Q. I have a 6020 aluminum part machined with a naphthenic cutting oil and a synthetic water soluble cutting fluid. The part has a black anodized finish on the outside and a bare aluminum surface that has an acrylic base coat that is not wetting out and is blotchy. What is the best cleaning procedure to prepare the bare aluminum surface for the acrylic base coat? H.A.
A. I assume you are performing two machining operations, one with a “straight” oil (naphthenic) and one with the synthetic fluid. Otherwise it’s unlikely you would be able to keep the naphthenic oil in suspension. Regardless of the machining steps, the next consideration would be your production process. In other words, high volume, low volume, level of automation, production floor plan, etc.
On one end of the spectrum (high volume), if your machining operations are done in a central cell location, a conveyorized aqueous spray washer would fit smoothly into your process. A less automated, medium volume process may steer you toward a single-stage cabinet-style wash system. Both of these systems would require an appropriate spray cleaner for the process. A very low volume, labor intensive process may suggest a small wash cabinet where parts are individually handled and washed with a “safety solvent” (a solvent that has a flash point above the combustible limit of 140ºF). You need to validate compatibility with either a solvent or aqueous solution by cleaning sample parts and coating with your acrylic base coat. I suggest finding suppliers by searching pfonline.com.