Corrosion behavior of carbon fibers and graphitized carbon fibers in hot phosphoric acid

It became clear that carbon fibers exhibited different graghitizability eve n treated at the same temperature depending on their precursor,and highly g raphitized carbon fibers had high corrosion resisitibility in hot phosphori c acid. Therefore, it was concluded that the corrosion resisitibility of th e PAFC electrode substrate in the hot phosphoric acid can be improved by us e of highly graphitizable carbon fiber as a raw material. Under a mild corr osion condition, graghitizability of the fiber surface was important for im proving corrosion resisitibility. Results showed that the corrosion of the carbon fiber occurred from a part of low graphitizability of the surface, a nd the carbon surface layer was converted to oxidized carbon compounds. In addition, specific surface area of the carbon fibers increased by corrosion to form micropores or surface roughness showing the extent of such changes depended greatly upon the graghitizability of the carbon fiber.