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PA Bulletin, Doc. No. 97-1348



[25 PA. CODE CHS. 121 AND 129]

Equivalency Determinations and Aerospace Manufacturing and Rework--VOC Emission Limitations

[27 Pa.B. 4325]

   The Environmental Quality Board (Board) proposes to amend Chapters 121 and 129 (relating to definitions; and standards for sources) to read as set forth in Annex A.

   The changes to Chapter 121 add definitions of terms used in the substantive sections of Chapter 129. A new § 129.73 (relating to aerospace manufacturing and rework) establishes requirements to control volatile organic compound (VOC) emissions from aerospace manufacturing and rework facilities. In addition, § 129.51 (relating to general) is being modified to remove the requirement that equivalency determinations be submitted to the Environmental Protection Agency (EPA) as a State Implementation Plan (SIP) amendment.

   This notice is given under Board Order at its meeting of July 15, 1997.

A.  Effective Date

   These proposed amendments will be effective upon publication in the Pennsylvania Bulletin as final rulemaking.

B.  Contact Persons

   For further information, contact Terry Black, Chief, Regulation and Policy Development Section, Division of Compliance and Enforcement, Bureau of Air Quality, 12th Floor Rachel Carson State Office Building, P. O. Box 8468, Harrisburg, PA 17105-8468, (717) 787-1663, or M. Dukes Pepper, Jr., Assistant Counsel, Bureau of Regulatory Counsel, Office of Chief Counsel, 9th Floor Rachel Carson State Office Building, P. O. Box 8464, Harrisburg, PA 17105-8464, (717) 787-7060.

C.  Statutory Authority

   This action is being taken under the authority of sections 5(a)(1) and 5(a)(13) of the Air Pollution Control Act (35 P. S. §§ 4005(a)(1) and 4005(a)(13)), which grants to the Board the authority to adopt regulations for the prevention, control, reduction and abatement of air pollution.

D.  Background of the Amendment

   Section 5(a)(13) of the Air Pollution Control Act (35 P. S. § 4005(a)(13)) specifically authorizes the Board to adopt regulations establishing alternative VOC emission limitations for aerospace coatings and solvents, including extreme performance coatings, which are required to be used by the United States Department of Defense, the United States Department of Transportation and the National Aeronautics and Space Administration or to meet military and aerospace specifications provided these alternative limitations are authorized by the Clean Air Act.

   The EPA has worked with the aerospace industry to develop control techniques and guidelines related to VOC emissions from aerospace manufacturing and rework operations. These proposed amendments incorporate the substantive provisions of the draft guidelines into the Department's air quality regulations.

   The Department of Environmental Protection (Department) worked with the Air Subcommittee of the Air and Water Quality Technical Advisory Committee (AWQTAC) in the development of these proposed amendments. At its April 17, 1997 meeting, the Air Subcommittee acting on behalf of AWQTAC recommended adoption of the proposed amendments.

