Aluminium pre-treatment consists of dipping the product in various chemicals to prepare the product prior to coating.
This process is paramount to coating aluminium because it seals the product and creates great adhesion properties, products that have not been pre-treated will fail due to the oxidisation process of the aluminium, and this in turn will push off the powder coat that had been previously applied.
The process begins with the aluminium being placed into an etching solution which will remove the surface layer in (microns), which removes any oxides or foreign substances.
It is then placed in deionised water to rinse any etching fluid from it before being placed in a chromate solution which acts as the protective coating and seals the aluminium, which stops oxidation and creates great adhesion.
Finally, it is rinsed in deionised water, which is the final stage of the pre-treatment prior to the powder coating process.
If an aluminium product is to be installed within 1km of coastal areas, it is highly recommended that an epoxy primer be used as the first coat prior to the finish coat to improve the durability.
The basic preparation treatment for this material, is to remove any dirt/grease with a solvent solution and thoroughly around any welded areas, prior to the powder coating process.
Preparation consists of sandblasting the product which would remove the surface layer of the object, freeing it of any foreign materials, scale or rust.
Then a Zinc primer would be applied to the object which would seal and add protection to it prior to final coat. Note: it is very important that the time scale between the sandblasting process and the first sealer coat is kept to an absolute minimum, this is because the object is open to the elements and almost immediately the oxidisation process starts, which is worse in damp conditions.
Once the zinc primer coat has cured, the final colour coat can be applied and again cured in the oven at temperatures around 200C.
Dura Galv Steel
This product is usually coated in a clear polymer coating which is used to protect it during the manufacturing and handling process.
Ideally it is beneficial to have the product lightly whip blasted and primed prior to coating to create greater adhesion properties.
Generally, this steel is usually fine to coat straight over in basic form, as long has it has not been fabricated.
If it is a fabricated item ie: it has welds, we would recommend the same pre-treatment process as the black/blue steel (External Use).
Hot Dipped Galvanised Steel (HDG)
This steel can be powder coated, but there are many factors to consider.
HDG has a galvanised coat which comes with many imperfections and commonly has lumps/bumps and tags associated with the finish.
Prior to the steel product being hot dip galvanised the customer should request that the product be “air quenched” and not “fluid quenched”, which means that once the product has been submerged in the galvanise solution it is left to “air cool” rather than use fluid to cool it down, this process is a must for any HDG item to be powder coated.
Next a whip blast is recommended, to remove any possible impurities and stabilise the surface.
Finally the coating process is the same as black/blue steel (external use), but this time using an epoxy primer instead of a zinc primer, before the top coat finish.