A novel in-situ phosphating coating system is developed by predispersing an optimum amount of phosphatizing reagents into the paint formulation. Five possible in-situ phosphatizing reagents are used in the formulation of a model solvent-borne polyester-melamine enamel paint system. The new formulation is then coated and cured on a cold-rolled steel surface. The chemical reactivity of phosphatizing reagents are studied via different analytical techniques. The results can be summarized as follows : (i) the phosphatizing reagents, being dispersed into the solvent-borne paints to form a stable self-phosphating organic coating, perform a successful in-situ phosphatization of the metal substrate; (ii) there is an observable lowering of T-g for the paint films, due to the acceleration of melamine self-condensation by the acidic nature of phosphatizing reagents, which can be corrected by optimizing the coating formulation; (iii) the organic phosphatizing reagents, which are more dispersable in a solvent-borne coating system, are very effective yet have less influence on the cross-linking density of the final film, thus giving a coating with higher AC impedance and providing a better corrosion protective performance.