Which aluminum alloy is used for low-pressure rigid lines?

• A. 6061-T6 aluminum alloy tubing
• B. 5052-O aluminum alloy tubing
• C. 1100-1/2 hard aluminum alloy tubing
• D. 3003-1/2 hard aluminum alloy tubing

Answer: (C)

Low-pressure rigid lines need tubing that can be bent into tight shapes without cracking, while also resisting corrosion and maintaining shape under vibration. Commercially pure aluminum in a half-hard temper hits that balance. The 1100 series offers excellent corrosion resistance and very good formability, and the half-hard designation provides enough strength to prevent kinks or deformation during bending and installation. This makes it well suited for rigid tubing in low-pressure systems.

Other alloys are either stronger and harder to form, which can complicate bending and flaring, or they don’t provide the same combination of ductility and corrosion resistance that low-pressure lines require.