A method of inhibiting oxidation of a porous carbon-carbon composite is disclosed and comprises the steps of: (a) contacting the carbon-carbon composite with an oxidation inhibiting composition comprising phosphoric acid or an acid phosphate salt, at least one aluminum salt, and at least one additional metal salt, the oxidation inhibiting composition penetrating at least some of the pores of the carbon-carbon composite; and (b) heating the carbon-carbon composite at a temperature sufficient to form a deposit from the oxidation inhibiting composition within at least some of the penetrated pores of the carbon-carbon composite. The foregoing oxidation inhibiting composition and carbon-carbon composites treated by the foregoing method are also disclosed.