Abstract
This review paper studied the potential of using metal oxides as a green corrosion inhibitor for different alloys in various aggressive corrosive environments. Metal oxides are widely used for various applications such as sensors, environmental remediation, nanoelectronics devices, solar cells, biomedical applications and clean energy production due to their unique electronic structure. Metal oxides exhibit low corrosion inhibition efficiency when used as corrosion inhibitors in bulk form but attain significantly higher inhibition efficiencies when used in nanostructured form. Increasing the concentration of the metal oxides significantly reduced the corrosion rate and enhanced the corrosion inhibition efficiency for various samples studied under different operating conditions due to the increased surface area to volume ratio as well as the enhanced adsorption of the oxides onto the surface of the substrates, thereby reducing the corrosion rate by decreasing the available sites for the dissolution reaction. However, the challenges of agglomeration and poor dispersion of nanoparticles were frequently reported at higher concentrations which contributed to observed reduced efficiencies. Barrier protection, electro-chemical inhibition, synergistic interactions with other inhibitors, self-healing properties, adsorption and passivation have been widely reported as the mechanism by which metal oxides protect the various substrates studied. The chemical and thermal stability of metal oxides in aggressive salt environments is a comparative advantage over other traditional organic and green inhibitors. The various methods of synthesis and characterization of metal oxide nanoparticles as well as their cost and associated safety and environmental concerns have also been discussed.