Coal-Tar Mastic Coating, Cold-Applied

Coal-Tar Mastic Coating by Cold-Application

PAINT SPECIFICATION NO. 33 – Coal-Tar Mastic Coating, Cold-Applied

1. Scope
1.1 This specification covers a cold-applied coal-tar mastic coat­ing for use on underground and underwater steel structures.

1.2 INTENDED USE: This coating, when applied over properly prepared carbon steel, is suitable for use on parts or structures exposed in Environmental Zones 2A (frequently wet by fresh water), 2B (frequently wet by salt water), 2C (fresh water immersion), 2D (salt water immersion), 3B (chemical exposure neutral), and 3C (chemical exposure alkaline). The coating is also suitable for use on hydraulic structures and pipe. It must be used with discretion for immersion in corrosive chemicals since the coating is dissolved by some organic solvents and attacked by oxidizing solutions.

1.3 This coal-tar mastic coating is intended for application by brush or spray for use by itself or as a primer in a multi-coat system.

2. Description
2.1 The coating described in this specification consists of a cold-applied, black, self-priming, heavy-duty protective coating. It is based on a blend of coal-tar pitch, selected sol­vents, and fillers.

2.2 The coal-tar mastic coating contains approximately 70 percent by volume of non-volatile film-forming solids. The theoretical spreading rate for a 380 µm (15 mil) dry film thickness is ap­proximately 1.8 m2/L (75 ft2/gal). Actual spreading rates can be significantly lower.

2.3. To prevent checking and alligatoring when exposed to sunlight, the coating must be top-coated with a coal-tar emulsion coating meeting SSPC-Paint 32, or other suitable topcoat.

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

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

3.4 ASTM INTERNATIONAL STANDARDS:
D 5 Standard Test Method for Penetration of Bituminous Materials
D 20 Standard Test Method for Distillation of Road Tars
D 36 Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)
D 92 Standard Test Method for Flash and Fire Points by Cleveland Open Cup Tester
D 453 Standard Test Method for Tar Acids in Creosote-Coal Tar Solutions
D 562 Standard Test Method for Consistency of Paints Measuring Krebs Unit (KU) Viscosity Using a Stormer-Type Viscometer
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 2794 Standard Test Method for Resistance of Organic Coatings to the Effects of Rapid Deformation (Impact)
D 3174 Standard Test Method for Ash in the Analysis Sample of Coal and Coke from Coal
D 3924 Standard Specification for Standard Environment for Conditioning and Testing Paint, Varnish, Lacquer, and Related Materials
D 3925 Standard Practice for Sampling Liquid Paints and Related Pigmented Coatings
D 6677 Standard Test Method for Evaluating Adhesion by Knife

3.5 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 maufacturing processes (see Notes 9.1 and 9.2).

4.2 MATERIAL: The coal-tar mastic coating shall be a homogeneous mixture composed only of coal-tar pitch, solvents, and inert non-water-absorbent mineral filler. The coal-tar pitch 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 pitch 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 CONDITION IN CONTAINER: The coating shall be smooth and uniform with a minimum of settling. Any solvent that separates shall be readily incorporated upon stirring.
5.2 FLASH POINT: When tested according to ASTM D 92 the flash point shall be a minimum of 35 °C (95 °F).
5.3 DISTILLATION: When tested according to ASTM D 20 to a temperature of 235 °C (455 °F), the coating shall have a residue content of 15 to 30 percent by weight (wt %). The residue from the distillation when tested according to ASTM D 5 shall have a penetration value of 5 to 25 mm (0.2 to 1 inch). The residue when tested according to ASTM D 36 shall have a softening point of 96 to 116 °C (205 to 240 °F).
5.4 ASH CONTENT: When tested according to ASTM D 3174, the coating shall have an ash content of 15 to 30 wt %.
5.5 TAR ACIDS: When tested according to ASTM D 453 (distillation to 300 °C [570°F]) the tar acids shall be less than 0.6 mL/100 g.
5.6 WORKING PROPERTIES: The 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 specified thickness, the coating shall not sag (see Section 6.1).

