Sacrificial anode alloy Al-Mn-Sn in Part 1 was applied to fin material of an evaporator brazed in vacuum. But corrosion potential of the fin became a less noble value of 20mV than tube (target above 50mV).As a result of studies, this is why Sn did not dissolve into the fin core material because of slow cooling rate after heating in vacuum. Moreover, when cooling rate is made below 30 Min. (610°C→70°C), Sn dissolved, at the same time corrosion potential of fin became a less noble value of above 50mV. Thus, evaporators made under such conditions show excellent resistance to corrosion.