Effect of Electrodeposition Parameters on Chemical Composition, Cathodic Current Efficiency, Hardness and Morphology of Zn-Ni Alloy Coatings

مهندسی متالورژی و مواد

Article 5, Volume 29, Issue 2 - Serial Number 18, November 2018, Pages 103-114   

Document Type: Original Articles

DOI: 10.22067/ma.v0i29.47786

Authors

Mahshid Tafreshi¹; Saeed Reza Allahkaram^{* 2}; Hassan Farhangi³

¹Islamic Azad University South Tehran Branch

²College of Engineering, University of Tehran

³University of Tehran

Abstract

Zn–Ni alloy coatings were electrodeposited from acidic sulphate baths. In this study, the effect of plating parameters and bath composition on the cathodic current efficiency, as well as hardness, morphology and chemical composition of the coatings were investigated. The morphology and chemical composition of the coatings were investigated using scanning electron microscopy equipped with EDAX analyzer. Results showed that surface morphology and chemical composition of the films were strongly dependent on the electrodeposition parameters. Ni content and hardness of the coatings were increased and the cathodic current efficiency was decreased by enhancing the bath temperature and Zn (II)/Ni (II) ratios, or reducing the current density and bath pH. Electron microscopy images showed that cracks appeared on the coatings surface with increasing temperature due to the high residual stress. In addition, the structure of the coatings became finer with increasing the current density, resulting in the formation of voids and porosities. Studies on the bath pH revealed that only the coatings which were deposited in baths with pH=2 had a dense and uniform surface. Moreover, increasing the Zn (II)/Ni (II) ratios in the bath caused brittleness of the coatings.

Keywords

Zn-Ni Alloy Coating; chemical composition; morphology; Cathodic Current Efficiency; Hydrogen Evolution

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