The oxidation behaviour of carbon/carbon composites, with the addition of various inhibitors, has been studied using thermodynamic analysis and microscopy. The effects of ZrB2, B, SiE(4), tetraethylorthosilicate (TEOS), tributylphosphate (TBP) and additions of treatment with H3PO4 were compared using L(8) orthogonal array table and analysed by the ANOVA-TM program.