Problem with Painting / Finishing of Non Ferrous Castings

In the use of copper and aluminum based castings I often have a variety of final finishes applied either air dried and/or heat cured. Great care is taken to polish, clean, and pretreat the castings prior to the application of final finish however occasionally corrosion will occur beneath the surface of the coating applied to the copper based castings or the paint will pop off of the aluminum casting. There is no specific order to this problem as one batch may not have a problem while another batch may have the problem widespread or sometimes with just a few pieces within a batch. The problem can show up almost immediately or sometimes weeks later. I have gotten a wide variety of feedback from various "informal" sources on this problem indicating such causes as the release of gases from the casting and/or the entrapment and later release of moisture, oils, polishing compounds, etc. I am trying to better understand what the cause might be and am looking for suggestions / solutions to this problem.

Hello,

If you are having outgassing problems, try heating the part prior to painting.