COATING SYSTEMS FOR SPECIFIC USES
5.1 General. Section 4 of this document provides general guidance for the selection of coating systems for wood, concrete/masonry, steel, galvanized steel, and aluminum surfaces. This section provides more detailed information on systems for specific structures or components of structures. These structures include metal storage tanks, pipe lines, towers, waterfront structures, siding, fences, and hot surfaces; concrete storage tanks, swimming pools, catchment basins, pavements, and floors; and wood floors. This section also describes problems associated with mildew on painted surfaces.
5.2 Painting New Construction. The designer of the first coating system for a new fuel tank, pipe line or other constructed facility has the unique opportunity to specify a system that can provide the best service. Much of the coating system – surface preparation, priming and in some cases application of the complete coating system – can be carried out in a shop environment where the environmental and application parameters can be controlled. By controlling these conditions, the surface can be very well prepared and the film properties obtained after curing are optimum. Further, worker safety and environmental controls may be more easily accomplished. Since the cost difference of a white metal blast as compared to a nearwhite blast may be small for new steel, and since the cost of the "best" materials may not be much greater than the cost of "poor" materials, the use of these procedures and materials should be considered when selecting the coating system. Maintenance painting is always more difficult than shop painting and frequent maintenance painting on constructed facilities may interfere unacceptably with the mission of the structure. Thus, in summary, it is recommended that high-performance systems be specified on new construction.
5.3 Fuel Storage Tanks. Steel fuel tanks are coated to keep the fuel clean and prevent leaks resulting from corrosion. Leaks can cause fires or serious contamination of soils or ground waters. Underground steel fuel tanks should also be cathodically protected or double walled to meet Department of Transportation requirements directed at environmental protection from fuel leaks.
For new tanks in most environments, effective performance of most chemically cured (e. g., epoxies and polyurethanes) has been obtained with a near-white finish (SSPC SP 10) before coating. However, it is essential that the surface preparation specified for a coating not be in conflict with that provided by the coating manufacturer on the written coating data sheet. In some cases, a coating manufacturer may state that a coating should only be used over a white-metal finish (SSPC SP 5). After application of the total system, it should be checked for holidays with a low-voltage holiday detector as described in the National Association of Corrosion Engineers (NACE) RPO188, Standard Recommended Practice, Discontinuity (Holiday) Testing of Protective Coatings. Any holidays that are located should be repaired.
Repair of damaged coatings will vary somewhat with the existing coating system. Normally, repairs are made with the type of coatings already on the tanks. If these are not available, another compatible coating system must be used. Compatibility of coatings can be determined as described in par. 5.6.2. Localized exposed steel should be spot abrasively blasted to an SSPC SP 10 condition and the intact coating surrounding these areas should be brush-off blasted (SSPC SP 7) to a 2-inch width. The patch of the same or a compatible coating system should be applied to steel and extend 2 inches onto the cleaned intact coating.
5.3.1 Interiors of Steel Fuel Tanks. Interiors of steel
storage tanks should be cleaned as described in NFGS-13219, Cleaning Petroleum Storage Tanks, and inspected regularly.
Because it may not be possible to do this conveniently, it is critical that they receive long-lasting, high-performance interior coating systems. Corrosion occurs most frequently on the floors of the tanks, where water is always present despite its frequent removal from sumps. Thus, the bottoms of steel tank interiors should be measured for adequate thickness before blasting and recoating is initiated. It may be necessary to fill pits with weld metal, apply a false bottom of fiberglass – reinforced plastic as described in NFGS-13217, Fiberglass-Plastic Lining for Steel Tank Bottoms (for Petroleum), or install a new replacement steel bottom. All steel storage tank interiors should be given a near-white blast (SSPC SP 10) immediately prior to priming. For many years, fuel tank interiors have been successfully lined with a three-coat epoxy system with a total dry film thickness of 9 mils. Coats of epoxy-polyamide conforming to Formulas 150, 151, and 152 of MIL-P-24441 have been the epoxy system most frequently used to line military steel fuel tanks. It is described in NFGS-09973, Interior Coating System for Welded Steel Petroleum Storage Tanks.
More recently, a urethane system was developed for lining steel fuel tanks. As described in NFGS-09970, Interior Coatings for Welded Steel Tanks (for Petroleum Fuels), it consists of a pretreatment wash primer, a polyurethane primer, a polyurethane intermediate coat, and a finish coat. The finish
coat may be a polyurethane or a special fluorinated polyurethane. These coatings currently exceed the VOC limit of 340 grams per liter that exists in many locations, the fluorinated polyurethane coating is very expensive, and the pretreatment wash primer and the primer contain chromate. However, because of the reported much longer life of the system with the fluorinated polyurethane finish, it is recommended for Navy fuel tanks, wherever it is legal to use it.
After application of each coat of interior paint, tank interiors must be thoroughly ventilated to remove organic solvent vapors and to assist in curing (solvent release) of coatings. Ventilation requirements vary with tank size, shape, and number of openings. Safety requirements and instructions of coating manufacturers should be followed. Heated air can also be used to accelerate curing of coatings. Blasting and painting hoses, as well as other electrical equipment, should be grounded and sparkproof. The local industrial hygienist can provide information on health and safety requirements for the lining operation. It is especially important to require holiday testing of the interior tank coatings. In this way, small defects can be found and repaired, preventing sites for premature initiation of corrosion.
5.3.2 Exteriors of Steel Fuel Tanks. The exterior coating of
steel fuel tanks is described in NFGS-09971, Exterior Coating System for Welded Steel Petroleum Storage Tanks. For new tanks, a system that has performed well is two coats of epoxy-polyamide (e. g., MIL-P-24441 Formulas 159 and 151) and a finish coat of aliphatic polyurethane (e. g., MIL-C-85285) to a total dry film thickness of at least 8 mils. The recommended surface preparation is an SSPC SP 10 near-white blast. Refer to par. 4.4.3 for maintenance painting of exterior tanks.
5.4 Steel Water Tanks. Newer steel water storage tanks
have welded sections. Older riveted or bolted tanks are still used, however, at some activities. The seam areas of such tanks are much harder to completely coat. Cathodic protection, as described in NFGS-13112, Cathodic Protection System (Steel Water Tanks), CEGS 16641, Cathodic Protection System (Steel Water Tanks), and MIL-HDBK-1004/10, Electrical Engineering Cathodic Protection, is recommended for water tank interiors to supplement the protection afforded by coatings. Corrosion of cathodically protected water tanks generally is usually concentrated at the top of the tank along sharp edges, crevices, and beams supporting the roof, where cathodic protection does not occur. Thus, it is important to coat and inspect these areas especially well.
