PURPOSE: To improve the corrosion resistance of fins and to satisfy lightweight and economical requirements by forming a specific zinc diffusion layer on the surfaces of fins.
CONSTITUTION: Fins are provided with a plurality of copper tubes circulating a heat- exchange medium and fin components consisting of copper or a copper alloy disposed between these tubes. At the surface portions of fins consisting of a copper alloy containing 0.01W0.13wt% of at least one member of tin or magnesium, zinc diffusion layers are formed. The zinc diffusion layer contains 0.003W0.04wt% of at least one member or more selected from the group consisting of phosphorus, arsenic and antimony. With respect to the content of phosphorus (P), arsenic (As) or antimony (Sb), with 0.003wt% or less of any of the components, the effect of corrosion resistance is not almost recognized. With 0.04wt% or more, the heat radiation of fins is lowered. The corrosion resisting effect of the zinc diffusion layer becomes large in accordance with the thickness of the zinc diffusion layer. When the thickness thereof exceeds 0.015mm, the corrosion resisting effect is saturated and simultaneously the lowering of the heat radiation of the fine is affected greatly. Therefore, the thickness thereof is set to 0.015mm or less, preferably in the range of 0.003W0.01mm.
HASEGAWA YOSHIHARU
NAGARA TOSHIO
SUSA SUMIO
SUGIZAKI TAKESHI
SATO KADOMASA
FURUKAWA ELECTRIC CO LTD
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