There’s old saying in the powder coating industry “start right- finish right” meaning that proper pre-treatment with is the foundation of quality long-lasting and durable finish. And in a word that means chemistry.
No other single factor influences the end result and reject ratio more than the proper pre- treatment chemistry. Whether coating aluminum or steel, plastics and ceramics. There is a specific pret-reatment formula that must be followed for each material type.
Today’s powder coating pre-treatment chemistry goes well beyond the removal of dirt, oil, grease and other contaminants. They are often used to seal parts from corrosion and to chemically etched them or give them a tooth for the powder to adhere to.
Depending on the type of material or metal
the pre-treatment process is different. For instance, when treating mild steel, there are three major forms of cleaning. They are; solvent-based degreasers, alkaline-based degreasers, and acid-base degreasers. Once the part has been fully cleaned and rinsed then it is phosphatized to prevent rust and corrosion. For more information please visit our publication library.
With aluminum the pretreatment process is completely different. Thanks to its tendency to oxidize within minutes of pretreatment. So with aluminum the part goes through the traditional stage one cleaning and stage II rinse, then it is covered with the chromium-based film to prevent re-oxidization.
Cast metals have yet another entirely different cleaning process. They are first cleaned either with and acid-base or alkaline-based de-greaser, then water rinsed and related in a similar fashion to aluminum.
Galvanized materials have a tendency to form a layer of zinc oxide or oil on the surface preventing the proper adhesion of the powder to the substrate so in the case of this material depending on whether it’s galvanized steel or galvanized aluminum, the pretreatment may be different, however in most cases it follows the same eight stage pattern which is alkaline degreasing, followed by a water rinse followed by an acidic degreasing followed by a water rinse followed by an alkaline activation followed by zinc phosphating followed by yet another rinse and finally a sealer. to learn more please visit our library section.