5.4.1 Interiors of Steel Water Tanks. Most states presently require or are expected to require the use of coating systems approved by the National Sanitation Foundation (ANSI/NSF Standards 60 and 61) for the lining of potable water tanks. Coating approval is based on tests (NSF Standards 60 and 61) for leaching of toxic materials. The tests do not address durability of the coatings for water immersion service. The coatings are usually epoxies. In states that have no requirements, the three – coat epoxy-polyamide system described in par. 18.104.22.168 for the interiors of steel fuel tanks can also be used, except that Formula 156 (red) is used in place of Formula 151 (gray) as the intermediate coat. Metal and coating repairs for water tanks can be made in the same manner as described for fuel tanks, but those for potable water tanks must be covered with an NSF-approved coating system, where these requirements prevail.
5.4.2 Exteriors of Steel Water Tanks. Exteriors of water tanks should be coated in the same manner as described in par. 5.3.2 for the exteriors of fuel tanks.
5.5 Other Steel Tanks. Steel tanks may contain waste
water, chemicals, or other corrosive materials. Cathodic protection is also recommended for these tanks. Refer to par. 5.4.
5.5.1 Interiors of Other Steel Tanks. Interiors of steel tanks containing waste water, chemicals, or other corrosive liquids should be coated with a suitable corrosion-resistant lining (e. g., fiberglass-reinforced polyester) to protect the steel from corrosion. Since there are no Federal specifications for such products, specialty coating suppliers should be consulted about them.
5.5.2 Exteriors of Other Steel Tanks. Exteriors of steel tanks containing wastewater, chemicals, and other corrosive liquids should be coated with the system described for steel fuel tank exteriors in par. 5.2.2.
5.6 Steel Distribution Lines. Steel distribution lines
containing water, fuel, or other liquids are coated to prevent loss of product from corrosion and contamination of soils and groundwater.
5.6.1 Steel Fuel Lines
22.214.171.124 Buried Steel Fuel Lines. Buried steel fuel lines must be coated and cathodically protected to meet Department of Transportation regulations and to provide their most economical protection.
a) The desired properties of coatings for buried, cathodically protected pipelines are:
(1) Good electrical insulation
(2) Good moisture resistance
(3) Good adhesion
(4) Resistance to cathodic disbonding
(5) Resistance to damage during handling
(6) Ease of repair
b) Coatings for piping to be buried should be applied in a shop under controlled conditions. Blasting with automatic equipment that recycles the abrasive should provide a high level of cleanliness (SSPC SP 5 or 10). Coatings that have been commonly used on buried piping include:
(1) Coal Tar Enamels – Coal tar enamels use different combinations of fiberglass and felt wraps to provide mechanical strength and thickness (1/8 inch or more). Their use has greatly declined because of environmental concerns about coal tar.
(2) Asphalt Mastics – Asphalt mastics are combinations of asphalt, sand, and other materials that are extruded over pipes at thicknesses up to 1/2 inch. They are quite moisture-resistant but lack resistance to both hydrocarbons and sunlight and, like coal tar enamels, are a health concern.
(3) Extruded Coatings – Extruded coatings typically have a 10 to 15 mil mastic base covered with a polyethylene or polypropylene outer jacket. They are sensitive to sunlight and must be covered if they are to be exposed to it for long periods of time.
(4) Fusion-Bonded Powder Coatings – Fusion-bonded powder coatings are usually applied by electrostatic spray to pre-heated pipe (400 to 500 degrees F) cleaned to a near-white surface (SSPC SP 10). The 10 to 30 mil coating is water-cooled before storage and subsequent use.
(5) Plastic Tapes – Polyethylene, vinyl, and coal tar tapes are available with different adhesives and thicknesses. Because they are relatively easily damaged, they are often installed with a secondary rock shield. Portable wrapping machines are also available for over-the-ditch application.
(6) Heat-Shrinkable Tapes – Heat-shrinkable tapes of polyolefin provide tight bonding to pipes. They are shrunk in place by heating at 300 to 400 degrees F. Their relatively high cost limits their use to special areas such as joints.
126.96.36.199 Immersed Steel Fuel Lines. Immersed pipes lines can be in fresh or salt water, near the surface where they are exposed to ultraviolet (UV) light or deep where UV light is not of concern. Further, some pipe lines are exposed to abrasion from particulates and debris in the water. A coating that has been successful in some applications is the three-coat epoxy system described for steel fuel tank interiors in par. 5.3.1. Vinyl coatings are effective where there is abrasion. The pipe lines can also be cathodically protected.
188.8.131.52 Aboveground Fuel Lines. Aboveground fuel lines can be coated much the same as fuel tank exteriors described in
par. 5.3.2. A petrolatum paste/tape system has also been used very effectively in protecting fuel lines under piers. The system can be applied by hand over wire-brushed steel. It is very easy to repair when damaged.
5.6.2 Steel Water Distribution Lines. Steel water
distribution lines should be coated as described for steel fuel distribution lines in pars. 184.108.40.206, 220.127.116.11, and 18.104.22.168, depending upon the environment, buried, immersed, or aboveground. Although buried steel water distribution lines do not present the same level of environmental hazard as do buried steel fuel lines, it is recommended that they be cathodically protected, as well as coated. For steel water distribution lines that are buried but not cathodically protected, use the three-coat epoxy-polyamide system described for steel fuel tank interiors in par. 5.3.1.
5.7 Communication Towers and Other Tall Structures. The
military has thousands of communication towers of various sizes and configurations in many geographical and climatic regions.
The tower designs and initial treatments of the steel construction materials often vary from site to site and within the same site. These variable factors often cause problems in obtaining cost-effective painting of the towers.
Many towers require either a painted pattern of alternate aviation orange and white markings for daytime visibility, or lighting (strobe for high towers). Requirements for marking and lighting are described in detail in Federal Aviation Administration (FAA) Advisory Circular 70/7460-1G. Compatibility of coatings can be determined as described in par. 5.6.2. The use of painted patterns over zinc-coated structures is a better choice over lighting for long-term use and operation of towers. While lighting may be less expensive in initial construction and maintenance, an unprotected bare zinc surface will erode and require more expensive repairs than a bare surface. Further, some studies have shown that the lifetime of the zinc plus organic coating system is significantly greater than the sum of just the zinc coating and of an organic coating. While painting automatically brings maintenance problems, these are normally much less than those occurring to unpainted towers. The orange and white colors required by the FAA are available in aliphatic polyurethane, alkyd, and latex formulations.
