Method for operating a cooling system for a fuel cell and cooling system for a fuel cell

The invention relates to a cooling circuit for a fuel cell system and a method for operating the cooling circuit, where prior to feeding a coolant to said cooling circuit a pre-conditioned coolant is prepared from a freshly prepared coolant, whereby the freshly prepared coolant is chemically passivated to form said pre-conditioned coolant. The coolant may be a mixture of alcohol and water (in particular glycol and water), and the freshly prepared coolant is circulating through a reactor chamber filled with a metal (e.g. aluminium) to form said pre-conditioned coolant.