ISO 4042:2022 Updates Fastener Electroplating Standard

The International Organization for Standardization (ISO) has revised its fastener electroplating standards.

ISO 4042:1999 was completely revised to take into account new developments related to hexavalent chromium free passivations, application of sealants and top coats, requirements for functional properties as well as results of research work to minimize the risk of hydrogen embrittlement. This revision was published in 2018.

The last editions of ISO 2081:2018 as well as ISO 19598:2016, which are general standards for electroplating, are not adequate to cover the requirements for electroplated fasteners dealt with in ISO 4042, especially with regard to hydrogen embrittlement and baking. Therefore, a new revision of ISO 4042:2018 was necessary to delete all references to these two general standards to avoid any contradictions.

For electroplated nuts, flat washers, and case-hardened screws, measures to mitigate the risk of hydrogen embrittlement, especially in relation to baking, have been revised to be consistent with revisions of ISO 898-2 and ISO 2702, and to reflect findings from the latest research works. For electroplated flat washers in accordance with ISO 898-3, it is generally accepted that tensile stress resulting from intended and unintended bending in service may increase the risk of hydrogen embrittlement. An appropriate test method to simulate such a scenario is currently under investigation.

The ISO 4042:2022 document specifies requirements for steel fasteners with electroplated coatings and coating systems. The requirements related to dimensional properties also apply to fasteners made of copper or copper alloys.

It also specifies requirements and gives recommendations to minimize the risk of hydrogen embrittlement, see 4.4 and Annex B.

It mainly applies to fasteners with zinc and zinc alloy coating systems (zinc, zinc-nickel, zinc-iron) and cadmium, primarily intended for corrosion protection and other functional properties:

With or without conversion coating,
With or without sealant,
With or without top coat,
With or without lubricant (integral lubricant and/or subsequently added lubricant).

Specifications for other electroplated coatings and coating systems (tin, tin-zinc, copper-tin, copper-silver, copper, silver, copper-zinc, nickel, nickel-chromium, copper-nickel, copper-nickel-chromium) are included in this document only for dimensional requirements related to fasteners with ISO metric threads.

The requirements of the ISO 4042:2022 document for electroplated fasteners take precedence over other documents dealing with electroplating. This document applies to steel bolts, screws, studs and nuts with ISO metric thread, to other threaded fasteners and to non-threaded fasteners such as washers, pins, clips and rivets.

NOTE Electroplating is also applied to stainless steel fasteners, e.g. for the purpose of lubrication in order to avoid galling. Information for design and assembly of coated fasteners is given in Annex A. This document does not specify requirements for properties such as weldability or paintability.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 1456, Metallic and other inorganic coatings — Electrodeposited coatings of nickel, nickel plus chromium, copper plus nickel and of copper plus nickel plus chromium
ISO 1463, Metallic and oxide coatings — Measurement of coating thickness — Microscopical method
ISO 1502, ISO general-purpose metric screw threads — Gauges and gauging
ISO 1891-2, Fasteners — Terminology — Part 2: Vocabulary and definitions for coatings
ISO 2082, Metallic and other inorganic coatings — Electroplated coatings of cadmium with supplementary treatments on iron or steel
ISO 2093, Electroplated coatings of tin — Specification and test methods
ISO 2177, Metallic coatings — Measurement of coating thickness — Coulometric method by anodic dissolution
ISO 2178, Non-magnetic coatings on magnetic substrates — Measurement of coating thickness — Magnetic method
ISO 3497, Metallic coatings — Measurement of coating thickness — X-ray spectrometric methods
ISO 3613, Metallic and other inorganic coatings — Chromate conversion coatings on zinc, cadmium, aluminium-zinc alloys and zinc-aluminium alloys — Test methods
ISO 4521, Metallic and other inorganic coatings — Electrodeposited silver and silver alloy coatings for engineering purposes — Specification and test methods
ISO 8991, Designation system for fasteners
ISO 9227, Corrosion tests in artificial atmospheres — Salt spray tests
ISO 15330, Fasteners — Preloading test for the detection of hydrogen embrittlement — Parallel bearing surface method
ISO 15726, Metallic and other inorganic coatings — Electrodeposited zinc alloys with nickel, cobalt or iron
ISO 16047, Fasteners — Torque/clamp force testing
ISO 16228, Fasteners — Types of inspection documents
ISO 21968, Non-magnetic metallic coatings on metallic and non-metallic basis materials — Measurement of coating thickness — Phase-sensitive eddy-current method
ASME B18.6.3, Machine Screws, Tapping Screws, and Metallic Drive Screws (Inch Series)