Aluminium is rarely left bare on a facade. It is finished to protect it, to give it colour, and to make it last. Three finishes cover almost every project: anodising, powder coating and PVDF coating. They look different, they behave differently outdoors, and they cost differently. Choosing well starts with knowing what each one actually is, because the names say little about the difference.
The three finishes
Anodising thickens the natural oxide layer on the surface of the aluminium by an electrochemical process. The finish is part of the metal rather than a coat on top, so it cannot peel. It keeps a metallic look and comes in a limited palette: natural silver, champagne, bronze and black. A typical coating class is 15 to 25 microns.
Powder coating applies a dry coloured powder with an electric charge, then bakes it into a hard, even film. It offers the full RAL colour range in matt, satin or textured finishes, and wood-grain or stone-effect options. A typical film thickness is 60 to 80 microns.
PVDF is a fluoropolymer coating chosen for high-UV external exposure, where colour and gloss need to hold for many years. It is available in metallic and solid shades. It is usually applied as a liquid paint in several coats and baked.
How they compare
Look
- Anodised
- Metallic and understated: it shows the metal.
- Powder coated
- Wide choice of colours and textures, including solid colours.
- PVDF
- Solid and metallic shades with a consistent colour and gloss.
Colours
- Anodised
- Limited: silver, champagne, bronze and black.
- Powder coated
- Full RAL range, plus wood-grain and stone-effect options.
- PVDF
- Solid and metallic shades. Ask for the available range.
Outdoors
- Anodised
- Good resistance, because the finish is part of the metal.
- Powder coated
- Good for exterior grades. Check the exposure against the powder's rated class.
- PVDF
- The most durable of the three in strong sun, which is why it is used for high-UV exposure.
Touch-up
- Anodised
- Hard to touch up invisibly. Damaged parts are usually replaced.
- Powder coated
- Touch-up is possible but can show. Larger damage means recoating or replacing.
- PVDF
- As for powder coating. Matching a later batch needs care.
Batch matching
- Anodised
- Shade can vary between batches, so process the full quantity together.
- Powder coated
- Consistent from one powder batch. Order enough to finish the job.
- PVDF
- Order the full quantity together to keep the colour matched.
Relative cost
- Anodised
- Moderate.
- Powder coated
- Usually the lowest of the three.
- PVDF
- Usually the highest of the three.
Preparation is half the finish
A coating is only as good as the surface under it. Before painting, aluminium is cleaned and given a chemical pre-treatment, often a chromate-free conversion coating, so the coating bonds properly and resists corrosion at the edges. Skipping or rushing this step is the most common reason a good coating fails early, usually as blistering or filiform corrosion, thin thread-like tracks of corrosion under the film. Ask the applicator to describe the pre-treatment, and ask for the coating's film thickness to be measured and recorded.
Anodising depends on the alloy as well. The same finish applied to different alloys, or to extrusions from different batches or suppliers, can show a slight difference in shade. It is another reason to source all the visible parts from one supply chain.
Standards you may see
Coatings are specified by their performance standards. Anodising is commonly referenced by a class, which is the average coating thickness; the Qualanod quality label is one scheme. Powder coatings are graded by durability, with Qualicoat classes among the widely used references. For liquid-applied paint, the AAMA 2603, 2604 and 2605 specifications describe increasing levels of durability, with 2605 the highest, the one usually associated with PVDF. Which one applies, and which warranty comes with it, is for the facade consultant to set and for the applicator to certify.
How to choose
- Start with exposure. Strong sun, pollution or a coastal setting calls for the most durable finish and proper pre-treatment.
- Decide the look. A metallic look suggests anodising or a metallic PVDF; a specific brand colour points to powder coating or PVDF.
- Match the finish across the facade. Different finishes, or different batches, can show a colour difference, so use one supplier and process for all the visible parts.
- Get the details in writing: the coating standard, film thickness, pre-treatment and warranty.
- Look at a large sample outdoors, not a small chip indoors. Colour changes dramatically between a shop light and the sun.
Looking after a finished facade
Any finish lasts longer if it is cleaned. Dirt, salt and pollution hold moisture against the surface and speed up ageing, and cleaning with plain water and a mild, non-abrasive detergent removes them. Avoid strong solvents, acids, alkalis and abrasive pads, which can attack coatings. Keep the cleaning schedule in the handover manual, because many warranties depend on it.
Which finish, where
There is no universal answer, but some patterns hold. In a coastal city, where salt and humidity attack the surface, a high-durability finish with careful pre-treatment is the safer choice, and cut edges and fixings need extra care. On a hot inland tower with strong sun year-round, PVDF is chosen for its colour retention, particularly in dark colours that heat up and fade fastest. For the inside face of a frame, or a sheltered position at ground level, a standard powder coat is usually enough, and it is the economical way to match a colour. Anodising suits a building that wants the quiet look of metal, and where the batch can be controlled.
Colour, gloss and consistency
Colour is judged against its surroundings. A sample that looks right on a bench can look different against stone, glass and sky. Gloss changes the effect as well: a matt surface looks softer and shows fewer marks, while a high gloss reflects more and shows every irregularity in the metal. Specify the colour by a recognised reference, state the gloss level, and agree how much variation between batches is acceptable. Keep a signed sample on file, because it is the reference that settles any disagreement years later.
What the warranty really covers
Coating warranties are specific. They typically cover defects such as peeling, blistering and excessive fading or chalking, within stated limits, for a stated number of years, and only if the product was applied and maintained as specified. They commonly exclude damage from impact, from harsh cleaning agents, and from conditions outside the specified environment, and may require records of cleaning. Read the warranty before you accept it, and ask who stands behind it: the applicator, the paint supplier or the fabricator.
Questions to ask the applicator
- Which standard and class does this finish meet, and is the coating certified by an independent scheme?
- What pre-treatment is used, and how is it controlled and recorded?
- What film thickness will be achieved, and how is it measured on the finished parts?
- How will the colour be matched from batch to batch, and how much variation is acceptable?
- What does the warranty cover, for how long, and what must we do to keep it valid?
- Can we see a finished sample, a full-size part, and a project that has been in use for several years?
Mistakes to avoid
- Choosing a finish by colour chip alone, without checking the performance grade.
- Mixing parts finished in different batches or by different applicators on one elevation.
- Ignoring edge protection: cut edges, drilled holes and welds need to be sealed or touched up.
- Using a standard powder coat on a coastal tower where a higher-durability finish was needed.
- Forgetting the cleaning regime, and then finding the warranty is void.
Fenza's finishes cover mill finish, anodised, powder coated and PVDF. See the aluminium line and finishes on the Manufacturing page, or ask us which suits your project.
General guidance for orientation, not a specification. Applicable standards, values and details are confirmed per project with the facade consultant.
