The Effect of Electrodeposition Current Density on Corrosion Behaviour and Microstructure of Nanostructured Ni Coating Electrodeposited from Deep Eutectic Solvent Containing Residual Water on Medium Carbon Steel
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Abstract
Environmentally friendly choline chloride/ethylene glycol-based deep eutectic solvent containing 0.2 M NiCl 2 •6H 2 O was employed to produce Ni coatings through pulse electrodeposition at different current densities of 2-30 mA cm -2 on AISI 1045 medium carbon steel. The effect of the current density on the microstructure, surface texture, and consequently and corrosion properties were studied. Granular growth-pattern covered by nano-sized platelets were developed on the surface at electrodeposition current densities of 2-16 mA cm -2 . Formation of NiO and Ni(OH) 2 along with metallic Ni was detected at the surface of the coating using X-ray photoelectron spectroscopy. Dominating factors, controlling corrosion mechanism, such as compactness, composition, layer thickness, and permittivity, as well as surface texture varied with the range of electrodeposition current density from 2-4 mA cm -2 to 8-16 mA cm -2 . Corrosion mechanism changed from localized to general by increasing the electrodeposition current density from 4 to 8 mA cm -2 . Removing the Ni surface texture for coatings prepared at 8 mA cm -2 , resulted in localized corrosion, namely pitting corrosion showing that the roughness developed during the electrodeposition from the DES is beneficial to corrosion protection.