Thermal spraying and adhesion of oxides onto graphite

Surface treatment of graphite (Cg), which is based on thermal spraying of o xides (Al2O3, ZrO2), is proposed to reduce graphite reactivity and permeabi lity toward oxygen. The study of coating adhesion allows recognition of the parameters that fav or mechanical and chemical bonds. It also indicates the pretreatment of gra phite, which leads to Cr3C2 or SiC bond coats. Different graphite-oxide sys tems mere examined and showed that adhesion particularly depends on the the rmal expansion coefficient mismatch between Cg, oxide, and the bond coat. Therefore, a post-treatment based on an impregnation with enamel of the por ous oxide is essential to obtain effective protection of the graphite again st the external environment.