Estimation of corrosion conditions of a phosphoric acid fuel cell

The changes in the anode and cathode potentials in the horizontal plane of a phosphoric acid fuel cell (PAFC), under various conditions of reactant gas pressure and its utilization, were studied using a single cell with twelve reference electrodes located around the cathode. Pressure-utilization (P-U) potential maps were obtained from the data at various reactant gas partial pressures (PO₂, PH₂) and their utilization (UO₂, UH₂). These maps show the corrosion conditions clearly. A PO₂-UO₂ potential map of maximum cathode potential showed that the cathode is corroded at high oxygen partial pressures and at low oxygen utilization. Cathode corrosion can occur over the entire cell surface. A PH₂-UH₂ potential map of maximum cathode potential showed that the cathode is corroded at high hydrogen utilization and at any hydrogen partial pressure. However, in this case, cathode materials corrodes at the fuel outlet; the potential does not climb to high values at the fuel inlet area. Fuel gas flowing in series resulted in a lower possibility for corrosion than parallel gas flow.