The graphite plate is easily suffered from corosion because of CO2 evolution when it acts as the positive electrode for vanadium redox flow battery. The aim is to obtain the initial potential for gas evolution on a positive graphite electrode in 2 mol dm(-3) H2SO4 + 2 mol dm(-3) VOSO4 solution. The effects of polarization potential, operating temperature and polarization time on extent of graphite corrosion are investigated by potentiodynamic and potentiostatic techniques. The surface characteristics of graphite electrode before and after corrosion are examined by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The results show that the gas begins to evolve on the graphite electrode when the anodic polarization potential is higher than 1.60 V vs saturated calomel electrode at 20 degrees C. The CO2 evolution on the graphite electrode can lead to intergranular corrosion of the graphite when the polarization potential reaches 1.75 V. In addition, the functional groups of COOH and C=O introduced on the surface of graphite electrode during corrosion can catalyze the formation of CO2, therefore, accelerates the corrosion rate of graphite electrode. (C) 2011 Elsevier Ltd. All rights reserved.