THE IMPORTANCE OF PRE-TREATMENT
Powder coating is not impervious to moisture so it alone will not stop metal from corroding. Without corrosion protection pre-treatment corrosion will quickly attack the metal, this can rapidly eat away under the surface of the powder coating, causing it to peel and flake off.
A quality pre-treatment provides a protective barrier to resist this corrosive attack and can add years to the life a product. The ultimate durability of any powder coated product is based on the quality of the pre-treatment applied to the metal product prior to powder coating.
The pre-treatment process carries out two functions; cleaning and conversion coating.
On our conveyorised systems the parts travel through various stages of the pre-treatment process. The first stages clean the parts by in line high-pressure sprays of heated water and detergent. This removes oil and dirt from the surface of the item to be coated.
The next stages apply a ‘conversion coating’, this converts the surface of the metal by depositing is a microscopic film of corrosion resistant crystals on the surface of the metal substrate, this also aids in adhesion of the powder coating. The corrosion resistant conversion coatings come in many forms, some specific to particular metals such as Chromate Conversion for aluminium. Ferric metal like steel have traditionally been pre-treated with iron or zinc phosphate.
The newly developed Zirconium or Silane pre-treatments which work effectively across a range of metals. They are also better for the environment and comply to RoHS requirements as they discharge no heavy metals or dangerous by-products into the waste discharge and require less energy to heat the solutions, reducing Green House Gas emissions.
Our largest powder coating line boasts a state of the art eight stage Zirconium based pre-treatment system. Zirconium pre-treatment is the ultimate in corrosion protection on metal products. When we had an automotive industry Hilustre coated products for Ford and Holden on this line to comply with their stringent corrosion resistance specifications.
Magnified 1000 time this photographs below shows the Zirconium microscopic conversion layer deposited on the metal surface.