E.  Summary of Regulatory Revisions

   The proposed changes to Chapter 121 add definitions of terms used in the substantive provisions in Chapter 129. Most of the definitions are coatings listed in Table II. The definitions include: ''ablative coating,'' ''adhesion promoter,'' ''adhesion bonding primer,'' ''adhesive primer,'' ''aerosol coating,'' ''aerospace coating operation,'' ''aerospace coating unit,'' ''aerospace primer,'' ''aerospace surface preparation,'' ''aerospace topcoat,'' ''aerospace vehicle or component,'' ''aircraft fluid systems,'' ''aircraft transparency,'' ''antichafe coating,'' ''antique aerospace vehicle or component,'' ''aqueous cleaning solvent,'' ''bonding maskant,'' ''chemical agent-resistant coating (CARC),'' ''chemical milling maskant,'' ''cleaning operation,'' ''cleaning solvent,'' ''closed-cycle depainting system,'' ''commercial exterior aerodynamic structure primer,'' ''commercial interior adhesive,'' ''compatible epoxy primer,'' ''compatible substrate primer,'' ''confined space,'' ''corrosion prevention system,'' ''critical use and line sealer maskant,'' ''cryogenic flexible primer,'' ''cryoprotective coating,'' ''cyanoacrylate adhesive,'' ''electric or radiation-effect coating,'' ''electrostatic discharge and electromagnetic interference (EMI) coating,'' ''elevated temperature skydrol resistant commercial primer,'' ''epoxy polyamide topcoat,'' ''exempt solvent,'' ''fire-resistant (interior) coating,'' ''flexible primer,'' ''flight testing coating,'' ''flush cleaning,'' ''fuel tank adhesive,'' ''fuel tank coating,'' ''hand-wipe cleaning operation,'' ''high temperature coating,'' ''insulation covering,'' ''intermediate release coating,'' ''lacquer,'' ''limited access space,'' ''metalized epoxy coating,'' ''mold release,'' ''nonstructural adhesive,'' ''operating parameter value,'' ''optical antireflection coating,'' ''part marking coating,'' ''pretreatment coating,'' ''radome,'' ''rain erosion-resistant coating,'' ''rocket motor bonding adhesive,'' ''rocket motor nozzle coating,'' ''rubber-based adhesive,'' ''scale inhibitor,'' ''screening print ink,'' ''sealant,'' ''seal coat maskant,'' ''self-priming topcoat,'' ''semiaqueous cleaning solvent,'' ''silicone insulation material,'' ''solids,'' ''solid film lubricant,'' ''space vehicle,'' ''specialty coating,'' ''specialized function coating,'' ''spray gun,'' ''structural autoclavable adhesive,'' ''structural nonautoclavable adhesive,'' ''temporary protective coating,'' ''thermal control coating,'' ''touch-up and repair operation,'' ''Type I chemical etchant,'' ''Type II chemical etchant,'' ''VOC composite vapor pressure,'' ''waterborne (water-reducible) coating,'' ''wet fastener installation coating'' and ''wing coating''.

   In addition, the definition of ''miscellaneous metal parts and products'' is being modified to exclude aerospace vehicles or components from the miscellaneous metal parts and products category.

   The changes to § 129.51(a)(6) remove the requirement that alternative compliance methods for meeting the VOC requirements contained in §§ 129.52, 129.67 and 129.73 (relating to surface coating processes; graphic arts systems; and aerospace manufacturing and rework) be submitted to the EPA as a SIP amendment. The proposal requires the alternative compliance method to be incorporated into a plan approval and operating permit which is subject to EPA review. This will streamline the process for establishing alternative compliance methods.

   A new § 129.73 establishes specific allowable VOC content requirements for aerospace coatings. The methodology for calculating the VOC content of coatings is provided in § 129.73(a)(3). Subsection (a)(4) of the proposed amendments establishes application techniques for applying aerospace coatings and subsection (a)(5) establishes exceptions to those coating technique requirements. Subsection (a)(6) establishes limitations for hand-wipe cleaning of aerospace vehicles or components and subsection (a)(7) establishes exceptions to the hand-wipe requirements. Subsection (a)(8)--(10) establishes requirements for cleaning solvent containers, spray gun cleaning and housekeeping. Subsection (a)(11) authorizes compliance through the use of approved air pollution control equipment. Finally, subsection (a)(12) establishes the recordkeeping requirements for aerospace manufacturing and rework facilities.

   This regulatory revision will be submitted to the EPA as an amendment to the SIP.

F.  Benefits, Costs and Compliance

   Executive Order 1996-1 requires a cost/benefit analysis of the proposed amendments.


   Overall, the citizens of this Commonwealth will benefit from these recommended changes because they streamline the procedures for implementing the Department's air quality program for establishing equivalencies and implement specific requirements for aerospace manufacturing and rework operations.

   Compliance Costs

   These proposed amendments may slightly reduce compliance costs by streamlining the equivalency process. The aerospace requirements should have no effect on compliance costs.

   Compliance Assistance Plan

   The Department plans to educate and assist the public and the regulated community with understanding the newly revised requirements and how to comply with them. This will be accomplished through the Department's ongoing regional compliance assistance program.

   Paperwork Requirements

   The regulatory revisions will reduce the paperwork related to complaints and odor investigations.

G.  Sunset Review

   This proposal will be reviewed in accordance with the sunset review schedule published by the Department to determine whether the proposed amendments effectively fulfill the goals for which they were intended.

H.  Regulatory Review

   Under section 5(a) of the Regulatory Review Act (71 P. S. § 745.5(a)), on August 12, 1997, the Department submitted a copy of the proposed rulemaking to the Independent Regulatory Review Commission (IRRC) and to the Chairpersons of the Senate and House Environmental Resources and Energy Committees. In addition to submitting the proposed amendments, the Department has provided IRRC and the Committees with a copy of a detailed regulatory analysis form prepared by the Department. A copy of this material is available to the public upon request.

