| 摘要 |
PROBLEM TO BE SOLVED: To improve the corrosion resistance without using a soln. contg. harmful metallic ions by forming a metal oxide film on the surface of a heat exchanger in specified thickness. SOLUTION: A heat exchanger is pretreated and then dipped in a soln. obtained by the hydrolysis of the alkoxides of such metals as Si, TI and Zr and the following polycondensation. The soln. is then removed by centrifugal splashing and dried to form a gel film. The gel film is calcined to form a metal oxide film consisting of SinO2 , etc., on the heat exchanger surface in 0.1-1.5μm thickness. Since a soln. contg. a harmful metallic ion is not used in this process, a waste liq. contg. harmful matter is not generated, and the waste liq. is easily treated. Further, as the film formed on the heat exchanger surface has the above-mentioned thickness, the corrosion resistance equivalent to that of the conventional chromated heat exchanger is attained.
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