Aluminium electrical conduit is metal tubing, usually in 6063 alloy, that protects and routes electrical cables. It weighs about a third as much as steel conduit of the same size, does not rust, is non-magnetic and serves as a low-impedance earthing path. This guide covers rigid, EMT and flexible types, the standards behind them, size and weight tables, and where aluminium is and is not the right choice.
Conduit is the protective raceway through which building and industrial cables are pulled. Metal conduit shields the conductors from impact, crushing, moisture and fire spread, and in most systems it also acts as the equipment earthing (grounding) conductor. Aluminium conduit does all of this at a fraction of the weight of steel.
Rigid aluminium conduit has been used in North American industrial and commercial installations for decades and is recognised alongside galvanised steel in the US National Electrical Code (NEC) and the Canadian Electrical Code. It is specified heavily in petrochemical plants, wastewater works, food plants, coastal buildings and data centres, and increasingly on rooftop solar and EV-charging projects, where corrosion resistance and easy handling matter.
Metline supplies aluminium tube and pipe in conduit alloys and dimensions, couplings stock, bar for fittings, and related extrusions, to conduit manufacturers, fabricators and project buyers worldwide. Where a project requires UL-listed or CSA-certified conduit, the listing is held by the conduit manufacturer and must appear on the product marking; tell us the requirement and we confirm what can be supplied for that project.
Heavy-wall, threaded conduit with the same outside diameter and wall as steel rigid conduit. Covered by ANSI C80.5 and UL 6A and installed under NEC Article 344. Supplied in 10 ft (3.05 m) lengths with tapered NPT threads and one coupling. Used outdoors, in industrial plants and in hazardous (classified) locations with suitable fittings.
Thin-wall, unthreaded tubing joined with set-screw or compression fittings. Covered by UL 797A and installed under NEC Article 358. Easy to bend by hand bender and cut on site. Used indoors and in dry or damp locations where heavy mechanical protection is not needed.
Helically wound, interlocked aluminium strip that bends freely, used for short connections to motors, transformers and vibrating equipment. Flexible metal conduit (FMC) is listed to UL 1 and installed under NEC Article 348; liquid-tight versions add a PVC or similar jacket.
| Feature | Rigid aluminium conduit | Aluminium EMT | Flexible aluminium conduit |
|---|---|---|---|
| Wall | Heavy (2.6 – 6.8 mm) | Thin (1.1 – 2.1 mm) | Interlocked strip |
| Joints | Threaded couplings | Set-screw or compression fittings | Screw-in or clamp connectors |
| Mechanical protection | Highest | Moderate | Low to moderate |
| Typical alloy | 6063-T1 (T5 in small sizes) | 6063 | Soft aluminium strip |
| Hazardous locations | Yes, with listed fittings | Generally no | Limited, with listed fittings |
| Main standards | ANSI C80.5, UL 6A | UL 797A | UL 1; IEC 61386-23 |
Conduit is made almost entirely from 6063, the architectural extrusion alloy, because it extrudes into seamless tube with a smooth bore, threads cleanly and resists corrosion well. Low copper content is important: copper reduces the corrosion resistance of aluminium, so conduit makers keep it to a minimum, and some describe their conduit as "marine grade" for this reason.
| Element | 6063 limits (wt %) | Effect in conduit |
|---|---|---|
| Silicon (Si) | 0.20 – 0.60 | Forms Mg2Si with magnesium for strength |
| Magnesium (Mg) | 0.45 – 0.90 | Main strengthening element |
| Iron (Fe) | ≤ 0.35 | Impurity; kept low for surface quality |
| Copper (Cu) | ≤ 0.10 | Kept low for corrosion resistance |
| Manganese, chromium, zinc, titanium | ≤ 0.10 each | Impurities or trace additions |
| Aluminium (Al) | Remainder | About 97.5 – 99.4 % |
Rigid conduit is commonly supplied in the T1 temper (cooled from extrusion and naturally aged), which gives enough strength for threading and field bending while keeping the metal ductile. Smaller sizes are sometimes supplied in T5. EMT uses 6063 in a temper that allows tight field bends without cracking. The interlocked strip of flexible conduit uses a soft, formable aluminium alloy. Where a customer needs extra strength, for example for long unsupported spans or custom raceways, 6061-T6 tube is an alternative.
Composition limits are the registered Aluminum Association values for 6063 (ASTM B221 / EN 573-3 EN AW-6063).
Rigid aluminium conduit shares its outside diameter and wall thickness with rigid steel conduit, so the same fittings, threading dies and fill tables apply. Metric designators are the trade-size equivalents used in the NEC. Weights below are calculated from the nominal dimensions at 2.70 g/cm³ and exclude couplings.
| Trade size (in) | Metric designator | Outside diameter (mm) | Nominal wall (mm) | Weight (kg/m) |
|---|---|---|---|---|
| ½ | 16 | 21.3 | 2.64 | 0.42 |
| ¾ | 21 | 26.7 | 2.72 | 0.55 |
| 1 | 27 | 33.4 | 3.20 | 0.82 |
| 1¼ | 35 | 42.2 | 3.38 | 1.11 |
| 1½ | 41 | 48.3 | 3.51 | 1.33 |
| 2 | 53 | 60.3 | 3.71 | 1.78 |
| 2½ | 63 | 73.0 | 4.90 | 2.83 |
| 3 | 78 | 88.9 | 5.21 | 3.70 |
| 3½ | 91 | 101.6 | 5.46 | 4.45 |
| 4 | 103 | 114.3 | 5.72 | 5.26 |
| 5 | 129 | 141.3 | 6.22 | 7.13 |
| 6 | 155 | 168.3 | 6.76 | 9.26 |
Outside diameters and walls follow the nominal values used for rigid metal conduit under ANSI C80.5; the standard sets the tolerances. Manufacturers’ published weights per 100 ft are slightly higher because they include the coupling.
