40 CFR Appendix A to Subpart GG of Part 63, Specialty Coating Definitions
Ablative coating - A coating that chars when exposed to open flame or extreme temperatures, as would occur during the failure of an engine casing or during aerodynamic heating. The ablative char surface serves as an insulative barrier, protecting adjacent components from the heat or open flame.
Adhesion promoter - A very thin coating applied to a substrate to promote wetting and form a chemical bond with the subsequently applied material.
Adhesive bonding primer - A primer applied in a thin film to aerospace components for the purpose of corrosion inhibition and increased adhesive bond strength by attachment. There are two categories of adhesive bonding primers: primers with a design cure at 250 °F or below and primers with a design cure above 250 °F.
Aerosol coating - A hand-held, pressurized, nonrefillable container that expels an adhesive or a coating in a finely divided spray when a valve on the container is depressed.
Antichafe coating - A coating applied to areas of moving aerospace components that may rub during normal operations or installation.
Bearing coating - A coating applied to an antifriction bearing, a bearing housing, or the area adjacent to such a bearing in order to facilitate bearing function or to protect base material from excessive wear. A material shall not be classified as a bearing coating if it can also be classified as a dry lubricative material or a solid film lubricant.
Bonding maskant - A temporary coating used to protect selected areas of aerospace parts from strong acid or alkaline solutions during processing for bonding.
Caulking and smoothing compounds - Semi-solid materials which are applied by hand application methods and are used to aerodynamically smooth exterior vehicle surfaces or fill cavities such as bolt hole accesses. A material shall not be classified as a caulking and smoothing compound if it can also be classified as a sealant.
Chemical agent-resistant coating (CARC) - An exterior topcoat designed to withstand exposure to chemical warfare agents or the decontaminants used on these agents.
Clear coating - A transparent coating usually applied over a colored opaque coating, metallic substrate, or placard to give improved gloss and protection to the color coat. In some cases, a clearcoat refers to any transparent coating without regard to substrate.
Commercial exterior aerodynamic structure primer - A primer used on aerodynamic components and structures that protrude from the fuselage, such as wings and attached components, control surfaces, horizontal stabilizers, vertical fins, wing-to-body fairings, antennae, and landing gear and doors, for the purpose of extended corrosion protection and enhanced adhesion.
Commercial interior adhesive - Materials used in the bonding of passenger cabin interior components. These components must meet the FAA fireworthiness requirements.
Compatible substrate primer - Includes two categories: compatible epoxy primer and adhesive primer. Compatible epoxy primer is primer that is compatible with the filled elastomeric coating and is epoxy based. The compatible substrate primer is an epoxy-polyamide primer used to promote adhesion of elastomeric coatings such as impact-resistant coatings. Adhesive primer is a coating that (1) inhibits corrosion and serves as a primer applied to bare metal surfaces or prior to adhesive application, or (2) is applied to surfaces that can be expected to contain fuel. Fuel tank coatings are excluded from this category.
Corrosion prevention system - A coating system that provides corrosion protection by displacing water and penetrating mating surfaces, forming a protective barrier between the metal surface and moisture. Coatings containing oils or waxes are excluded from this category.
Critical use and line sealer maskant - A temporary coating, not covered under other maskant categories, used to protect selected areas of aerospace parts from strong acid or alkaline solutions such as those used in anodizing, plating, chemical milling and processing of magnesium, titanium, high-strength steel, high-precision aluminum chemical milling of deep cuts, and aluminum chemical milling of complex shapes. Materials used for repairs or to bridge gaps left by scribing operations (i.e. line sealer) are also included in this category.
Cryogenic flexible primer - A primer designed to provide corrosion resistance, flexibility, and adhesion of subsequent coating systems when exposed to loads up to and surpassing the yield point of the substrate at cryogenic temperatures (−275 °F and below).
Cryoprotective coating - A coating that insulates cryogenic or subcooled surfaces to limit propellant boil-off, maintain structural integrity of metallic structures during ascent or re-entry, and prevent ice formation.
Cyanoacrylate adhesive - A fast-setting, single component adhesive that cures at room temperature. Also known as “super glue.”
Dry lubricative material - A coating consisting of lauric acid, cetyl alcohol, waxes, or other non-cross linked or resin-bound materials which act as a dry lubricant.
Electric or radiation-effect coating - A coating or coating system engineered to interact, through absorption or reflection, with specific regions of the electromagnetic energy spectrum, such as the ultraviolet, visible, infrared, or microwave regions. Uses include, but are not limited to, lightning strike protection, electromagnetic pulse (EMP) protection, and radar avoidance. Coatings that have been designated as “Classified National Security Information” by the Department of Defense are exempt.
Electrostatic discharge and electromagnetic interference (EMI) coating - A coating applied to aerospace vehicles and components to disperse static energy or reduce electromagnetic interference.
Elevated-temperature Skydrol-resistant commercial primer - A primer applied primarily to commercial aircraft (or commercial aircraft adapted for military use) that must withstand immersion in phosphate-ester (PE) hydraulic fluid (Skydrol 500b or equivalent) at the elevated temperature of 150 °F for 1,000 hours.
Epoxy polyamide topcoat - A coating used where harder films are required or in some areas where engraving is accomplished in camouflage colors.
