Water-Borne Epoxy Topcoat for Steel Surfaces

Water-Borne Epoxy Topcoat

PAINT SPECIFICATION NO. 34 – Water-Borne Epoxy Topcoat for Steel Surfaces

1. Scope
1.1 This specification covers an ambient-cured, two-component water-borne epoxy coating that is intended for use as a finish coat in multicoat water-borne epoxy systems for steel.

1.2 Topcoats are categorized according to performance levels (Sections 2.3, 6, and 7).

1.3 Topcoats meeting this specification, when used with an appropriate primer, are suitable for exposures in Environmental Zones 1A (interior, normally dry), 1B (exterior, normally dry), 2A (frequently wet by fresh water), 2B (frequently wet by salt water), and 3C (chemical exposure, alkaline).

1.4 The specified topcoat is intended for application by brush, spray, or roller over primed surfaces prepared in accordance with the manufacturer’s recommendations.  It is suitable for use as a water-borne epoxy topcoat in a two-coat system or as an intermediate coat and topcoat in a three-coat system, to be applied in accordance with the manufacturer’s recommendations.

2. Description
2.1 COMPOSITION
2.1.1 The topcoat specified is based on a reactive oxirane (epoxy) functional resin with amine or acid functional curing agents.
2.1.2 The major volatile component by weight is water. Refer to ASTM D 3792 or ASTM D 4017 for determination of the water content of paints.
2.2 VOLATILE ORGANIC COMPOUND (VOC) CONTENT: Consult applicable government regulations to determine maximum allowable VOC content and the proper VOC test method for a particular application. The supplier should provide VOC information on the coating as supplied (in the container) and as applied (in the field after recommended thinning).
2.3 PERFORMANCE LEVEL: The finish coat shall be classified according to exposure performance achieved as follows, based on testing of primed systems as specified.
Level 1 Accelerated Testing (Section 6)
Level 2 12-Month Exterior Exposure (Section 7.2)
Level 3 36-Month Exterior Exposure (Section 7.3)
2.3.1 If no performance level is specified, Level 2 is assumed.

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.
3.2 If there is a conflict between the requirements of any of the cited reference standards and this specification, the requirements of this specification shall prevail.
3.3 SSPC SPECIFICATIONS:

3.4 ASTM INTERNATIONAL STANDARDS:
A 36 Specification for Carbon Structural Steel
B 117 Practice for Operating Salt Spray (Fog) Apparatus
D 523 Test Method for Specular Gloss
D 562 Test Method for Consistency of Paints Measuring Krebs Unit (KU) Viscosity Using a Stormer-type Viscometer
D 609 Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings, and Related Coating Products
D 610 Test Method for Evaluating Degree of Rusting on Painted Steel Surfaces
D 714 Test Method for Evaluating Degree of Blis­tering of Paints
D 823 Practices for Producing Films of Uniform Thickness of Paint, Varnish, and Related Products on Test Panels
D 1200 Test Method for Viscosity by Ford Viscosity Cup
D 1475 Test Method for Density of Liquid Coatings, Inks, and Related Products
D 1654 Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments
D 2243 Test Method for Freeze-Thaw Resistance of Water-Borne Coatings
D 2244 Test Method for Calculation of Color Differ­ences from Instrumentally Measured Color Coordinates
D 2369 Test Method for Volatile Content of Coatings
D 2574 Test Method for Resistance of Emulsion Paints in the Container to Attack by Micro­organisms
D 3359 Test Methods for Measuring Adhesion by Tape Test
D 3363 Test Method for Film Hardness by Pencil Test
D 3792 Test Method for Water Content of Water-Reducible Paints by Direct Injection into a Gas Chromatograph
D 3924 Specification for Standard Environment for Conditioning and Testing Paint, Varnish, Lacquer, and Related Materials
D 3925 Practice for Sampling Liquid Paints and Related Pigmented Coatings
D 3960 Practice for Volatile Organic Compound (VOC) Content of Paints and Related Coatings
D 4017 Test Method for Water in Paints and Paint Materials by Karl Fischer Method
D 4060 Test Method for Abrasion Resistance of Organic Coatings by the Taber Abraser
D 4417 Test Methods for Field Measurement of Surface Profile of Blast Cleaned Steel
D 4585 Practice for Testing the Water Resistance of Coatings Using Controlled Condensation
G 92 Practice for Characterization of Atmospheric Test Sites

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

3.6 NACE INTERNATIONAL STANDARD:
RP 0287 Field Measurement of Surface Profile of Abrasive Blast Cleaned Surfaces Using Replica Tape

3.7 U.S. ENVIRONMENTAL PROTECTION AGENCY:
40 CFR Chapter 1, Part 60, Appendix A, Method 24— Determination of Volatile Matter Content, Density, Volume Solids and Weight Solids of Surface Coatings

4. Composition
4.1 The manufacturer is given latitude in the selection of materials, provided the topcoat system meets the require­ments of the specification. Materials shall be those used in good commercial practice and entirely suitable for the purpose intended under normal conditions.
4.2 The coating shall comply with applicable state and local VOC regulations as measured by EPA Method 24, ASTM D 3960, or other required methods. If no method is specified, use EPA Method 24. The supplier should provide information on the coating as supplied in the container and as thinned for application if VOC is to be added in thinning.

