Clear (natural)
Undyed film that keeps the metallic look of the base sheet. The most durable choice outdoors.
Surface-finished sheet
Anodised Aluminium Sheet
Anodised aluminium sheet carries a hard, transparent layer of aluminium oxide grown electrochemically from the metal itself, which protects it against corrosion and wear and can be coloured. It is not a paint: the film is part of the surface and will not peel. Metline supplies pre-anodised sheet and coil and anodising-quality sheet in 1050, 1100, 5005, 5052 and 6061, with coating thickness and colour to order, to customers worldwide.
- Alloys
- 1050 · 1100 · 5005 · 5052 · 6061
- Coating
- 5 – 25 µm; hard anodic up to 50 µm+
- Finishes
- Clear, colours, brushed, bright
- Standards
- ISO 7599 · EN 12373 · MIL-A-8625
What is anodised aluminium sheet?
In anodising, the sheet is made the anode in an acid electrolyte, usually sulphuric acid. Current converts the surface aluminium into a layer of aluminium oxide that grows partly into and partly out from the original surface. The film is made of millions of fine hexagonal pores, which can be filled with dye or metal salts for colour and are then closed by sealing.
The result is a surface far harder than the base metal, with excellent resistance to weathering and handling marks, a metallic look that paint cannot match, and no flaking because the coating is not a separate layer. Anodised sheet is used for building facades, signage, lighting reflectors, appliance and electronics panels, nameplates, interior trim and anywhere a durable metallic finish is wanted.
Sheet can be anodised in two ways. Coil (continuous) anodising runs the coil through the anodising line at speed, which gives very consistent colour from sheet to sheet and is economical for large areas; the sheet is then cut and formed after anodising. Batch anodising treats cut sheets or finished parts on racks, so it is used when parts are fabricated first or when thicker or hard coatings are needed.
Which alloys anodise best?
The alloy controls how clear, uniform and bright the anodic film looks. Elements such as silicon, copper and iron form particles that do not anodise, so they cloud or darken the film. For decorative work, order "anodising quality" (AQ) sheet, which is produced with tighter control of chemistry and grain size.
| Alloy | Anodised appearance | Strength | Typical use |
|---|---|---|---|
| 1050 / 1070 / 1085 | Very clear and bright; best for reflectors and bright finishes | Low | Lighting reflectors, nameplates, decorative trim |
| 1100 | Clear, uniform | Low | Signage, panels, general decorative sheet |
| 5005 | Excellent match to 6063 extrusions; the architectural standard | Medium | Facades, cladding, curtain-wall panels |
| 5052 | Good, slightly yellower than 5005 | Medium–high | Electronics enclosures, marine and transport panels |
| 6061 | Good; can look slightly grey | High | Machined parts, structural panels, hard anodising |
| 2024 / 7075 | Darker, less uniform; poor for decoration | Very high | Functional and hard anodising only |
Coating thickness classes and where to use them
Coating thickness is the main driver of durability. EN ISO 7599 designates classes by minimum average thickness in micrometres (AA 5, AA 10, AA 15, AA 20, AA 25). In North America, Aluminum Association architectural Class II is 10 – 18 µm (0.4 – 0.7 mil) and Class I is 18 µm (0.7 mil) and above. The table gives common guidance.
| Class (ISO 7599) | Minimum average thickness | Typical exposure |
|---|---|---|
| AA 5 | 5 µm | Indoor decorative parts in dry conditions; often on coil-anodised sheet |
| AA 10 | 10 µm | Indoor use and parts that will be handled |
| AA 15 | 15 µm | Outdoor use in mild, rural environments |
| AA 20 | 20 µm | Outdoor use in urban and industrial environments |
| AA 25 | 25 µm | Severe outdoor, coastal and marine environments |
| Hard anodic (Type III) | Typically 25 – 75 µm | Wear surfaces, sliding parts, abrasion resistance |
Military and aerospace orders often specify MIL-A-8625: Type II (sulphuric acid) and Type III (hard coat), with Class 1 undyed and Class 2 dyed. Thicker films are harder wearing but crack more easily when the sheet is bent.