Fire-resistant (interior) coating - For civilian aircraft, fire-resistant interior coatings are used on passenger cabin interior parts that are subject to the FAA fireworthiness requirements. For military aircraft, fire-resistant interior coatings are used on parts subject to the flammability requirements of MIL-STD-1630A and MIL-A-87721. For space applications, these coatings are used on parts subject to the flammability requirements of SE-R-0006 and SSP 30233.
Flexible primer - A primer that meets flexibility requirements such as those needed for adhesive bond primed fastener heads or on surfaces expected to contain fuel. The flexible coating is required because it provides a compatible, flexible substrate over bonded sheet rubber and rubber-type coatings as well as a flexible bridge between the fasteners, skin, and skin-to-skin joints on outer aircraft skins. This flexible bridge allows more topcoat flexibility around fasteners and decreases the chance of the topcoat cracking around the fasteners. The result is better corrosion resistance.
Flight test coating - A coating applied to aircraft other than missiles or single-use aircraft prior to flight testing to protect the aircraft from corrosion and to provide required marking during flight test evaluation.
Fuel tank adhesive - An adhesive used to bond components exposed to fuel and that must be compatible with fuel tank coatings.
Fuel tank coating - A coating applied to fuel tank components to inhibit corrosion and/or bacterial growth and to assure sealant adhesion in extreme environmental conditions.
High temperature coating - A coating designed to withstand temperatures of more than 350 °F.
Insulation covering - Material that is applied to foam insulation to protect the insulation from mechanical or environmental damage.
Intermediate release coating - A thin coating applied beneath topcoats to assist in removing the topcoat in depainting operations and generally to allow the use of less hazardous depainting methods.
Lacquer - A clear or pigmented coating formulated with a nitrocellulose or synthetic resin to dry by evaporation without a chemical reaction. Lacquers are resoluble in their original solvent.
Metalized epoxy coating - A coating that contains relatively large quantities of metallic pigmentation for appearance and/or added protection.
Mold release - A coating applied to a mold surface to prevent the molded piece from sticking to the mold as it is removed.
Nonstructural adhesive - An adhesive that bonds nonload bearing aerospace components in noncritical applications and is not covered in any other specialty adhesive categories.
Optical anti-reflection coating - A coating with a low reflectance in the infrared and visible wavelength ranges, which is used for anti-reflection on or near optical and laser hardware.
Part marking coating - Coatings or inks used to make identifying markings on materials, components, and/or assemblies. These markings may be either permanent or temporary.
Pretreatment coating - An organic coating that contains at least 0.5 percent acids by weight and is applied directly to metal or composite surfaces to provide surface etching, corrosion resistance, adhesion, and ease of stripping.
Rain erosion-resistant coating - A coating or coating system used to protect the leading edges of parts such as flaps, stabilizers, radomes, engine inlet nacelles, etc. against erosion caused by rain impact during flight.
Rocket motor bonding adhesive - An adhesive used in rocket motor bonding applications.
Rocket motor nozzle coating - A catalyzed epoxy coating system used in elevated temperature applications on rocket motor nozzles.
Rubber-based adhesive - Quick setting contact cements that provide a strong, yet flexible, bond between two mating surfaces that may be of dissimilar materials.
Scale inhibitor - A coating that is applied to the surface of a part prior to thermal processing to inhibit the formation of scale.
Screen print ink - Inks used in screen printing processes during fabrication of decorative laminates and decals.
Seal coat maskant - An overcoat applied over a maskant to improve abrasion and chemical resistance during production operations.
Sealant - A material used to prevent the intrusion of water, fuel, air, or other liquids or solids from certain areas of aerospace vehicles or components. There are two categories of sealants: extrudable/rollable/brushable sealants and sprayable sealants.
Silicone insulation material - Insulating material applied to exterior metal surfaces for protection from high temperatures caused by atmospheric friction or engine exhaust. These materials differ from ablative coatings in that they are not “sacrificial.”
Solid film lubricant - A very thin coating consisting of a binder system containing as its chief pigment material one or more of the following: molybdenum, graphite, polytetrafluoroethylene (PTFE), or other solids that act as a dry lubricant between faying surfaces.
Specialized function coatings - Coatings that fulfill extremely specific engineering requirements that are limited in application and are characterized by low volume usage. This category excludes coatings covered in other Specialty Coating categories.
Structural autoclavable adhesive - An adhesive used to bond load-carrying aerospace components that is cured by heat and pressure in an autoclave.
Structural nonautoclavable adhesive - An adhesive cured under ambient conditions that is used to bond load-carrying aerospace components or for other critical functions, such as nonstructural bonding in the proximity of engines.
Temporary protective coating - A coating applied to provide scratch or corrosion protection during manufacturing, storage, or transportation. Two types include peelable protective coatings and alkaline removable coatings. These materials are not intended to protect against strong acid or alkaline solutions. Coatings that provide this type of protection from chemical processing are not included in this category.
Thermal control coating - Coatings formulated with specific thermal conductive or radiative properties to permit temperature control of the substrate.
Touch-up and Repair Coating - A coating used to cover minor coating imperfections appearing after the main coating operation.
Wet fastener installation coating - A primer or sealant applied by dipping, brushing, or daubing to fasteners that are installed before the coating is cured.
Wing coating - A corrosion-resistant topcoat that is resilient enough to withstand the flexing of the wings.