A composite hydrophilic anticorrosion film was prepared on LF21 aluminum alloy substrate by the dip coating of sol gel process,
aiming at eliminating the white powder and water bridge on the surface of aluminum heat exchanger of an air conditioner. The effectiveness of the resulting composite film in preventing the water bridge on the Al alloy was examined, while the corrosion behavior of the composite film was investigated using neutral salt spray test and electrochemical test. It was found that the composite film had good hydrophilic and anticorrosion properties. Namely, the composite hydrophilic film was able to greatly decrease the water contact angle on the surface of the aluminum fins from 50°~60°to 10°~15° and hence to effectively eliminate the water bridge effect. Moreover, no obvious change was observed in the appearance of the coated Al alloy sample being sprayed in the salt fog for 500 h. At the same time, the composite hydrophilic film on the Al alloy substrate had a much larger electrochemical impedance than the uncoated Al alloy substrate and hence was capable of significantly increasing the
corrosion resistance of the Al alloy. The complex film met the need of aluminum alloy fins of the air conditioner in terms of its good hydrophilicity and corrosion resistance.