We recently had a customer question about how to prep bare aluminum before applying touch up paint. Because it is bare metal, we definitely need to prime it for adhesion. But does aluminum (or steel) get a special treatment, such as etching primer or something else? Here's the process we recommend.
The Question: "Hi! I'm interested in buying your touch up paint kit, I own an alfa romeo giulia quadrifolio, which has aluminum doors. I have a small chip where it seems as the paint has completely come down to the metal. I am wondering if the primer in this kit is applicable to the QV model which has a aluminum doors."
The Answer: When preparing aluminum for paint, it is important to either use a self-etching primer, or use a special metal prep wipe for aluminum. The reason is, etching primer has a special formulation that contains chemicals that micro-etch the surface of the aluminum for the best bond possible. Follow the manufacturer's directions, which are typically to apply it (brush or spray) in two thin coats. Noe that it is often necessary to seal the etching primer coat with a second coat of regular primer.
If you don't have an etching primer, you can use a metal prep wipe such as this one from BASF: https://refinish.basf.us/products/2000-advanced-prep-wipes/
If you use a prep wipe, make sure you apply the first coat of ScratchesHappen primer within ten minutes of prepping it. Then, for your second coat, you don't use the metal prep wipe, just apply the primer as usual to seal it.
The ScratchesHappen primer works well over bare aluminum (and steel and plastic), and we recommend the use of a metal prep wipe for aluminum or steel.