PTI's Magnesium Coatings department offers three types of coatings for magnesium. Our processing of Magnesium includes Anodizing (Dow 17), Chemical Conversion (Dow 7), and Chromic Acid (Dow 19).
PTI's experience with Magnesium goes beyond coating of conventionally machined components to include coatings on components produced by newer techniques such as Thixotropoic Molding. Our staff can advise customers on which coating method is most suitable to their needs, Dow 7, Dow 17 or Dow 19.
Dow 7 is a good choice for both new and overhauled parts that have dissimilar materials such as inserts, or where conditions will tolerate a less robust and less costly alternative to Dow 17. Dow 7 is a chemical conversion coating which results in no appreciable dimensional change to the component. The surface of components coated with Dow 7 is changed to a brassy or dark brown finish depending on the alloy. PTI can forward parts to local vendors for painting as well, saving our clients time and lowering shipping expenses.
Dow 17 is an anodic process that imparts a hard, corrosion resistant coating to all Magnesium components regardless of alloy. The Dow 17 process results in a green or dark green surface finish that varies with alloy. After the Dow 17 process, the parts resistance to corrosive elements and abrasion are greatly improved and the surface is now ready for post-treatments including painting.
Chromic acid, also known as Dow 19, is a treatment that is used on magnesium parts that need a spot touch-up to repair minor damage or a temporary coating to prevent corrosion between production processes. Parts can be coated with Dow 19 by manual application or by immersion in a tank of Chromic Acid. After Dow 19 coating, parts appear to be a brassy brown color but can vary slightly depending of the alloy. There is no appreciable dimensional change to the component from the Chromic Acid process.