By Chris Mansfield – QUALICOAT Chair
Architectural powder coating is renowned for its ability to give aluminium windows, doors, and facades a tough and visually appealing finish. The secret to the durability and longevity of powder-coated windows and doors lies in the pre-treatment process. This process prepares the aluminium surface to ensure a strong bond and protection against corrosion.
Architectural Aluminium Powder Coating is applied using the well-known method of spraying electrostatically charged fine polyester-based powders onto an earthed aluminium profile. Coated aluminium products are then heated to an optimum temperature to melt the powder, allowing it to flow and chemically cross-link into a sustainable coating. As the product cools, the coating sets, and the finish is complete. However, like most applied opaque coatings, the finish may appear aesthetically pleasing, but the coating can conceal a multitude of underlying issues on the metal’s surface. If contaminants are present or a pre-treatment process is inadequate, a failure of the coating will become evident over time.
Prior to powder coating architectural aluminium, it is imperative that the aluminium surface undergoes a ‘pre-treatment’ process. This process typically includes cleaning and an etch stage to remove contaminants and a subsequent passivation or conversion coating to ‘seal’ the surface of the aluminium. This conversion coating also provides a ‘key’ for the adherence of the coating. These extremely thin conversion coatings can be formed using a chromate, non-chromate process or a very thin anodising process. Whilst chromate processes are still approved in the global QUALICOAT Specification, in the UK chromates are not allowed in architectural powder coating processes.
Modern, chrome-free pre-treatment systems are meticulously engineered to deliver performance characteristics that are comparable to or surpass those of conventional chromate-based processes. Once powder-coated, these systems exhibit exceptional corrosion resistance, a crucial factor in project applications where materials are subjected to harsh weather conditions and environmental pollutants. Furthermore, chrome-free pre-treatments enhance the adhesion of powder coatings, ensuring enduring finishes that withstand peeling, chipping, and fading. This durability holds significant importance in high-visibility projects, such as commercial buildings, residential complexes, home improvement projects and public infrastructure, where aesthetic and functional longevity are of utmost importance.
For architectural powder coaters, a pre-treatment plant represents a substantial investment, often costing as much, if not more, than the powder coating line itself. Few powder coating lines in the United Kingdom possess this substantial facility, and those that do will assert that they powder coat to BS EN 12206-1 or as most coaters now do, obtain a license to powder coat to the more comprehensive QUALICOAT Specification.
Regrettably, in an attempt to reduce costs through the supply chain, installers of architectural aluminium products may employ powder coaters who often lack the appropriate pre-treatment lines required by BS EN 12206-1 for architectural powder coatings. Furthermore, there is the possibility that some coaters who do possess the correct pre-treatment systems may not have adequate controls in place, resulting in varying coating quality, even though they may claim to adhere to BS EN 12206-1.
In contrast, a QUALICOAT-licensed applicator must employ a pre-treatment system that is QUALICOAT-approved and utilise powder systems that are also QUALICOAT-approved. This ensures that quality is maintained throughout the coating process. In contrast to BS EN 12206-1, QUALICOAT license holders are subject to random inspections twice a year to verify compliance with the QUALICOAT Specification. Licensed coaters who fail these third-party inspections will lose their license.
Being licensed by QUALICOAT does not incur a cost premium for a powder coater, in fact the opposite, it can help reduce costly failures for coaters as many more checks are in place for a quality process and production output.
The most suitable specification for any architectural powder coating project, commercial or residential, should simply be “coated by a QUALICOAT-licensed applicator.” Recognised globally, with a global supply chain and local licensed coaters, a QUALICOAT Specification can be supplied on any continent.
Should you wish to attend a members meeting and apply for membership of QUALICOAT please get in touch. All QUALICOAT UK & Ireland members are available to offer advice and can be found on the Association website at qualicoatuki.org
