3003 vs 3105 Prepainted Aluminium Coil for Gutters and Downpipes: An EN 612 Guide

A gutter coil can look perfectly acceptable while it is still on the pallet and fail as soon as it reaches the roll former. Typical problems include edge wave, inconsistent feeding, paint cracking around tight radii, colour variation between batches and marks caused by poor coil winding. For a rainwater-system manufacturer, the correct alloy is only the starting point.

AA3003 and AA3105 are both widely used for gutters, downpipes and roofline components. They belong to the aluminium-manganese family, offer good corrosion resistance and can be supplied in formable tempers. Their practical differences matter when a factory is trying to balance line speed, profile stiffness and forming reliability.

Where coated aluminium is used in a roof drainage system

The same material family may be converted into:

• half-round and box gutters;

• round, square or rectangular downpipes;

• elbows and offset sections;

• outlets, stop ends and connector covers;

• fascia covers, copings and flashings;

• colour-matched roofline accessories.

The European Coil Coating Association notes that prepainted metal is widely used for gutters and downpipes and that an appropriate internal-side coating can improve durability. It also points out the value of using a consistent coated product across roofing, cladding and rainwater components, where uniform weathering and colour are important.

AA3003: the dependable forming choice

AA3003 is often selected when ductility and uncomplicated roll forming are the main priorities. In an appropriate temper, it performs well for curved gutter profiles and downpipes with multiple forming stations. It is also a practical base material for components that will be folded, seamed or locally shaped after roll forming.

For buyers changing from another supplier, 3003 is frequently the easier grade to trial because many existing tool sets and profile designs are already familiar with its forming behaviour.

Typical reasons to specify 3003 include:

• reliable roll forming for standard gutter geometries;

• good resistance to normal atmospheric corrosion;

• a useful balance between ductility and finished-profile stability;

• broad availability in common building-product tempers.

AA3105: useful when additional strength is required

AA3105 contains magnesium in addition to manganese and is commonly chosen when the finished profile needs somewhat higher strength while retaining workable formability. It can be a good fit for downpipes, box profiles and long components where shape retention and handling stiffness are important.

However, the temper must be matched to the tool geometry. Moving to a harder material without a line trial may create springback or coating stress at a tight fold. A buyer should compare not only alloy names but also mechanical-property ranges and actual profile results.

Typical reasons to specify 3105 include:

• improved stiffness for some profiles;

• good performance in continuous roll forming when the temper is correctly selected;

• suitability for building-envelope components exposed outdoors;

• consistent colour-coated supply for coordinated roof systems.

3003 or 3105: which should a factory choose?

Choose 3003 when the profile has demanding curves, the current process is sensitive to springback, or the main objective is forgiving formability. Consider 3105 when the finished component needs more rigidity or when it is already the validated grade on the customer's line.

This is not a decision that should be made from a data sheet alone. Send the supplier a drawing, the number and approximate severity of forming stations, seam details and the current temper. A short trial coil can reveal more than a broad "gutter-grade" description.

PE, HDP or PVDF coating?

The coating system should reflect the climate, colour and commercial positioning of the finished gutter.

Polyester (PE) is a cost-effective option for standard residential and light-commercial systems. It offers a wide colour range and good forming behaviour when the coating formulation is designed for roll forming.

High-durability polyester (HDP) may be considered where improved outdoor durability is required without moving to a fluoropolymer specification.

PVDF is normally evaluated for demanding exterior projects, high UV exposure or long-term colour-retention requirements. The final performance depends on the complete coating system, including pretreatment, primer, topcoat, curing and back coat - not on the resin name alone.

For a gutter, the reverse side should not be ignored. Condensation and standing moisture can affect the inside surface. The back-coat type and thickness should be written into the order rather than left as an unspecified factory default.

What EN 612 does - and does not - mean for the coil buyer

DIN EN 612:2005 covers eaves gutters with bead-stiffened fronts and seamed rainwater pipes made from metal sheet. It concerns the finished gutter and downpipe product. It does not replace the purchasing specification for the incoming aluminium coil.

For the coil itself, European buyers may also refer to EN 1396 for coil-coated aluminium sheet and strip, EN 573-3 for chemical composition and relevant EN 485 requirements for wrought aluminium sheet and strip. Coating properties can be tested using the EN 13523 series.

In practical terms, a gutter manufacturer should tell the coil supplier which finished-product standard is being followed, then define the incoming material properties needed to achieve it.

Ding‘ang's gutter-coil supply options

Ding‘ang supplies AA3003 color-coated aluminium coil for down gutters and AA3105-H24 coated aluminium for gutter production.

Typical project options include:

• 3003 or 3105 aluminium substrate;

• formable tempers selected around the profile;

• approximately 0.3 to 1.2 mm metal thickness, subject to project review;

• PE, HDP or PVDF coating by agreed specification;

• matte, semi-gloss or glossy appearance;

• RAL, Pantone or sample-based colour matching;

• parent coils or strip slit for the production line;

• protective packaging in eye-to-wall or eye-to-sky orientation.

These values describe the available product platform, not a universal gutter specification. Final tolerances, coating thickness and test criteria should be written into the purchase order and confirmed on the approved sample.

Five checks before approving a new coil

1. Run enough material to reach normal line speed, rather than forming only a short hand-fed sample.

2. Inspect the tightest bends and seams under magnification for coating cracks or pick-off.

3. Measure profile dimensions and springback at the start, middle and end of the trial.

4. Compare colour and gloss under controlled lighting against the approved master.

5. Check the inside surface, slit edges, coil telescoping and packaging after transport.

Frequently asked questions

Is 3003 softer than 3105?

As a general tendency, 3003 is often selected for easier forming and 3105 for somewhat greater strength. Temper and actual mechanical-property limits can be more important than the alloy name, so compare the complete specification.

Is PVDF necessary for every European gutter?

No. Many gutter systems use polyester coatings successfully. PVDF or another higher-durability system may be justified by the exposure category, colour-retention requirement or warranty strategy of the finished system.

Can Dingang supply small slit coils for gutter machines?

Dingang can supply parent coil and customised slit widths. Provide the required strip width, inside diameter, maximum outside diameter, coil weight and winding orientation so the packing and slitting plan can be confirmed.

Can the supplier certify that my finished gutter complies with EN 612?

The finished gutter manufacturer remains responsible for its product conformity. The coil supplier can provide agreed incoming-material documentation and test results that support the manufacturer's validation.

Request a line-trial specification

Send Ding’ang your gutter or downpipe drawing, current alloy and temper, thickness, strip width, colour, coating system and annual volume. We will review the application and prepare a trial-coil proposal for your production line.