The primer coatings covered by this specification are corrosion-inhibiting and chemical resistant, intended for spray application to most aircraft substrates. These coatings are compatible with polyurethane and epoxy topcoats (see 6.1.1) and may be used as alternatives to MIL-PRF-23377 for many applications. However, primer coatings containing water, such as these coatings, should not be used on iron or bare carbon steel, nor for the wet installation of fasteners of faying surfaces. Type II primer coatings are intended for use where low infrared reflectance is required. Class N may not be substituted for Class C1 or C2, unless authorization for its use is given by the engineering authority for the system or item to which the primer coating is to be applied. These primer coatings are formulated for the unique performance requirements of military aircraft. These requirements include adhesion to a wide variety of metals and composites, flexibility to withstand tactical maneuvers at low temperatures, corrosion resistance in a marine environment, resistance to leaking aircraft fluids, and low-infrared reflectance for stealth in combat.