Polymer films are often pre-treated to alter surface properties resulting in improved adhesion and wettability. The objective of the present work was to demonstrate the applicability of surface-sensitive techniques in the analysis of polymer films coated with thin overlayers. The surface or interphase region of sodium oleate coated polyethylene terephthalate (PET) films was studied by angle dependent x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The effect of corona discharge pre-treatment on sodium oleate coating adhesion was of particular interest. The PET films were analyzed at five separate stages of production; between forward drawing of the PET and corona discharge pre-treatment, both prior to and after sodium oleate coating, after biaxially drawing of the coated film, and, as a final film, after annealing. A comparison was made between corona discharge pre-treated films and otherwise experimentally identical films, which has not been pre-treated. It was determined that corona discharge pre-treatment causes increased surface oxygen on the PET films. This effect disappears with time until XPS analysis shows no difference between treated and untreated films. However, PET films which had been forward drawn, corona discharge pre-treated, immediately coated with sodium oleate, biaxially drawn and then annealed, showed the enhanced surface oxygen after several months of storage. It has been proposed that the mechanism for this phenomenon includes the ionic interaction between the sodium of sodium oleate and the surface oxygen groups, as well as, the increased crystallinity of the PET brought about by the annealing process. Corona discharge processing of polymer films such as PET or polyethylene has been used previously as a means of enhancing adhesion minutes before an adhesion promoter was required. The process described above now allows long-term storage of films with enhanced adhesion properties which in turn makes these films more versatile and practical commercially. / M.S.