Process for operating a high temperature fuel cell stack

Process for shut-down of a high temperature fuel cell stack, the process comprising the following steps: a) connecting the fuel cell stack in parallel to a power supply unit at a predefined temperature and/or voltage of the fuel cell stack, b) applying a voltage from the power supply unit of between 700 to 1500 mV per fuel cell across the fuel cell stack irrespective of the electromotive force of the fuel cell stack, c) establishing the fuel cell stack at open circuit voltage (OCV) while maintaining the voltage per fuel cell from the power supply unit, d) disconnecting the fuel supply from the fuel cell stack, and e) cooling down the fuel cell stack.