Evolution of physical and mechanical characteristics of deposited composite coatings on A356 mild steel

This research investigated the development of Zn-SnO 2 /Zn-Al 2 SiO 5 thin film on A356 mild steel using the electrodeposition technique. The developed coating was attained in 2.0 V for 10 min at a constant current density of 1.5 A/cm 2 . The electroplating process was maintained at a constant stirring rate of 250 rpm, temperature of 45 °C, 10 g of SnO 2 was used for the bath while Al 2 SiO 5 was varied from 5 to 15 g. The surfaces of coated samples were characterized using a scanning electron microscope (SEM). The effects of 3.56% NaCl on the coated and uncoated sample were examined via the potentiodynamic polarization technique, employing Autolab PGSTAT 101 Metrohm potentiostat with NOVA software of version 2.1.2. The outcome of the experiment revealed that the electrodeposited Zn-SnO 2 /Zn-Al 2 SiO 5 exhibits better stability, improved microhardness, excellent microstructural qualities, and outstanding corrosion resistance. The Zn-10SnO 2 -15Al 2 SiO 5 -coated steel exhibits the lowest corrosion rate of 0.0473 mm/year, representing 99.32% reduction in corrosion rate compared to the uncoated sample. Similarly, a corrosion current density (jcorr) value of 20.5 μA/cm 2 was recorded for the uncoated sample which is much greater than the jcorr of the coated samples. This shows that the coating minimizes the exchange of current within the steel. The hardness value of the Zn-10SnO 2 -15Al 2 SiO 5 -coated steel was higher than other coated samples and 17.51% higher than the uncoated steel, and this indicates improvement in the mechanical property of the steel.