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GUIDELINES: POWDER COATING
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Powder Coating is a fast growing method of adding colour to metal
surfaces. Like galvanizing it is carried out under carefully controlled
conditions in a factory. For this reason the maximum size of the steel
fabrication to be powder coated will be limited, but powder coatings
can be applied successfully to hot dip galvanized surfaces.
The thermal characteristics of galvanized steel are almost identical to
those of un-galvanized steel for powder coating purposes and there are
many examples of steel which has been galvanized and then powder coated
However, the pre-treatment of the galvanized surface will depend upon
which of the many powder types such as polyester, epoxy, or hybrid is
being used. This usually includes a form of chemical pretreatment such
as chromating or phosphating, gentle heat treatment, followed by
application of the powder. The successful application of a powder
coating to any metallic surface requires the multistep instructions
provided by the powder manufacturer to be respected in every detail For
this reason an experienced or approved applicator should be asked to do
the work. As with wet painting, a full range of colours is available.
Powder coating of galvanized steel for architectural applications is
covered at present by BS EN 13438.
It is important that the galvanizer is advised that work is to be
subsequently powder coated and post-galvanizing treatments agreed with
the powder coater.
A limited number of direct application products are now available for use on galvanized steel work. Given adequate preparation work, the use of direct application paint negates the need for any chemical or mechanical pre-treatment to be conducted. These products are known to have been used in a variety of applications.
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