5.7.1 New Towers. Today, new tower components are usually built with galvanized structural steel or steel thermally sprayed with zinc metal, if too large to be placed in a dipping tank.
22.214.171.124 New Galvanized Steel Towers. Galvanizing applications for steel tower components are typically heavy (e. g., 4 to 7 mils of zinc) and accomplished by hot dipping. Whether thermally sprayed or hot dipped, the zinc coating can provide several years of protection by itself. However, it will subsequently be necessary to apply a paint system to extend this corrosion protection, after the zinc is consumed. Because quality painting of towers after erection is both difficult and expensive, it is always best to apply organic coatings beforehand, preferably in a shop setting. Surface preparation and painting of tower components in a shop can be accomplished under controlled conditions to provide optimum protection of the metal. Shop cleaning of zinc-coated surfaces is normally limited to detergent washing to remove loose contaminants and/or solvent cleaning (SSPC SP 1) to remove grease or oil. Sometimes, a thin film of grease or oil is applied at the factory to protect galvanizing from corrosion during exterior storage. Also, new galvanizing is sometimes treated with chromate corrosion inhibitors for corrosion protection during storage. Such treatment should specifically be excluded in specifications for galvanized steel components to be coated.
Galvanized steel components are best protected with one coat each of epoxy-polyamide (e. g., MIL-P-24441 Formula 150) and aliphatic polyurethane (e. g., MIL-C-85285) coatings as described above. If a delay of over 4 days occurs before topcoating, the finish coat of polyurethane may not adhere because of the solvent resistance of the nearly fully cured epoxy coat. A thin (2-mil wet film thickness) film of the epoxy primer applied and allowed to cure to a tacky finish (e. g., 4 hours) will provide a suitable surface for the polyurethane finish coat. Epoxy and urethane coatings must have at least a 6-hour pot life for practical coating of towers in place. Oil-based paints (including oil/alkyds) are not recommended because of the inherent incompatibility of oil-based paints with the alkaline surface of galvanizing. Premature failure by peeling is predictable.
A two-coat latex system (e. g., 1-1/2 mils dry film thickness each of MIL-P-28577 primer and MIL-P-28578 topcoat or SSPC PAINT 24) can also be used on galvanizing, but the protection and gloss and color retention may not be quite as good as with the epoxy/polyurethane system. The corrosivity of the exposure environment should be considered when choosing between the two systems.
126.96.36.199 New Thermally Sprayed Steel Towers. Thermally sprayed zinc is relatively porous and protects steel by cathodic protection. It should be sealed to provide maximum protection. Application of epoxy polyamide MIL-P-24441, Formula 150 thinned 50/50 has been very effective in sealing of thermally sprayed ship components. Where restrictions on the solvent (VOC) content prevail, sealing can be accomplished with a mist coat. Sealing should be followed with a full coat of Formula 150 applied at the usual 3-mil dry film thickness and a finish coat of aliphatic polyurethane (e. g., 2 mils dry film thickness of MIL-C-85285).
Some private companies have successfully coated thermally sprayed steel components with a single, heavy (e. g., 6 to 8 mils dry film thickness) coat of commercially available aluminum-filled epoxy mastic. Such a product is not covered by Government or industry specifications.
188.8.131.52 New Steel Towers. If new steel tower legs are not galvanized or thermally sprayed with a zinc coating, use of an inorganic zinc coating should be considered if the coating can be applied in the shop. A controlled shop environment can provide the proper conditions for obtaining a very corrosion-protective inorganic-zinc coating. These coatings (e. g., SSPC SP 5 surface preparation and MIL-P-24648, inorganic zinc) have been shown to provide long-term service with minimal maintenance requirements. If the coating must be applied in the field, an organic zinc-rich coating is probably preferred since they are more forgiving of surface preparation lapses and can be applied and cured over a wider range of environmental conditions. For either system, an intermediate coat of epoxy polyamide (e. g., MIL-P-24441, Formula 150) and a finish coat of aliphatic polyurethane (e. g., MIL-C-85285) can complete the system.
5.7.2 Existing Towers. It is best to repair damaged tower
coatings on existing towers on a regular schedule before the damage becomes significant. To repair or topcoat existing coatings, it is necessary to know the generic type of the present coating. The same or another compatible coating must be used.
In some cases (e. g., with vinyl or chlorinated rubber coatings), another generic type coating may have to be used, because the old one is no longer permitted by many local environmental regulations.
Before contracting any tower painting, it is necessary to determine if any existing paint on the tower contains lead. Lead may be present as one or more components of alkyd paints or as pigmentation for the aviation orange color. Unless the absence of lead is definitely known, samples should be taken and submitted to a laboratory for analysis. Refer to NFGS-13283 or CEGS 02090 for information on removal, containment, and disposal of lead-containing paint. If the generic type of the existing finish coat is not known, a compatible coating may be selected by merely determining its solvent solubility. To do this, soak a cloth in methyl ethyl ketone or acetone, rub it against the existing paint, and visually check for pickup of paint. The paint is classified as "solvent soluble" if paint is picked up, and as "solvent insoluble" if not.
The common practice of applying paint by glove is not recommended. It produces neither a continuous nor a uniformly thick paint film. Roller application is also not recommended because of difficulties in coating irregular surfaces. Spray application by portable equipment produces the most attractive finish but generally produces much overspray. Electrostatic spraying can eliminate overspray, if it is available on high platforms. Spray cans can provide a quick cosmetic touch-up for small damaged areas. Brushing is generally the most practical application method to coat sharp edges, crevices, and corners.
It also can produce a relatively uniform, continuous film.
184.108.40.206 Towers With Only Cosmetic Coating Defects. Maintenance painting to correct fading, discoloration, or limited intercoat peeling should be undertaken when the existing aviation orange on the upper portion of the tower fails to meet the requirement of the color tolerance chart of the FAA (refer to Advisory Circular 70/7460-1G). Whatever the construction material, the only surface preparation that is required is removal of loose contaminants with a bristle brush or by washing. One or two coats of acrylic latex finish (e. g., TT-E-2784), as required for complete hiding of the existing paint, should be applied to the cleaned surfaces. Normally, weathered exterior coatings are sufficiently textured for good adhesion and general compatibility of latex topcoats. However, severe chalking of the old coating may present an adhesion problem for latex coatings.