5. Standard Testing Conditions
5.1 The standard testing conditions shall be in accor­dance with the standard atmosphere in ASTM D 3924, unless indicated otherwise. Standard temperature shall be 23 ± 2 °C (73.5 ± 3.5°F), and standard relative humidity 50 ± 5%.
5.2 The standard substrate shall be 3.2 mm (1/8 in.) thick ASTM A 36 hot rolled steel abrasive blasted in accordance with SSPC-SP 10 to a profile of 50 ± 13 micrometers (2.0 ± 0.5 mils) unless indicated otherwise. Measure blast profile in accordance with ASTM D 4417 or NACE RP0287. Sealed and primed chart paper may be used to perform the film irregularity test discussed in Section 6.10.
5.3 The substrate shall be primed with a compatible water­borne epoxy primer, as defined in SSPC-Paint 28, Section 5.3.
5.4 The topcoat shall be applied following the manu­facturer’s recommendations for cure times and method of application.

6. Laboratory Performance Testing Requirements
6.1 For Level 1 (Accelerated Testing), the coating shall meet the requirements of Sections 6.2 through 6.13. For Level 2 and Level 3 (Exterior Exposure), the coating shall meet the requirements of Section 7 in addition to the requirements in Section 6.
6.2 RESISTANCE TO MICROORGANISMS IN CONTAINER: The coating shall be resistant to attack by micro­organisms when tested in accordance with ASTM D 2574.
6.3 FREEZE-THAW RESISTANCE: Test each of the components separately in accordance with ASTM D 2243. At the end of three cycles there shall be no gelling, coagulation, lumps, coarse particles, or viscosity change in excess of 10 Krebs Units per ASTM D 562.
6.4 PACKAGE STABILITY: Perform the following tests: Place each component in an appropriate closed container (i.e., a lined metal or plastic can) in an oven for one month at 52° ± 1°C (125° ± 2°F). There shall be no viscosity change in excess of 10 Krebs Units when tested in accordance with ASTM D 562. The cured film shall produce a uniform appearance when applied at recommended film thicknesses.
6.5 MECHANICAL STABILITY: Test each component separately by filling a one-quart friction top can three-quarters full and closing the can tightly. Rotate on a jar roller for one week at 120-170 rpm. There shall be no indication of separa­tion, coagulation, or changes in viscosity greater than 10 Krebs Units (per ASTM D 562).
6.6 POT LIFE: The term “pot life,” as used for solvent-borne or solventless epoxies, generally does not have the same meaning for water-borne epoxies. The usable pot life of mixed components of water-borne epoxies cannot be determined simply by measuring changes in viscosity. Thoroughly mix together both components of the coating to yield one quart of mixed material. Allow this mixture to stand at the standard conditions specifi ed in Section 5.1 for the pot life specified by the manufacturer. At the end of this time period, the mixed coating shall show no evidence of gelation and must meet the requirements of Sections 6.7 through 6.13. The cured film shall show no significant change in color or gloss as measured by ASTM D 2244 and D 523, respectively. These methods contain definitions of the degree of difference between original color or gloss and final color or gloss deemed to be significant by visual observation.
6.7 LABORATORY APPLICATION PROPERTIES: Thoroughly mix together both components of the coating. Allow the mixed material to stand for the manufacturer’s specified induction time (if any). Apply the coating in accordance with the manufacturer’s recommendations to a primed, vertical steel substrate under the standard conditions specified in Sections 5.1 through 5.4. Allow the coating to dry in a well-ventilated room or chamber free from drafts and dust in diffuse light. There shall be no runs, sags, streaks, laps, pinholing, or cratering.
6.8 ADHESION: Apply one coat of the coating to a primed panel prepared as specified in Section 5.2. Condition the panel for seven days at standard temperature and humidity (Section 5.1). Evaluate adhesion in accordance with ASTM D 3359, Method B, using one mm spacing. A rating of 5B is required.
6.9 RECOAT TESTS: Apply a second coat of topcoat to a panel prepared as defined in Section 6.7, following the manufacturer’s recommendations. There shall be no picking up or rolling up of the previous coat(s) during application. After 24 hours, the system should appear smooth and uniform.
6.10 FILM IRREGULARITY: Apply one coat of the topcoat by the drawdown method to a 10 x 20 cm (4 x 8 in) primed panel, as prepared in Section 5.2, to produce the manufacturer’s recommended DFT. Sealed and primed chart paper may also be used as a substrate for this test. Allow to dry for 24 hours under the standard conditions specified in Section 5.1. There shall be no mud-cracking, alligatoring, or other film irregularities noted upon examination.
