Described is a coating composition adapted to enhance the adhesion of a coating or film to a substrate. The coating composition includes 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 an adhesion enhancing amount of an epoxy-containing material having at least two epoxy groups. The coating composition is free of colloidal particles chosen from silica, alumina or a mixture 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.