Electrolytic preparation of cyclic multilayer Zn-Ni alloy coating using switching cathode current densities
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2010
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Abstract
Cyclic multilayer alloy (CMA) coating of Zn-Ni was developed on mild steel using single bath technique, by proper manipulation of cathode current densities. The thickness and composition of the individual layers were altered precisely and conveniently by cyclic modulation of cathode current densities. Multilayer coatings, having sharp change in compositions were developed using square current pulses. Gelatin and sulphanilic acid (SA) acid were used as additives. Laminar deposits with different configurations were produced, and their corrosion behaviors were studied, in 5% NaCl solution by electrochemical methods. It was observed that the corrosion resistance of CMA coating increased progressively with number of layers (up to certain optimal numbers) and then decreased. Cyclic voltammetry study demonstrated the role of gelatin and SA in multilayer coating. The coating configuration has been optimized for the peak performance against corrosion. The substantial decrease of corrosion rate, in the case of multilayer coatings was attributed to the changed intrinsic electric properties, evidenced by Electrochemical Impedance Spectroscopy (EIS) study. The surface morphology and its roughness were examined by Atomic Force Microscopy (AFM). The surface and cross-sectional view of coatings were examined, using Scanning Electron Microscopy (SEM). X-ray photoelectron spectrum (XPS) study was carried out for surface analysis. The relative performance of pure Zn, monolithic and CMA coatings were compared and discussed. © 2010 Springer Science+Business Media B.V.
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Keywords
Cathode current density, Corrosion behavior, Corrosion studies, Current pulse, ELectrochemical methods, Electrolytic preparation, Mild steel, Multi-layer-coating, Multi-layered, NaCl solution, Number of layers, Optimal number, Peak performance, Relative performance, Sectional views, SEM, Single bath, Sulphanilic acid, Switching current densities, X ray photoelectron spectra, Zn-Ni alloy, Acids, Alloys, Atomic force microscopy, Carbon steel, Corrosion rate, Corrosion resistance, Corrosive effects, Current density, Cyclic voltammetry, Electric properties, Electrochemical corrosion, Electrochemical impedance spectroscopy, Electrochemical properties, Magnetrons, Metal cladding, Multilayers, Optimization, Scanning electron microscopy, Sodium chloride, Surface analysis, Surface morphology, X ray photoelectron spectroscopy, Zinc, Zinc alloys, Coatings
Citation
Journal of Applied Electrochemistry, 2010, 40, 11, pp. 2051-2059