Aluminum coil 3105 and 3003 are the two dominant alloys for roofing, cladding and insulation jacketing. This guide compares the two alloys on strength, formability and cost, with selection guidance for residential roofing, industrial cladding and HVAC insulation.
Aluminum coil is widely used for residential roofing, industrial wall cladding, and HVAC insulation jackets where its light weight, corrosion resistance and formability are valued. Two Al-Mn alloys dominate this segment: 3003, the traditional general-purpose alloy, and 3105, the slightly higher-strength alloy developed for roofing and siding applications. The two are closely related and often interchangeable, but the call between them matters when the panel design is strength-limited.
What 3003 and 3105 Share, and Where They Differ
Both 3003 and 3105 are Al-Mn alloys with about 1.0–1.5% manganese for strength and good corrosion resistance. The key difference is that 3105 has a small addition of magnesium (about 0.3–0.8%), which raises the yield strength by about 15–20% over 3003 in the H14 or H16 temper. In practical terms, 3105-H14 gives minimum yield of about 22,000 psi (150 MPa), versus about 18,000 psi (125 MPa) for 3003-H14. Both alloys are weldable, formable and corrosion resistant, and both accept paint and anodizing well.
When 3105 Is the Right Specification
3105 aluminum coil is the right specification for residential roofing panels, wall cladding, soffits, fascia, gutter stock, and downspouts. The higher strength allows slightly thinner gauges to be used for the same panel stiffness, saving weight and material cost. Most North American residential coil stock is 3105, and it is increasingly the dominant alloy for these applications in Asia and the Middle East as well. For prepainted roofing, 3105 is the standard substrate that paint systems are designed to adhere to.
When 3003 Is the Right Choice
3003 aluminum coil is the right specification for HVAC insulation jackets, ductwork, equipment casings, chemical equipment housings, and other applications where the slight strength disadvantage of 3003 is irrelevant and the broader availability and slightly lower cost matter. 3003 is also the standard alloy for deep-drawn cookware and for many general sheet metal applications. For insulation jacketing on pipes and ducts, 3003-H14 in 0.4–0.6 mm thickness with a plain mill or embossed stucco finish is the typical specification.
Surface Finish, Coating and Anodizing
Both 3003 and 3105 are produced in mill finish, stucco embossed finish, painted (PVDF or polyester), and anodized versions. Stucco embossing is the most common finish for insulation jacketing because it hides minor surface imperfections and resists fingerprints. For architectural roofing and cladding, a painted PVDF finish (Kynar 500 or equivalent) gives the longest color and chalk retention. Anodized finishes are also used for premium architectural panels, giving a hard, durable surface with excellent color consistency.
What to Specify on the Aluminum Coil RFQ
State the alloy and temper (3105-H14 or 3003-H14), the thickness, the coil width, the surface finish (mill, stucco, painted, anodized), and any color or coating specification. For roofing and cladding, default to 3105; for HVAC jacketing and general sheet metal, 3003 is the standard. Confirm the mill supplies the test report per EN 10204 3.1 with the actual chemistry and yield strength, since 3105 with insufficient magnesium can give the same strength as 3003 and the panel design will under-perform.
Related Resources from Baobin Steel
- Aluminum coil catalog – 3003, 3105 and other alloys
- Aluminum sheet – flat stock for fabrication
- Request a quote – send your coil spec for aluminum pricing