Evaluation of corrosion resistance of electrodeposited nanocrystalline Ni–Fe alloy coatings

Abstract

Nickel–iron alloys with a compositional range of 24–80 wt-% iron were electrodeposited on a copper substrate from a sulphate-based bath and using a stirring rate of 100 rev min⁻¹. The effect of applied current density and Ni²⁺/Fe²⁺ metal ion ratio of plating bath on the properties of alloy coatings was examined. Crystal structure and grain size of Ni–Fe alloy coatings were investigated using X-ray diffraction technique. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy were used to analyse the surface morphology and chemical composition of coatings. Microhardness test was applied to evaluate the hardness of the coatings. Finally, the electrochemical behaviour of the Ni–Fe alloy coatings was studied by a polarisation test in 10 wt-% H₂SO₄ solution. Results revealed that current density and plating bath composition had a strong effect on the characteristics of coatings. As the iron content of alloys produced increased, their corrosion resistance improved with the best corrosion resistivity being achieved at a metal ion ratio of 0.5 and applied current density of 2.5 A dm⁻².

Keywords:

• Electrodeposition
• NiFe alloy
• FeNi₃
• Nanocrystalline structure
• Corrosion
• Microhardness