the susceptibility to heat degradation of an autodeposited coating in which the principal organic constituents are copolymers of vinylidene chloride in which vinylidene chloride residues constitute at least half the weight of the total binder phase in the autodeposited coating is improved if the wet autodeposited coatings are rinsed , before being later dried and cured , with a water - based liquid rinse that comprises dissolved phosphate ions in a concentration that corresponds stoichiometrically to at least 0 . 5 g / l of tripolyphosphate ions . the water - based liquid rinse preferably has a strongly alkaline ph and also comprises dissolved organic molecules that are effective chelating agents for dissolved iron cations by reason of having in each molecule at least two carboxyl , carboxylate , and / or other hydroxy moieties .