Aluminium EMT uses the same outside diameters and nominal walls as steel EMT, so standard EMT connectors, couplings and benders fit. The thin wall keeps weight very low:
| Trade size (in) | Outside diameter (mm) | Nominal wall (mm) | Weight (kg/m) |
|---|---|---|---|
| ½ | 17.9 | 1.07 | 0.15 |
| ¾ | 23.4 | 1.24 | 0.23 |
| 1 | 29.5 | 1.45 | 0.35 |
| 1¼ | 38.4 | 1.65 | 0.51 |
| 1½ | 44.2 | 1.65 | 0.60 |
| 2 | 55.8 | 1.65 | 0.76 |
| 2½ | 73.0 | 1.83 | 1.10 |
| 3 | 88.9 | 1.83 | 1.35 |
| 3½ | 101.6 | 2.11 | 1.78 |
| 4 | 114.3 | 2.11 | 2.01 |
| Standard / code | Scope |
|---|---|
| ANSI C80.5 | Electrical rigid metal conduit, aluminium: dimensions, threads, coupling, bending and finish requirements |
| UL 6A | Electrical rigid metal conduit, aluminium, red brass and stainless steel: safety listing requirements |
| UL 797A | Electrical metallic tubing, aluminium and stainless steel |
| UL 1 | Flexible metal conduit, including aluminium |
| NEC Articles 344, 358, 348 | Installation rules for rigid metal conduit, EMT and flexible metal conduit (US) |
| NEC 300.6 | Corrosion protection; aluminium conduit in concrete or in contact with soil needs supplementary protection |
| CSA C22.2 No. 45.2 | Rigid metal conduit in aluminium and other non-ferrous metals (Canada) |
| IEC 61386-1, -21, -23 | Conduit systems for cable management: general, rigid and flexible (international / EN 61386) |
| ASME B1.20.1 | Tapered pipe threads (NPT) used on rigid conduit |
| ASTM B221 / B241 | Extruded tube and seamless pipe material specifications for the aluminium itself |
A note on accuracy: some online sources list IEC 61386-24 for flexible conduit (part 24 covers conduit buried underground; flexible conduit is part 23) and ASTM B308 as a salt-spray standard (B308 is a specification for 6061-T6 structural profiles). Check the scope of any standard quoted in a tender before relying on it.
| Property | Rigid aluminium | Galvanised rigid steel | PVC conduit |
|---|---|---|---|
| Weight (2 in trade size) | About 1.8 kg/m | About 5.4 kg/m | Very light |
| Corrosion in industrial and coastal air | Excellent; no coating to wear through | Good until zinc is consumed | Excellent |
| Corrosion in concrete and soil | Needs supplementary protection | Often needs extra coating | Excellent |
| Magnetic | No | Yes | No |
| Acts as earthing conductor | Yes, low impedance | Yes | No; separate earth wire needed |
| Mechanical protection | High | Highest | Low to moderate |
| Fire behaviour | Non-combustible | Non-combustible | Combustible; smoke and fumes |
| Thermal expansion | 23 µm/m·°C | 12 µm/m·°C | About 50 – 70 µm/m·°C |
In practice aluminium is the best choice for exposed runs in corrosive atmospheres, high-level and roof installations where weight and handling matter, and installations near sensitive equipment. Steel remains preferable where the conduit will be cast into concrete or buried without extra protection, or where the highest crush resistance is required. PVC dominates underground ducts and very wet locations but cannot serve as an earth path and needs expansion fittings on long runs.
| Application | Typical type | Why aluminium |
|---|---|---|
| Chemical, petrochemical and refinery plants | Rigid | Resists industrial atmospheres; light for rack and pipe-bridge installation |
| Wastewater and water treatment | Rigid | Resists humid, sulphide-bearing air better than galvanised steel in many cases |
| Food and beverage plants | Rigid, EMT | No rust flakes; tolerates frequent wash-down with suitable fittings |
| Coastal and marine buildings | Rigid | Withstands salt-laden air without coating maintenance |
| Data centres, hospitals, labs | EMT, rigid | Non-magnetic, low voltage drop, fast to install overhead |
| Rooftop solar and EV charging | Rigid, EMT | Light on roofs, UV-stable, corrosion resistant outdoors |
| Motors, pumps and machines | Flexible | Absorbs vibration and movement at equipment connections |
| Hazardous locations | Rigid with listed fittings | Accepted for classified areas under the electrical code |
Yes. The US National Electrical Code covers aluminium rigid metal conduit under Article 344 and aluminium EMT under Article 358, and the Canadian Electrical Code recognises it too. The product must be listed for the purpose, and aluminium in concrete or in contact with soil needs supplementary corrosion protection.
About one third the weight for the same trade size. A 2 in rigid aluminium conduit weighs roughly 1.8 kg per metre, compared with about 5.4 kg per metre for galvanised rigid steel.
Yes. Rigid aluminium conduit and aluminium EMT are recognised as equipment grounding (earthing) conductors when installed with listed fittings. Aluminium’s good conductivity gives a low-impedance fault path; use conductive thread compound to keep joints reliable.
Only with supplementary corrosion protection such as a factory coating, wrapping or sleeving, as required by NEC 300.6. Fresh concrete is alkaline and may contain chlorides, both of which attack bare aluminium.
6063 is standard, typically in the T1 temper for rigid conduit, with low copper content for corrosion resistance. 6061-T6 tube can be used where extra strength is needed for custom raceways.
Compared with steel conduit, yes. Because aluminium is non-magnetic, AC circuits in aluminium conduit have lower reactance and therefore lower voltage drop and less inductive heating of the raceway, which helps on long feeders.
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