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11 GENERIC SEALER SPECIFICATION
1. SCOPE
This specification provides a general specification for sealers to be used on thermally sprayed
metal coatings. A sealer is defined as a material applied to infiltrate and close the pores of a
thermal spraying deposit for the purpose of improving the life expectancy of the thermally
sprayed metal coating. A sealer is not intended to provide a dielectric barrier coating over
the surface and is not intended to provide an aesthetic finish coat. Further intermediate or
topcoats applied over the seal coat must be used for barrier coating protection and aesthetic
purposes.
This specification does not cover intermediate and finish coatings. Intermediate and finish
coats must be compatible with the thermally sprayed metal coating and sealer.
2. APPLICABLE DOCUMENTS
2.1 AASHTO, "Thermally Sprayed Metal Coating Guide."
2.2 U.S. Army Corps of Engineers (USACE) Guide Specification for Construction
CEGS-09965, Section 09965, Painting: Hydraulic Structures.
2.3 MIL-STD-2138A (SH), "Metal Sprayed Coatings for Corrosion Protection Aboard
Naval Ships."
2.4 ASTM D1210, "Test Method for Fineness of Dispersion of Pigment-Vehicle Systems."
2.5 ASTM D2794 (Modified), "Test Method for Resistance of Organic Coatings to the
Effects of Rapid Deformation (Impact)."
2.6 ISO 8502-3, "Clear Cellophane Tape Test."
2.7 The sealer manufacturer's product technical data sheets.
3. SAFETY AND ENVIRONMENTAL
3.1 Safety
3.1.1 Solvents used for cleaning or to apply sealers or topcoats (e.g., acetone,
xylene, or alcohol) emit vapors that are harmful and can be fatal.
3.1.1.1 Use solvents only with adequate ventilation or proper respiratory
protection and other protective clothing as needed. Avoid breathing
solvent vapors and skin contact with solvents.
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3.1.1.2 Most solvents are also flammable liquids. All solvent tanks must have
lids and be covered when not in use. Take proper safety precautions.
3.1.1.3 Keep all solvents and flammable materials at least 50 ft (15.2 m) away
from welding, oxyfuel cutting and heating, and thermal spraying
operations.
3.1.2 Sealers and paint coats are typically applied by spray application. Spray
application is a high-production rate process that may rapidly introduce very
large quantities of toxic solvents and vapors into the air.
3.1.2.1 Airless spray systems operate at very high pressures. Very high
fluid pressures can result in penetration of the skin on contact with
exposed flesh.
3.1.2.2 Tip guards and trigger locks should be used on all airless spray guns.
The operator should never point the spray gun at any part of the body.
3.1.2.3 Pressure remains in the system even after the pump is turned off and
can only be relieved by discharging or "blow-down" through the gun.
3.1.3 The contractor should maintain current MSDSs for all materials used on the
job. These materials include cleaning solvents, compressed gases, thermal
spray wires or powders, sealers, thinners, and paints or any other materials
required to have an MSDS (as specified in CFR 29 Part 1910, Section 1200).
The MSDSs should be readily available to all personnel on the job site in a
clearly labeled folder.
3.2 Environmental
3.2.1 Ensure compliance with the purchaser's and all pertinent government agency
requirements and regulations for air-quality and hazardous-materials control.
3.2.2 The applicator and the purchaser should coordinate the specific requirements,
responsibilities, and actions for the containment, storage, collection, removal,
and disposal of the debris produced by the thermal spray coating operations.
3.2.3 All sealers must comply with federal, state, and local volatile organic
compound (VOC) requirements for the area in which they are to be applied.
4. MATERIAL
4.1 The sealer must have the characteristics listed below.
4.1.1 The sealer must be capable of penetrating the pores of the thermally sprayed
metal coating. Pigmented sealers must have a particle size nominally 5-fineness
of grind (ASTM D1210).
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4.1.2 The sealer must be capable of being applied to a low film thickness of
0.003 in. (76 µm) or less.
4.1.3 The sealer must be compatible with the thermally sprayed metal coating. For
example, on zinc thermally sprayed coating, do not use a sealer that saponifies
the zinc.
4.1.4 The sealer must be compatible with intermediate coats and topcoats.
4.1.5 The sealer must be suitable for the intended service.
4.1.6 The sealer must meet local regulations on VOC content.
4.1.7 The sealer must meet all color and other aesthetic requirements for the
application.
4.2 Acceptable materials for steel pilings include those listed below.
4.2.1 Vinyl butyral wash primer (SSPC Paint 27). This is suitable for use over zinc,
aluminum, and 8515 weight percent (wt%) zinc/aluminum. Thin wash
primer per manufacturer's instructions and apply to a dry film thickness of
0.0005 in. (12.7 µm).
