The effects of gaseous oxygen on the corrosion behaviour of platinum-free and platinum-dispersed Vulcan XC-72 carbon electrodes in 85% $H_3PO_4$ solution at 145℃ have been investigated by using linear sweep voltammetry and fourier transform infrared spectroscopy at room temperature. Linear sweep voltammetry experiments were made in 1M $H_3PO_4$ solution in the applied potential range from -300 to $1200mV_SCE$ at a scan rate of $100mVs^{-1}$ on the platinum-free and platinum-dispersed carbon electrodes previously for 1-8h subjected to a constant applied potential of $700mV_RHE$ in 85% $H_3PO_4$ solution at 145℃ with concurrent oxygen and nitrogen gas blowing. The faradaic reactions on dispersed platinum during linear sweep voltammetry experiment were inhibited by the selective adsorption of iodide ions onto the platinum surface. As result, only anodic current peak associated with surface oxide previously formed in $H_3PO_4$ solution apperaed on linear sweep voltammogram in the potential range of 200 to $700mV_SCE$. The current peak increased with increasing time of exposure to 85% $H_3PO_4$ solution at the constant applied potential of $700 mV_SCE$. The amount of the surface oxides was determined by integration of the current peak with respect to time (potential axis). The presence of oxygen reduced the amount of the surface oxide and at the same time the rate of the surface oxide formation as compared to nitrogen blowing. The results of analysis of fourier tansform infrared spectroscopy were consistent with those of linear sweep voltammetry analysis. Considering the carbon surface oxide formation, followed by $CO_2$ evolution, it is suggested that the reaction products, such as water molecules, due to oxygen reduction on dispersed platinum surface facilitate $CO_2$ evolution rather than carbon surface oxide formation on carbon surface in 145℃, 85% $H_3PO_4$ solution at $700mV_RHE$.
