Weld-Through Inorganic Zinc Primer

Inorganic Zinc Primers

PAINT SPECIFICATION NO. 30 – Weld-Through Inorganic Zinc Primers

1. Scope
1.1 This specification covers a group of inorganic zinc primers that can protect carbon steel during the fabrication process, permit welding to specification requirements, and be over-coated.

1.2 The major pigment component in this coating is zinc dust and the binder is inorganic.

1.3 This specification defines the minimum compositional and laboratory performance requirements for characterizing a group of zinc primers. It is to be used in conjunction with SSPC-PS Guide 22.00, SSPC-PS Guide 12.00, and other SSPC specifications covering surface preparation, application, thickness, inspection, and safety.

2. Description
2.1 GENERAL
2.1.1 The zinc primers described in this specification consist of zinc dust, an inorganic vehicle, and selected additives, as required.

2.1.2 This specification covers inorganic zinc primers that are used as weld-through pre-construction primers. Frequently, zinc primers are applied by an automatic process to steel plate. Once applied, zinc primers need not be removed. It can be welded through, touched-up, and overcoated prior to being placed in service. If the resultant system will be exposed to acidic (<pH 5) or caustic (>pH 10) immersion, the primer should be removed.

2.2 PIGMENTATION
2.2.1 The major pigment component in these coatings is zinc dust of the type described in ASTM D 520 (see Note 12.1).
2.2.2 Other pigment components may include welding enhancers, curing aids, tinting colors, suspension agents, and pot-life control agents.
2.3 VEHICLE TYPES: The vehicle shall be an inorganic self-curing silicate, or other material, as described in Section 4.1 (see Note 12.2).

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.

3.3 SSPC STANDARDS AND JOINT STANDARDS:

3.4 ASTM INTERNATIONAL STANDARDS:

¹A 572 Standard Specification for High-Strength Low-Alloy Columbium-Vanadium Structural Steel
* A36 Standard Specification for Carbon Structural Steel
B 117 Standard Practice for Operating Salt Spray (Fog) Apparatus
D 185 Standard Test Methods for Coarse Particles in Pigments, Pastes, and Paints
D 520 Standard Specification for Zinc Dust Pigment
* D 562 Standard Test Method for Consistency of Paints Measuring Krebs Units (KU) Viscosity Using a Stormer-Type Viscometer
D 823 Standard Practices for Producing Films of Uniform Thickness of Paint, Varnish, and Related Products on Test Panels
D 1146 Standard Test Method for Blocking Point of Potentially Adhesive Layers
* D 1296 Standard Test Method for Odor of Volatile Solvents and Diluents
* D 1475 Standard Test Method for Density of Liquid Coatings, Inks, and Related Products
* D 1535 Standard Practice for Specifying Color by the Munsell System
* D 1640 Standard Test Methods for Drying, Curing, or Film Formation of Organic Coatings at Room Temperature
D 1654 Standard Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments
D 2369 Standard Test Method for Volatile Content of Coatings
D 2371 Standard Test Method for Pigment Content of Solvent-Reducible Paints
D 2621 Standard Test Method for Infrared Identification of Vehicle Solids from Solvent-Reducible Paints
D 3278 Standard Test Methods for Flash Point of Liquids by Small Scale Closed Cup Apparatus
D 3359 Standard Test Methods for Measuring Adhesion by Tape Test
D 3925 Standard Practice for Sampling Liquid Paints and Related Pigmented Coatings
D 4417 Standard Test Methods for Field Measurement of Surface Profile of Blast Cleaned Steel
* D 5894 Standard Practice for Cyclic Salt Fog/UV Exposure of Painted Metal, (Alternating Exposures in a Fog/Dry Cabinet and a UV/Condensation Cabinet)

3.5 AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI) STANDARD:

²Z129.1 Hazardous Industrial Chemicals— Precautionary Labeling

3.6 FEDERAL SPECIFICATIONS AND STANDARDS:

³* FED-STD-141 Paint, Varnish, Lacquer and Related Materials: Methods of Inspection, Sampling and Testing
Method 3011 Condition in Container

¹ ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.

