Effect of Mechanical Agitation on Cr-Al<sub>2</sub>O<sub>3</sub> Nanocomposite Coatings Fabricated from Trivalent Chromium Electrodeposition

Abstract

In the present work, Cr-Al2O3 nanocomposite coatings were electrodeposited onto a copper substrate using a modified trivalent chromium electroplating bath with the addition of 80nm Al2O3 powder. The effects of mechanical agitation of electrodeposition bath on Al2O3 particles dispersion and particles embedment were studied. The Cr-Al2O3 nanocomposite samples were subjected to different tests to characterize their surface morphology, crystalline structure, and mechanical properties. The crystalline structure, composition and surface morphology of the deposits were studied by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FESEM). The corrosion resistance test was carried out by electrochemical polarization method. The microhardness was studied via Vickers Microhardness Test. The variation in the microhardness as a main property to achieve enhancement of Al2O3 incorporations with Cr matrix. From the EDX analysis, Cr-Al2O3 nanocomposite deposited at 200 rpm stirring speed showed the highest weight percentage (wt%) of alumina. The hardness results showed the Cr-Al2O3 composite coating has the best performance at 200 rpm stirring speed which the hardness increased 32.3 % compared to that of Cr coating. The corrosion current density (icorr) of Cr-Al2O3 coating achieved highest value at 200 rpm. This result revealed that the corrosion resistance of Cr-Al2O3 coating decreases with increasing Al2O3 particles content.