   If IRRC has objections to any portion of the proposed amendments, it will notify the Department within 30 days of the close of the public comment period. The notification shall specify the regulatory review criteria which have not been met by that portion. The Regulatory Review Act specifies detailed procedures for the Department, the Governor and the General Assembly to review these objections before publication of the final-form regulations.

I.  Public Comment and Board Public Hearings

   Public Hearings

   The Board will hold three public hearings for the purpose of accepting comments on the proposed amendments. The hearings will be held at 10 a.m. on the following dates and at the following locations:

September 23, 1997 Department of Environmental
1st Floor Meeting Room
Rachel Carson State Office
400 Market Street
Harrisburg, PA
September 25, 1997 Department of Environmental
Southwest Regional Office
500 Waterfront Drive
Pittsburgh, PA
September 29, 1997 Upper Merion Township Building
175 West Valley Forge Road
King of Prussia, PA

   Persons wishing to present testimony at the hearings must contact Kate Coleman at the Environmental Quality Board, P. O. Box 8477, Harrisburg, PA 17105-8477, (717) 787-4526, at least 1 week in advance of the hearing to reserve a time to present testimony. Oral testimony will be limited to 10 minutes for each witness and three written copies of the oral testimony must be submitted at the hearing. Each organization is requested to designate one witness to present testimony on its behalf.

   Persons with a disability who wish to attend the hearings and require an auxiliary aid, service or other accommodations to participate, should contact Kate Coleman at (717) 787-4526 or through the Pennsylvania AT&T relay service at (800) 654-5984 (TDD) to discuss how the Department may accommodate their needs.

   Written Comments

   In lieu of or in addition to presenting oral testimony at the hearings, interested persons may submit written comments, suggestions or objections regarding the proposed amendments to the Board, 15th Floor Rachel Carson State Office Building, P. O. Box 8477, Harrisburg, PA 17105-8477. Comments received by facsimile will not be accepted. Comments must be received by October 29, 1997. In addition to the written comments, interested persons may also submit a summary of their comments to the Board. This summary may not exceed one page in length and must be received by October 29, 1997. The summary will be provided to each member of the Board in the agenda packet distributed prior to the meeting at which the final-form regulations will be considered.

Electronic Comments

   Comments may be submitted electronically to the Board at A subject heading of the proposal and return name and address must be included in each transmission. Comments submitted electronically must also be received by the Board by October 29, 1997.


   (Editor's Note: Proposals to amend § 121.1 remain outstanding at 27 Pa.B. 1822, 1829, 2130 and 4340 (April 12, 1997, May 3, 1997 and August 23, 1997).

   Fiscal Note: 7-326. No fiscal impact; (8) recommends adoption.

Annex A






§ 121.1.  Definitions.

   The definitions in section 3 of the act (35 P. S. § 4003) apply to this article. In addition, the following words and terms, when used in this article, have the following meanings, unless the context clearly indicates otherwise:

*      *      *      *      *

   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 insulating barrier, protecting adjacent components from the heat or open flame.

*      *      *      *      *

   Adhesion promoter--A very thin coating applied to an aerospace vehicle or component substrate to promote wetting and to 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° or below and primers with a design cure above 250°.

   Adhesive primer--A coating applied to an aerospace vehicle or component that does one of the following:

   (i)  Inhibits corrosion and serves as a primer when applied to bare metal or other surfaces prior to adhesive application.

   (ii)  Is applied to surfaces that can be expected to contain fuel, with the exception of fuel tanks.

   Aerosol coating--A coating expelled from a hand-held, pressurized, nonrefillable container in a finely divided spray when a valve on the container is depressed.

   Aerospace coating operation--An operation using a spray booth, tank or other enclosure of an area, such as a hangar, for applying a single type of coating (for example, primer). Using the same spray booth for applying another type of coating (for example, topcoat) constitutes a separate coating operation for which compliance determinations are performed separately.

   Aerospace coating unit--A series of one or more coating applicators and any associated drying area or oven wherein a coating is applied, dried and cured. A coating unit ends at the point where the coating is dried or cured, or prior to a subsequent application of a different coating. It is not necessary to have an associated oven or flashoff area to be included in this definition.

