A phosphate-based antioxidation coating for carbon/carbon composites

Four kinds of phosphate antioxidative coatings with different compositions were prepared using a slurry brushing method, and were characterized by weight loss kinetics, thermal cyclic performance and seawater immersion tests. Changes in the microstructure of the coating before and after oxidation were also characterized using SEM and XRD. Results show that the antioxidative properties of a coating are determined by the self-healing, compactness, adherence, and chemical inertness of the coating, which are all determined by the composition. The weight loss kinetic study under oxidative conditions show that between 600 and 700°C, the oxidation is controlled by kinetics with an activation energy of 139 kJ/mol. Between 700 and 800°C, the oxidation is controlled by diffusion with an activation energy of 93 kJ/mol.