Abstract:
A method for forming a heat insulating film includes: a step of subjecting an aluminum alloy constituting a surface of a base material to an anodic oxidation treatment to form an anodic oxidation coating film having pores formed in the surface thereat a step of coating on the surface of the anodic oxidation coating film a sealing material that includes a silicon-based polymer solution and particles of a heat insulating material that are dispersed in the silicon-based polymer solution and are particles having an average particle diameter that is larger than an average pore diameter of the pores; and a step of drying and baking the sealing material to form a sealing coating film.