Development of UPP Nanoparticles reinforced Zn-ZnO-MgO Composite Coating for Corrosion-resistance, Hardness and Microstructure Properties Enhancement of Mild Steel for Advanced Applications

Abstract The numerous industrial application of mild steel despite its susceptibility to degradation on exposure to the environment has called for the continuous search for materials that can protect its surface from contaminants which could affect its inherent properties. This paper therefore examined the corrosion-resistance, hardness and microstructure properties of unripe plantain peel (UPP) nanoparticles reinforced Zn-ZnO-MgO composite coatings deposited on the surface of mild steel. The corrosion properties of the coated steel samples were investigated using the potentiodynamic polarization technique, utilizing simulated seawater (3.65% NaCl solution) as the test medium. The hardness of the coated steel samples was studied using the Brinell hardness method, while the microstructure properties were investigated using XRD and SEM/EDS. The as-received mild steel sample was observed to exhibit a hardness value and corrosion rate of 136.8 kgf/mm2 and 8.6272 mm/year, respectively, while the Zn-10ZnO-10MgO coated mild steel sample exhibited a hardness value and corrosion rate of 246.5 and 1.7698 mm/year, respectively. Relative to the other samples, the Zn-10ZnO-10MgO-6UPP coated mild steel (sample coated with 10 g/L of ZnO, 10 g/L of MgO and 6 g/L of UPP) exhibited a highest hardness value and lowest corrosion rate of 254.8 kgf/mm2 and 0.6645 mm/year, respectively. These corrosion rate and hardness values of the Zn-10ZnO-10MgO-6UPP coated mild steel sample showed that the unripe plantain peel nanoparticles further enhanced the strengthening and passivating ability of Zn-ZnO-MgO-UPP coating. The SEM micrographs revealed that the Zn-ZnO-MgO-UPP coating possessed a more refined microstructure relative to the Zn-ZnO-MgO coating, signifying the grain refining ability of the unripe plantain peel nanoparticles. The EDS additionally indicated the occurrence of crucial and dispersion strengthening elements in the coatings. The XRD profile of the coatings exhibited high intensities, which signified that the coatings have high stability, good texture with microstructural and chemical homogeneity.