Aluminum is an ultra-light metal, making it an optimal choice for low cost and lightweight pipe nipples. However, because they are vulnerable to corrosion, aluminum pipe nipples are not recommended for wet or salty environments.

Applications of Aluminum Structural Pipe Fittings
Aluminum pipe nipples, a kind of threaded pipe fittings, are used only in specialty applications where their uses and limitations are understood. They are not designed for use in general shop water or air plumbing layouts (refer to traditional metals like brass, steel/malleable iron, stainless steel, plastics, etc. for general plumbing applications).