6.11 RUST AND BLISTER RESISTANCE:
6.11.1 Sample Preparation: Spray apply coat(s), per the manufacturer’s recommendation, to four primed panels prepared in accordance with the standard testing conditions specified in Sections 5.1 through 5.4. Allow the system to dry for up to 14 days. Seal all edges and the back side of each panel with a coating that will provide the necessary protec­tion to these surfaces. Scribe a five cm (two inch) vertical line through the lower middle portion of the panels to expose the underlying metal before testing. The conditions of making the scribe shall conform to ASTM D 1654.
6.11.2 Salt Spray Test: Expose duplicate panels in the salt fog cabinet for 800 hours according to ASTM B 117. At the end of the 800 hours, immediately examine the panels for rusting, blistering, and creepage. The rusting shall not exceed 8 according to SSPC-VIS 2 or ASTM D 610. The blistering shall not exceed 8F according to ASTM D 714. Check creepage from the scribe according to ASTM D 1654, Procedure A. A minimum rating of 7 (1.6 mm [1/16 in.] or less) is required. After examining the panels, immediately remove the coating fi lm with a suitable organic solvent as recommended by the manufac­turer. If scraping is necessary to remove the coating film, do so using a piece of soft wood such as a tongue depressor. Do not use a metal spatula or a razor blade. Examine the bare steel substrate. Rusting shall not exceed 8 as judged by the criteria listed above, and rust creep shall not exceed 3.2 mm (1/8 inch) from the center of the scribe.
6.11.3 Condensation: Expose the other pair of duplicate panels in a Cleveland Condensing Cabinet for 750 hours at 38°C (100°F) according to ASTM D 4585. At the end of 750 hours, immediately examine the panels for rusting, blistering, and creepage. The rusting shall not exceed 8 according to SSPC-VIS 2 or ASTM D 610. The blistering shall not exceed 8F according to ASTM D 714. Check creepage from the scribe according to ASTM D 1654, Procedure A. A minimum rating of 7 (1.6 mm [1/16 inch] or less) is required. After examining the panels, immediately remove the coating film, using a suit­able organic solvent as recommended by the manufacturer. If scraping is necessary, do so using a piece of soft wood such as a tongue depressor. Do not use a metal spatula or a razor blade. Examine the bare steel substrate. Rusting shall not exceed 8 as judged by the criteria listed above, and rust creep shall not exceed 3.2 mm (1/8 in.) from the center of the scribe.
6.12 ABRASION RESISTANCE: Apply two coats of the topcoat to three primed steel panels meeting the size require­ments noted in Section 6.1 of ASTM D 4060. Allow the panels to dry for up to 14 days according to the standard testing condi­tions specified in Sections 5.1 through 5.4. An average weight loss of no more than 140 mg is required when tested according to ASTM D 4060 with CS17 wheels for 1000 cycles.
6.13 EARLY WATER RESISTANCE: Apply one coat of the topcoat in accordance with the standard testing condi­tions specified in Sections 5.1 through 5.3 within 24 hours after priming. After six hours, immerse one-half of the panel in distilled water for five minutes. Remove and allow the system to condition for 10 minutes at standard temperature (see Section 5.1). The exposed section of the panel shall have the same hardness, gloss, and color as the unexposed section when checked according to ASTM D 3363, D 523, and D 2244, respectively.

7. Exterior Performance Requirements
7.1 Two sets of triplicate panels shall be prepared as specified in Section 6.11.1.
7.2 LEVEL 2 EXTERIOR EXPOSURE: Triplicate test specimens shall be exposed for a minimum of 12 months on a test fence at an industrial or marine exposure site having a minimum annual mean precipitation of 635 mm (25 in.) per year. Other criteria for classifying the environment such as corrosion rate of bare steel or bare zinc, or mean annual temperature, may also be required when agreed to by purchaser and supplier. Each specimen shall meet the following requirements:

• Rust rating of 8 or better in accordance with SSPC VIS 2/ASTM D 610
• Maximum scribe undercutting of 1.6 mm (1/16 in.) per ASTM D 1654

7.3 LEVEL 3 EXTERIOR EXPOSURE: Triplicate test specimens shall be exposed for a minimum of 36 months on a test fence at an industrial or marine exposure site having a minimum annual mean precipitation of 635 mm (25 in.) per year. Other criteria for classifying the environment such as corrosion rate of bare steel or bare zinc, or mean annual temperature, may also be required when agreed to by purchaser and supplier. Each specimen shall meet the following requirements:

