To provide a solder tank, a solder heater and a surface treatment method of a base metal in which cracks and separation are less liable to occur in the surface even when thermal stresses act, and secularly consistent corrosion resistance is ensured for a tin alloy such as lead-free solder.

An intermediate metal layer 21 to cover a surface of a base metal in contact with a tin alloy such as lead-free solder for a solder pot and a solder heater and a surface protective layer 20 consisting of ceramics are successively formed by thermal spraying.