Metallic copper pigments are just metal powders with shiny, reflective, wide surface particles.  One of such powders is copper powder with product code CU7005F.  In art related industries however this product is known as Gold Leaf or Gold Powder.  Such terms only describe the look or appearance of the product. This product does not contain any gold at all. It is just copper, but it looks like red gold.

While gold does not rust at all, copper based gold leaf products need to be protected against rusting by wax, varnish or any other protective layer.

Particles of metallic pigments are usually coated with about 0.5% emulsifying wax/ grease that protects them against rusting, but it also makes it possible for such powders to easily disperse in any water based or oil based carrier.

Learn more about copper pigment CU7005F