1xxx, 3xxx, and 5xxx Series Aluminum: What the Numbers Mean for Coil Buyers.

What does the first digit of an alloy number actually mean?

It identifies the primary alloying element, except for 1xxx, where it denotes minimum aluminum purity instead. Wrought aluminum alloys use a four-digit number maintained by the Aluminum Association, published in full in its Teal Sheets. A 3003 or a 5052 is held to the same registered composition limits regardless of which mill rolled it, though temper, gauge and finish still vary by supplier and order.

The series that matter for coil coating, 1xxx, 3xxx and 5xxx, are all non-heat-treatable: their strength comes from rolling and temper, not a precipitation-hardening heat treatment cycle. Because that temper is never set by a heat-treatment reaction, it is generally less sensitive to a coil coating line's short bake cycle than a heat-treatable alloy's temper is, though the actual effect still depends on alloy, temper, peak metal temperature and dwell time.

What is 1xxx aluminum, and when is it the right call?

1xxx alloys are at least 99% aluminum, with only trace additions. That purity gives excellent corrosion resistance, high formability, and good electrical and thermal conductivity, at the cost of being the lowest-strength series in general use.

1xxx coil is specified for applications that value the finish and corrosion behavior of near-pure aluminum over mechanical performance, rather than for strength.

What is 3xxx aluminum, and why is it the default for coil?

Adding manganese as the primary alloying element produces the 3xxx series: meaningfully better strength than 1xxx, while keeping good formability and the corrosion resistance the non-heat-treatable family is known for.

3003 and 3105 are the common examples, used across cladding, general fabrication and coil coating work. If someone says "3000 series aluminum" without naming a specific alloy, they are almost always describing this general-purpose middle ground between the purity of 1xxx and the higher strength of 5xxx.

What is 5xxx aluminum, and when do you need it over 3xxx?

Magnesium as the primary addition produces the 5xxx series, generally the highest-strength range among non-heat-treatable coil alloys, with corrosion resistance well regarded in marine and humid environments. Reach for it when a project needs more strength or aggressive-environment resistance than 3xxx offers.

5052 is a commonly specified alloy here. See 5052 vs 6061 for how 5xxx compares against the heat-treatable alternative some specifications reach for out of habit.

One caveat specific to higher-magnesium 5xxx grades: alloys such as 5083 and 5456, at roughly 4 to 5.5% magnesium, are documented as more susceptible to intergranular and exfoliation corrosion after sustained exposure above roughly 65°C, as magnesium precipitates along grain boundaries over that kind of prolonged service exposure. Marine and structural specs for those alloys often call for stabilized tempers such as H116 or H321. This is a different phenomenon from a coil coating line's brief bake cycle, and does not apply the same way to the lower-magnesium grades most common in coil coating. Orbit's own 5xxx program is 5005, 5052 and 5754, all well below the magnesium range where this is a documented concern.

What about 2xxx, 6xxx and 7xxx? Do they ever show up in coil coating?

Rarely, and usually as a sign worth double-checking. 2xxx alloys use copper as the primary addition, are heat-treatable, valued for strength-to-weight in aerospace, but generally lower in corrosion resistance than many other aluminum families without additional protection, so uncommon in exterior coil work.

6xxx alloys, aluminum-magnesium-silicon, are heat-treatable and dominate extrusions and structural framing, covered in more detail in 5052 vs 6061. 7xxx alloys use zinc as the primary addition, are heat-treatable, and are among the highest-strength aluminum series, again mostly in aerospace and high-performance structural applications rather than coated coil.

What about 4xxx and 8xxx?

Two more series exist outside coil coating. 4xxx alloys use silicon as the primary addition and are mostly used as welding and brazing filler wire, such as 4043 and 4047, rather than sheet or coil. 8xxx covers alloys built around other elements, including iron, tin and lithium, for specialized uses such as battery foil, packaging, and aerospace and electronics applications. Neither shows up in coil coating specifications in practice.

Is the alloy number alone a complete specification?

No. The series establishes the general range of strength and formability available; temper determines where the specific coil you receive actually sits within it. Non-heat-treatable alloys are supplied in H-series tempers: the first digit after the H indicates the treatment (H1 strain hardened only, H2 strain hardened then partially annealed, H3 strain hardened then stabilized, specific to magnesium-bearing alloys like 5xxx), and the second digit, 1 through 9, indicates the degree of strain hardening, from soft and formable to harder and less forgiving of tight bends.

A specification that names only the four-digit alloy and leaves temper unstated is incomplete: two coils of the same alloy in different tempers can behave quite differently on a forming line. We cover this in our alloy and temper guide for coil coating.

Why does a spec sometimes show a hyphen after the alloy number?

Because it is combining two pieces of information: the alloy series before the hyphen, and the temper after it. A spec that reads "5052-H32" or "3003-O" is naming what the metal is made of and what condition it was left in after rolling, in one string.

Confusing the two, or dropping the temper half when copying a spec forward, is a common way a coil order ends up not matching what the project needed.

What should I do with a drawing that only lists "aluminum"?

Treat the series as a starting point. Ask what the part needs to do: hold a shape under load, form tightly without cracking, or resist a specific environment, and the right series usually becomes clear.

Orbit's rolling program covers the 1xxx, 3xxx and 5xxx families, in rolled coil from 0.20 to 2.00 mm thick and up to 1650 mm wide, in coils up to 10 tonnes. Coated coil runs up to 1.60 mm thick and up to 1350 mm wide. We confirm series and temper against your specification rather than defaulting to one alloy across every job.

How do the series compare at a glance?

Common questions

References

• Aluminum Association — Teal Sheets: registered alloy list and composition limits for every wrought series.
• 5083 aluminum alloy: composition and 65°C service temperature note supporting the 5xxx caveat above.
• 5456 aluminum alloy: composition and exfoliation-corrosion susceptibility for the same caveat.