PPG Training

Custom Restoration Guide 2018

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Page 33 of 155

34 METAL TREATMENT Although chemically treating metal and aluminum is the best way to provide corrosion protection for your project, some areas restrict their use due to VOC or heavy metal restrictions. Always check local regulations before beginning your project. Oftentimes, this process is complicated because these products must be rinsed with water. This can be difficult to manage on some vehicles. The process is easy on parts—such as fenders, hoods, doors, etc.—when the part can be kept wet with SX chemicals, then rinsed and dried. The process is harder on larger parts because SX chemicals cannot be allowed to dry before rinsing. Sometimes many hands are required to perform this operation. If help is not available, it may be easier to sand parts or smaller areas, one at a time. The same day that the metal treatment process is completed, remember to apply a coat of epoxy primer to prevent the metal from rusting, oxidizing or becoming contaminated. Do not sand metal treatments; simply apply epoxy primer. HERE IS HOW IT WORKS The acid in Metal Cleaner (SX579) first attacks the metal at the crystalline grain boundaries. This causes the phosphate crystals to begin to grow along these grain boundary lines. After the grain boundaries are attacked, the acid begins to etch the grain surfaces and phosphate crystals appear at these sites. The resulting mass of growing phosphate crystals spreads over the surface and quickly grows into one another. The final surface appears smooth to the unaided eye; however, the iron phosphate surface has left a rough surface to which the epoxy primer can adhere.

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