INFLUENCE OF CURRENT DENSITY ON MORPHOLOGY AND ROUGHNESS OF SONOELECTRODEPOSITED Zn-Co-Al2O3 NANOCOMPOSITE COATINGS

Nanocomposite Zn-Co-Al2O3 coatings were electrodeposited from three different solutions, at 1, 2, 4 and 6A/dm2 current densities. Electrodeposition time was same for all samples, 15 minutes. Steel plates were used as cathodes while the anode was made of 99.99% pure zinc. All samples were mechanically and chemically prepared before electrochemical deposition of the Zn-Co-Al2O3 nanocomposite coating. Electroplating solutions were prepared from the chemicals of p.a. purity and aluminium oxide nanoparticles. All solutions possesed the same chemical composition, they differed only in the concentration of Al2O3. Solution R1 was without Al2O3, while solutions R2 and R3 contained 2g/dm3 and 5g/dm3 Al2O3, respectively. All experiments were performed in an electrochemical cell, with a volume of 100cm3 at room temperature and atmospheric pressure. The surface of the obtained coatings was examined by Leica EZ4 HD optical microscope at a 100x magnification, while the roughness was measured by TR200 device. Based on the obtained results, it can be concluded that the thickness of the obtained Zn-Co-Al2O3 coatings depends on the current density, but also on the composition of the solution. With increasing current density, the thickness of the coating increases, as well as the roughness of the deposited coatings, while the current utilization decreases with increasing current density, no matter of plating solution composition. The morphology of the coatings was generally uniform and compact with good adhesion.