Coating compositions having improved direct to metal adhesion

The invention relates to a composition comprising a combination of compounds providing improved "direct to metal" adhesion and coating compositions comprising said composition. The coating compositions of the invention have improved adhesion when applied directly over metal substrates, especially untreated metal substrates such as galvanized steel, unsanded aluminum and unsanded cold-rolled steel. More particularly, the invention provides a composition comprising (I) an effective amount of a first compound having an acid number of from 70 to 120 mg KOH/g, a hydroxyl number of from 200 to 400 mg KOH/g, a number average molecular weight of from 300 to 700, and which is the reaction product of (a) at least one difunctional carboxylic acid, (b) at least one trifunctional polyol, (c) at least one chain stopper, and (d) phosphoric acid, and (II) an effective amount of a second compound comprising a carboxy phosphate ester having the formula:wherein R is an C5-C40 aliphatic group in which one or more aliphatic carbon atoms are substituted with lateral or terminal -COOR1 groups, wherein R1 is H, metal, ammonium, C1-C6 alkyl, or C6-C10 aryl, M is hydrogen, metal or ammonium and x is a number from 0 to 3.