Insights · Reference
Aluminium is the lightweight specialist of duct materials — about a third the weight of steel and naturally corrosion-resistant, but softer and dearer. This reference covers the 3003 alloy, where aluminium beats galvanized and stainless, what changes when you form it, and how SBKJ spiral machines roll it up to 3.0 mm.
Aluminium is a specialist choice, not a default. It earns its place where weight matters — long rooftop runs, suspended duct, and semi-rigid flexible aluminium duct — where corrosion resistance is needed but stainless would be over-specification, and in some marine and architectural work. Against the alternatives: galvanized is cheaper and stronger for ordinary air; stainless wins for harsh chloride or hygienic environments; aluminium wins on weight. See galvanized vs stainless vs aluminium for the full trade-off.
Almost all HVAC aluminium duct is 3003-H14 — a manganese alloy chosen for its balance of formability and corrosion resistance. It spiral-winds and folds cleanly, takes a lock seam, and is the alloy behind both rigid spiral aluminium duct and the semi-rigid flexible aluminium duct used for connections. It is about one-third the weight of steel for the same volume, which is the whole point: lighter duct means lighter supports and easier handling on long runs.
Aluminium is fast to cut but softer to form: spring-back is noticeable and the TDF flange tolerance is tighter, so tooling clearances need adjusting. A machine rated for aluminium accounts for this; running it on a steel-only setup gives loose seams and out-of-tolerance flanges.
This is where SBKJ machines differentiate. The SBTF-1602 and SBTF-2020 spiral tubeformers carry a 0.4–3.0 mm aluminium rating — heavier than their 0.4–2.0 mm galvanized range, and heavier than most spiral machines handle in aluminium. The lighter SBTF-1500 and 1500C do not roll aluminium at all. So if you make heavy-gauge aluminium round duct, the machine choice narrows to the 1602 or 2020.
Aluminium uses its own gauge scale (Brown & Sharpe), but for duct it is simplest to specify in millimetres — the same 0.4–3.0 mm band the machines form. Per square metre, aluminium costs roughly 1.2× galvanized, but because it is so much lighter the installed weight (and the structure to carry it) drops. For the steel gauge-to-millimetre reference, see the gauge & thickness chart; for how aluminium duct is formed end to end, see how HVAC duct is made.
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Where weight matters (long/suspended runs, flexible duct), for mild corrosion where stainless is overkill, and some marine/architectural work. About 1/3 the weight of steel, naturally corrosion-resistant, but softer and dearer than galvanized.
3003-H14 — a manganese alloy with good formability and corrosion resistance, used for spiral and semi-rigid flexible aluminium duct.
On SBKJ machines, 0.4–3.0 mm — the SBTF-1602/2020 carry the 0.4–3.0 mm aluminium rating (heavier than their galvanized range). The SBTF-1500/1500C do not roll aluminium.
Fast to cut, but softer — spring-back is noticeable and TDF tolerance is tighter, so tooling clearances need adjustment on a machine rated for aluminium.
Forming aluminium duct and need a machine rated to 3.0 mm? Tell us your diameter and gauge and an SBKJ engineer replies within 12 hours — not a salesperson.
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