Machinery & Manufacturing
The Key to Architectural Powder Coating Sustainability
Architectural Aluminium Powder Coating is applied using the well known methodology of spraying electrostatically charged fine polyester based powders onto a product . Coated aluminium products are then heated to an optimum temperature to melt the powder which allows it to flow and chemically cross-link into a sustainable coating . As the product cools the coating sets and the finish is complete . The problem is , like most applied opaque coatings , the finish may look good , but the coating can hide a multitude of problems on the surface of the metal . If contaminants are present , or a pre-treatment process is lacking , a failure of the coating will become evident over time .
Prior to powder coating architectural aluminium , it is crucial that the aluminium surface is subject to a ‘ pre-treatment ’ process which includes an etch stage to remove contaminants and then a passivation or conversion coating to ‘ seal ’ the surface of the aluminium which also provides a ‘ key ’ for the adherence of the coating . These very thin conversion coatings can be formed of a non-chromate or a very thin anodising process .
For an architectural powder coater a pre-treatment plant is a significant investment often costing as much , if not more than the powder coating line itself . Few powder coating lines in the UK have this substantial facility and those that do will claim to powder coat to BS EN 12206-1 or become licensed to powder coat to the more substantial QUALICOAT specification .
Often in an attempt to reduce costs through the supply chain , installers of architectural aluminium products will use powder coaters who often do not possess the correct pre-treatment lines . There is also the possibility that some coaters who do have the correct pre-treatment systems do not have suitable controls in place and the quality of the coatings can vary , even though they can claim to coat to BS EN 12206-1 .
A QUALICOAT licensed applicator , on the other hand , must use a pre-treatment system that is QUALICOAT approved and utilise powder systems that are also approved by QUALICOAT , this ensures quality is maintained through the coating process . Furthermore , QUALICOAT licence holders are randomly inspected twice a year to ensure the QUALICOAT specification is being met . Licensed coaters who fail these third-party inspections , will lose their licence .
So , the best specification for any architectural powder coating project should simply be ‘ coated by a QUALICOAT licensed applicator ’. Known across the globe , with a global supply chain and local licensed coaters , a QUALICOAT specification can be supplied on any continent .
Powder coat failures fall into two broad categories , that of a complete failure of the coating where it simply peels off and failure called ‘ filiform corrosion ’. This is where oxidisation forms at the edge of a cut or punched hole in the aluminium and appears under the coating as spider like strands of corrosion . Often this failure is seen several years after installation and indicates poor pre-treatment prior to powder coating .
Other problems with powder coating can include fading of colour , loss of gloss and ‘ chalking ’ of the surface finish . The first two are generally a normal ageing process and the powder coating should still adhere fully to the aluminium and continue to protect the aluminium .
74 JANUARY 2025 CLEARVIEW-UK . COM