The secret to any successful painting process begins with the cleaning process. The performance of powder coating is significantly influenced by its ability to adhere properly to the substrate material. Surface preparation is the most important factor affecting adhesion in the powder coating process. The presence of even small amounts of surface contaminants, oil, grease, oxides etc. can physically impair and reduce coating adhesion to the substrate.
Many fabricators struggle with the surface preparation of metal fabricated parts due to the lack of adhesion on the edge of parts processed through the laser. During the laser cutting process oxygen is used an assist gas during laser cutting of mild steel. The oxygen causes an exothermic reaction that creates heat, which helps the laser cut through the metal. The oxygen creates an oxidized edge that makes it difficult for powder coatings to adhere to the area exposed to the laser cutting.
To provide adequate cleaning A-1 Fabricators & Finishers provides a 5 stage cleaning process that removes this oxidation and allows for proper adhesion of the powder paint to the material. Listed below are the 5 stages and a brief description of each stages function.
Stage1: Acid – Descale or Laser Etch
1st step of the process is the spray application of a liquid acidic compound used to remove laser edge oxides and heat scale.
- Removes Laser Edge Oxide
- Removes Heat scales
Product is then rinsed with a water spray to stop the acid cleaning process
Stage 3: Iron Phosphate – Cleaner/Coater
Parts are then sprayed with an acid cleaning concentrate that also applies an iron phosphate conversion coating. The coating provides an etching on the material that enhances paint adhesion.
- Provides etching enhancing adhesion
Stage 4: Rinse
Product is again water spray rinsed to stop the phosphate etching process.
Stage 5: Seal/Rinse
Final stage applies a sealer that is safe for all metals. Sealer application provides a rust inhibitor that prevents flash rust of materials.
- Safe for all metals
- Controls flash rust
- Improves salt spray and humidity test results
To assure proper adhesion is achieved in the cleaning process prepared samples are Cross Hatch Tested at a minimum of twice per shift. A crosshatch pattern is made though the film to the substrate. Detached flakes of coating are removed by brushing with a soft brush. Pressure-sensitive tape is applied over the crosshatch cut. Tape is smoothed into place by using a pencil eraser over the area of the incisions. Tape is removed by pulling it off rapidly back over itself as close to an angle of 180º. Adhesion is assessed on a 0 to 5 scale, reference ASTM D3359-09E2 Test Method B for Cross Cut Tape Test Requirements. Click on link to review testing process. https://www.youtube.com/watch?v=EyzzUVjEGnU