220.127.116.11 Zinc-Coated Steel Tower Components With Deteriorated Organic Coatings. Zinc-coated steel (either galvanized or thermally sprayed) with damaged organic coatings should be scrubbed with a bristle brush to clean the exposed metal surface and remove loose coatings. The coatings should also be lightly sanded, if necessary, to feather edge the damaged areas. If the old paint is oil, alkyd, latex, vinyl or solvent soluble, apply one coat each of latex primer and finish to the exposed zinc coating and overlay it 1 inch onto the surrounding tight coating. If the repaired area matches the intact paint, it will not be necessary to topcoat the undamaged areas.
If the existing finish coat is polyurethane, epoxy, or solvent insoluble, apply one coat of epoxy primer and one coat of aliphatic urethane finish to damaged areas. Again, if the match is good, topcoating of undamaged areas will be unnecessary.
If an inorganic zinc-primed steel component has suffered topcoat damage, it should be repaired with the original topcoat system. If the inorganic zinc primer itself is damaged, it should be repaired with a zinc-rich epoxy primer (e. g., MIL-P-24441, Formula 159) and then given an epoxy intermediate coat and an aliphatic polyurethane finish coat. Sometimes, corrosion of the galvanizing has been so severe that underlying steel is exposed. Such areas should be treated as described below for steel tower components.
18.104.22.168 Steel Tower Components (With No Zinc Coating) With Damaged Organic Coating. Steel components of towers that have never received a zinc coating and currently have damaged coatings should be hand (SSPC SP 2) or power tool (SSPC SP 3 or 11) cleaned to remove rust and loose paint. The preferred method of surface preparation is SSPC SP 11. This method not only removes all visible rust but also produces a roughened surface so that it is considered comparable to SSPC SP 6. Powered needle guns and grinders with flexible wheels and disks can produce the SSPC
SP 11 surface. The steel should be cleaned and primed the same day, before flash rusting occurs.
If the old paint is oil, alkyd, latex, vinyl or solvent soluble, apply two coats of alkyd primer to the exposed steel to a total of 3 mils dry film thickness and overlay it 1 inch onto the surrounding tight coating. A primer with raw linseed oil (e. g., SSPC PAINT 25) will penetrate the surface better but dry relatively slowly. A totally alkyd primer (e. g., TT-P-645) will dry faster but may not penetrate the surface as well. After priming, apply two alkyd or silicone alkyd (e. g., MIL-E-24635, Enamel, Silicone Alkyd Copolymer (Metric)) finish coats at the same thickness. Two additional coats of primer followed by one or more latex finish coats can be used instead of the alkyd finish coats, if the alkyd finish coats are unavailable because of environmental regulations. If the repaired area matches the intact paint, it will not be necessary to topcoat the undamaged areas.
If the existing finish coat is urethane, epoxy, or solvent insoluble, apply two coats of epoxy primer and one coat of aliphatic urethane finish. Again, if the match is good, topcoating of undamaged areas will be unnecessary.
5.7.3 Galvanized Steel Guy Lines for Towers. Tall towers are
usually supported with galvanized steel stranded guy lines.
These are frequently coated with a commercial preservative grease, as they are installed. These greases or pastes are most frequently petroleum or drying oil products. Care should be taken not to contaminate the guys before they are coated. Some equipment is available for applying the grease after installation of guys. Equipment for remote application is described in NCEL Techdata Sheet 76-04. Galvanized steel anchor support systems securing guys in place can also be protected by preservative greases.
5.8 Waterfront Structures. The coating of steel waterfront structures is described in NFGS-09967, Coating of Steel Waterfront Structures. Coating systems are best applied in a shop under controlled conditions. Systems which have provided good protection have included abrasively blasting to a near-white condition (SSPC SP 10) and application of one of the following coating systems:
a) Epoxy polyamide system – e. g., three coats of MIL-P-24441 starting with Formula 150 primer (each 3 mils dry film thickness).
b) Coal tar epoxy-polyamide System – e. g., two coats of SSPC PAINT 16 (each 8 mils dry film thickness).
Repainting or spot repairing coatings in or below tidal areas is a real problem. Quick-drying lacquers that can dry between tidal changes are not permitted at many locations because of VOC restrictions. One approach to resolve the problem is to use a cofferdam to apply suitable materials such as MIL-P-24441 or SSPC PAINT 16 that can cure underwater. Another approach is to use viscous splash-zone compounds that are applied manually or thinner epoxy materials that can be applied underwater by brush, roller, or pads.
5.9 Hydraulic Structures and Appurtenant Works. Coating of
hydraulic structures and associated pipe lines and equipment is described in CWGS 09940, Painting: Hydraulic Structures and
Appurtenant Works. Cathodic protection of gates is described in CWGS 16643. Coatings for use on locks and dams must have good abrasion resistance in addition to providing good corrosion control. Vinyl systems have worked well for many years.
5.10 Factory Finished Metal Siding. Factory-finishing of steel, galvanized steel, or aluminum siding is usually accomplished by specialized procedures (e. g., coil coating) using commercial products. It is best to consult the manufacturer of the siding for recommended coating repair methods.
5.11 Chain Link Fences. Chain link fences are usually made of galvanized steel (refer to NFGS-02821, Chain Link Fences and Gates, or CEGS 02831, Fence, Chain Link). Occasionally, they are made of vinyl-clad steel or aluminum-coated steel. As the protective metals or vinyl corrode or erode away, they may need coating to further protect them and/or to restore an attractive finish. The fencing must be washed with a detergent solution to remove loose contaminants before coating with a long-nap roller or electrostatic spray equipment. The coating system should be composed of two coats of acrylic latex (e. g., TT-E-2784) or one coat each of epoxy-polyamide (e. g., MIL-P-24441, Formula 150) and aliphatic polyurethane (MIL-C-85285).
5.12 Hot Steel Surfaces. Mufflers, stacks, and other hot steel surfaces are not protected by conventional coatings, because they are quickly burned away. Even thin fused aluminum coatings such as TT-P-28 provide only limited protection, provided that they are fused properly. (These coatings must be exposed to at least 400 degrees F for a short time for fusion to take place.) Such steel surfaces are better protected by thermally sprayed zinc (withstand up to 700 degrees F) or aluminum (withstand up to 1600 degrees F or higher when sealed) after blasting to a white metal finish (SSPC SP 5). Thermal spraying of aluminum is described in DOD-STD-2138(SH), Metal Spray Coatings for Corrosion Protection Aboard Naval Surface Ships (Metric).
