Preparation of Expansive Ceramic Coating on Magnesium Alloy at Room Temperature and Flame Retardant Mechanism at 1100 ℃

Advanced magnesium alloys with light weight and high strength have been widely used in aerospace industry and hydrogen storage and transportation. However, magnesium alloys have certain safety risks, due to their active chemical properties and low ignition point. These characteristics make them susceptible to potential explosions and deflagrations. Therefore, in response to the limitations of magnesium alloys for current thermal protection technology, we developed an expansive ceramic heat insulation coating that can be applied through integrated spraying at room temperature. The flame retardant performance and mechanism of the coating have been systematically studied. The coating demonstrates an expansion rate up to 300%, effectively reducing the back temperature to below 500 ℃. Additionally, the coating exhibits a mass loss rate ranging from 30% to 40%, maintaining a wreckage strength of 110-190 kPa. When subjected to flame ablation at 1100 ℃, the expansive ceramic heat insulation coating shows exceptional flame retardant and thermal insulation capabilities, without degradation in mechanical strength. The incorporation of expanded carbon layer and expanded graphite introduces a multi-scale pore structure in the coating, which effectively hinders the conduction of heat and oxygen. Furthermore, the dense and robust structure formed owing to the exceptional mechanical properties and self-healing properties of MoAlB (MAB) phase significantly enhances the wreckage strength. Such coating demonstrates outstanding comprehensive flame retardancy even in extreme environments.