Colouring and sealing
Electrolytic colour
Tin or other metal salts deposited at the bottom of the pores give light-fast bronze, champagne and black shades suitable for facades.
Organic dyes
Bright colours such as red, blue and gold. Many dyes fade in sunlight, so they are mainly for interior use.
Brushed or bright
Mechanical brushing or chemical brightening before anodising gives a satin or mirror finish under the film.
Hot-water or nickel seal
Sealing closes the pores, locking in colour and maximising corrosion resistance. Seal quality is tested by acid dissolution (ISO 3210) or admittance (ISO 2931).
Batch matching
Colour varies slightly between batches and alloys. For large facades, order from one production run and approve limit samples.
Bending, cutting and joining anodised sheet
The anodic film is a ceramic: it is hard but cannot stretch. When pre-anodised sheet is bent, the film on the outside of the bend develops fine cracks ("crazing"). Thin films (5 – 10 µm) on soft tempers tolerate tight bends with little visible effect; thick architectural films need larger radii, and bends should run across the rolling direction where possible. Always trial-bend a sample in the actual coating before production.
- Cutting: shear or saw with sharp tools; cut edges are bare aluminium and will dull over time outdoors
- Drilling and punching: support the decorative face and keep protective film on to avoid scratches
- Joining: rivets, screws, adhesive tapes and structural adhesives; welding destroys the finish locally
- Electrical contact: the film is an insulator, so earth connections need the coating removed or a penetrating fastener
- Cleaning: neutral detergent and water; avoid alkaline cleaners and abrasive pads, which attack the film
Supply range and quality checks
Typical supply range
- Thickness
- About 0.3 – 3 mm for pre-anodised sheet; thicker sheet and plate batch anodised
- Sizes
- 1000 × 2000, 1220 × 2440, 1250 × 2500, 1500 × 3000 mm, coil or cut to size
- Tempers
- O, H14, H24, H32 depending on alloy and forming needs
- Finishes
- Clear, champagne, bronze, black, gold and custom colours; matt, satin, brushed or bright
- Protection
- PE or PVC film on the decorative face; interleaving paper on request
- Quality checks
- Coating thickness by eddy current (ISO 2360), seal quality, colour against approved sample, visual inspection
Specification for architectural work commonly references EN 12373-1 or Qualanod requirements; confirm the standard with your order.
References and standards
- EN ISO 7599 – Anodizing of aluminium and its alloys: method for specifying decorative and protective anodic oxidation coatings
- EN 12373-1 – Aluminium and aluminium alloys: anodizing, method for specifying decorative and protective coatings
- MIL-A-8625 – Anodic Coatings for Aluminum and Aluminum Alloys
- ISO 2360 – Non-conductive coatings on non-magnetic substrates: eddy-current thickness measurement
- Aluminum Anodizers Council – anodizing reference information
Anodised (anodized) aluminium sheet: frequently asked questions
Can anodised aluminium sheet be bent?
Yes, but the oxide film cracks on the outside of the bend. Thin coatings on soft tempers bend well with little visible crazing; thick coatings need generous radii. Trial a sample, or fabricate first and anodise afterwards.
What coating thickness do I need outdoors?
At least 15 µm for mild exposure, 20 µm for urban and industrial sites, and 25 µm for coastal or marine locations, following EN ISO 7599 classes.
Which alloy is best for anodising?
1050 and 1100 give the brightest, clearest finish; 5005 is the architectural standard and matches 6063 extrusions; 5052 and 6061 are used where more strength is needed.
Does anodised aluminium fade?
Clear and electrolytically coloured finishes are very light-fast. Many organic dyes fade in sunlight, so dyed colours are best for interior use unless a light-fast dye is specified.
Is anodised sheet electrically conductive?
No. The anodic film is an electrical insulator. Remove the coating locally or use a penetrating fastener where an electrical or earth connection is needed.
What is the difference between anodising and powder coating?
Anodising converts the surface into oxide and keeps a metallic look; it cannot peel. Powder coating is a paint layer on top, available in any colour and gloss, but it can chip.
Need anodised aluminium sheet?
Send alloy, thickness, size, coating class and colour. Our team will confirm the finish and quote a delivered price.
