During the voltammetry of carbon supports for proton exchange membrane fuel cells (PEMFCs), including commercial carbon blacks, graphitized carbon black and multi-wall carbon nanotubes (MWNTs), in deaerated 0.5 M H2SO4 solution results in mass changes as observed by using in situ electrochemical quartz crystal microbalance (EQCM). The mass change and corrosion onset potential during electrochemical carbon corrosion indicate that oxides are formed and accumulated on the carbon surface, leading to an increase in mass. A decrease in the mass is associated with carbon loss from the gasification of carbon surface oxides into carbon dioxide. High BET surface area carbon blacks ECP600 and ECP 300 have a carbon loss of 0.0245 ng cm(-2) s(-1) and 0.0144 ng cm(-2) s(-1) and as compared to 0.0115 ng cm(-2) s(-1) for low surface area support XC-72 and so they are less resistant to corrosion. Graphitized XC-72 and MWNTs, with higher graphitization have higher carbon corrosion onset potential at 1.65 V and 1.62 V and appear to be more intrinsically resistant to corrosion. (c) 2010 Published by Elsevier B.V.