NPFC - MIL-PRF-32647
ZINC‐NICKEL ELECTROPLATING FOR FASTENERS
|Publication Date:||4 January 2021|
This specification covers requirements for an electrodeposited zinc‐nickel (Zn‐Ni) alloy plating with a hexavalent chromium‐free conversion coating and supplementary top coat or sealant. This MIL specification selects desired options from ASTM F1941/F1941M and details additional requirements, such as plating composition and torque/tension behavior of the plating on surrogate threaded fasteners. Although developed for threaded steel fasteners, this plating may be used on other steel products. While other plating thickness and supplementary treatment options are available for unique applications, the requirements of this specification are limited to the ASTM F1941/F1941M codes specified herein. This specification is intended for use on new fasteners and fasteners which previously may have specified coatings containing cadmium or hexavalent chromium, substances which have been added to the Aerospace and Defense Declarable Substances List ("AD‐DSL").
The electrodeposited plating covered by this specification is intended for use as a corrosion protective coating. Color is NOT a requirement of this specification. However, yellow plating... View More
The electrodeposited plating covered by this specification is intended for use as a corrosion protective coating. Color is NOT a requirement of this specification. However, yellow plating appearance is discouraged as this color implies the presence of hexavalent chromium in industry. Sealants or top coats may affect the underlying plating and conversion coating appearance. Typical color will range from gray to silver. Processes used for cleaning and deposition on parts heat‐treated to, or having ultimate tensile strength of 160 KSI (or HRC 36) or greater, should be such that hydrogen embrittlement is minimized. Guidance is provided in the referenced ASTM F1941/F1941M.View Less