Coal-Tar Emulsion Coating

How To Apply Coal-Tar Emulsion Coating

PAINT SPECIFICATION NO. 32 – Coal-Tar Emulsion Coating

1. Scope
1.1 This specification covers a coal-tar emulsion coating to be used as a protective weather coat for hot- or cold-applied bituminous coatings on steel structures. It may also be used over suitable primers as a protective coating for above ground steel structures subjected to atmospheric exposure and the deleterious effects of oxidation and ultraviolet radiation.

1.2 It is suitable for use on parts or structures exposed in Environmental Zone 1B (exterior, normally dry). It can also be used in heavy industrial environments such as Zones 3A (chemical exposure acidic), 3B (chemical exposure neutral), and 3C (chemical exposure alkaline) where color is not a prime consideration.

2. Description
2.1 The coating is a water emulsion of coal tar and may contain selected fillers. It is a thick, heavy-duty, cold-applied protective coating intended for use on steel substrates coated with hot- or cold-applied bituminous coatings or other suitable primers.

2.2 The coating contains approximately 40 percent by vol­ume non-volatile film-forming solids. The theoretical spreading rate for a 380-µm (15-mil) dry film thickness is 1.1 m2/L (43 ft2/gal). Actual spreading rates can be significantly lower.

3. Referenced Standards
3.1 The latest issue, revision, or amendment of the refer­enced documents in effect on the date of invitation to bid shall govern unless otherwise specified. Those documents marked with an asterisk (*) are referenced only in the Notes or the Appendix, which are not requirements of this specification.

3.2 If there is a conflict between the requirements of any of the cited reference documents and this specification, the requirements of this specification shall prevail.

3.3 SSPC STANDARDS:

3.4 ASTM INTERNATIONAL STANDARDS:1
D 244 Standard Test Methods and Practices for Emulsified Asphalts
D 1141 Standard Practice for the Preparation of Substitute Ocean Water
* D 1475 Standard Test Method for Density of Liquid Coatings, Inks, and Related Products
D 1640 Standard Test Methods for Drying, Curing, or Film Formation of Organic Coatings at Room Temperature
* D 2369 Standard Test Method for Volatile Content of Coatings
D 2939 Standard Test Methods for Emulsified Bitumens Used as Protective Coatings
D 3924 Specification for Standard Environment for Conditioning and Testing Paint, Varnish, Lacquer, and Related Materials
D 4587 Standard Practice for Fluorescent UV-Condensation Exposures of Paint and Related Coatings
D 6132 Standard Test Method for Nondestructive Measurement of Dry Film Thickness of Applied Organic Coatings Using an Ultrasonic Gage
D 6677 Standard Test Method for Evaluating Adhesion by Knife
D 7091 Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to Ferrous Metals and Nonmagnetic, Non-conductive Coatings Applied to Non-Ferrous Metals

3.5 FEDERAL STANDARDS:
MIL-PRF-2104 Lubricating Oil, Internal Combustion Engine, Combat/Tactical Service

3.6 AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI) STANDARD:
Z129.1 Hazardous Industrial Chemicals ­Precautionary Labeling

4. Composition Requirements
4.1 The manufacturer is given wide latitude in the selec­tion of raw materials and manufacturing processes (see Notes 9.1.and 9.2).
4.2 RESIN REQUIREMENT: The coating shall be an emulsified coke-oven coal tar of such consistency as to be readily applicable either by brush or by spray. The coating may be formulated to contain mineral filler. The coal tar used in this coating is defined as a product obtained from the distillation of high-temperature crude coke oven tar, which in itself is a product obtained during the destructive distillation of coal in slot ovens operated at a temperature above 700 °C (1300 °F). The coal tar shall be composed primarily of a complex combination of condensed ring aromatic hydrocarbons of three or more members. The coating shall not contain asphalt or asbestos.

5. Requirements of Liquid Coating
5.1 RESIDUE: The percent by weight (wt %) of residue by evaporation shall be a minimum of 45 wt % when tested in accordance with ASTM D 2939.
5.2 ASH CONTENT: The ash content of the residue shall be from 25 to 40 wt % when tested in accordance with ASTM D 2939.
5.3 WATER CONTENT: The percent by weight of water shall not be greater than 50 wt % when tested in accordance with ASTM D 244.
5.4 CONDITION IN CONTAINER: Moderate water sepa­ration, without packing hard in the container, is acceptable. Any water that separates shall be readily incorporated upon stirring.
5.5 WORKING PROPERTIES: The coal-tar emulsion coating shall be de­signed for application by brush or spray in accordance with the Directions for Use (see Section 7.3). When applied to vertical surfaces at the manufacturer’s specified thickness, the coating shall not sag (see Section 6.1).
5.6 ODOR: The coating shall not have a pronounced or unduly objectionable odor.

