Phosphonate-containing two-component coating system, its preparation and use

The invention relates to two-component coating systems comprising as component (a) one or more polyisocyanates, as component (b) one or more of component (a) reactive, oligomeric and / or polymeric compounds, and as component (c) one or more phosphonates, selected from the group of phosphonic diesters and diphosphonic diesters, wherein (i) component (b) are all contained in two-component coating system of component (a) contains reactive, oligomeric and / or polymeric compounds, and (ii) component (b) is at most 15 wt. -%, based on the total weight of component (b), containing oligomeric and / or polymeric compounds carrying amino groups reactive toward isocyanate. The invention further provides a process for preparing the two-component coating systems and the use of these coating systems as a clearcoat, in particular for automotive multi-layer coating.