Link: http://adteputek.com/b2evolution/blog2.php/2010/02/15/taking-into-consideration-the-substrates

When selecting an adhesive one needs to take into consideration the substrates surface energy as a factor in determining which adhesive is used and whether a primer is necessary. All metals have a high surface energy and thus are relatively easy to bond to. High Surface Energy Plastics include Kapton® (Polymide), Phenolic, Nylon, Alkyd Enamel, Polyester, Epoxy Paint,Polyurethane Paint, ABS, Polycarbonate, PVC (Polyvinyl Chloride), Noryl®, Acrylic, and Polane® Paint. I recently had a project for bonding to two small injection molded pieces made of pvc resin for a presentation laser pointer. I selected the Parfix 3422 Ethyl Cyanoacrylate, as a surface insensitive adhesive was not needed. Low surface Energy Plastics include PVA, Polystyrene, Acetal, EVA, Polyethylene, Polypropylene, Tedlar®, and Teflon®. These might include both a Surface Insensitive Adhesive and a Primer.

Link: http://en.wikipedia.org/wiki/primer_usage

Anaerobic adhesives include retaining compounds, threadlockers, gasketing compounds, and thread sealers. Anaerobics cure in the absence of air and the presence of metal ions, primers ensure proper performance of the Anaerobic Machinery Adhesive when assembling inactive metal parts, which are low in metal ions. The following are inactive metals: Gold, Silver, Iconel, Magnetite steel, Black Oxide, Magnesium, Cadmium, Pure Aluminum, Zinc, Galvanized Steel, Stainless Steel, Titanium, Plated Parts, and Anodized Aluminum. The following are active metals: Iron, Plain Steel, Copper, Brass, Bronze, Nickel, Manganese, Monel, y Kovar. Primers are especially important for challenging assemblies of metal parts that are cold, have large gaps or deep threads.