SIST EN ISO 4042:2022

SLOVENSKI STANDARD
oSIST prEN ISO 4042 rev:2020
01-januar-2020
Vezni elementi - Sistemi galvanskih prevlek veznih elementov (ISO/DIS 4042:2019)
Fasteners - Electroplated coating systems (ISO/DIS 4042: 2019)
Verbindungselemente - Galvanisch aufgebrachte Überzugsysteme (ISO/DIS 4042:2019)
Fixations - Systèmes de revêtements électrolytiques (ISO/DIS 4042: 2019)
Ta slovenski standard je istoveten z: prEN ISO 4042 rev
ICS:
21.060.01 Vezni elementi na splošno Fasteners in general
25.220.40 Kovinske prevleke Metallic coatings
oSIST prEN ISO 4042 rev:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 4042 rev:2020

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oSIST prEN ISO 4042 rev:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 4042
ISO/TC 2/SC 14 Secretariat: DIN
Voting begins on: Voting terminates on:
2019-11-13 2020-02-05
Fasteners — Electroplated coating systems
Fixations — Systèmes de revêtements électrolytiques
ICS: 21.060.01
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 4042:2019(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2019

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COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
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Published in Switzerland
ii © ISO 2019 – All rights reserved

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Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 General characteristics of the coating . 2
4.1 Coating metals or alloys and main purposes . 2
4.2 Build-up of basic electroplated coating systems . 3
4.3 Coating systems and coating processes. 4
4.4 Internal hydrogen embrittlement. 4
4.4.1 General. 4
4.4.2 Fasteners with hardness below 360 HV . 5
4.4.3 Fasteners with hardness equal to and above 360 HV and up to 390 HV . 5
4.4.4 Fasteners with hardness above 390 HV . 5
4.4.5 Fasteners in accordance with ISO 898-1, ISO 898-2 and ISO 898-3 . 6
4.4.6 Baking and test requirements for case-hardened and tempered screws . 7
4.4.7 Work-hardened fasteners . 8
4.4.8 Fasteners with bainitic structure . 8
4.5 Baking . 8
5 Corrosion protection and testing . 9
5.1 General . 9
5.2 Neutral salt spray test (NSS) for zinc based coating systems . 9
5.3 Sulfur dioxide test (Kesternich test) .10
5.4 Bulk handling, automatic processes such as feeding and/or sorting, storage and
transport . .11
6 Dimensional requirements and testing .11
6.1 General .11
6.2 Fasteners with ISO metric thread .12
6.2.1 Coating thickness .12
6.2.2 Gaugeability and assemblability .12
6.3 Other fasteners .13
6.4 Test methods for thickness determination .13
7 Mechanical and physical properties and testing .15
7.1 General .15
7.2 Appearance .15
7.3 Corrosion resistance related to temperature .15
7.4 Torque/clamp force relationship .15
7.5 Determination of hexavalent chromium .15
8 Applicability of tests .15
8.1 General .15
8.2 Tests mandatory for each lot .15
8.3 Tests for in-process control.16
8.4 Tests to be performed when specified by the purchaser .16
9 Designation system .16
9.1 General .16
9.2 Designation of electroplated coating systems for the order .17
9.3 Examples of designation of hexavalent chromium free electroplated coating
systems for fasteners .18
9.4 Designation of fasteners with electroplated coating systems for labelling .19
10 Ordering requirements for electroplating .19
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11 Storage conditions .20
Annex A (informative) Design aspects and assembly of coated fasteners .21
Annex B (informative) Hydrogen embrittlement consideration .29
Annex C (informative) Corrosion protection related to zinc coatings with chromate
conversion coatings .33
Annex D (informative) Coating thickness and thread clearance for ISO metric screw threads .34
Annex E (informative) Coating systems tested in accordance with ISO 9227, NSS —
Evaluation of cabinet corrosivity for the neutral salt spray test .42
Annex F (informative) Obsolete designation codes for electroplated coating systems on
fasteners according to ISO 4042:1999 .52
Bibliography .55
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Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 2, Fasteners, Subcommittee SC 14, Surface
coatings.
This fourth edition cancels and replaces the third edition (ISO 4042:2018), which has been technically
revised. The main changes compared to the previous edition are as follows:
— introduction of a statement in Clause 1 (Scope) that requirements of ISO 4042 for electroplated
fasteners supersede other general ISO standards dealing with electroplating;
— extension of the scope to all threaded fasteners;
— all references to ISO 2081 and ISO 19598 removed;
— improvement of the descriptions of the reference test areas (including Figure 2) in 6.4.
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Introduction
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, and the
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 regards to hydrogen embrittlement and baking. Therefore a new revision was
necessary to delete all references to these two standards to avoid any contradictions.
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DRAFT INTERNATIONAL STANDARD ISO/DIS 4042:2019(E)
Fasteners — Electroplated coating systems
1 Scope
