Could someone please explain what is thermal oxidation of the carbon brakes? In my company SOP after landing we don’t switch on the brake fans immediately after the HOT annunciation comes on on the BRAKE FANS push button. Instead we are told to wait for a period of 5 mins after landing to allow for thermal equalisation of the brakes and to prevent oxidation of brake surface hotspots. 

What exactly does this mean?
Catalytic oxidation of carbon occurs when a catalyst, such as an
  alkali metal(s), is present. When a catalyst is present, the
  temperature at which thermal oxidation occurs is lowered. Airplanes
  equipped with carbon brakes are susceptible to catalytic oxidation
  caused by exposure to alkali metal runway deicers. - Boeing Aero
  Magazine


Brake manufacturers produce Oxidation resistant brakes. The effects of can be obtained by using carbon brakes, or using a coating on the brake rotor and friction surfaces. 

Best practices for carbon brake application according to Airbus.