To prevent a liquid from impregnating into a gap section by using a water-repellent material or a material coated with the water-repellent material as the material of a liquid contact section or the gap section existing on the liquid contact section.

A spigot coupling section is provided with a flange section 2 at the lower end of a barrel section 1 and a spigot section 5 at the upper end of the flange section 4 of a barrel section 3. The coating 7 of a water- repellent material is applied to connection sections such as the front of the spigot section 5, the inner face of the barrel section 1, and the inner face of the barrel section 3. Fluororesin coating, fluororesin lining or a fluororesin paint is used for the coating 7 of the water-repellent material, for example. When the spigot coupling section is assembled, a slight gap exists between the lower end of the barrel section 1 and the upper end of the barrel section 3, however both sides of this gap section are covered by the coating 7 of the water-repellent material, thus a corrosive liquid flowing on the inner faces of the barrel sections 1, 3 is prevented from impregnating by the water repelling action of the coating 7.