This 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 this document for electroplated fasteners supersede other general ISO standards
dealing with electroplating.
This document applies to 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.
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.
2 Normative references
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
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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 3231, Paints and varnishes — Determination of resistance to humid atmospheres containing sulfur dioxide
ISO 3497, Metallic coatings — Measurement of coating thickness — X-ray spectrometric methods
ISO 3613:2010, 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 6988, Metallic and other non organic coatings — Sulfur dioxide test with general condensation of
moisture
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)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1891-2 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
reference panel
reference material that is to be exposed to check the corrosivity level of the test cabinet used for
fastener testing
4 General characteristics of the coating
4.1 Coating metals or alloys and main purposes
Electroplated coating systems for steel fasteners are primarily applied for corrosion protection and
functional properties, such as torque/clamp force relationship.
In addition, other functional properties or decorative properties can be specified; see Annex A.
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Commonly used electroplated coatings for fasteners are given in Table 1 in relation with their main
purposes. Additional information, such as designation or decorative aspects, can be found in other
relevant ISO standards listed in the last column of Table 1.
Table 1 — Electroplated coatings in accordance with their main purposes and related
ISO standards
Coating metal(s)
Main purpose of
Nature ISO standard
the coating for
Symbol Element
Zn Zinc Metal P/D/F —
ZnNi Zinc-nickel Alloy P/D/F ISO 15726
ZnFe Zinc-iron Alloy P/D/F ISO 15726
a
Cd Cadmium Metal P/F ISO 2082
Ni Nickel Metal D/F ISO 1456
Ni+Cr Nickel+chromium Multi-layer D ISO 1456
Cu+Ni Copper+nickel Multi-layer D ISO 1456
Cu+Ni+Cr Copper+-nickel+chromium Multi-layer D ISO 1456
CuZn Brass Alloy D —
CuSn Copper-tin (bronze) Alloy F —
Cu Copper Metal F/D —
Ag Silver Metal F/D ISO 4521
CuAg Copper-silver Alloy F —
Sn Tin Metal F ISO 2093
SnZn Tin-zinc Alloy F/P —
P corrosion protection
F functional properties
D decorative properties (colour, aspect)
a
Cadmium is restricted or prohibited for many applications (remaining cadmium users are predominantly military and
aerospace industries).
4.2 Build-up of basic electroplated coating systems
Figure 1 shows basic electroplated coating systems.
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Key
1 only metal layer(s)
2 metal layer(s) + conversion coating
3 metal layer(s) + conversion coating + additional lubricant
4 metal layer(s) + conversion coating + sealant/top coat
5 metal layer(s) + conversion coating + sealant/top coat + additional lubricant
Figure 1 — Basic electroplated coating systems (schematic)
A conversion coating increases corrosion protection on zinc, zinc alloys and cadmium coatings. It may
be a passivation (chromium VI free) or a chromatation (chromium VI containing). The conversion
coating can also provide better adhesion for additional layer(s) and/or additional colour/paint.
An additional sealant/top coat (with or without integral lubricant) may be chosen to increase corrosion
resistance and to achieve other specific properties (e.g. torque/clamp force properties, resistance to
chemicals, mechanical resistance, aspect, colour, thermal stability, increased electrical resistance, UV
radiation resistance). The selection of the nature of a sealant or top coat should be based on desired
additional properties.
An additional lubricant may be applied to adjust or amend the torque/clamp force relationship.
4.3 Coating systems and coating processes
The type and geometry of the fasteners should be considered when selecting a coating system and the
related coating process (see Annex A) as well as hydrogen embrittlement considerations (see Annex B).
The electroplating process shall be under control, in accordance with a recognized standard and/or a
specification by agreement with the customer.
4.4 Internal hydrogen embrittlement
4.4.1 General
If the three following conditions are concurrently present for fasteners:
— with high tensile strength or hardness or which have been case-hardened and tempered or cold
worked to high hardness,
— which are under tensile stress,
— which have absorbed hydrogen,
there is a risk of Internal Hydrogen Embrittlement (IHE), see annex B.
The susceptibility to IHE increases with increasing hardness of the fastener material. Appropriate
measures for prevention of IHE for quenched and tempered fasteners depending on hardness are
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specified in Table 2. For fasteners in accordance with ISO 898-1, ISO 898-2 and ISO 898-3, Tables 3, 4
and 5 apply.
Table 2 — Measures related to IHE for quenched and tempered fasteners with regard to
hardness
360 HV 390 HV

