Microstructure and corrosion behaviour of ZnNiP thin film alloys in deep eutectic solvent ionic liquids

Abstract

Ternary ZnNiP alloy thin films were electroless deposited from aqueous chloride electrolytes on mild steel foils. The films were characterized by scanning electron microscopy (SEM) and dispersive X-ray microanalysis (EDAX). The corrosion behaviour of ZnNiP thin films alloys was investigated in two deep eutectic solvent ionic liquids (DES) with different chemical structure at 353K and compared with corrosion in 3.5% NaCl aqueous solution at 273K. The films were characterized by X-ray photoelectron spectroscopy (XPS) to determine their chemical composition in the initial stage and after corrosion. The nature of corrosion morfology has been investigated by and electron microscopy and XPS. The value of the lowest corrosion protection efficiency was of 48.14% and the highest value was of 77.96%. The results confirmed the high corrosion resistance of ZnNiP alloy plated sheet in all ionic liquids systems tested and the results were corelated with corrosion data in aqueous solution. The passive layer consists of Zn and Ni oxides but also of the chemical compounds of nitrogen which were formed on the surface of the ZnNiP thin films during the corrosion process.