Exterior primer
Exterior primer means the first layer and any subsequent layers of identically formulated coating applied to the exterior surface of an aerospace vehicle or component where the component is used on the exterior of the aerospace vehicle. Exterior primers are typically used for corrosion prevention, protection from the environment, functional fluid resistance, and adhesion of subsequent exterior topcoats. Coatings that are defined as specialty coatings are not included under this definition.
Source
40 CFR § 63.742
Scoping language
Terms used in this subpart are defined in the Act, in subpart A of this part, or in this section as follows: