6.3.6 Tape Coatings  There are two main types of tape coatings: particulate and evaporated. The earliest coated data tapes used metal oxides similar to video tape, whereas more recent data tapes use metal particles (MP). Pure iron with inert ceramic and oxide passivation layers is dispersed in polymer binders which are applied evenly to a PET or PEN base-film or substrate which in turn provides dimensional stability and strength under tension. Some of the highest density data tapes currently on the market now use evaporated metal foil coatings of cobalt alloys and similar material to those used on hard disks. This achieves a much higher purity of magnetic material and allows thinner coatings. Most metal-evaporated (ME) tapes have a protective polymer coating similar to the binder material on MP tapes. The more recent formulations include a ceramic protective layer as well. Several of the early ME tapes failed during heavy usage due to de-lamination (Osaki 1993:11).