The effect of electrolysis on graphite fiber-polymer matrix composites used as electrodes in a simulated seawater electrolyte was studied with interest in the impact of several composite construction variables. It was found that the electrochemical behavior is a function of the matrix polymer as well as the fiber orientation. Cathodic performance was found to be stable, while anodic performance was not. Anodic behavior was not singularly dominated by oxidation of the graphite but was affected by geometric considerations caused by the differing orientations of the fibers as well as the result of the fibers being incorporated into a polymer matrix.The ac electrochemical disinfection of ion-conducting liquids is an electrolysis process which generates a species lethal to micro-organisms (1, 2). Since this technology utilizes a modified alternating current and voltage, a limitation is placed on the type of material which can be employed as an electrode. On initial analysis, graphite appears to be an ideal material for this process; it possesses good electrical conductivity; demonstrates good chemical resistance, has low chlorine and oxygen overpotentials, and produces a volatile oxidation product which consumes no electrical energy upon repolarization. Efforts to improve the electrochemical performance and structural stability of bulk graphite electrodes has led to the investigation of graphite fiber-polymer matrix composites as possible electrode materials (3, 4). A preliminary screening of various polymer composite systems indicated that certain materials were superior to bulk graphite in this application while others failed miserably. A thorough understanding of composite performance under anodic, cathodic and, eventually, ac conditions is therefore required to properly characterize these materials. This paper is concerned with the electrochemical stability of five composite systems during dc electrolysis.Carbon has three allotropic forms: carbon, graphite, and diamond. Both carbon and graphite are used extensively in commercial electrochemical applications, including battery electrodes, fuel cells (hydrogen anodes and air cathodes) (5-8), industrial electrolytic processes (9) and in counterelectrodes for corrosion control of various structures. Carbon has also gained popularity as indicator electrodes in cyclic voltammetry (10-12). In spite of the importance of carbon in these various applications, its electrochemical properties until recently have received little attention and are not particularly well understood.The microstructures of carbon materials vary widely. There are several hundred grades of commercial carbons and graphites available and though each is composed almost exclusively of carbon atoms, each possesses quite distinctive properties. In many cases, these properties are determined by the microstructure which in turn is determined by the precursor and processing conditions.The structural basis of nearly all carbonaceous materials is the layer plane of carbon atoms which forms the hexagonal...