Patent ID: 7503381

Claim:
A rust prevention and hydrophilization treatment method for a flux-brazed aluminum-made heat exchanger which comprises subjecting the heat exchanger to a rust prevention treatment by the use of a zirconium base compound and/or a titanium base compound, and thereafter subjecting the heat exchanger to a hydrophilization treatment by means of a hydrophilization treatment agent composition, said composition comprising: (1) 40 to 90% by mass of polyvinyl alcohol having a degree of saponification of at least 90%; (2) 3 to 40% by mass of polyoxyalkylene-modified polyvinyl alcohol in which 0.01 to 20% of pendant groups of the polyvinyl alcohol are polyoxyalkylene ether groups represented by the general formula (1): wherein n is an integer from 1 to 500, R 1 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R 2 is a hydrogen atom or a methyl group; (3) 1 to 30% by mass of an inorganic cross-linking agent which reacts with hydroxyl groups of the polyvinyl alcohol and modified polyvinyl alcohol; and (4) 1 to 20 % by mass of a guanidine compound having a biguanide structure, represented by the general formula (4), and/or a salt thereof: