METHOD FOR INHIBITING GROWTH OF OXIDE FILM AT THE TIME OF HEAT TREATMENT OF ALUMINUM OR ALUMINUM-ALLOY MATERIAL AND PRODUCTION THEREFOR

摘要

PURPOSE:To remarkably inhibit the growth of an oxide film even if an Al or Al-alloy material is subjected to subsequent heating treatment at high temp. by previously allowing fluorine to exist in a surface oxide film. CONSTITUTION:An Al or Al-alloy material is treated with an F- ion-containing solution in which the proportion of F is regulated to =about 100ppm and also pH is regulated to =about 5, by which F is allowed to exist desirably by =about 0.01atomic% in the surface oxide film of the above Al or Al-alloy alloy material. Further, it is desirable that F in the above oxide film forms a complex compound together with the oxide film. By the above method, at the time, e.g., of joining fins and tubes composed of the Al-alloy material by means of brazing to assemble a heat exchanger, remarkable growth of the oxide film on the surface of the Al-alloy material can be prevented at the time of the above brazing operation. Accordingly, a superior heat exchanger having high joining strength between fins and tubes can be provided.