Galvanized pipe fittings are used for countless outdoor and industrial applications because of the material's ability to protect against corrosion and salt. Galvanized pipe and fittings may be used in most applications with the exception of underground lines. While they work best with cold water lines, they may be used with hot water as well. The main advantage of using galvanized fittings is their superior rust resistance when compared to black and copper fittings. Galvanized pipe fittings should not be used with gas applications.