   Aerospace primer--The first layer and subsequent layers of identically formulated coating applied to the surface of an aerospace vehicle or component. Primers are typically used for corrosion prevention, protection from the environment, functional fluid resistance. Adhesion of subsequent coatings. The term does not include primers that are defined as specialty coatings.

   Aerospace surface preparation--The removal of contaminants from the surface of an aerospace vehicle or component or the activation or reactivation of the surface in preparation for the application of a coating.

   Aerospace topcoat--A coating that is applied over a primer on an aerospace vehicle or component for appearance, identification, camouflage or protection. The term does not include topcoats that are defined as specialty coatings.

   Aerospace vehicle or component--A fabricated part, processed part, assembly of parts, or completed unit, with the exception of electronic components, of any aircraft including but not limited to, airplanes, helicopters, missiles, rockets and space vehicles.

*      *      *      *      *

   Aircraft fluid systems--Systems that handle hydraulic fluids, fuel, cooling fluids or oils.

   Aircraft transparency--An aircraft windshield, canopy, passenger windows, lenses and other components which are constructed of transparent materials.

*      *      *      *      *

   Antichafe coating--A coating applied to areas of moving aerospace components that may rub during normal operations or installation.

   Antique aerospace vehicle or component--An antique aircraft, as defined by 14 CFR Part 45 (relating to identification and registration marking), or components thereof. An antique aerospace vehicle would not routinely be in commercial or military service in the capacity for which it was designed.

*      *      *      *      *

   Aqueous cleaning solvent--A solvent in which water is at least 80% by weight of the solvent.

*      *      *      *      *

   Bonding maskant--A temporary coating used to protect selected areas of aerospace parts from strong acid or alkaline solutions during processing for bonding.

*      *      *      *      *

   Chemical agent-resistant coating (CARC)--An exterior topcoat applied to aerospace vehicles or components designed to withstand exposure to chemical warfare agents or the decontaminants used on these agents.

   Chemical milling maskant--A coating that is applied directly to aluminum aerospace vehicles or components to protect surface areas when chemically milling the component with a Type I or II etchant. The term does not include bonding maskants, line sealers and critical use and seal coat maskants. The term does not include maskants that must be used on an individual part or subassembly with a combination of Type I or II etchants and any of the above types of maskants (for example, bonding, line sealers, and critical use and seal coat). The term also does not include maskants that are defined as specialty coatings.

   Cleaning operation--Spray-gun, hand-wipe and flush cleaning operations.

   Cleaning solvent--A liquid material used for hand-wipe, spray gun or flush cleaning. The term includes solutions that contain VOCs.

*      *      *      *      *

   Closed-cycle depainting system--A dust free, automated process that removes permanent coating in small sections at a time, and maintains a continuous vacuum around the area being depainted to capture emissions.

*      *      *      *      *

   Commercial exterior aerodynamic structure primer--An aerospace vehicle or component 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 which meet the Federal Aeronautics Administration (FAA) fireworthiness requirements.

*      *      *      *      *

   Compatible epoxy primer--An aerospace vehicle or component 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.

   Compatible substrate primer--Either compatible epoxy primer or adhesive primer applied to aerospace vehicles or components.

*      *      *      *      *

   Confined space--A space that is the following:

   (1)  Is large enough and so configured that an employe can enter and perform assigned work.

   (2)  Has limited or restricted means for entry or exit (for example, fuel tanks, fuel vessels, and other spaces that have limited means of entry).

   (3)  Is not suitable for continuous employe occupancy.

*      *      *      *      *

   Corrosion prevention system--A coating system applied to aerospace vehicles or components 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 applied to aerospace vehicles or components, 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 or 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 (that is, line sealer) are also included in this category.

   Cryogenic flexible primer--A primer applied to aerospace vehicles or components 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 applied to aerospace vehicles or components 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. The term is also known as ''super glue.''

*      *      *      *      *

   Electric or radiation-effect coating--A coating or coating system applied to aerospace vehicles or components 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. The term excludes coatings that have been designated ''classified'' by the Department of Defense.

   Electrostatic discharge and electromagnetic interference (EMI) coating--A coating applied to space vehicles, missiles, aircraft radomes and helicopter blades 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 applied to aerospace vehicles or components when harder films are required or in some areas where engraving is accomplished in camouflage colors.

