Formation of Protective Coatings on Graphite by a Microspark Oxidation Method

Models, mechanisms, and criteria of formation of protective coatings on graphite by a microspark oxidation method (MSO) are considered. It is established that a prerequisite for the graphite MSO is the deposition of a barrier film of a valve metal oxide at the graphite surface. Optimum regimes of the graphite MSO in aqueous solutions of sodium aluminate are determined. Protective coatings on graphite comprising α-phase aluminum oxide are obtained. It is concluded that the graphite MSO should be viewed as a version of MSO of metals, which involves the electrochemical deposition (at high voltages that cause the anode to microspark) of oxide films consisting of electrolyte components on graphite, as opposed to a version of MSO of metals, which involves the formation of an anodic film consisting of electrolyte components and the intrinsic oxide.