The conversion coatings covered by this specification are intended for use, throughout the Department of Defense, on aluminum and aluminum alloy substrates that are not anodized. They are used to repair anodize coatings on aluminum. They are designated as a post treatment to ion-vapor deposition (IVD) aluminum used on many military platforms as a cadmium alternative or galvanic corrosion inhibitor. Type I and II conversion coatings provide corrosion protection on unpainted items, as well as improve adhesion of paint finish systems on aluminum and aluminum alloys. Conversion coatings covered by this specification exceed commercially available products due to the nature of their use on aircraft. All conversion coating applications in accordance with this specification are assumed to use type I unless the use of type II is specified. Type II may not be substituted for type I, for either Class IA or Class 3, unless authorization for its use is given by the acquisition activity or engineering authority for the system or item on which the conversion coating is applied.