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  4. ASTM F1136/F1136M Specification

ASTM F1136/F1136M Grade 1/2/3/4/5 Zinc/Aluminium Coated Fasteners

Stud Bolts, Nuts, Screws, Threaded Rod & Washers

ASTM F1136/F1136M specification covers the basic requirements for water-based zinc/aluminum dispersion inorganic basecoats and optional sealers and topcoats for fasteners. The basecoat can contain chrome (C) or be non-chrome (NC).
These coatings are applied by conventional dip-spin, dip-drain, or spray methods to ferrous parts which can be handled through a cleaning, coating, and baking operation, and which are not adversely affected by baking temperatures up to 330°C [626°F].
ASTM F1136/F1136M Coating process does not induce the possibility of internal hydrogen embrittlement providing that the fasteners have not been cleaned or pre-treated with an acid or phosphate.Alkaline cleaning or vapor degreasing is required along with shot blasting to remove rust or scale. The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
ASTM F1136/F1136M standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of ASTM F1136/F1136M standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

F1136/F1136M Coated Fasteners, Bolts, Screws, Nuts & Washers

ASTM F1136/F1136M Classifications

Grade No. Topcoat Type Coating Thickness Coating Weight Minimum SST Hours (h)
Metric Average (mil) Inch Average (mil) Metric Average (g/m2) Inch Average (oz/ft2) (C) (NC)
ASTM F1136/F1136M Grade 1 None 4 to 5 0.16 to 0.20 16 to 20 0.052 to 0.066 240 -
ASTM F1136/F1136M Grade 2 None 5 to 8 0.20 to 0.31 20 to 28 0.066 to 0.092 500 240
ASTM F1136/F1136M Grade 3 Clear Sealer 6 to 12 0.24 to 0.47 22 to 34 0.072 to 0.111 1000 720
ASTM F1136/F1136M Grade 4 None 8 to 15 0.31 to 0.59 28 to 50 0.092 to 0.164 1000 500
ASTM F1136/F1136M Grade 5 Lubricated Sealer 6 to 12 0.24 to 0.47 22 to 34 0.072 to 0.111 1000 720
ASTM F1136/F1136M Grade 6 Pigmented Topcoat 8 to 15 0.31 to 0.59 23 to 40 0.075 to 0.131 500 500
  • ASTM F1136/F1136M Grade 1 requires a minimum basecoat thickness of 4μm [ 16g/m2] or 0.16 mil (0.052 oz/ft2). This is usually applied in two coats to bulk parts, or one coat to racked parts. No topcoat is applied in ASTM F1136/F1136M Grade 1.
  • ASTM F1136/F1136M Grade 2 requires a minimum basecoat thickness of 5μm [ 20 g/m2] or 0.20 mil (0.066 oz/ft2). This is usually applied in two coats to bulk parts, or one coat to racked parts. No topcoat is applied in ASTM F1136/F1136M Grade 2.
  • ASTM F1136/F1136M Grade 3 requires a minimum basecoat thickness of 5μm [ 20 g/m2] or 0.20 mil (0.066 oz/ft2) and a single coat of the clear sealer. The sealer provides additional corrosion protection and greater lubricity than ASTM F1136/F1136M Grade 2.
  • ASTM F1136/F1136M Grade 4 requires a minimum basecoat thickness of 8μm [ 28 g/m2] or 0.31 mil (0.092 oz/ft2). This is usually applied in three coats to bulk parts, or one to two coats to racked parts. No topcoat is applied in ASTM F1136/F1136M Grade 4.
  • ASTM F1136/F1136M Grade 5 requires a minimum basecoat thickness of 5μm [ 20 g/m2] or 0.20 mil (0.066 oz/ft2) and a single coat of the lubricated sealer. The sealer provides additional corrosion protection than ASTM F1136/F1136M Grade 2 and greater lubricity than ASTM F1136/F1136M Grade 3.
  • ASTM F1136/F1136M Grade 6 requires a minimum basecoat thickness of 5μm [ 20 g/m2] or 0.20 mil (0.066 oz/ft2) with various pigmented topcoats applied. The topcoats can be black or various other colors.

ASTM F1136/F1136M Requirements

Appearance
The coating shall have a uniform appearance free from tears and other discontinuities which may affect the appearance or performance of the coating, or both.
Adhesion
The coating shall show less than 5 % removal following the tape adhesion test. Due to the nature of the coating, some removal is expected, but removal of the coating to expose the substrate indicates poor adhesion and is cause for rejection.
Corrosion Resistance
The coating shall be capable of withstanding exposure to salt spray test (SST) for the minimum hours (h) specified in Table 1. Unless otherwise defined, acceptable corrosion resistance shall be Rust Grade 6 or higher (see Test Method D610 for definition) on significant surfaces (see Terminology F1789 for definition).
Blisters
There shall be no signs of blisters after testing in accordance with Test Methods
Thread Fit
The coating shall not have an adverse effect on normal installation and removal practices as determined by the proper GO thread gage. The thickness of the coating is limited by the basic thread size (3A GO gage for external threads, 2B GO gage for internal threads). Where greater thickness is necessary, the internal threads may be produced oversized (before coating) providing the finished product (after coating) meets all the specified mechanical properties. Where mechanical properties are not specified, oversizing is subject to the approval of the purchaser.
Hydrogen Embrittlement
When specified in the purchase order, the applicator shall certify that the process did not expose the parts to acid or phosphating to guarantee the absence of internal hydrogen embrittlement.

ASTM F1136/F1136M Test Methods

Corrosion
Corrosion resistance shall be tested in accordance with Practice B117 followed by Test Method D610 to rate the amount of corrosion.
Coating Thickness
The coating thickness shall be determined by magnetic induction, X-ray fluorescence spectroscopy, microscopic examination of a cross-section taken perpendicular to the significant surfaces, or weigh-strip-weigh method. When using magnetic induction, or X-ray fluorescence, an average of ten measurements on the flat surface of one part shall be used. NOTE : The weigh-strip-weigh method involves weighing the test specimen before and after the coating is stripped. The method requires a reagent that does not attack the base metal (for example, 20 % NaOH).
Adhesion
Adhesion of the coating shall be tested in accordance with Test Methods D3359 Scribe-Grid Test, where practical. Determination if base material is exposed may be done by visually inspecting the part, or exposing the part to salt spray test (see Practice B117) for 96 h and observing if red rust occurs.
Hydrogen Embrittlement
When specified in the purchase order, testing shall be conducted in accordance with Test Methods F606, F606M or F1940. In the event that hardness reductions occur in test specimens due to coating curing times and temperatures, testing shall be conducted alternatively in accordance with Test Method F1624.