Surface World July 2019 Surface World July 2019 | Page 196

QUALICOAT UK & IRELAND First we have the issue of potential corrosion of the aluminium under the powder coating which will result in blistering under the powder coated surface. Secondly, we have the performance of the coating, basically a resistance to UV. This is where the coating can fade or chalk over time. as a result of free-radical UV degradation of the polymer matrix. As the polymer matrix gradually breaks down it exposes the pigment and inorganic fillers contained within the paint film. Importantly this can be relatively easily removed from the film by adopting a regular cleaning regime. Powder coating is not impermeable, water and air can, and will, penetrate its thickness, so we have to ensure that the aluminium is very carefully pretreated. This pretreatment consists of cleaning and etching the aluminium prior to applying a pretreatment system, chrome based or chrome- free, which will completely seal the aluminium surface and offer a good ‘key’ for the powder coating to adhere to. A quality pretreatment is crucial to getting a long lasting powder coat finish. Pretreatment systems can be immersive or sprayed, but the plant investment and space to do this correctly is excessive hence the reason why ‘general’ powder coaters do not have this as a standard process. Fade on the other hand, whilst also UV catalysed, is a different mechanism. Generally bright, clean organic pigmented colours such as bright yellow, orange & reds are more susceptible to pigment fade which will occur on almost any applied finish. More recently, we have seen the availability of flash anodised pretreatment systems become available in the UK. This system of pretreatment can cope with the harshest of environments and can be specified where access to finishes make it difficult to offer regular maintenance. There is what is known as a ‘Marine Class’ of coating, or ‘Seaside’ Class under QUALICOAT. This is where powder coating is going to be placed near to coastal regions and offers a deeper etch of the aluminium for a more robust pretreatment application. Flash anodising can also be specified in these more severe weather rated areas. Once powder coating is applied and cured correctly, the powder coating on the project will be subject to UV (Ultra Violet) attack over time, this can become evident in two ways. First, ‘chalking’ on the surface can occur, these are which deposits and are LIVE 2020 194 Powder coatings are now available in three Classes, 1, 2 & 3. Most low rise city projects are coated in Class 1 powders, but there is a growing increase in the specification of Class 2 powders in the UK. Class 2 powders have a higher resistance to attack from UV and have reduced UV degradation as a result. So in closing, for a long architectural powder coating life, make sure your Powder Coater has the pretreatment system and experience in place, or just talk to, a QUALICOAT member and specify for peace of mind. Copies of the current fi fteenth edition of the QUALICOAT Standard, complete with amendments and updates, are freely available through the UK Association website, www.qualicoatuki. org together with an up-to-date list of Powder Suppliers, Pretreatment Suppliers and Applicators. Printed literature and telephone support is available from QUALICOAT UK & Ireland Head Offi ce in Birmingham on 0121 601 6746 or email enquiries@qualicoatuki. org. The Association can also be followed on Twitter @Qualicoat. Surface World Live 2020 will be returning to Hall 11 at the NEC in Birmingham. The next show will be held on the 18th & 19th March 2020. - we have everything covered 2019 - 2020 If you are interested in booking a stand then call Nigel Bean on 01442 826826 or send him an email at [email protected] read online: www.surfaceworld.com