Powder coating vs anodising for export windows
Powder coating and anodising are the two standard finishes for export aluminium windows. Powder coating wins on colour range — any RAL, two coats at 60–80 µm — and on corrosion schedules; anodising wins on metallic appearance, surface hardness and long-term cost for plain silver and grey series. Most export specifications use powder for coloured façades and anodised natural where the metal look is wanted.
What each finish actually is
Anodising is electrochemical: the profile goes into a sulphuric acid bath and the surface itself grows into an aluminium oxide layer, typically 15–20 µm for architectural series. The colour is the metal, not a film on top of it. That is why an anodised frame scratches to the same colour — there is no coating to chip through.
Powder coating is a dry electrostatic process. The profile is converted (chrome-free treatment), coated with polyester powder, then baked at 180–200 °C into a continuous film. A two-coat system lands at 60–80 µm, and the colour library is the RAL chart — which is why "powder-coated RAL" is the line item on most export schedules.
Where powder coating wins
Colour. Every project we have quoted with a specific façade colour — anthracite 7016, jet black 9005, cream 1015 — ran as powder, because anodising cannot reach those colours. Woodgrain transfer also starts from a powder base, so wood-aluminium programmes that need a specified exterior colour are powder on the outside and timber film or stain inside.
Corrosion schedules. Coastal work (Florida, the Australian east coast, the Gulf of Mexico) is specified with a salt-spray test on the coating — commonly 480 h, sometimes 1,000 h for marine lines. A properly cured powder system holds those schedules; anodising is then an additional layer, not a substitute, where the spec calls for both.
Where anodising wins
The metallic look. Anodised natural and anodised silver carry the grain of the extrusion, which plain powder cannot fake. For slim-frame systems and dark-anodised hardware-matched frames it reads more expensive than a flat powder colour, which is why several of our fixed-glazing lines default to anodised on the visible face.
Abrasion and maintenance. The oxide layer is harder than the base metal, so handling marks during container loading show less. There is also no film to cure badly: a line that is down for powder baking is down for everything, which matters on long-lead programmes.
How to choose, market by market
- United States: coloured façades as powder with the salt-spray schedule your insurer asks for; anodised natural for silver series where the architect specifies it.
- Australia & NZ: coastal sites on the salt-fog hardware and powder schedule; anodised for the plain-frame look on hinterland work.
- South-East Asia: humidity and UV favour the two-coat powder system; woodgrain transfer is the common interior/ exterior pair.
- Africa: high UV and dust favour powder on the exterior; anodised holds up well where maintenance visits are sparse.
What we test
Coated profiles go through salt-spray per project schedule, cross-hatch adhesion, and film thickness audit before they enter the sash line. The report for the finish you specified ships with the document pack — the finish on the drawing and the finish on the sample are the same one, verified.
Questions
Polyester powder is rated for outdoor UV; the realistic shift over a decade is lightness and a little chalk, not a colour change. Specify against a physical chip in daylight, not a screen value.