² American National Standards Institute, 1819 L Street, NW, Suite 600, Washington, DC 20036. Standards downloadable from www.ansi.org.

³ FED STD 141 Available from USA Information Systems, Inc. 1092 Laskin Road, Suite 208, Virginia Beach, Va. 23451. This standard is available on-line from www.usainfo.com.

4. Composition Requirements
4.1 VEHICLE REQUIREMENT
4.1.1 The vehicle may consist of water-reducible self-curing vehicles, including water soluble alkali metal silicates, quaternary ammonium silicates, phosphates, and modifications thereof. These coatings dry by evaporation of water and cure by chemical reaction to yield water-insoluble films.
4.1.2 The vehicle may consist of solvent-reducible self-curing vehicles, including ethyl and other organic silicates, polymeric modifications of these silicates, and titanates. These systems are dependent upon moisture in the atmosphere to complete hydrolysis to yield an insoluble film.
4.1.3 Other organic vehicle components may be included but should constitute only a minor part of the total vehicle.
4.2 TOTAL SOLIDS: The total solids shall be a minimum 55% by weight when measured in accordance with ASTM D 2369.
4.3 ZINC REQUIREMENT: The zinc dust shall conform with the requirements of ASTM D 520, and shall constitute a minimum of 65% by weight of the total film solids (see Notes
12.1 and 12.3).

5. Standard Testing Conditions
5.1 TEST PANELS: The hot rolled steel test panels shall conform to ASTM A 572. Panel size shall be 100 x 150 x 3.2 mm (4 x 6 x 1/8 inches) or greater. Test panels shall be solvent cleaned in accordance with SSPC-SP 1 prior to blast cleaning. The test panels shall be blast cleaned in accordance with SSPC-SP 10 and have a nominal anchor profile of 25 to 50 micrometers (1.0 to 2.0 mils). The blast profile shall be measured in accordance with ASTM D 4417, Method C.
5.2 APPLICATION: The coating shall be spray-applied as a single coat in accordance with the manufacturer’s written recommendations.
5.3 DRY FILM THICKNESS: The dry film thickness (DFT) shall be 15 to 25 micrometers (0.6 to 1.0 mils). The DFT shall be measured in accordance with the method described in SSPC-PA 2, Appendix 5.
5.4 CURE: Before any testing, the coating shall be dried and cured in accordance with the manufacturer’s written recommendations.
5.5 SCRIBING: Scribe two parallel lines on the face of the coated panels so as to expose the underlying metal before testing. The lines shall be at least 2.5 cm (1 inch) from the edge, the top, and the bottom of each panel and at least 5 cm (2 inches) from each other. Each scribe shall be at least 6 cm (2.4 inches) long. The scribes may run vertically or at an angle across the face of the panel. Follow the scribe-making procedure described in ASTM D 1654.
5.6 BACKS AND EDGES: Coat and seal all edges and the back side of each panel with a coating or tape that will provide the necessary protection to these surfaces.

6. Requirements of Liquid Coating
6.1 MIXING: The components of zinc primers shall be mixed and dispersed as required to produce a product that is uniform, stable, free from grit, and conforms to the requirements of this specification. After mixing, the coarse particles and skins retained as residue on a standard 60 mesh screen shall be no more than 0.5% by weight of total paint, regardless of type, in accordance with ASTM D 185.
6.2 POT LIFE: The pot life of  zinc primers, when mixed and ready for application in accordance with the manufacturer’s written instructions, shall not be exceeded. Pot life with adjust­ments for temperature and humidity shall be provided by the coating manufacturer. Properly mixed and applied material used up to the end of the pot life shall pass the adhesion test described in Section 7.2.
6.3 STORAGE LIFE: Neither the vehicle of the multi­-component primer nor the ready-mixed primer shall show thickening that is detrimental to performance or application properties. The components or primer shall exhibit no curdling, gelling, gassing, or hard caking after being stored unmixed for nine months from the date of manufacture in a tightly sealed, unopened container at a temperature of 4 to 32°C (40 to 90°F). (See Note 12.4.)
6.4 WORKING PROPERTIES: This material is primarily designed for automatic application by either conventional or airless spraying. The mixed paint shall spray easily to form a continuous film at approximately 20 micrometers (0.8 mils) dry film thickness. The film should show no streaking, running, sagging, or other objectionable features when applied in accor­dance with ASTM D 823, Method D, and dried in a vertical position (see Note 12.5).
6.5 FLASH POINT: The minimum flash point, as determined by ASTM D 3278, should be “none” for inorganic water-based zinc dust coatings, and a minimum of 4.4°C (40°F) for solvent-based inorganic zinc primers (Type I).