6. Laboratory Physical Tests of Applied Films
Unless otherwise specified herein, or in referenced test methods, properties will be tested at standard atmospheric conditions as specified in ASTM D 3924.
6.1 SAG: The coating shall not sag when tested as follows: Press a strip of 2.5 cm (1 inch) masking tape across the full width of a solvent-cleaned 75 x 150 mm (3 x 6 inch) cold-rolled steel panel. The tape shall be parallel to and centered on the shorter axis of the panel. Apply the material to the panel at a wet film thickness of 965 ± 50 µm (38 ± 2 mils). The application may be made with a doctor blade according to ASTM D 1640. Immediately after applying the material, carefully remove the masking tape and stand the panel in a vertical position (with the bare strip horizontal) in a draft-free 23 ± 3 °C (73 ± 5 °F) location. Examine the panel after 24 hours. Sagging or running of the coating into the bare area shall constitute failure of the material to pass the sag test.
6.2 ADHESION: A single coat of the material shall be ap­plied to a dried bituminous coating such as SSPC-Paint 33 at a wet film thickness of 965 ± 50 µm (38 ± 2 mils). Ninety-six hours after application, the adhesion shall be tested according to ASTM D 6677. The adhesion value shall be 10.
6.3 WATER ABSORPTION: Determine the water absorp­tion by the following method:

• Record tare weights of three aluminum panels, each 75 x 150 x 0.8 mm (3 x 6 x 1/32 inch)
• Apply one coat of the coating to a uniform wet film thickness of 965 ± 50 µm (38 ± 2 mils).
• After the coating has dried for 96 hours, dip each panel momentarily in distilled water, wipe lightly with a paper towel, and weigh each panel to determine the weight of coating on the panel.
• Immerse the coated panels in distilled water at temperature of 23 ± 3° C (73 ± 4 °F) per ASTM D 3924 for 15 days
• Remove the panels, wipe lightly with a paper towel, and weigh again.
• Subtract the weights recorded after the initial dipping from those taken after the 15-day immersion to determine the weight of water absorbed.
• Determine the weight percent of water absorbed by the coating for each test panel.

The average of the three weight percents shall be no more than 10. In addition, the coal-tar emulsion coating on each panel shall show no observable signs of softening or separation.

6.4 RESISTANCE TO OIL: Apply the coal-tar emulsion coating to two wire-brushed, coal-tar naphtha solvent-cleaned mild steel panels, each 75 x 150 x 3 mm (3 x 6 x 1/8 inch) to a uniform wet film thickness of 965 ± 50 µm (38 ± 2 mils). After the coating has dried for 96 hours, immerse the coated panels in MIL-PRF­2104, grade 30 lubricating oil, for 24 hours. The coating shall exhibit no observable softening. There shall be no observable loss of adhesion, or any other deterioration.
6.5 ACCELERATED WEATHERING: To three aluminum panels, each approximately 75 x 150 x 0.8 mm (3 x 6 x 1/32 inch) [size may vary as required by accelerated weathering unit], apply two coats of the coating to produce a uniform dry film thickness of 760 ± 50 µm (30 ± 2 mils), as measured by ASTM D 7091 or ASTM D 6132, using protocol provided in SSPC-PA 2, Appendix 5. Apply the two coats at right angles to each other, with a drying period of 24 hours between coats. After the second coat has dried for 96 hours, subject the coated panels to 15 days of accelerated weathering in accordance with ASTM D 4587. At the end of the period, examine visually for disbonding, cracking, crazing, or alligatoring. Alligatoring configurations on the immediate surface but not through to the substrate are acceptable.
6.6 WATER RESISTANCE: Prime three aluminum panels, each approximately 75 x 150 x 0.8 mm (3 x 6 x 1/32 inch) with a bituminous coating such as SSPC-Paint 33. After thorough drying, apply a single coat of the material at a wet fi lm thick­ness of 965 ± 50 µm (38 ± 2 mils). After 96 hours, immerse the coated panels in substitute ocean water meeting the requirements of ASTM D 1141 for 15 days. The coating shall not soften or delaminate from the primer.

