Choosing an Architectural Powder Coater
December 2019

First of all it is important to say that ‘architectural powder coating’ on aluminium is different to ‘general powder coating’ and powder coating on steel substrates. Powder coating products that are primarily used indoors require a basic pretreatment to seal and offer a key for the final finish. Powder coating used outdoors and in particular used in construction need a completely different and more robust pretreatment system.

Powder coating, whilst a substantial and stable finish, is porous and allows both water and air to reach the pretreatment system used. Aluminium is a metal which naturally oxidises and forms a protective finish when subject to air and moisture. So whilst a powder coat finish may offer good initial adhesion, with an incorrect pretreatment, which does not passivate the surface of the aluminium, reacts with this permeated water to form salts that break the powder surface bond which allows the coating to simply flake off.

Both QUALICOAT and BS EN 12206:2004 offers a detailed, descriptive methodology of pretreating aluminium prior to powder coating and offers a range of tests to be conducted during production to ensure that the pretreatment is robust for an outdoor application whilst offering a complete air and water seal to the aluminium surface.

Even for the smallest of projects coated for external use, choose your powder coater carefully. If they promote themselves as fully compliant with BS EN 12206:2004 or carry a QUALICOAT licence, which is easily checked on the QUALICOAT UK & Ireland website, then this should be sufficient. If you can visit the powder coater you will see a great deal of emphasis placed on a multistage pretreatment process dedicated to pretreating very long lengths of aluminium profile, 6m or more. In fact the emphasis on the powder coating production would primarily be aluminium profile for windows, doors and curtain walls.

Undertaking work for any client or contractor will require architectural aluminium to be either coated to QUALICOAT or British Standard, ignoring this compliance could cost many more times the coatings costs in the future - is the gamble worth it?

Copies of the new sixteenth edition of the QUALICOAT Standard, is available through the UK Association website, www.qualicoatuki.org together with an up-to-date list of approved Powder Suppliers, approved Pretreatment Suppliers and licensed Applicators.