7. Laboratory Physical Tests of Applied Films
7.1 MUDCRACKING: The coating, when applied and cured in accordance with Sections 5.2 and 5.4 to a 64 micrometers (2.5 mils) minimum dry film thickness, shall show no signs of mud-cracking (see Note 12.6).
7.2 ADHESION: The coating, when applied, dried, and cured in accordance with Section 5, shall be tested per ASTM D 3359, Method B. There shall be no separation of the coating or delamination of an entire square. The adhesion rating shall be no less than grade 3B.
7.3 BLOCKING RESISTANCE: When applied and cured as specified, test panels shall not stick when tested in accor­dance with ASTM D 1146.
7.4 DRYING TIME
7.4.1 When applied in accordance with Sections 5.1 through 5.3 and cured at 24°C (75°F) and 50 to 60% relative humidity, zinc primers shall dry-to-handle within the time specified in the manufacturer’s technical data (see Note 12.7).
7.4.2 When applied at ambient conditions and then dried at 150°C (300°F), the zinc primer shall dry-to-handle within the time specified in the manufacturer’s technical data.
7.5 WELDABILITY: Weldability requirements shall be determined by specific contract requirements. The primer shall not be removed in the path of the welds. Reference to double fillet weld test has been deleted in this revision. Generally, 9.5 mm thick x 150 mm wide x 0.6 m long (3/8 inches thick x 6 inches wide x 2 feet long) steel plates may be used. Actual plate sizes and thicknesses shall be determined by the specific process to be qualified. Weld quality inspections and final acceptance of the welding procedure shall be in accordance with either the AWS Structural Welding Code D1.1, or as defined in the contract specification.
7.6 RECOATABILITY: This primer, when applied over properly prepared steel surfaces, shall be compatible with the specified adjacent coating (i.e., intermediate coat or topcoat).

8. Accelerated Laboratory Weathering Test
8.1 SALT FOG EXPOSURE TEST: Triplicate panels prepared per Section 5 shall be exposed in a salt fog cabinet in accordance with ASTM B 117 for 750 hours. There shall be no blistering or rusting of the coated portion, and no undercutting at the scribe, on any test panel. Slight rusting in the scribe mark will be permissible, and resulting staining should be ignored. Strips 6 mm (1/4 inch) wide along the edges of the panel may be ignored (see Notes 12.8 and 12.9).

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.