A B C
No supplemental process veri- Supplemental process verifica-
Supplemental process verification and/or
fication or product testing with tion and/or product testing with
product testing with regard to IHE
regard to IHE regard to IHE
OR
AND AND
No baking necessary Baking Baking
(at the choice of the fastener manufacturer) (baking temperature and dura-
tion shall be specified)
See 4.4.2 See 4.4.3 and B.6 See 4.4.4 and B.6
4.4.2 Fasteners with hardness below 360 HV
When electroplating fasteners with specified maximum hardness below 360 HV (A in Tables 2, 3, 4
and 5), no supplemental process verification with regard to IHE and no baking are necessary.
4.4.3 Fasteners with hardness equal to and above 360 HV and up to 390 HV
When electroplating fasteners with specified maximum hardness equal to and above 360 HV and up to
and including 390 HV (B in Tables 2, 3, 4 and 5), baking is not required provided supplemental process
verification and/or product testing with regard to IHE have been performed. However, the purchaser is
free to require baking generally.
For fasteners in this specified hardness range, electroplating does not pose a risk of IHE. In case of a
failure in a product test, it cannot be assumed that baking the parts would have prevented such failure:
the metallurgical and physical conditions of the fastener material should be investigated for non-
conformances. For more information, see B.4.
4.4.4 Fasteners with hardness above 390 HV
When electroplating fasteners with specified maximum hardness above 390 HV (C in Tables 2, 3 and 5),
baking is required; see B.4 for minimum recommended baking temperature and duration.
The following exemptions apply:
— for fasteners which are not specified to be under tensile stress by design or standard (e.g. set screws
in accordance with ISO 898-5), baking is not required (see B.2),
— induction hardened ends (e.g. for thread forming screws) shall not be considered for determining
measures related to IHE in relation to Table 2, because they are normally not subjected to tensile
stress provided that the end protrudes through the mating thread.
For alkaline zinc-nickel electroplatings (and nickel content from 12 % to 16 %), it is possible to avoid
baking because of low risk of IHE (see B.3). The decision not to carry out baking shall be based on
testing (see B.6) and be agreed between the supplier and the purchaser.
NOTE For acid zinc-nickel electroplatings, studies have shown similar benefits as for alkaline zinc-nickel
electroplating, however more data is necessary with regard to baking avoidance.
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4.4.5 Fasteners in accordance with ISO 898-1, ISO 898-2 and ISO 898-3
For fasteners in accordance with ISO 898-1, ISO 898-2 and ISO 898-3, Tables 3, 4 and 5 apply.
Table 3 — Measures related to IHE for fasteners in accordance with ISO 898-1
Property class
Bolts, screws and studs in
≤ 9.8 10.9 12.9 and 12.9
accordance with ISO 898-1
A B C
No supplemental process Supplemental process ver- Supplemental process ver-
verification or product ification and/or product ification and/or product
Measures related testing with regard to IHE testing with regard to IHE testing with regard to IHE
to IHE
AND OR AND
No baking necessary Baking Baking a
Baking temperature and
At the choice of the fasten-
— duration shall be specified
er manufacturer
(see also B.4)
See 4.4.2 See 4.4.3 and B.6 See 4.4.4 and B.6
a
For alkaline zinc-nickel electroplatings (and nickel content from 12 % to 16 %), the decision not to carry
out baking shall be based on testing (see B.6) and be agreed between th
...