Maintaining the Architectural Powder Coating Colour
Typical installation of architectural powder coating
As with any applied finish exposed to British weather, it is important that a maintenance regime is put in place to keep it performing and looking well for many years. If neglected, over time atmospheric pollutants are deposited on the surface of finishes and if not removed, these pollutants can affect the colour and surface finish. So what should we be specifying by way of finish and maintenance?
Aluminium window and facade longevity starts with a high quality aluminium substrate pretreatment followed by a quality powder coat finish as provided by a licensed QUALICOAT applicator. Often overlooked in the specification process, the pretreatment of the aluminium substrate is crucial as this process needs to completely seal the surface of the aluminium, whilst offering a good key for the powder coating to adhere to. Despite the powder coating being of a consistent thickness, powder coatings are air permeable and if the pretreatment is poorly applied or non-existent, oxidisation of the aluminium substrate over time will cause the finish to lift. QUALICOAT UK & Ireland applicators are routinely inspected by independent test house IFO to ensure the latest QUALICOAT specification is being adhered to which ensures that a robust consistent pretreatment is applied.
Prior to handover of any new installation or building, coated aluminium fenestration will be cleaned down professionally and checked to ensure that the finish is not damaged. It is crucial to have any areas of impact or abrasion damage professionally repaired to ensure a valid warranty is offered across the whole installation. During cleaning, all the protective tape must be removed from the inside and outside of powder coated surfaces as if this is left on for an extensive time, the tape’s low-tack adhesive can often degrade, especially in UV light, and become firmly attached to the powder coating.
Once handed over to the client, in normal use such as in cities, the powder coat finish should simply be washed down at yearly intervals with clean water or with a ph neutral mild detergent solution in water. This should be enough to protect the visible surface of the powder coat for many years and can simply be done during the cleaning of windows. The powder coat finish wash down is especially important where squeegee bars are used to clean the glass, as their use tends to place the residue of the airborne contaminants directly on the powder coated frame which may begin to etch into the surface finish of the coating. During maintenance, window cleaners must ensure that all powder coated surfaces are wiped clear of glass cleaning residue.
Whilst the original colour of the powder coating can be affected over time by contaminants in the atmosphere, we also need to consider UV degradation. Ultra violet light can fade rich colours, especially rich bold red’s and blue’s. UV exposure can also reduce finish gloss levels over time.
Elevations exposed to sunshine and effected by UV degradation can display a surface ‘chalking’, which is appears as a whitening of the surface. Chalking is caused by UV radiation which brings the binder in the powder coat to the surface and is not an indication that the powder coating has failed but is an indication that cleaning has been neglected. Again, regular cleaning cycles should keep any chalking to a minimum. Should a product or facade be allowed to fall into this state, there are specialist cleaning companies who should be able to clean and restore the facade to its original colour.
Powders can be supplied in various grades of durability to suit a project application. Premium powder compositions use more expensive and robust materials to offer life expectancies well beyond thirty years and often similar life expectancy of the building itself. QUALICOAT has created quantifiable performance classifications for architectural organic coatings. In Europe there are three distinct classes of performance - Classes One, Two & Three.
The key parameter to distinguish the performance of these classes is their ‘weathering’ ability. That is to say, the ability to maintain a consistent colour and gloss level over time. To ‘weather’ well, the organic coating must resist the deleterious affects of Light (in particular UVa & UVb), temperature and humidity. The globally accepted method for this ‘natural weathering’ test is conducted in Florida, USA. Sample panels are set for external exposure at a given angle 5° South. Powders are then classified over time exposure on a given scale. In the UK the standard class used is ‘Class One’ for most installations, but where prestigious buildings are being constructed, a more robust ‘Class Two’ is being specified on a growing number of specifications.
On new and refurbished commercial building projects, powder coated facades will always be accompanied with a cleaning and maintenance regime from the company who coated the aluminium profiles. These will offer a minimum cleaning regime which will need to be adhered to as well as being regularly recorded. This will ensure the coated finish is maintained within the applicators warranty and will help, should there be any claim in the future. Warranties offers vary in length and are dependent on the powder coat finish used and the location of the installation. For example, where the coating is close to the sea, a marine grade or QUALICOAT ‘Seaside’ specification for the coating should be specified and the cleaning regime will often be increased to at least three monthly intervals as the atmosphere is more corrosive.
Crucial to any maintenance regime is preventative maintenance and powder coating is no exception, if the coating has become damaged, exposing the aluminium, it should be repaired as soon as possible. For repair, either contact the original coater, or approach any QUALICOAT approved applicator who can normally offer guidance.
To determine the best specification for any given project, a call through to a QUALICOAT licensed applicator should assist any specifier.
QUALICOAT UK & Ireland offer a basic guide which can be downloaded from their website. This can be referred to as where the original maintenance information has been mislaid and not available to refer to.
The current QUALICOAT Specification is freely available for download via the Association’s website, qualicoatuki.org and offers an up-to-date list of licensed UK and Ireland Powder Suppliers, Pretreatment Suppliers and Applicators. Telephone support is available from QUALICOAT UK & Ireland Head Office in Birmingham on 0330 236 2800, the Association can also be followed on Twitter @Qualicoatuki.