10. Inspection
10.1 All materials supplied under this specification shall be subject to timely inspection by the purchaser or his authorized representative. The purchaser shall have the right to reject any materials supplied that are found to be defective under this specification (see Notes 12.10 and 12.11).  In case of dispute, unless otherwise specified, the arbitration or settlement procedure, if any, 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 vehicle or pigment or mixed paint 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 and testing 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 a requirement of this specification.
12.1 LEAD LEVEL IN ZINC DUST: ASTM D 520 speci­fies three types of zinc dusts for use as  pigments in protective coatings. Type I is a general grade in which no maximum level of lead is specified. Type II is a high-purity grade with a maximum lead level of 0.01% by weight. Type III is the highest purity grade, with a maximum lead level of 0.002% by weight. Any grade of zinc dust can be used in the zinc coatings covered by this specification. However, it is important to note that if Type I zinc is used, it is possible to exceed the permissible exposure limit (PEL) for lead when the products are removed by abrasive blasting. For additional information relating the lead content of the coating to worker exposure to lead during blasting see Gary L. Tinklenberg and Denise M. Doezema, “Health Concerns for Workers Using Zinc-Rich Coatings,” Journal of Protective Coatings and Linings, Vol. 15, No. 5 [May 1998], pp 36-46. In addition to lead, cadmium and other toxic metals may pose a health hazard. Placing overly restrictive requirements on some materials may result in the inability of manufacturers to produce products meeting this specification.
12.2 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 less than or equal to 650 g/L (5.4 lb/gal).
12.3 Some zinc dust containing primers with less than 65% zinc by weight in the dry film, or other non-zinc containing primers, may pass the performance requirements of this speci­fication.
12.4 STORAGE ENVIRONMENT: Inorganic zinc primers should not be stored at temperatures below 4°C (40°F) or at temperatures above 32°C (90°F). Storage in direct sunlight should also be avoided.
12.5 COVERAGE: In actual practice, a coverage of 9 to 15 m2/L (400 to 600 ft2/gal) will be expected over flat blast cleaned surfaces.
12.6 MUDCRACKING DEFINITION: A surface condition, when viewed without magnification, that is characterized by cracks that extend into or through the body of the zinc-rich primer. The appearance of the surface is that of a dried mud puddle.
12.7 Pre-construction primers should be applied at tempera­tures between the minimum and the maximum ambient and substrate temperatures as recommended by the manufacturer. The substrate temperature should be at least 3°C (5°F) above the dew point. When the dew point is within 6 °C (10°F) of the substrate temperature, adequate air movement across the surface should be maintained to ensure the necessary evaporation rate for drying.
12.8 Coatings that fail the ASTM B 117 test may perform well under actual service conditions. For most coatings, the use of ASTM D 5894 instead of ASTM B 117 has proven to be a more reliable predictor of performance. However, it appears that untopcoated zinc rich primers may still be reasonably evaluated using ASTM B 117.
12.9 ADDITIONAL RESISTANCE TESTS: Because of the diversity of potential service environments, the user may require the zinc primer (after appropriate topcoating) be further exposed and qualified.
12.10 The procurement documents should establish the responsibility for samples, testing, and any required affidavit certifying full compliance with the specification.
12.11 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.
12.11.1 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.

Example: A common quality assurance test is density (weight per gallon) as measured by ASTM D 1475. The inter-laboratory reproducibility at the 95% confidence level tells us that because of errors associated with the method, any two measurements of the same material can differ by as much as 1.8%, without the measurements being considered suspect. This only represents the precision of the measurement technique and does not account for normal variances in the manufactured product.

The acceptable range for paint density must be stated. For example, a composition specification may state this requirement as 10.0 ± 0.2 lb/gal, 10.0 lb/gal ± 2%, or as a range from 9.8 to 10.2 lb/gal. The manufacturer of proprietary products should provide this information. Using these values, if the manufacturer’s lab measures the density to be 9.8 lb/gal, the product meets the specifi­cation and the paint is shipped to the job. Because of the lab-to-lab variation of 1.8%, the user’s lab may measure the density of this sample to be as low as 9.8 less 1.8% of 9.8 (equals 9.6) lb/gal. Similarly, for the high end, the manufacturer may measure density of 10.2 lb/gal, while the user measures 10.2 plus 1.8% of 10.2 (equals 10.4) lb/gal. The pass/fail criteria for the user to accept a batch of paint should therefore be 9.6 to 10.4 lb/gal.

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.

12.11.2 Recommended Quality Assurance Tests:
Recommended quality assurance tests include, but are not limited to, infrared analysis (ASTM D 2621), viscosity (ASTM D 562), weight per gallon (ASTM D 1475), total solids (ASTM D 2369), dry time (ASTM D 1640), percent pigment (ASTM D 2371), color (ASTM D 1535), condition in container (FED­STD-141, Method 3011), and odor (ASTM D 1296).

PAINT SPECIFICATION NO. 30 – Weld-Through Inorganic Zinc Primers