Chemical conversion coatings represent those coatings formed by contacting a metallic substrate with a “chemical” solution that “converts” or “changes” the metallic surface from its original composition. The “conversion” process may arise via chemical or electrochemical interaction at the metallic surface, and produces a “coating” that is an integral part of the metal substrate. The presence of this “conversion coating” provides an increase in the corrosion resistance of the metal substrate, both with and without a subsequently applied organic film, and an increase in the adhesive capability of the metal substrate toward further organic film applications. Typical conversion coatings that are widely used in industry are phosphates (zinc, iron, manganese, calcium-zinc), chromates, chrome-free coatings, oxides (chemically or electrochemically formed); where each coating type provides the necessary properties that meet a particular requirement of industry
