| 摘要 |
PROBLEM TO BE SOLVED: To provide a chemical conversion treatment agent by which segregated matter caused by a brazing filler metal present on the substrates of a fin and a tube of a heat exchanger made of aluminum can be removed and cleaned, and a satisfactory chemical conversion coating can be formed after that. SOLUTION: The chemical conversion treatment agent is used after treatment for a base material consisting of aluminum or an aluminum alloy at 10 to 70 deg.C for 5 sec to 5 min by using an acidic aqueous solution. The acidic aqueous solution has pH of <=2, and contains; (a) the salt of metals of Fe, Ni, Co, Mo and/or Ce and/or the acid salt of the metals in 0.01 to 5 mass% of the acidic aqueous solution; and (b) inorganic acid. The chemical conversion treatment agent contains; (c) Zr and/or Ti in 0.001 to 1 mass% of the chemical conversion treatment agent; (d) trivalent chromium ions or the salt thereof in 0.1 to 1,000 ppm of the chemical conversion treatment agent; and (e) fluoride.
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