The Electrodeposition of Amorphous/Nanocrystalline Ni–Cr Alloys from ChCl–EG Deep Eutectic Solvent

Abstract

The electrodeposition of Ni–Cr alloy was studied in choline chloride-ethylene glycol deep eutectic solvent (ChCl–EG DES) containing NiCl2·6H2O and CrCl3·6H2O. Voltammetric analysis reveals that the presence of Ni(II) ions can promote the deposition of Cr to form Ni–Cr alloy. Electrodeposited Ni–Cr alloy coatings were characterized by EDS, XRD, SEM and HR-TEM. It was found that the deposition potential and metal ion concentration ratio (CNi(II)/CCr(III)) play a central role in controlling the composition and surface morphology of the resultant Ni–Cr alloy coatings. Increasing the deposition potential and higher CNi(II)/CCr(III) ratio is favorable to increase the Cr content of alloy coatings. The structure of Ni–Cr alloys is strongly depended on the Cr content. It changes from a nanocrystalline fcc Ni(Cr) solid solution to amorphous phase (metallic glass) when the Cr content in the alloys increases from 7.3 at% to 14.7 at%. The amorphous Ni–Cr alloy coating (25.2 at% Cr) obtained in DES (CNi(II)/CCr(III) = 1:6) at −0.90 V exhibits the highest resistance, which is superior to pure chromium sheet.