||Coating composition compriling: A) at least one ~r otigomer prepared fr'Om reactants compriSing 8) 20 -60 wt.% of 81 Iaast ooe POIyoJ. b) 5 -30 wt. % of at least one potycarboxytic acid selected from the grol.q) of cyclic pofycarboxyJic ~., the t$ter& or the anhydrides tJweof, wt\erein I'Ie C8rbo~ gmups are sepef'ated by 3 carbon atoms or fess, and from the group of a,p.. saturated acyclic poiycarboxylic acid., the esters or the an"-ydrides thereof, and c) 20 -eo wI. % of at leaatone monocwboxylic acid, the sum of the wI. % indicated for the reactants (8), (b), and (c) aMys beq 100 wi. %, and the oligomer being 8 Iow-YiscoIity oligomer tta~ a viSCO$ity of less then 30 Pa..s at 23.C having 8 weight average mofec:utar weigtrt Mw of less than 5,000, and 8 ~roxyf number In the range 01200 to 400 mg KOHfg oligomer, and B) at least one polyfsocyanate.