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 two solvent-cleaned 75 x 150 mm (3 x 6 inch) cold-rolled steel panels. 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 760 ± 50 µm (30 ± 2 mils) on one panel and to a thickness of 380 ± 25 µm (15 ± 1 mil) on the second panel. The coating application shall be made with a doctor blade according to ASTM D 1640. Immediately after applying the material, carefully remove the masking tape and hang the first panel in a vertical position (with the bare strip horizontal) in a draft-free 23 ± 3 °C (73 ± 5 °F) location for 24 hours. Hang the second panel at 71 ± 3 °C (160 ± 5 °F) for 1 hour. At the end of the time periods, sagging or running of the coating into the bare area shall constitute failure of the material to pass the sag test.
6.2 THERMAL STABILITY: Expose the first coated sag panel (see Section 6.1) to 60 ± 3 °C (140 ± 5 °F) for 16 hours. Allow the panel to cool at room temperature for one hour, then expose to -23 ± 3 °C (-9 ± 5 °F) for four hours. The coating shall not loosen, check, crack, peel, run, sag or otherwise lose protective value.
6.3 DRY TIME: When tested according to ASTM D 1640, a 560 ± 50 µm (22 ± 2 mils) wet film thickness shall meet the set-to-touch requirement in less than 6 hours and the dry-to­recoat requirement in less than 24 hours.
6.4 ADHESION: Apply 2 coats of the coating to a wire-brushed, solvent-cleaned (xylene) mild steel panel. Each coat shall have a dry film thickness of 380 ± 25 µm (15 ± 1 mil) measured in accordance with SSPC-PA 2, using the protocol given in SSPC-PA 2 Appendix 5. The time between coats shall be 24 hours. Ninety-six hours after application of the second coat, the intercoat adhesion shall be tested according to ASTM D 6677. The adhesion value for the coating, both to the bare steel and to itself, shall be 10.
6.5 IMPACT: Apply coal-tar mastic coating to two wire-brushed, sol­vent-cleaned (xylene), mild steel plates, each 150 x 150 x 3 mm (6 x 6 x 1/8 inch), to a uniform dry film thickness of 760 ± 50 µm (30 ± 2 mils). Dry 72 hours, then test each panel separately, coated side up, according to ASTM D 2794 using the 15.9 mm (0.625 inch) indenter and 1.13 kg-m (98 inch-pounds) of force. The coating shall exhibit no visible chipping
or cracking and shall have firm adhesion outside an area of radius 6.4 mm (1/4 inch) from center of impact.
6.6 RESISTANCE TO ALKALI: Apply the coating to a clean glass panel at a uniform dry film thickness of 760 ± 50 µm (30 ± 2 mils). Dry the panel for 24 hours, then suspend vertically in 5 percent sodium hydroxide so that one-half of the coating is immersed. After 30 hours, lightly rub the fi lm with a wet rounded glass rod. The coating shall show no evidence of deterioration.

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 Mastic, Cold-Applied

This coating is used to provide corrosion protection to steel structures used in underground and underwater services. It will perform best if applied over blast-cleaned steel. When applied to surfaces prepared according to SSPC-SP 1, SSPC­SP 2, or SSPC-SP 3 performance longevity is shortened.

Mix coal-tar mastic coating thoroughly before use. Under normal condi­tions, no thinning should be necessary. Thin coating only if necessary, using only solvent recommended by manufacturer.

If applied by brush, technique must be developed to en­sure application of proper 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 film thickness, or, if none is speci­fied, to a minimum of 380 µm (15 mils) dry or approximately 540 µm (21 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. Under normal conditions this coating will dry for re-coating or outdoor exposure in 24 to 48 hours, but it will remain soft for long periods.

To prevent checking and alligatoring when exposed to sunlight, this coating must be top-coated with coal-tar emulsion coating meeting SSPC-Paint 32, or other suitable topcoat.

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, protective coatings, or methods specified herein, or of the specification or standard itself.

8.2 This 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 his 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 240 and 300 g/L (2.0 and 2.5 lb/gal).

9.2 The procurement documents should establish the responsibility for samples, testing, and any required affidavit certifying full compliance with the specification.

9.3 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.

9.3.1 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.

9.4 Recommended Quality Assurance Tests: Recommended quality assurance tests include but are not limited to viscosity (ASTM D 562), weight per gallon (ASTM D 1475), and total solids (ASTM D 2369).

9.5 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. 33 – Coal-Tar Mastic Coating, Cold-Applied