5.13 Concrete Fuel Tanks. The DOD has many concrete fuel tanks (mostly underground) that were built during World War II. They have been lined with the cloth-reinforced latex coating system described in NFGS-09980, Interior Linings for Concrete Storage Tanks (for Petroleum Fuels), epoxy systems, and other systems. Cloth-latex reinforced systems have been found to work as well as any. However, they may not work well over concrete that is contaminated with oil. Oil contamination is difficult to remove and latex coatings do not bond well on this surface.
5.14 Concrete Swimming Pools. Concrete swimming pools
require periodic painting to keep them watertight and attractive. Even fiberglass-reinforced plastic pools may require refinishing to restore them to an acceptable appearance should they fade or chalk significantly. Chlorinated rubber coatings (e. g., TT-P-95, Type I) have been used effectively for many years for lining pools. Although these coatings are high in VOCs (solvent content), they have received a temporary exemption for coating concrete pools in most locations with vOc limitations. Epoxy coatings perform well on interior concrete pools, but some of them chalk to such an extent, even underwater, that the water is clouded in exterior pools. Waterborne pool coatings have not proven to be durable.
a) Exterior pools are usually coated in the spring before the swimming season when the temperature is between 50 and 80 degrees F. New concrete pools should be allowed to cure at least 2 months before painting. The first step in preparing concrete pools for painting is to make necessary repairs:
cracks and holes cracks and spalls
b) Repair small cracks and holes with a non-shrinking patching compound. Cracks greater than 1/2 inch and spalls should be repaired with cementitious material (e. g., a mix containing two parts of clean, hard, sharp sand to one part of Portland cement). The repair area should be thoroughly wetted and enough water added to the mix to make a heavy paste.
c) After repairs have been made, any efflorescence or laitance on the surface of the concrete should be removed by brushing with a dry bristle brush, treating with 5 to 10 percent muriatic (hydrochloric) acid, and rinsing with clear water.
Mildew should be removed as described in par. 5.18, and body oils should be removed with trisodium phosphate or other detergent.
Any deteriorated old paint should be removed by wire brushing or careful light abrasive blasting.
d) Application of chlorinated rubber paint should occur in two coats to completely dry surfaces. The first coat is best applied by brush to fill the concrete pores, but the second can be applied by roller or spray. A minimum of 24 hours should occur between coats to ensure complete evaporation of solvent from the first coat. Painting of individual walls should continue until completion to avoid lap marks where the work was interrupted. Because the coating dries very fast, it may be necessary to paint walls in the shade or at night during hot weather. A minimum of 7 days should elapse between painting of the pool and filling it with water.
5.15 Concrete Catchment Basins. Concrete catchments are used by some activities with limited water supplies to collect rainwater for both industrial and domestic use. The catchments are usually sealed with a coating material and the joints caulked with a flexible material to minimize water losses. Both of these materials must be approved for potable water use, if the collected water is to be for domestic use.
Thick cementitious coatings have been used satisfactorily for many years to seal catchments. The Government of Bermuda requires catchments to be free from unsightly mildew. This is often a limiting factor there for cementitious coatings, since their textured surfaces become mildew-defaced much sooner than smooth coatings. Treatment with hypochlorite solution, as described in par. 4.17, can restore mildew-defaced catchments to a cosmetically pleasing appearance.
Acrylic latex elastomeric coatings have been found to perform very well on concrete catchments. They provide excellent resistance to water migration, weathering, and mildew. A primer is usually required for good adhesion.
5.16 Chemically Resistant Finishes for Concrete Floors.
Chemically resistant urethane coatings (resistant to fuels and hydraulic fluids) are sometimes used to impart improved lighting to work areas such as under aircraft. Because of the smoothness of these coatings, skid resistance is usually imparted by sprinkling granules into the wet coating. Such a system is described in A-A-50542, Coating System: Reflective, Slip-
Resistant, Chemical-Resistant Urethane for Maintenance Facility Floors. A commitment to maintenance is essential when deciding to coat a concrete floor. Cleaning and repair will be needed on a frequent and regular basis to maintain the reflectivity and appearance of the floors.
Chemical resistance may also be required for floors where chemicals or hazardous waste is stored to permit rapid neutralization and removal without contaminating other stored materials. The coating should be chosen to be resistant to the stored materials, so that it is best to consult the activity industrial hygienist. Chemical-curing polyurethane or epoxy systems as described for fuel tank interiors in par. 4.2.1 are good candidates.
5.17 Slip-Resistant Floors. A slip-resistant coating is often applied as a finish for other coating systems to prevent accidental slipping. The resistance is imparted by sprinkling granules in the wet coating. MIL-E-24635 is used for alkyd systems and MIL-C-24667, Coating System, Non-Skid, for Roll or Spray Application (Metric) for epoxy systems. The MIL-C-24667 may also be used on alkyd systems where MIL-E-24635 may exceed local VOC limitations.
5.18 Fouling-Resistant Coatings. Antifouling coatings are often used over a coating system that imparts corrosion resistance to ships or other structures to be immersed in sea water. A toxic material, usually copper ion, is slowly leached into the sea water to deter attachment and growth of biological fouling organisms. MIL-P-24647, Paint System, Anticorrosive and Antifouling, Ship Hull is normally recommended for this purpose. It has a large list of qualified products. Such a copper – containing product should not be used on an aluminum boat, because direct contact of a copper product with aluminum will result in accelerated galvanic corrosion. Commercial organo-tin antifouling paints are permitted on aluminum boats. There are restrictions on their use on large Navy ships.
5.19 Mildew-Resistant Coatings. Mildew growth on painted or unpainted surfaces of buildings can cause unsightly defacements, especially at tropical and subtropical locations. This occurs on interior and exterior surfaces of steel, concrete/masonry, asbestos-cement, or wood. Mildew can also damage delicate communications and utilities equipment. In addition serious bronchial problems may be associated with living in quarters contaminated with mildew-covered surfaces. The different species of microorganisms usually present in mildew growths include molds, yeast, algae, and bacteria. These same organisms are found on mildew-defaced surfaces throughout the world. The darkly pigmented organisms are most conspicuous and contribute to most of the defacement.
