Described is a coating composition adapted to enhance the adhesion of a polymeric coating or film applied to a substrate. The coating composition is interposed between the substrate and the polymeric coating and comprises (a) at least one coupling agent, partial hydrolysates thereof or mixtures thereof in a concentration greater than 25 weight percent, based on the weight of the total composition, and (b) an adhesion enhancing amount of an epoxy-containing material having at least two epoxy groups. The coating composition is substantially free of photochromic materials and colloidal particles chosen from silica, alumina or mixtures thereof. Also described is a process for using the coating composition and articles coated with the composition and additional coatings and films which can be photochromic.