What Is 3003 Aluminum Alloy? | The Workhorse Manganese Alloy

3003 is a non-heat-treatable aluminum-manganese alloy prized for formability, moderate strength, and corrosion resistance.

Most sheet-metal jobs don’t need a high-strength structural alloy. They need material that bends easily, welds without drama, and shrugs off years of weather — and that is precisely the niche 3003 aluminum fills. For anyone comparing metals at the supplier, knowing what 3003 aluminum alloy is and what it isn’t saves a wasted order.

3003 is a 3xxx-series aluminum-manganese alloy, also designated UNS A93003. Manganese is the main alloying element at 1.0–1.5%, joined by small amounts of copper (0.05–0.20%), iron, and silicon, with aluminum as the balance. That chemistry has one important consequence: the alloy is non-heat-treatable. No furnace cycle will harden it, so strength comes entirely from cold working — rolling, drawing, and forming the metal as it’s processed.

What Makes 3003 Aluminum Alloy Different?

3003 aluminum sits between soft commercial-purity grades and heat-treatable structural alloys. It is noticeably stronger than 1100 aluminum, yet well below alloys such as 6061, which is why it never appears in load-bearing framework designs.

What 3003 offers instead is an unusual balance of working properties. Sheets bend, stamp, spin, draw, and brake-form readily without cracking, and the alloy welds well with common methods. Corrosion resistance is good to excellent in atmospheric and moisture exposure, which covers the conditions most sheet-metal parts actually face. Fabricators also like how predictably it shears and rolls — less tooling wear and fewer rejected parts.

The non-heat-treatable label isn’t a flaw; it’s what keeps the alloy simple to process. Heat-treatable alloys need a furnace step that adds cost and limits how much forming can happen afterward. Cold working hardens 3003 progressively, so parts can be formed first and pick up stiffness as the metal is rolled or drawn.

3003 Aluminum Properties By Temper

The properties of 3003 change sharply with temper, so no single number describes the whole grade. H tempers are work-hardened to different degrees; the typical figures below follow MatWeb’s 3003 aluminum datasheet.

Physical constants hold fairly steady across tempers: density near 2.73 g/cm³, a melting range of roughly 1,190–1,210°F, thermal conductivity around 180 W/m·K, elastic modulus about 69.5 GPa, and electrical conductivity near 44% IACS.

Elongation is where tempers separate most clearly. The annealed O temper stretches 28–30% before breaking, making it the choice for deep drawing and spinning; fully work-hardened H18 manages only 3–4%, so it resists bending but holds its shape under load. Whatever temper you buy, treat datasheet “typical” values as reference points, not guaranteed minimums — at least one supplier flags that its published figures are not required to meet the grade. Spec sheets also vary by source and product form; an older Atlas Steels datasheet revised in October 2013 lists slightly different numbers than newer references, another reason to confirm the exact temper and product form before ordering.

Where 3003 Aluminum Is Used — And Where It Isn’t

You’ll find 3003 wherever a part has to be formed and then face the outdoors. The standard applications list includes cookware and bakeware, heat exchangers, roofing and siding, storage tanks, general sheet and coil stock, and decorative or fabricated parts. All of them lean on the same combination: formability plus corrosion resistance at a moderate strength that costs less than structural grades.

• Cookware and bakeware that needs even heat spread and easy cleaning.
• Heat exchangers and fin stock that get formed into tight shapes.
• Roofing, siding, and gutters exposed to years of weather.
• Storage tanks holding water or mild chemicals.
• General sheet, coil, and decorative fabricated parts.

The limits matter just as much. 3003 is not a universal corrosion answer — severe marine or industrial chemical environments can still attack it, so those applications deserve a more specialized alloy. Welding works, but joint quality depends on proper equipment and process control. If you’re ready to buy sheet stock, our tested roundup of the best 3003 aluminum sheet options compares thicknesses, tempers, and suppliers side by side.

The one-line summary: 3003 is a formable, weldable, corrosion-resistant aluminum-manganese sheet alloy — stronger than 1100 aluminum, not heat-treatable, and the right pick whenever the job involves bending and weather exposure rather than carrying heavy structural loads.