5.19.1 Factors Affecting Mildew Growth. Factors that affect likelihood of mildew growth include:
a) Weather – Higher temperatures and dampness promote growth, and light inhibits it.
b) Building Design – Rough surfaces assist pickup of spores and dirt, roof overhang keeps wall surfaces damp longer, poor drainage, and porous substrates such as wood retain moisture; alkalinity on concrete surfaces inhibits growth; and air exchange, temperature, and humidity may control growth.
c) Paint – Textured, tacky, and peeling paint pick up and retain spores and dirt; incompletely removed mildew may rapidly reinfect new paint; drying oils in paints may be used as nutrients. Mildewcides in paints can control the growth of mildew organisms.
5.19.2 Use of Mildewcides in Paints. Mercury-containing mildewcide additives were used very successfully in paints for many years to control mildew growth. Only a small amount of the mercury compound leaching from the paint was necessary to kill microorganisms. Unfortunately, it also contaminated the environment with toxic material. Thus, mercury-containing mildewcides are no longer used in paints. EPA has approved alternative nonmercurial compounds for use as paint mildewcides. Some of these products, however, have not proven to be effective in retarding mildew growth.
5.19.3 Removal of Mildew. Mildew must be killed before repainting a mildewed surface to obtain control of the mildew.
If spores are just painted over, the mildew will quickly grow and become unsightly. When a surface is to be cleaned for repainting, scrub with a solution of 2/3 cup of trisodium phosphate, 1 liquid ounce of household detergent, 1 quart of 5-1/4 percent sodium hypochlorite (available as household bleach), and 3 quarts of warm water. Use rubber gloves with this caustic solution and rinse it from the surface with water after scrubbing. It will degrade alkyd and other oil-based coatings, but this will be no problem, if the surface is to be repainted.
An alternate procedure is to remove all the visible mildew by waterblasting at about 700 pounds per square inch (psi) and kill the rest by rinsing with a solution of 1 quart of 5-1/4 percent sodium hypochlorite and 3 quarts of warm water.
If a painted surface is to be merely cleaned without repainting, apply the scrubbing solution without the trisodium phosphate to avoid damage to the paint. Apply it first to a small test area to see if the hypochlorite bleaches the paint.
If it does, merely clean with detergent and water.
Mildew on field structures can be distinguished from dirt with bleach. Common household hypochlorite bleach will cause mildew, but not dirt, to whiten.
5.20 Pavement Markings. Asphalt and concrete airfield and
road pavements on military bases are generally striped with paint to show center and sidelines, as well as other information.
These markings are described in NFGS-02761, Pavement Markings, and CEGS 02580, Joint Sealing in Concrete Pavements for Roads and Airfields.
5.20.1 Painted Markings. Military airfields and roadways have been successfully marked with alkyd paints for many years. Chlorinated rubber was added to the alkyd resin to obtain faster drying times. More recently, environmental restrictions on total paint solvent have in many geographical locations eliminated or restricted the use of these marking paints. Thus, most pavements at military activities are marked with latex paints today.
Yellow marking paints constitute a possible safety and environmental problem. Historically, a lead chromate pigment has been used to impart this color because it is relatively light, stable, and inexpensive. Lead pigments were recently restricted from use in consumer paints because of concerns that dust from weathering paints might be ingested by children. More recently, concern has been expressed about the hazards of chromate pigments. New regulations impose restrictions on the removal of old paints containing lead and chromium because of possible adverse health effects the dust produced may have on workers or residents in the area. Also, residues of lead and chromate – containing paints may constitute hazardous waste which must be specially handled, stored, and disposed of properly. This has lead to the virtual elimination of lead and chromium constituents in paint. The State of California Department of Transportation and other state highway departments have had good success with yellow striping paints with organic pigments that do not constitute a health or environmental hazard.
22.214.171.124 Specifications for Marking Paints. Currently, there are five federal specifications for marking paints.
Specification TT-P-85, Paint, Traffic and Airfield Marking, Solvent Base is for a solvent-based traffic and airfield marking paint, available in white and yellow. Alkyd formulations have generally been used, even though no specific generic type is required. Paints of this specification are high in VOCs and so cannot be used in areas where such paints are prohibited (urban areas with air pollution). Water-based marking paints conforming to TT-P-1952 are used in such areas, as well as in areas without such restrictions.
a) Specification TT-P-87, Paint: Traffic, Premixed,
Reflectorized is for a premixed, solvent-based, reflectorized traffic paint, available in white and yellow. Low index of refraction (road) beads are premixed with the paint before packaging. The embedded beads are reported to be exposed as vehicular traffic erodes away the marking. They are not suitable for use on airfields because of the low index of refraction beads.
b) Specification TT-P-110, Paint, Traffic, Black (Nonreflectorized) is for a solvent-based, black,
nonreflectorized traffic paint generally made with alkyd binders. It is used mostly to outline white or yellow markings to make them stand out or to obliterate old markings on asphalt pavements. Such paints are not VOC-conforming, and there is no specification for a black water-based marking paint.
c) Specification TT-P-115, Paint, Traffic (Highway, White and Yellow) is for a solvent-based traffic paint, available in white and yellow. Once, this specification called for alkyd formulations for conventional-dry paints and chlorinated rubber – alkyd formulations for fast dry types. This is no longer the case. Because of VOC and safety concerns described below, this specification is no longer recommended.
d) Specification TT-P-1952, Paint, Traffic and Airfield Marking, Water Emulsion Base is for a water-based traffic and marking paint, available in white or yellow. Currently, there are no environmental restrictions on its use. Acrylic and polyvinyl acetate resins are most frequently used in paints conforming to this specification.
e) Specifications TT-P-85, TT-P-115, and TT-P-1952 are formulated to permit glass beads to be dropped into the wet paint immediately after spray application to provide night retroreflectivity. Coarse beads are evenly dropped into wet TT-P-87 paint to impart immediate retroreflectivity.
126.96.36.199 Specification for Reflective Glass Beads.
Specification TT-B-1325, Beads (Glass Spheres) Retro-Reflective is for beads (glass spheres) to impart retroreflectivity to painted markings. Lights from a plane or car are reflected back to the eyes of the pilot or driver. Type I (low index of refraction) is intended for use on roads. It is available in Gradations A (coarse-drop on), B (fine-premix), and C (fine-drop on). Type II (medium index of refraction), Gradation A (coarse – drop on) is not commercially available today. Type III (high index of refraction) is intended for use on airfield pavements.
