This chapter opens by discussing the the need for accelerated testing and the role of carbon in reducing the cost of PEM and PAFC fuel cells. Equation 11.1 describes the electrochemical conversion of carbon and water to CO2 and points to graphitization of the carbon to reduce the carbon activity. The oxidation potential is defined, reported for selected samples and used in a simplified Butler-Volmer equation (11.2) to quantify the kinetically controlled carbon corrosion rate. This equation also shows the carbon surface area exposed to electrolyte directly proportional to the carbon corrosion rate and the possible use of the water partial pressure as an acceleration factor. Experimental design and three generations of testing are discussed, culminating in out of cell hardware that exposes separator plates to the actual conditions important in degrading the component. “Equivalent stack operation hours” is used as the time scale to present weight loss data as a function of time at potential. 200 KW power plant fleet durability is presented and it documents the utility of this accelerated testing approach.