The present invention is directed towards novel sulfonic acid esters as catalysts for crosslinking of polymers having hydroxyl, carboxyl, and amide functional groups with a crosslinking agent and resin compositions containing the same. The present invention provides polymeric film coatings which have superior hardness, impact resistance, adhesion, improved blister resistance, salt spray characteristics and flexibility. These catalysts are especially effective in coil primer formulations containing calcium ion exchange anticorrosive pigments, where traditional blocked acid catalysts are ineffective.