Powder Coating Washer Stages – A Complete Guide
One of the most critical steps to getting good results from powder coating is properly preparing your product prior to applying powder coating. Common options for powder coating preparation include dipping, or washing parts through a wash treatment system. Dipping is similar to a wash treatment as chemicals are used to clean the product surface, etch it, and protect it. Whether your consider a dip tank powder coating treatment or washer, both rely on chemicals to properly prepare the surface. This guide will cover powder coating washer stages, what the differences are between 3, 5, or additional wash stages, and common chemical treatments that are used for each powder coating washer stage.
Steps Common to All Powder Coating Washers and Pre Treatments
Steps that are common to all powder coating pre treatments including properly washing the part so that any soil and debris left on the surface is removed. Proper pre treatment of a product surface prior to powder coating ensures you do not have issues like fish eye and surface contaminant when you powder coat your part. One important note with washing, washing systems will not remove certain contaminants like stickers, gum, or rust typically. These types of contaminants have to be removed by sandblasting or specific cleaners before using a pre treatment powder coating washer. It is critical to remove rust prior to a powder coating washer because rust will work its way through your powder coating causing your powder finish to fail. Chemicals used for cleaning for powder coating for steel surfaces are typically alkaline based cleaners. For aluminum surfaces alkaline and acid based cleaners are used.
Protective Chemical Treatment – Iron or Zinc Phosphate
After cleaning the part the next step that is universal between powder coating washers both dip and wash treatment systems is a protective chemical rinse. There are two primary protective chemical rinses that are used in powder coating pre treatment. First is Iron Phosphate and second is a Zinc Phosphate protective coating. Both pre treatments serve to provide additional resistance to corrosion and as a base for your powder coating to adhere to. They significantly improve the length of time your powder coated surface will resist corrosion. Between the two Iron Phosphate are typically lower cost and easier to maintain but do not offer the longevity of protection that zinc phosphate treaments due, iron phosphate can be used on steel and aluminum. Zinc phosphate protective treatments offer superior protection over iron phosphate but require more maintenance and upkeep of your powder coating washer.
Common to all powder coating washers is a rinse stage. The rinse stage removes chemical pre treatments which is critical to ensure your surface is free from any chemical contaminants used in surface prep prior to applying your powder coating and to remove any residual contaminants on the products surface as water itself is also a cleaner. This process is typically done with properly balanced water that is different than general tap water.
A final stage common to all different powder coating wash systems whether 3 or 5 stage washers or a dip system is a seal stage. In the seal stage any final contaminant is removed from the product surface and the phosphate whether zinc or iron is sealed in place at a proper ph that is suitable for powder coating. This stage can use a variety of chemicals depending on the protective treatment that is used and other factors.
Differences in 3 and 5 Stage Treatment Systems
While both 3 and 5 stage systems will have a cleaner, phosphate protective chemical application, and sealer there are a few differences between each system as well. Here are the key differences.
3 Stage Powder Coating Washer Systems
3 stage powder coating washer systems will differ from a 5 stage system. The biggest difference in a 3 stage wash system is that cleaning and phosphatizing will typically be combined in a stage. This can result in slightly less effective part cleaning as two steps are being combined into a single step making a 3 stage system less efficient at cleaning than a 5 stage system. There will also be less rinse stages which can result in slightly less effective removal of cleaners and phosphate protective coatings.
5 Stage Powder Coating Washer Systems
5 Stage powder coating washer systems separate cleaning the surface from phosphating rinsing the surface. The cleaner is typically alkaline based which is far superior to acid based rinses and will better clean the surface. Additionally having cleaning and phosphatizing separate results in better protection of the substrate. However additional stages will have an additional cost compared to a three stage system.
Final Thoughts on Powder Coating Washer Stages
While all powder coating washers will have some shared stages like rinse, phosphatizing, and cleaning, 3 and 5 stage washers will have differences in the protection they provide and the quality of surface cleanliness. Ultimately which washer will be right for your application will depend on the specification of protection required by the end customer or your application.