• Rust rating of 8 or better in accordance with SSPC VIS 2/ASTM D 610
• Maximum scribe undercutting of 3 mm (1/8 in.) per ASTM D 1654

8. Material Quality Assurance
8.1 The manufacturer should measure and record batch testing information that would allow certification that a batch meets the necessary standards established by the manufacturer for the topcoat as tested per Section 6.
8.2 CONDITION IN CONTAINER: Each component as received shall show no evidence of livering, skinning, or hard settling of the pigment. The inside of the container shall not be corroded. The material shall be easily dispersed in the liquid portion by hand stirring to form a smooth, homogeneous coating.
8.3 COLOR: The color shall be as specified in the procurement documents.
8.4 POT LIFE: Mix the topcoat as specified in Section 6.6. Allow the mixed topcoat to stand at standard conditions (Section 5.1) for the pot life specified by the manufacturer. At the end of this time period, the mixed topcoat shall show no evidence of gelation or change in color or gloss once applied and cured.
8.5 VISCOSITY: The viscosity of the mixed topcoat shall be determined in accordance with ASTM D 62. Variance shall be within ± 5 Krebs Units or equivalent units of another viscometer of the viscosity of the previously qualified topcoat.
For viscosities lower than 55 KU, a number 4 Ford Cup shall be used in accordance with ASTM D 1200. Variations shall be within ± 5 seconds of the viscosity of the previously qualified coating.
8.6 DENSITY: Density of the mixed topcoat shall be determined in accordance with ASTM D 1475. Variance shall be within ± 50 g/l (0.4 lb/gal) of the nominal density of the previously qualified topcoat.
8.7 SOLIDS BY WEIGHT: Solids by weight of the mixed topcoat shall be determined in accordance with ASTM D 2369. Variance shall be within ± 2% of the nominal percent solids by weight of the previously qualified topcoat.

9. Labeling
9.1 Labeling shall conform to ANSI Z129.1.
9.2 Technical data shall be provided for at least all data elements categorized as “essential” in SSPC-Guide 13.
9.3 MARKING OF CONTAINERS: Each container of each component shall be legibly marked with the following information:
Name: Water-Borne Epoxy Topcoat for Steel Surfaces
Specification: SSPC-Paint 34
Component:
Color:
Lot Number:
Batch Number:
Stock Number:
Date of Manufacturer:
Quantity of Coating in Coating in Container:
Information and Warnings as may be required by Federal and State Laws:
Manufacturer’s Name and Address:

9.4 DIRECTIONS FOR USE: Directions for use of water­borne epoxy topcoat must include information on storage, surface preparation, mixing, thinning, application, usable pot life, and recoatability.

10. Inspection
10.1 All materials (coatings) supplied under this speci­fication are subject to timely inspection by the purchaser or his authorized representative. The purchaser shall have the right to reject any materials supplied which are found to be defective under this specification (see Note 12.5). In case of dispute, unless otherwise specified, the arbitration or settle­ment procedure established in the procurement documents shall be followed. If no arbitration or settlement procedure is established, then a procedure mutually agreeable to the purchaser and material supplier shall be used.
10.2 Samples of paints may be requested by the purchaser and shall be supplied upon request along with the manufac­turer’s name and identification for the materials. Samples may be requested at the time the purchase order is placed or may be taken from unopened containers at the job site.
10.3 Unless otherwise specified, the sampling shall be in accordance with ASTM D 3925.

11. Disclaimer
11.1 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.
11.2 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.

12. Notes
Notes are not requirements of this specification.
12.1 VOC information should be supplied on the label and the technical data sheet.
12.2 ASTM D 3960 and EPA Method 24 are methods commonly used to determine VOC, but these methods may not be acceptable to all jurisdictions.
12.3 The 250 meter (800-ft) lot at the LaQue Center, Wrightsville (Kure) Beach, NC and the Neville Island and coke works sites in Pittsburgh, with average bare steel corrosion rates of 25 to 76 micrometers (one to three mils) per year based on panels exposed for 12 months, have been shown suitable for this specification’s exterior exposure. The test coatings used to establish the performance requirement were evaluated at these test sites. Specific details of the rust and undercutting results are available from SSPC.
12.4 The supplier should also furnish information on the volume solids and the theoretical spreading rate (square meters per liter for one micrometer of dry coating [square feet per gallon for one mil of dry coating]).
12.5 The procurement documents should establish the responsibility for samples, testing, and any required affidavit certifying full compliance with the specification.

PAINT SPECIFICATION NO. 34 – Water-Borne Epoxy Topcoat for Steel Surfaces