The electrodeposition of paints has found wide spread interest. In an electrocoating process, aqueous dispersed macroions deposit on a work piece through the action of an electric field. Complete automotive bodies were electrocoat-primed in a pilot installation in the Ford Manufacturing Development Center and subsequently completed vehicles were subjected to test runs on the Ford Arizona Proving Grounds to determine the corrosion resistance of the electrocoatings. Based on results of these test track runs, electrocoating tanks were installed in a number of Ford assembly plants.A comparison of salt spray tests, 40-cycle test track runs, and cars that have been reacquired from customers after five-year use in the Detroit area as methods for evaluating the durability of electrocoats is presented. Improvements in electrocoating are continuing, particularly in their ability to protect recessed areas against corrosion.