4.2.2 U.S. Army Corps of Engineers paint specification V-766E vinyl acetatevinyl
chloride copolymer (CEGS-09965).
4.2.3 MIL-P-24441 Formula 150 polyamide epoxy thinned after the required period
of induction with an equal volume amount of super hi-flash Naptha (boiling
range 315°F to 353°F [157°C to 179°C]). The thinned coating shall not
exceed local VOC limits (see MIL-STD-2138A [SH]).
4.2.4 Polyamide epoxy thinned 50 percent with approved solvent (or as directed
by manufacturer) and applied to 1.5-mil (38.1-µm) dry film thickness.
4.2.5 High-solids low-penetrating epoxy.
4.2.6 Penetrating polyurethane.
4.2.7 Coal tar epoxy. This is suitable for use over zinc, aluminum, and 8515 wt%
zinc/aluminum. Thin approximately 20 percent and apply to 0.004 to 0.006
in. (101 to 152 µm).
4.2.8 Aluminum epoxy mastic. This is suitable for use over zinc, aluminum, and
8515 wt% zinc/aluminum. Thin to the maximum extent per manufacturer's
recommended extent and apply to 0.003 to 0.004 in. (76 to 101 µm).
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4.2.9 Tung-oil phenolic aluminum (TT-P-38). Suitable for use over zinc,
aluminum, and 8515 wt% zinc/aluminum. Thin about 15 percent by volume
and apply to a dry film thickness of 0.0015 in. (38 µm).
5. APPLICATION
5.1 Apply all paint sealer and topcoating according to SSPC-PA-1, "Shop, Field and
Maintenance Painting," and the paint manufacturer's recommendations for use of the
product with a thermally sprayed metal coating system. The thermally sprayed metal
coating before sealing shall have a uniform appearance. The coating shall not contain
any of the following: blisters, cracks, chips or loosely adhering particles; oils or other
internal contaminants; pits exposing the substrate; or nodules.
5.2 Surfaces that have had the thermally sprayed metal coating applied shall be inspected
and approved by the inspector. The sealer shall be applied within 8 hours of the
thermally sprayed metal coating application. If this is not possible, verify that the
surface has not been contaminated and is dust free (cellophane tape test [ISO 8502-
3]). Visible oxidation of the thermal spray coating requires that the surface be further
prepared to remove the oxidation by brush blasting. Subsequent paint coats are
applied in accordance with the requirements of the painting schedule.
5.3 Blow down surfaces to be sealed using clean, dry compressed air to remove dust.
5.4 Where moisture is present or suspected in the thermal spray coating pores, heat the
surface to 120°F (49°C) to remove the moisture prior to the seal coat application.
When possible, the steel on the reverse side of the thermally sprayed metal coating
should be heated to minimize oxidation and contamination of the thermally sprayed
metal coating prior to sealing.
5.5 Apply sealers by conventional or airless spraying. Vinyl-type sealers must be applied
using conventional spray techniques.
5.6 Thin sealers as recommended by the sealer manufacturer to effectively penetrate
the TSMC.
5.7 Unless otherwise specified by the manufacturer or the project specifications, apply
the sealer at a spreading rate resulting in a theoretical 1.5-mil (38-µm) dry film
thickness.
5.8 Apply intermediate coats and topcoats as soon as the sealer is dry and preferably
within 24 hours, in accordance with the coating manufacturer.
6. QUALITY CONTROL
6.1 Visually confirm complete coverage during application. Look for uniform coverage
using tint and wetness of the surface as guides.
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6.2 Measure the thickness of the topcoat per SSPC-PA-2 using a Type 2 fixed-probe
gauge. The measurement may be made on either a companion coupon or the sealed
thermal spray coating if the thermal spray coating thickness has been previously
measured. Alternately, the thickness can be measured destructively using ASTM
D4138, Test Method A. This method has the advantage of being able to observe all
the layers; however, this type of measurement should be minimized because the areas
tested must be repaired in order to maintain the coating integrity.
6.2.1 As an alternative, measure the thickness of the sealer as applied to a flat panel
that was attached to the surface being sealed. Refer to SSPC-PA-2.
6.3 Note and correct areas with deficient sealer coverage. Correct by adding sealer.
Additional testing is necessary to determine the extent of the area with deficient sealer
or paint thickness. The sealer thickness must be checked prior to the application of
subsequent paint coats, and the measurement procedure repeated for the sealer and paint.
6.4 As applied to thermally sprayed metal coatings on a steel substrate, sealer must meet
a minimum drop weight impact requirement of 188 ft-lbs (254 N-m) when tested in
accordance with ASTM D2794 (Modified).
