Electrodeposition of ternary Zn–Ni–Sn alloys from an ionic liquid based on choline chloride and their characterisation

Abstract

Ternary Zn–Ni–Sn alloy coatings with a range of compositions were potentiostatically electrodeposited on steel substrates from a deep eutectic solvent-based electrolyte. The effect of electrodeposition potential on the morphology, chemical and phase compositions, and corrosion behaviour of the deposits was analysed. The co-deposition mechanism of Zn–Ni–Sn alloys was found to be normal whereby increasing the electrodeposition potential enhanced the ternary alloy Zn content (active element) and greatly suppressed the alloy Sn and Ni content (noble elements). The X-ray diffraction phase analyses showed that Ni in the deposits exists in the form of metal compounds including β-Ni₃Sn₂ as well as γ-NiZn₃. The improved corrosion resistance observed in all ternary alloys was attributed to their compact morphology, phase content and chemical composition. Comparison of corrosion performances shows that ternary Zn–Ni–Sn alloys are superior for sacrificial corrosion protection of steel metallic substrates compared to binary Zn–Sn and Zn–Ni alloys.

Keywords:

• Electrodeposition
• Deep eutectic solvent
• Zn–Ni–Sn alloy
• Corrosion resistance

Acknowledgement

We would like to thank the Department of Materials Science and Technology, Harare Institute of Technology, Harare, Zimbabwe for providing experimental facilities.