*      *      *      *      *

   Exempt solvent--Specified organic compounds that have been designated by the EPA as having negligible photochemical reactivity and are listed in 40 CFR 51.100 (relating to requirements for preparation, adoption and submittal of Implementation Plans).

*      *      *      *      *

   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 that are subject to the flammability requirements of MIL-STD-1630A and MIL-A-87721. For space applications, these coatings are used on parts that are subject to the flammability requirements of SE-R-0006 and SSP 30233.

   Flexible primer--A primer applied to aerospace vehicles or components 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.

*      *      *      *      *

   Flush cleaning--Removal of contaminants such as dirt, grease, oil and coatings from an aerospace vehicle or component or coating equipment by passing solvent over, into or through the item being cleaned. The solvent simply may be poured into the item being cleaned and then drained or assisted by air or hydraulic pressure or by pumping. The term does not include hand-wipe cleaning operations where wiping, scrubbing, mopping or other hand action is used.

*      *      *      *      *

   Fuel tank adhesive--An adhesive used to bond aerospace vehicle components exposed to fuel and which must be compatible with fuel tank coatings.

   Fuel tank coating--A coating applied to aerospace vehicle fuel tank components for the purpose of corrosion or bacterial growth inhibition and to assure sealant adhesion in extreme environmental conditions.

*      *      *      *      *

   Hand-wipe cleaning operation--Removing contaminants such as dirt, grease, oil and coatings from an aerospace vehicle or component by physically rubbing it with a material such as a rag, paper or cotton swab that has been moistened with a cleaning solvent.

*      *      *      *      *

   High temperature coating--An aerospace vehicle or component 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 on aerospace vehicles or components 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.

*      *      *      *      *

   Limited access space--Internal surfaces or passages of an aerospace vehicle or component to which coatings cannot be applied without the aid of an airbrush or a spray gun extension for the application of coatings.

*      *      *      *      *

   Metalized epoxy coating--A coating applied to aerospace vehicles or components that contains relatively large quantities of metallic pigmentation for appearance or added protection, or both.

   Miscellaneous metal parts and products--Items made of ferrous or nonferrous metals, including, but not limited to, large farm machinery, small farm machinery, small appliances, commercial and industrial machinery, fabricated metal products, and items listed under the Standard Industrial Classification Code 3300 through 3900. The term does not include cans, coils, automobiles, light-duty trucks, metal furniture, magnet wire, large appliances, [fully assembled exteriors of airplaces] aerospace vehicles or components and automobile refinishing and customized top coating of automobiles and trucks, if production since January 1, 1987, has not exceeded 34 vehicles per day.

*      *      *      *      *

   Mold release--A coating applied to an aerospace vehicle or component mold surface to prevent the molded piece from sticking to the mold as it is removed.

*      *      *      *      *

   Nonstructural adhesive--An adhesive applied to aerospace vehicles or components that bonds nonload bearing aerospace components in noncritical applications and is not included in any other specialty adhesive categories.

*      *      *      *      *

   Operating parameter value--A minimum or maximum value established for a control equipment or process parameter that, if achieved by itself or in combination with one or more other operating parameter values, determines that an owner or operator has complied with an applicable emission limitation.

   Optical antireflection coating--A coating, applied to aerospace vehicles or components, with a low reflectance in the infrared and visible wavelength ranges that is used for antireflection on or near optical and laser hardware.

*      *      *      *      *

   Part marking coating--Coating or ink used to make identifying markings on aerospace materials, components and assemblies. These markings may be either permanent or temporary.

*      *      *      *      *

   Pretreatment coating--An organic coating that contains at least 0.5% acids by weight and is applied directly to metal surfaces of aerospace vehicles and components to provide surface etching, corrosion resistance, adhesion and ease of stripping.

*      *      *      *      *

   Radome--The nonmetallic protective housing for aerospace electromagnetic transmitters and receivers (for example, radar, electronic countermeasures).

   Rain erosion-resistant coating--A coating or coating system used to protect the leading edges of parts such as flaps, stabilizers, radomes and engine inlet nacelles 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--A quick setting contact cement applied to aerospace vehicles and components that provides 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 an aerospace vehicle component prior to thermal processing to inhibit the formation of scale.

*      *      *      *      *

   Screen print ink--An ink used in screen printing processes during fabrication of decorative laminates and decals for aerospace vehicles and components.

   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.

