| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of ant nest-like corrosion on copper heat transfer tubes by subjecting the copper heat transfer tube surfaces to a surface treatment to maintain the pH of these surfaces at a specific range. SOLUTION: The pH of the copper heat transfer tube surfaces in the copper heat transfer tube exposed portions, etc., of a plate fin type heat exchanger is kept at 4 to 8.6 by a galvanizing treatment or coating application of a zinc-containing coating material containing zinc powder or a zinc compound, such as zinc phosphate, by which the ant nest-like corrosion induced by the fall of the pH of the condensed water on the copper heat transfer tube surfaces by the organic acidic component adhered to the copper heat transfer tube surfaces is prevented. Fin materials, such as aluminum- magnesium alloys, which elute the chemical material to suppress the degradation in the pH of the condensed water stored in the contact parts between the plate fins and copper heat transfer tubes of the plate fin type heat exchanger are used in the contact parts. An equally preferable alternative is to prevent the occurrence of the ant nest-like corrosion by the dissolution of corrosion resistant oxidized film by subjecting the contact parts to the treatment, such as plating treatment to elute the chemical material to suppress the degradation in the pH or coating material coating application.
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