Influence of Zn-Ni alloy electrodeposition techniques on the coating corrosion behaviour in chloride solution

The aim of this research work is to optimize the plating conditions during electrodeposition of Zn-Ni alloys. Electrodeposits of Zn-Ni alloys have been synthesized from sulphate bath using cyclic voltammetry and chronopotentiometry techniques under different conditions. X-ray diffraction measurements reveal that the alloys consisted of < gamma >-Ni5Zn21 and pure zinc phases. The composition and morphology of the deposits have been also studied and discussed. The surface analyses indicate that the deposition took place with the formation of Zn-Ni alloy coatings, containing at least 10 wt.% Ni. In order to obtain better barrier properties and corrosion resistance, coated steel samples have been immersed in 3% NaCl solution and studied using potentiodynamic stripping and electrochemical impedance spectroscopy. The process of dezincification is reduced when the coated steel is electroplated by chronopotentiometry (5 mA and 10 mA). In addition, these samples exhibit an improved morphology and fine grain size as compared with deposits electroplated by cyclic voltammetry. (c) 2009 Elsevier B.V. All rights reserved.