7. Labeling
7.1 Labeling shall conform to ANSI Z129.1.
7.2 Technical data shall be provided for at least all data elements categorized as “essential” in SSPC-Guide 13.

7.3 DIRECTIONS FOR USE: The following directions for use shall be supplied with each container of coating:

Directions for Use of Coal-Tar Emulsion Coating

This emulsion coating is primarily designed to be used as a topcoat over hot- or cold-applied bituminous coatings. It may also be used as a protective coating over other suitable primers for atmospheric protection of metal substrates in heavy industrial atmospheres.

Mix coating thoroughly before use. Under normal condi­tions, no thinning should be necessary. Thin only when neces­sary, using only clean potable water.

If applied by brush, a proper technique must be developed to ensure application of correct thickness. If coating large areas, spray application is recommended using either high pressure airless or conventional spray equipment designed for the application of mastics.

Apply to the specified dry film thickness, or, if none is specified, 380 µm (15 mils) or approximately 965 µm (38 mils) wet. The surface to be coated shall be dry, the surface tem­perature shall be at least 3 °C (5 °F) above the dew point, and the temperature of the surface shall be over 4.5 °C (40 °F). Do not apply outdoors in rainy weather or if freezing temperatures are expected before the coating dries. Under normal condi­tions, this coating will be dry for re-coating in two to six hours.

High relative humidity may require 24 to 48 hours between coats. After the surface dries, the coal-tar emulsion coating will remain soft for long periods.

Protect stored containers from freezing.

8. Disclaimer
8.1 While every precaution is taken to ensure that all information furnished in SSPC standards and specifications is as accurate, complete, and useful as possible, SSPC cannot assume responsibility nor incur any obligation resulting from the use of any materials, coatings, or methods specified herein, or of the specification or standard itself.

8.2 This coating specification does not attempt to address prob­lems concerning safety associated with its use. The user of this specification, as well as the user of all products or practices described herein, is responsible for instituting appropriate health and safety practices and for ensuring compliance with all governmental regulations.

9. Notes
Notes are not requirements of this specification.
9.1 VOC CONTENT: Each coating, after recommended thinning, must conform to published government regulations regarding volatile organic compound (VOC) content. VOC information should be supplied on the label or the technical data sheet. Various governmental agencies may have different VOC limits or use different methods of testing. The owner may modify this specification as necessary to specify a particular VOC content limit consistent with local regulations. Coatings meeting the composition and performance requirements of this specification usually have a VOC level between 70 and 110 g/L (0.6 and 0.9 lb/gal).

9.2 QUALITY ASSURANCE TESTS: If the user chooses, tests may be used to determine the acceptability of a lot or batch of a qualified coating. The quality assurance tests are used to determine whether the supplied products are of the same type and quality as those originally tested and certified for acceptance. The selected tests should accurately and rapidly measure the physical and chemical characteristics of the coating necessary to verify that the supplied material is substantially the same as the previously accepted material. All of the quality assurance tests must be performed on the originally submitted qualification sample. The results of these tests are used to establish pass/fail criteria for quality assur­ance testing of supplied products.

9.2.1 Establishing Quality Assurance Acceptance Criteria: Many ASTM test methods contain precision and bias statements. Specification developers should be cognizant of the fact that these statements exist. Quality assurance test criteria should not be more stringent than the inter-laboratory precision of the test methods used. The specifier may require additional technical data to satisfy quality assurance or local regulatory requirements.

Where precision and bias data are not available for a given test method, determine the standard deviation of a minimum of five measurements taken on the originally tested and certi­fied material. The pass/fail criterion is that the measurement of the test sample shall fall within two standard deviations of the target value. The contracting parties must agree on a target value.

9.3 Recommended Quality Assurance Tests: Recom­mended quality assurance tests include but are not limited to weight per gallon (ASTM D 1475), total solids (ASTM D 2369), and odor (ASTM D 1296).

9.4 The procurement documents (project specification) should establish the responsibility for inspection and for any required affidavit certifying compliance with the specification. The procedures and times of inspection should be agreed upon by those responsible for establishing the requirements and those responsible for performing the work.

PAINT SPECIFICATION NO. 32 – Coal-Tar Emulsion Coating