BS 7371-3:2009

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Application and type of coating
5 Coating
6 Chromate treatment or topcoat
7 Suitability of coatings for components with parallel threads
8 Information to be documented and supplied to the coater
9 Identification
Annexes
Annex A (normative) - Coating thickness for threaded parts
Annex B (normative) - Measurement of coating thickness
Annex C (informative) - Guidance on procedures that may be
                        adopted to accommodate thick coatings
Bibliography

Describes requirements for coatings applied by the electrolysis of solutions of zinc.

This Part of BS 7371 specifies requirements for coatings applied by the electrolysis of solutions of zinc. NOTE The coatings consist principally of zinc and can be lubricated to give controlled torque/clamping force properties when required (see, for example, BS 7371-2). In addition to the requirements in this Part of BS 7371, the requirements in BS 7371-1 which are applicable to zinc electroplated coatings apply. This Part of BS 7371 also specifies requirements for: the coating thickness; the type of conversion treatment or topcoat to be applied; quality assessment of the corrosion resistance of unused coated parts when subjected to neutral salt spray testing (for example BS EN ISO 9227); and an adhesion test. Zinc electroplated coatings covered by this Part of BS 7371 are for use on fasteners and accessories where the following apply: A coating giving galvanic protection is required for ferrous fasteners. A substrate is required to improve the corrosion resistance of subsequent coatings on ferrous fasteners, e.g. organic. The risk of hydrogen embrittlement of high tensile steel fasteners is acceptable.