1. Clean the substrate: Teflon® coatings should be applied over clean substrates. If there are any contaminants on the part, the coating will have defects and not perform as well. You can use chemical washes, solvent cleaning, or degreasing, but make sure all the residue from the cleaning has been removed. Gloves should be worn after cleaning to avoid getting fingerprints on the metal. Fingerprints and any residual oil not removed during cleaning may show up as stains on the cured coating.
2. Preheat the part: If you heat the substrate at the cure temperature for the coating, it will help remove any residual oils and minimize the effects of humidity. Also, with most ferrous metal, this step will temporarily protect against flash rusting. If you are using acid primer, the blue oxide that forms increases the adhesion of the coating.
3. Roughen the surface: Grit blasting is the most commonly used method to increase the surface profile of the substrate, improve adhesion, and remove any contaminants left over from cleaning. DuPont recommends surface profiles of at least 100 microinches (2.5 microns), and 200-250 microinches (5.1-6.5 microns) are frequently used. DuPont recommends aluminum oxide as your blast media, but there are other options such as glass beads and walnut shells. Commonly used air pressures range from 80 to 100 psi, but the pressure you use depends on your substrate. Make sure the profile is uniform and fully covers the whole surface. Excessive or high pressure grit blasting causes pits, scratches, and cuts that can result in a bad finish, so be careful not to overdo it. If your part is too small to grit blast, zinc or iron phosphate conversion coatings can be used to increase coating adhesion.
4. Cure the coating: Curing is the last step to good adhesion of your Teflon® coatings. Reaching and maintaining proper cure temperatures for a sufficient period of time to cure the coating is one of the most important factors in achieving a finish with optimal adhesion performance. Don’t forget: all temperatures mentioned in the Fact Sheets refer to metal temperatures, so the part itself must reach the recommended cure temperature. Ovens should be calibrated at least twice per year, and thermocouples should be used to check part temperatures. Each coating has different curing instructions, so always check the Fact Sheets first, and always follow the cure schedule very carefully.
Have a Blast, But Keep It Safe!
Click here to check out Intech Marketplace’s selection of blast gloves and suits. Blast gloves keep your hands and arms safe while you’re grit blasting your substrate. Blast suits are also important to provide for your employees because they are designed specifically to protect against harsh blasting environments.
Intech Marketplace makes shopping for blasting equipment and other coating products easy because all the supplies you need for your shop are just a click away in a single location. If you’re not sure what you need, call 302-366-8530 for help selecting products.
