A crosslinkable composition is provided including copolymer particles having phosphorus acid groups dispersed in an aqueous medium, and polycarbodiimide, wherein the crosslinkable composition is substantially free of water soluble phosphorus acid compounds. Also provided is a process for forming the crosslinkable composition and a method for crosslinking the crosslinkable composition. The crosslinkable composition is useful as a coating composition to prepare coatings for various substrates including metal, wood, glass, paper, and leather.