The invention relates to two-component coating systems comprising as component (a) one or more polyisocyanates, as component (b) one or more oligomeric and/or polymeric compounds that are reactive with component (a), and as component (c) one or more phosphonates selected from the group of phosphonic diesters and diphosphonic diesters, where (i) component (b) comprises all oligomeric and/or polymeric compounds that are present in the two-component coating system and are reactive with component (a) and (ii) component (b) contains not more than 15% by weight, based on the total weight of component (b), of oligomeric and/or polymeric compounds which carry isocyanate-reactive amino groups. Additionally provided by the invention are a process for preparing the two-component coating systems, and the use of these coating systems as a clearcoat, more particularly for multicoat automobile finishing.