   Seal coat maskant--A coating applied over a maskant on aerospace vehicles and components to improve abrasion and chemical resistance during production operations.

*      *      *      *      *

   Self-priming topcoat--A topcoat that is applied directly to an uncoated aerospace vehicle or component for purposes of corrosion prevention, environmental protection and functional fluid resistance. More than one layer of identical coating formulation may be applied to the vehicle or component. The coating is not subsequently topcoated with any other product formulation.

   Semiaqueous cleaning solvent--A solution in which water is a primary ingredient (>60% by weight of the solvent solution as applied must be water).

*      *      *      *      *

   Silicone insulation material--An insulating material applied to exterior metal surfaces of aerospace vehicles for protection from high temperatures caused by atmospheric friction or engine exhaust. These materials differ from ablative coatings in that they are not ''sacrificial.''

*      *      *      *      *

   Solids--The nonvolatile portion of the coating that after drying makes up the dry film.

   Solid film lubricant--A very thin coating, applied to aerospace vehicles or components, consisting of a binder system which contains 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.

*      *      *      *      *

   Space vehicle--A manmade device, either manned or unmanned, designed for operation beyond earth's atmosphere. This definition includes integral equipment, such as models, mock-ups, prototypes, molds, jigs, tooling, hardware jackets and test coupons. The term also includes auxiliary equipment associated with test, transport and storage, that through contamination can compromise the space vehicle performance.

   Specialty coating--A coating applied to aerospace vehicles or components that, even though it meets the definition of a primer, topcoat or self-priming topcoat, has additional performance criteria beyond those of primers, topcoats and self-priming topcoats for specific applications. These performance criteria may include, but are not limited to, temperature or fire resistance, substrate compatibility, antireflection, temporary protection or marking, sealing, adhesively joining substrates, or enhanced corrosion protection.

   Specialized function coating--A coating applied to aerospace vehicles or components that fulfills extremely specific engineering requirements that are limited in application and are characterized by low volume usage. This category excludes coatings included in other specialty coating categories.

   Spray gun--A device that atomizes a coating or other material and projects the particulates or other material onto a substrate.

*      *      *      *      *

   Structural autoclavable adhesive--An adhesive, cured by heat and pressure in an autoclave, that is used to bond load carrying aerospace components.

   Structural nonautoclavable adhesive--An adhesive that is cured under ambient conditions that is used to bond load carrying aerospace components or 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 of aerospace vehicles or components. Two types include peelable protective coatings and alkaline removable coatings. These materials are not intended to protect against strong acid or alkaline solutions. The term does not include coatings that provide protection from acid or alkaline chemical processing.

*      *      *      *      *

   Thermal control coating--A coating formulated with specific thermal conductive or radiative properties to permit temperature control of the aerospace vehicle or component substrate.

*      *      *      *      *

   Touch-up and repair operation--That portion of the coating operation that is the incidental application of coating used to cover minor imperfections in the coating finish or to achieve complete coverage. The term includes out-of-sequence or out-of-cycle coating.

*      *      *      *      *

   Type I chemical etchant--A chemical milling etchant which contains varying amounts of dissolved sulfur but which does not contain amines.

   Type II chemical etchant--A chemical milling etchant that is a strong sodium hydroxide solution containing amines.

*      *      *      *      *

   VOC composite vapor pressure--The sum of the partial pressures of the compounds defined as VOC's and is determined by the following calculation:


   Wi = Weight of the ''i''th VOC compound, grams.

   Ww = Weight of water, grams.

   We = Weight of non-HAP, nonVOC compound, grams.

   MWi = Molecular weight of the ''i''th VOC compound, G/G-mole.

   MWw = Molecular weight of water, G/G-mole.

   MWe = Molecular weight of exempt compound, G/G-mole.

   PPc = VOC composite partial pressure at 20°, MM HG.

   VPi = Vapor pressure of the ''i''th VOC compound at 20°, MM HG.

*      *      *      *      *

   Waterborne (water-reducible) coating--A coating which contains more than 5% water by weight in its volatile fraction, as applied.

*      *      *      *      *

   Wet fastener installation coating--A primer or sealant applied to aerospace vehicles or components by dipping, brushing or daubing on fasteners which are installed before the coating is cured.

*      *      *      *      *

   Wing coating--A corrosion-resistant topcoat applied to aerospace vehicles or components that is resilient enough to withstand the flexing of the wings.

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