Microstructural evolution and characterization of super-induced MgO composite on zinc-rich coatings

AbstractThe effect of Zn-MgO deposition prepared through direct electrolytic co-deposition on mild steel was studied. The experiment was conducted at current density between 0.5 and 1 A/cm−2. The morphologies of the coated surfaces were characterized using Atomic Force Microscope (AFM), high resolution Nikon Optical Microscope (OPM) and Scanning Electron Microscopy attached with Energy Dispersive Spectrometer (SEM/EDX). The corrosion behavior was studied using linear potentiodynamic polarization method in 3.5% simulated environment. The phase change was evaluated using X-ray Diffractogram (XRD). The microhardness characteristics of the obtained deposits were analyzed with dura scan hardness tester. The stability of the ceramic composite was determined using heat-treatment processes at 200 oC for 4 h. The results show that the structural behavior and corrosion resistance of the coating is dependent on the composite induced particulate and applied current density. It is found that increasing MgO contents beyond optimum level does not cause increase in microhardness progression. A decrease in applied current maximally influences the deposit adhesion characteristics. The enhanced thermal stability of 236.4 HVN for Zn-20MgO at 0.5 A/cm2 alloy and increase corrosion behavior was thus attributed to its chemical composition, phase content and the synergistic effect of Zn and MgO on the carbon steel