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
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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