188.8.131.52 Application of Painted Markings. Although the five above marking paint specifications are different from each other, each is applied at about the same thickness. Some achieve this by specifying a 15-mil wet film thickness, which results in a dry film thickness of half that, since they contain 50 percent solids by volume. Others specify a spreading rate of 100 to 110 square feet per gallon. The water-based paint of specification TT-P-1952 must be applied at temperatures at or above 45 degrees F. The other products, which are solvent based, can be applied at even lower temperatures. Surfaces to be marked must be well prepared for painting, free from dirt, oil and grease, other surface contaminants, and from loose, peeling, or poorly bonded paint. If removing lead-containing traffic marking paints (e. g., some yellows), environmental and worker safety regulations apply. Refer to Section 3 for more information.
When airfield markings are to be reflectorized, TT-B-1325, Type III beads are applied immediately after spray application at the rate of 10 pounds per gallon of paint.
Roadways are reflectorized with TT-B-1325, Type I beads applied at the rate of 6 pounds per gallon of paint. In both cases, any more beads would have insufficient paint available to be retained. Type I beads have a much lower specific gravity than Type III beads.
For marking pavements, striping machines (specially equipped trucks) are used. They have tanks that hold large quantities of paints and beads. Striping machines for airfields have arrays of multiple spray gun and bead dispensers and necessary power and support equipment to apply long painted lines 3 feet wide. The spray guns and dispensers are adjusted to give a uniform paint thickness and bead density across the entire width of the marking.
184.108.40.206 Inspection of Marking Operation. Inspection procedures for monitoring contracts for striping airfields are distinctly different from other painting inspections. They are presented below in the general order in which they might be used.
a) Procedure 1: General Appearance of Paint and
Beads. Visual examination of paint in the can and beads is done to check for any apparent deficiencies. Products with apparent discrepancies should receive a laboratory analysis or be replaced. Product labels should also be checked to verify that they are the ones specified. Paints must be homogeneous in color and consistency. They should be stirred to assure that they are free of settling, skinning, caking, strings, and foreign bodies and have a viscosity suitable for spraying. Method 3011.2 of FED-STD-141, Paint, Varnish, Lacquer, and Related Materials: Methods of Inspection, Sampling, and Testing describes precisely how to check for "Condition in Container." Beads must be clean, dry, free flowing, and free of air intrusions. They should be only a few extremely large, small, or out-of-round beads. Type I beads have a pure white color; Type III beads have a brownish cast.
b) Procedure 2: Sampling of Paint and Beads. Paints
and beads may be sampled for immediate analysis or merely taken for later use, if problems arise later. In any event, it is necessary to procure samples that authentically represent the material to be applied to the pavements. Incompletely cleaned paint tanks may contain significant amounts of water or another batch of paint. Incompletely emptied bead tanks may contain beads of another type. Paint and bead samples should be taken from drums or sacks to determine whether the supplier’s material meets all requirements. Excessive mixing of latex marking paints should be avoided prior to testing, because their wetting agents cause them to froth when heavily mixed, and this may result in testing errors. Excessive stirring of beads may cause smaller or lighter density beads to migrate to the bottom of the container. Full sampling and inspection procedures are presented in Method 1031 of FED-STD-141.
c) Procedure 3: Percent by Weight of Paint Total
Solids and Pigment. These tests are run to provide information on the paint composition and a quick check for its conformance to specification. These tests are done with the same sample using ASTM D 2369, Volatile Content of Coatings and ASTM D 3723,
Pigment Content of Water-Emulsion Paints by Low-Temperature Ashing. By using the relationships percent total solids equals percent binder plus percent pigment and percent total solids equals 100 minus percent volatile, results of the two referenced test procedures can provide data on any of these components (e. g., solvent, binder, pigment, and total solids). Testing should be done in triplicate to indicate repeatability. The percent by weight of total solids (or the percent volatile) of latex paints is determined by measuring the loss of weight after the solvent has been evaporated off by heating the sample at 110 degrees C for 2 hours. The percent by weight of pigment is determined by measuring the weight after further heating of the samples for 1 hour at 450 degrees C to burn up the organic binder.
d) Procedure 4: Specific Gravity of Paints. In ASTM
D 1475, Density of Paint, Varnish, Lacquer, and Related Products, a metal cup of precisely selected volume is weighed first empty and then filled with paint until it is forced out a hole in the cap. The additional weight is a direct measure of specific gravity.
e) Procedure 5: Paint Binder Identification. ASTM D
2621, Infrared Identification of Vehicle Solids From Solvent – Reducible Paints can readily identify the generic type of marking paints as 100 percent acrylic. Only a small sample of the wet or dry (e. g., 1 square inch) paint is necessary.
f) Procedure 6: Specific Gravity of Beads. The
specific gravity of beads can easily be determined by field personnel with access to an inexpensive balance following the procedure of par. 4.3.5 of TT-B-1325. A sample of dried and weighed beads (about 60 g) is placed in a glass graduated cylinder containing 50 ml of xylene, and the resultant increase in volume is noted. The specific gravity is then determined by simple division:
Specific Gravity = Weight of Sample (about 60 g)
New Total Volume – 50 ml
g) Procedure 7: Index of Refraction of Beads. The
index of refraction of glass beads can be determined by immersing them in standard liquids with different refractive indexes and observing whether the beads blend into the liquid. Blending occurs when the liquid has a higher refractive index than do the beads. Indentations of a ceramic spot plate can be conveniently used for holding the beads and liquid. Run this test when substitution of TT-B-1325, Type I beads for Type III beads is suspected. This is normally suspected from a low specific gravity value in Procedure 6.
h) Procedure 8: Preparation of Drawdowns for
Determining Retroreflectivity. Drawdown specimens are prepared using a metal drawdown bar as described in ASTM D 823, Producing Films of Uniform Thickness of Paint, Varnish, and Related Products on Test Panels. A paint film of 16 mil or other wet film thickness is screeded onto a the white surface of a black and white chart by drawing it across the paper in front of a bar of proper clearance. Immediately after this action, beads are manually sprinkled into the wet paint. After drying, the drawdowns are measured with a retroreflectometer. The instrument can be held in either direction, since the application procedure does not have a directional effect.
