Burndy Penetrox A consists of a natural (petro- leum) base vehicle in which zinc particles are suspended. For aluminum to aluminum, aluminum to copper applications and aluminum conduit threads. It is not recom- mended for use with rubber and polyethylene insulated conductors. UL Listed to 600 volts. When stored in its original container in cool (under 100 degrees F) dry environment, Penetrox oxide inhibiting compound will remain workable and functional for 5 years from the date marked on the container provided it is mixed per instructions prior to use.