Investigation of hardness, microstructure and anti-corrosion properties of Zn-ZnO composite coating doped unripe plantain peel particles

Abstract

The use of mild steel for several engineering applications despite its vulnerability to degradation on exposure to environmental contaminants has called for the incessant search for durable materials that can reliably protect its surface. This paper examined the hardness, microstructure and anti-corrosion properties of Zn-ZnO composite coating doped with unripe plantain peel (UPP) particles. The hardness of the coatings was examined using the Brinell hardness technique, while the anti-corrosion properties were studied employing potentiodynamic polarization technique, using 3.65% NaCl solution (simulated seawater) as the test medium. The microstructure properties were investigated using SEM/EDS and XRD. The results of the experiment show that the as-received mild steel exhibited the hardness and corrosion rate of 136.8 kgf/mm2 and 8.6272 mm/year, respectively, while the Zn-ZnO coated mild steel exhibited hardness and corrosion rate of 254.6 kgf/mm2 and 3.0954 mm/year, respectively. The optimal performing Zn-ZnO-UPP coated mild steel exhibited a hardness and corrosion rate of 260.3 kgf/mm2 and 1.5290 mm/year, respectively. This indicated that the UPP particles further enhanced the strengthening (binding force at the steel/coating interface) and the passivating tendency of Zn-ZnO coating. More so, the SEM images revealed that the Zn-ZnO-UPP coating exhibited a more refined microstructure than the Zn-ZnO coating, indicating the grain refining ability of the UPP nanoparticles. The XRD profile of the coatings exhibited high intensities, indicating good texture, high stability, chemical and microstructural homogeneity. These improvements in properties indicated that the Zn-ZnO-UPP coating can be used for the protection of mild steel components in marine environments.