the use of additives, Polyethylene Glycol (PEG) and Thiocarbiamide in the formulation of electrolytic baths. The characterizations of the coatings obtained from the corrosive process were performed by electrochemical impedance spectroscopy (EIE) and potentiodynamic polarization curves using a 3% (m/V) NaCl solution. In general, the polarization curves showed very similar results in the corrosion protection behavior of the alloy studied using separately or mixed additives.