i) Procedure 9: Surface Preparation. Inspection of
pavement surfaces prepared for marking with paint is basically determining whether the surface is clean enough and sound enough to permit tight bonding of the paint. Cleaning of concrete for painting is described in ASTM D 4258, Surface Cleaning Concrete for Coating. Of the several procedures described for cleaning, high-pressure water blasting with truck-mounted equipment is almost always the procedure selected for rubber and paint removal. Washing with an aqueous detergent solution may be necessary to remove oil, grease, and tightly bonded dirt. The extent of paint removal should be verified visually. If only loose paint is to be removed prior to restriping, the remaining paint can be checked with a dull putty knife to determine whether only sound paint remains. After a build-up of five coats (a dry film thickness of 37 mils), the film becomes rather inflexible and subject to cracking, and the skid resistance significantly reduced. Thus, complete removal of the old marking is recommended at this time. From a standpoint of eliminating the hazard of hydroplaning on wet pavements, it is not necessary to remove 100 percent of the rubber build-up on runways. From a standpoint of surface preparation for marking pavements, however, virtually complete removal is more important. While one contractor was observed to be able to achieve 100 percent removal with his equipment without apparent difficulty, others could not do so using their equipment without considerable expense and damage to the pavement. It may be necessary to settle for less than 100 percent (e. g., 90 percent) removal to permit competitive bidding until the technology for 100 percent removal becomes widely available.
j) Procedure 10: Check of Application Equipment.
Paint spray guns and bead dispensers should be checked to determine that they are properly metered and functioning.
Metering can be checked individually, directing paint or beads into a container for collection. To check for proper application and overlap of paint patterns (fans) from spray guns and beads from dispensers, apply a small area of paint and beads onto roofing paper or other disposable material taped to the pavement.
k) Procedure 11: Monitoring of Marking Operation.
The prevailing conditions should be recorded before starting to apply markings. This includes temperature; dew point, if solvent-based paints are used; rain or prospects of rain; wind; type of equipment used; and any unusual conditions. Wind can cause overspray of the paint onto the beads to significantly reduce their retroreflectivity. General weather forecasts are normally available from operations offices. A variety of thermometers are available for measuring temperature, and inexpensive sling psychrometers are usually used for measuring humidity and dew point. Photography can be an excellent method of recording conditions. Solvent-based paints should not be applied unless the temperature is at least 5 degrees above the dew point and above 40 degrees F and rising or if rain is expected within an hour. In addition, water-based paints should not be applied when the temperature is below 45 degrees F. Paint should be applied when the wind is over 5 mph, unless it can be shown that the marking can be applied properly with the existing equipment. None should ever be applied when the wind is over 10 mph. The marking should be continuous (no underlap at all or overlap of adjacent spray patterns greater than 1/4 inch) with a constant color that matches the standard or submittal, and free from wind-blown dust and dirt. The edges of the marking should be relatively sharp and straight. The marking should be touched with a finger to determine if complete drying has occurred within the time specified for the paint. Dried paints should be probed with a dull putty knife to determine that they are well bonded.
The beads should be relatively uniformly spread across and along the marking. At least 25 beads should be found in every square inch, to obtain desired level of retroreflectivity.
l) Procedure 12: Wet Film Thickness of Stripes. Wet
film thickness can easily be determined using the procedure of ASTM D 1212, Measurement of Wet Film Thickness of Organic Coatings. A metal or plastic gage with calibrated notches cut into each of four faces is used for this purpose. The face calibrated for the desired wet film thickness is pushed squarely into a freshly painted surface and withdrawn. The wet film thickness of the marking is equal to the depth of the deepest notch with paint on it. A sample of wet paint without beads must be applied to a rigid test panel by the striping machine in a test run. It is best made on roofing paper or other disposable material to avoid contamination of a pavement. Obviously, a series of plates secured across the width of 3-foot-wide stripes must be used for each test run to determine localized application rates.
m) Procedure 13: Dry Film Thickness of Paint Film.
The dry film thickness of a paint film can be estimated from the wet film thickness by the relationship:
Thickness = Wet Film Thickness x Percent Solids by Volume
Dry film thickness of paint applications can be determined quite precisely using a magnetic gage as described in ASTM D 1186, Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to a Ferrous Base. A ferrous plate is coated with marking paint by the striping machine but no beads are applied. The paint is allowed to cure completely before its dry film thickness is determined by magnetic gage. Again, a series of test plates must be used on runway stripes to determine thicknesses across the stripe. Tin-plated steel panels used in paint elongation testing by ASTM D 522, Mandrel Bend Test of Attached Organic Coatings are convenient to use for this purpose.
n) Procedure 14: Spreading Rate of Paint. After the
wet film thickness of a marking has been made, as described above, the spreading rate of the paint can be estimated by the relationship:
Spreading Rate of Wet Paint
in Square Feet/Gallon = 1600_________
Wet Film Thickness in Mils
From a practical standpoint, it is easier to specify a paint’s wet film thickness than its spreading rate.
o) Procedure 15: Retroreflectivity of Pavement
Markings. Measure the retroreflectivity of airfield markings for conformance to contract specification using a Mirolux 12 or Erickson instrument. In addition to following the instrument manufacturer’s instructions, these precautions should be taken:
(1) Keep an extra fully charged battery available.
(2) Frequently check instrument calibration.
(3) Systematically make five measurements across stripes at each test site rather than in the direction of or opposite to application to avoid directional effects.
(4) Select numerous random test areas to obtain representative measurements.
Use of a portable computer while making retroreflectivity measurements can greatly accelerate the procedure. This is especially important on busy runways with limited access time. Typically, a two-person team has a driver who stays in the vehicle keeping radio contact with the tower, recording data into the computer and driving to the different test locations. The other team member measures retroreflectivities and calls out the data to the driver.
5.20.2 Alternative Markings. A variety of tapes, buttons, and reflectorized squares have been successfully used to mark roadways. Tapes have been used at military installations to provide temporary markings. They may be damaged by turning wheels of heavy trucks. None of these alternative marking materials are recommended for use on runways because of concern for foreign object damage.
5.21 Wooden Floors. The surface preparation (scraping and
sanding) and coating of wooden floors is described in NFGS-09900 and CEGS 09900. These finishes include stains and alkyd and moisture-curing coating systems. For hardwood floors for gymnasium-type use, a selection can be made from the MFMA Heavy Duty and Gymnasium Finishes for Maple, Beech and Birch Finishes. The products addressed include sealers, heavy-duty finishes, gymnasium-type finishes, moisture-cured urethane finishes, and water-based finishes. The individual suppliers should be contacted for special applications such as handball and racquetball.