The corrosion stability of a series of carbon supports of various porous structure and morphology: commercial carbon blacks, carbon–carbon composite, and multiwall carbon nanotubes was studied using start-stop protocol cycling (1–1.5 V vs reversible hydrogen electrode (RHE) potential range with 0.5 V/s of scan rate) in an electrochemical cell at 25 °C using 0.1 M HClO4 as electrolyte. Two stability regions were revealed for the first time depending on the cycle number. The first one is characterized by a constant value of quinone/hydroquinone (QH) transition potential. In the second part anode and cathode QH peaks gradually shift toward higher and lower potentials respectively, which is due most likely to a complete degradation of the supports. We proposed an effective resistance (Reff) as the corrosion stability parameter that can be easily obtained from the cyclic voltammetry (CV) data. Based on these results, a model of corrosion of porous carbon materials supported on glassy carbon rod was proposed. It was shown that the decrease in the Reff of the samples in the initial stages of degradation is due to the increase in the number of QH groups on the surface, while a sharp increase in the Reff upon further cycling can be explained by a decrease in the number of contacts between the carbon grains.