ORIGINAL PAPER Electrolytic preparation of cyclic multilayer Zn–Ni alloy coating using switching cathode current densities K. Venkatakrishna • A. Chitharanjan Hegde Received: 2 April 2010 / Accepted: 5 September 2010 / Published online: 18 September 2010 Ó Springer Science+Business Media B.V. 2010 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 coat- ings, 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 electro- chemical 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 con- figuration 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 Elec- trochemical 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. Keywords Multilayered Zn–Ni alloy  Switching current densities  Corrosion study 1 Introduction Recently, electrodeposition of composition modulated multilayered alloys (CMMA) of Zn–M (where M = Fe group metals like Ni, Co and Fe) has received more attention in surface engineering because of their excellent corrosion resistance, increased mechanical strength and micro hard- ness etc. [1, 2]. Codeposition of two metals requires that their individual reversible potentials are reasonably close to each other in the specific bath. This is the case when their standard potentials are close, when the concentration of one of the metals in solution is properly tuned, or when com- plexing agent that forms complexes with different stability constants is added. Eliaz and Gileadi [3] have recently reviewed the principles of alloy codeposition and the phe- nomenon of anomalous codeposition (ACD) in the frame work of a more comprehensive review of induced codepo- sition. The term anomalous codeposition was coined by Brenner [4] to describe an electrochemical deposition pro- cess in which the less noble metal is deposited preferentially under most plating conditions. This behavior is typically observed in codeposition of iron group metals or in code- position of iron group metal with Zn [5, 6]. There are two major ways to produce CMA electrode- posits. One of which is the dual bath technique (DBT), and other one is single bath technique (SBT) [7, 8]. The DBT involves the deposition of constituents from two separate plating baths in an alternate manner. Any combination of layers can be formed, provided that each can be individually deposited, and very thin metal or alloy films can easily be formed. However, DBT has some drawbacks. First it is K. Venkatakrishna  A. Chitharanjan Hegde (&) Electrochemistry Research Laboratory, Department of Chemistry, National Institute of Technology Karnataka, Srinivasnagar 575 025, India e-mail: achegde@rediffmail.com 123 J Appl Electrochem (2010) 40:2051–2059 DOI 10.1007/s10800-010-0186-7