Bhat, R.S.Hegde, A.C.2026-02-052011Surface Engineering and Applied Electrochemistry, 2011, 47, 2, pp. 112-11910683755https://doi.org/10.3103/S1068375511020141https://idr.nitk.ac.in/handle/123456789/27266Cyclic multilayer alloy (CMA) deposits of Zn-Ni were developed on mild steel from sulphate bath having thiamine hydrochloride (THC) and citric acid (CA) as additives. CMA coatings were developed galvanostatically using triangular current pulses, under different conditions of cyclic cathode current density (CCCD's) and number of layers. The corrosion behaviors of the coatings were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy methods, and were compared with that of monolayer Zn-Ni alloy of same thickness. At optimal configuration, CMA coating represented as, (Zn-Ni)<inf>2.0/5.0/300</inf> was found to exhibit ?40 times better corrosion resistance compared to monolayer alloy, (Zn-Ni)<inf>3.0</inf>. Cyclic voltammetry study demonstrated that THC and CA have improved the appearance of the deposit by complexation with metal ions. The corrosion protection efficacy of CMA coatings was attributed to the difference in phase structure of the alloy in successive layers, evidenced by XRD analysis. The formation of multilayer and corrosion mechanism was analyzed by Scanning Electron Microscopy (SEM) study. © 2011 Allerton Press, Inc.Cathode current densityCorrosion behaviorCorrosion mechanismsMild steelNano-structuredNumber of layersOptimal configurationsSEMSulphate bathThiamine hydrochlorideTriangular currentXRD analysisZn-Ni alloyAlloysCarbon steelCitric acidCorrosion resistanceDepositsElectrochemical corrosionElectrochemical impedance spectroscopyMetal ionsMonolayersMultilayersProtective coatingsScanning electron microscopySpectroscopic analysisVelocity measurementZincZinc alloysCyclic voltammetry