copper and acrylic

​Because copper can oxidize and corrode, we have taken to recommending that people “prime” the copper with Incralac, which is a protective coating made for copper statuary and other art objects.  You can usually find it through conservation supply stores, such as Talas or Conservation Support Systems, to name two:
http://www.talasonline.com/search?keywords=incralac

http://www.conservationsupportsystems.com/product/show/incralac-solvent-based/metal-coatings

We have tested the adhesion of our own GOLDEN Heavy Body and Fluid acrylics onto Incralac and so far it has been excellent. We have not tested other brands but have no reason to suspect they would perform differently, but testing is always recommended. Even in terms of our products since our own testing is but a snapshot in time and products constantly change.
Also,  keep in mind this is a bit of an off-label use for this product which is normally employed as a topcoat, and we also have not had very long-term experience using it as a primer. However, it should be a stable coating when used indoors, and remains the best solution we can think of if wanting to preserve the look of the copper.  But Kristin and Brian, the two conservators on MITRA, might have additional thoughts.

Finally, and especially if you are using the Incralac at high gloss, you might also want to consider adding something like GOLDEN’s GAC 200 into our paints at a 1:1 ratio on the first pass. It helps promote adhesion to non-porous surfaces and gives the acrylic a harder film. 
Hope that helps.

Sarah Sands
Senior technical Specialist
Golden Artist Colors