FILM FORMING METHOD OF CORROSION RESISTANT FILM, CORROSION RESISTANT MEMBER ON WHICH CORROSION RESISTANT FILM IS FORMED, HEAT EXCHANGER, AND FUEL CELL SYSTEM

Provided is a film forming method of a corrosion resistant film having a corrosion resistance under acidic atmosphere and a corrosion resistant member on which the corrosion resistant film is coated. The film forming method of the corrosion resistant film includes: bringing a substrate made of aluminum into contact with an aqueous solution containing sulfate ions and fluoride ions; and heating the substrate to boil the aqueous solution on a surface of the substrate and forming a corrosion resistant film containing at least oxygen, fluorine, and sulfur in the aluminum derived from the substrate on the surface of the substrate.