PURPOSE: To maintain hydrophilic property over a long period of time even under severe conditions in use by forming a hydrophilic coating film contg. specified amts. of oxides of Si, Al and B and having uniform pores of a specified size on the surface of a heat exchanger.
CONSTITUTION: A hydrophilic coating film contg., by mol, 50-90% SiO2, 3-40% Al2O3 and 3-40% B2O3 when constituent elements of the film made of oxide of at least Si, Al and B are expressed as oxides and having uniform pores of ≤10μm pore diameter is formed on the metal surface of a heat exchanger or an evaporator. Excellent water resistance and mechanical strength are ensured and a porous material penetrates into the film by the surface tension of water and exhibits hydrophilic property. Hydrophilic property due to the surface energy of the film itself is also exhibited.
KIDA KENJI
YAMAGUCHI YOSHIKAZU
