This specification establishes the basic requirements for non-electrolytically applied zinc-flake composite corrosion protective coating systems for fasteners. The requirements apply to appearance, adhesion, corrosion resistance, blisters, thread fit, hydrogen embrittlement, and total coefficient of friction. The coating systems covered by this specification do not contain hexavalent chromium, lead, cadmium, or mercury. This specification is intended for corrosion protection of inch and metric series threaded fasteners as well as for non-threaded fasteners such as washers and pins. This specification also covers test methods, application, inspection, and certification.

1.1 This specification covers the basic requirements for non-electrolytically applied zinc-flake composite corrosion protective coating systems for fasteners (See Note 1).

Note 1: The coating systems do not contain hexavalent chromium, lead, cadmium, or mercury.

1.2 This specification is intended for corrosion protection of inch and metric series threaded fasteners with minimum nominal diameters of 0.250 in. for inch series and [6.00 mm] for metric as well as for non-threaded fasteners such as washers and pins.

1.3 This coating system may be specified to consist of a zinc-flake basecoat, or a zinc-flake basecoat and topcoat (See Note 2).

Note 2: For threaded fasteners, the coating system will typically consist of a zinc-flake basecoat and topcoat.

1.3.1 The basecoat is a zinc-rich material containing aluminum flakes dispersed in a compatible liquid medium. The zinc-flake basecoat may be specified to contain integral lubricant.

1.3.2 Topcoats may be organic or inorganic in composition depending upon the specified requirements.

1.3.2.1 Organic topcoats consist of polymer resins, aluminum, dispersed pigments, and are colored in their applied state.

1.3.2.2 Inorganic topcoats consist of water-dispersed silicate compounds and are transparent in their applied state.

1.3.2.3 Topcoats contain integral lubricants and are applied in conjunction with zinc-flake basecoats to form a coating system with enhanced performance attributes such as increased corrosion resistance, total coefficient of friction properties, chemical resistance, and color.

1.4 These zinc-flake basecoats and topcoats are applied by conventional dip-spin, dip-drain, or spray methods to fasteners which can be handled through a cleaning, coating, and curing operation. The maximum curing temperature is 482°F [250°C].

1.5 The friction properties of the coating system may be determined by a standard test to verify process control or by a part specific test which requires the purchaser to establish and communicate technical criteria.

1.6 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.

1.7 This 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 this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.