STUDY OF Zn-Ni ALLOY COATINGSMODIFIED BY NANO-AL2O3 PARTICLES INCORPORATION

Abstract

Zn–Ni–Al2O3 nano-composite coatings were electrodeposited on mild steel using a novel sol enhanced electroplating method. The effect of alumina sol on the electrodeposition process, and coating properties was investigated using, X-ray diffraction, scanning electron microscopy (SEM), measurement of microhardness and chronoamperometry and electrochemical impedance spectroscopy were studied in a solution of 3% NaCl. The results indicated that the electro-crystallization processes of Zn–Ni and Zn–Ni–Al2O3 were governed by a three-dimensional nucleation process controlled by diffusion. XRD results showed that the phase structure of both alloy and composite coatings was single Ni5Zn21-γ phase, and the addition of alumina sol in the Zn-Ni matrix increases the microhardness, and we note the maximum hardness is obtained for 50 g/L Al2O3. Conversely, these coatings showed smaller crystallite size and Surface of coatings was uniform and compact, the values of Rct and Zw increase, while the values of Cdl decrease with increasing alumina nano-particles content values for the Zn–Ni– Al2O3 alloy clearly confirm the better corrosion resistance.