One alloy extrudes, the other carries load. Here is where the line falls, and why a 2.0 mm channel in 6061 is a specification nobody can price.
6063-T5 for the channel that frames the sign, 6061-T6 for the bracket or gantry that carries it. 6063 extrudes fast, comes out with a smooth surface that anodises evenly, and takes the 60–110 mm widths and 2.0–4.0 mm wall sections a sign frame needs. 6061 is stronger but harder to extrude into a thin open profile and costs more per metre. Putting 6061 in a channel section is usually a specification written by someone who has not priced the extrusion.
The two alloys are both Al-Mg-Si, both heat-treatable, both about 2.70 g/cm³. The difference is how much of each alloying element is present and what that does to extrudability. 6063 is the extrusion alloy; 6061 is the structural alloy. A sign frame uses the first, its supports use the second.
6063 sits at the low end of the magnesium and silicon range, which is why it pushes through a die at speed with a clean surface and why hollow, thin-walled profiles are practical in it. 6061 carries more magnesium and silicon plus a little copper, which raises strength after a full solution treatment and artificial ageing (T6) — at the cost of extrusion speed and surface quality. Both are supplied as extruded profiles; neither is a sheet product in this context.
| Property | 6063-T5 | 6061-T6 | Why it matters here |
|---|---|---|---|
| Typical tensile strength | ~150–200 MPa | ~290–310 MPa | 6061 carries more load per section |
| Typical yield strength | ~110–170 MPa | ~240–275 MPa | Decides bracket design, not channel width |
| Density | 2.70 g/cm³ | 2.70 g/cm³ | Weight is a wash between them |
| Extrusion speed and surface | Fast, smooth | Slower, more marking | 6063 gives the finish anodising needs |
| Thin hollow sections | Practical at 2.0 mm wall | Difficult below 3 mm | Decides whether a 2.0 mm channel is available |
| Anodising response | Even, predictable | Less uniform | Coastal and architectural work |
Strength figures are typical handbook ranges for the temper, not a mill certificate. Ask for the actual certificate for the heat you are buying if the number is structural.
Folded sheet is a legitimate option and often the cheapest way to stiffen a small panel. It loses on three counts as the panel grows. A folded channel has a radius at each corner, so the section is not as stiff as its nominal depth suggests. It has a continuous seam or open edge where water sits. And it cannot be anodised as a structural section with the same predictability as an extrusion, because the bend area takes the finish differently.
Where folded sheet wins: short runs, unusual depths, panels under about 1200 mm where a 25 mm fold is enough, and jobs where the frame is painted rather than anodised.
Rarely for the channel itself, often for the parts bolted to it. T6 buys strength through a full solution treatment and artificial ageing; T5 in 6063 is cooled and aged after extrusion and is strong enough for a frame that only has to hold a panel flat. The case for T6 appears when the channel is also the structural member — a cantilever bracket, a gantry beam, a sign that hangs from a single point — and even then the right answer is usually a 6061 bracket rather than a 6061 channel.
Write the alloy, the temper, the section drawing with wall thickness, the length and the surface treatment. "Aluminium channel 60 × 40" is not a specification — two suppliers will quote two different wall thicknesses and two different tempers against it.
Composition limits and mechanical property ranges for 6063 and 6061 are registered with ASM International in the ASM Handbook series on aluminium alloys; the European designations are EN AW-6063 and EN AW-6061 under the EN 573 registration system administered by CEN. Temper designations follow EN 515.
Sources: ASM International, Materials Park, OH · CEN, Brussels. Cited 30 October 2026.
Yes, and it is done where a channel doubles as a structural member. Expect a higher price per metre, a thicker minimum wall and a rougher as-extruded surface than the same section in 6063.
6063-T5 is the normal sign-frame temper: extruded, cooled and aged, dimensionally stable and strong enough for the panel loads involved. T6 is specified when the section is structural.
No. Extruded aluminium profiles fall under HS 7604 regardless of whether the alloy is 6063 or 6061; what changes is the commercial description on the invoice, not the heading.
2.0 mm is the practical minimum for a 60–110 mm sign channel in 6063; 3.0–4.0 mm appears on larger panels and on wind-exposed sites. Wall thickness, not alloy, is usually what decides whether a frame stays straight.
Specification questions are answered by the same person who quotes the job.