Intensified metallic effect and improved tribocorrosion resistance through microwave-based fabrication of metallic powder coatings

In this paper, metallic powder coatings (MPC) were investigated as base powder coatings incorporating metallic flakes, providing finishes with a sparkly metallic effect. While MPC offers environmental advantages over liquid coatings by eliminating the usage of solvents, it presents challenges in achieving an intensified and stable metallic effect required by high-end products. This is primarily due to the limitations of the friction-based bonding technique, such as non-selective heating, employed in the current commercial production of MPC. To address this challenge, a microwave-based bonding method was developed that utilizes microwave energy as the heating source instead of stirring friction. This innovative approach leverages the selective heating properties of microwaves to produce qualified MPCs suitable for high-end products. Compared to the current friction-based method with a heating rate of approximately 4 ∘ C/min, microwave heating achieved a significantly faster heating rate of approximately 16 ∘ C/min, owing to the interface polarization effect. The microwave heating engendered a heightened efficacy in forging bonds between coating particles and Al flakes. As a consequence, in scenarios where equal weight percent of Al flakes was introduced, the microwave-treated specimens evinced a stronger metallic effect and enhanced stability compared to friction-heated ones. Furthermore, three-dimensional images of the Al flakes in the coating confirmed that microwave-heated films manifested an elevated flip-flop effect. Tribocorrosion test outcomes underscored that microwave-heated films exhibited higher open circuit potentials (OCP), indicating superior corrosion resistance, alongside better wear resistance compared to friction-heated ones. The microwave-based method obtained stronger and more stable MPCs with better corrosion and wear resistance, showing the promising potential for the expansion of MPC applications into the domain of high-end commodities.