ISO/TR 15922:2011

TECHNICAL ISO/TR
REPORT 15922
First edition
2011-12-15
Corrected version
2012-01-15
Metallic and other inorganic coatings —
Evaluation of properties of dark-stain
phenomenon of chromated coiled or
sheet products
Revêtements métalliques et autres revêtements inorganiques —
Évaluation des propriétés du phénomène de tache foncée des produits
chromés enroulés ou en tôle d’acier
Reference number
©
ISO 2011
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ii © ISO 2011 – All rights reserved

Contents Page
Foreword .Lv
Introduction ..v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Information to be supplied by the producer to the user or purchaser . 3
4.1 Essential information . 3
4.2 Additional information . 3
5 Apparatus . 3
6 Test methods . 4
6.1 General . 4
6.2 Procedures . 5
6.3 Qualitative test method for determination of the property of dark stain. 5
6.4 Quantitative test method for determination of property of dark stain . 6
Annex A (normative) Measurement of colour intensities . 7
Bibliography . 9
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In exceptional circumstances, when a technical committee has collected data of a different kind from that
which is normally published as an International Standard (“state of the art”, for example), it may decide by a
simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely
informative in nature and does not have to be reviewed until the data it provides are considered to be no longer
valid or useful.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO should not be held responsible for identifying any or all such patent rights.
ISO/TR 15922 was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings,
Subcommittee SC 8, Chemical conversion coatings.
In this corrected version the publication date has been corrected on the cover page.
iv © ISO 2011 – All rights reserved

Introduction
The existence of the dark- or black- stain phenomenon related to chromated hot-dip metallic zinc and
electroplated-zinc steel products has been known, but the cause for the occurrence of this phenomenon so
far does not appear to have been rationalized. One possible reason for this incidence is due to the packed or
stacked storage conditions of coils and sheets in high temperature, pressure and high relative humidity (RH)
conditions.
The test method specified in this Technical Report employs exposure of unstacked specimens to accelerated
environmental storage conditions. Specimens made from unstacked product representing the unstressed
condition typify the outer surface of the coil-packed product whilst similar specimens, when subjected to
applied stress, temperature and humidity, represent the inner-surface layers of the packed coil and stacked
sheet products and signify the stressed condition of those layers.
The properties are determined qualitatively by test methods to confirm the presence of chromated layers and
quantitatively by a colorimetric method. The colorimetric method measures the radiance of the surface and
analyses the difference in luminosity or intensity before and after the tests are performed.
TECHNICAL REPORT ISO/TR 15922:2011(E)
Metallic and other inorganic coatings — Evaluation of
properties of dark-stain phenomenon of chromated coiled or
sheet products
WARNING — This Technical Report may not be compliant with some countries’ health, safety and
environmental legislations and calls for the use of substances and/or procedures that may be
injurious to health if adequate safety measures are not taken. This Technical Report does not address
any health hazards, safety or environmental matters and legislations associated with its use. It is
the responsibility of the producers, purchasers and/or user of this Technical Report to establish
appropriate health, safety and environmentally acceptable practices and take appropriate actions to
comply with any national, regional and/or International rules and regulations. Compliance with this
Technical Report does not, in itself, confer immunity from legal obligations.
1 Scope
This Technical Report describes the methods to evaluate the properties of dark-stain phenomenon observed
in chromate conversion-coated coiled and sheet products.
Chromate conversion coatings, with trivalent or hexavalent chromium ions, are applied to hot-dip metallic zinc
and electroplated-zinc steel products to enhance corrosion resistance of the components.
When zinc-coated packed coiled and sheet products with conversion coatings are unpacked after long-term
storage at elevated temperature and high relative humidity (RH), the surface of the sheet products appears
tarnished. This discolouration appears as dark or black stain and influences the appearance and corrosion
resistance, when parts are produced using these affected sheets.
2 Normative references
The following referenced documents are indispensable for the application 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 3613, Metallic and other inorganic coatings — Chromate conversion coatings on zinc, cadmium, aluminium-
zinc alloys and zinc-aluminium alloys — Test methods
ISO 3892, Conversion coatings on metallic materials — Determination of coating mass per unit area —
Gravimetric methods
ISO 4520, Chromate conversion coatings on electroplated zinc and cadmium coatings
ISO 6789, Assembly tools for screws and nuts — Hand torque tools — Requirements and test methods for
design conformance testing, quality conformance testing and recalibration procedure
IEC 60068-2-30, Environmental testing — Part 2-30: Tests — Test Db: Damp heat, cyclic (12 h + 12 h cycle)
IEC 60068-3-5, Environmental testing — Part 3-5: Supporting documentation and guidance — Confirmation
of the performance of temperature chambers
IEC 60068-3-6, Environmental testing — Part 3-6: Supporting documentation and guidance — Confirmation
of the performance of temperature/humidity chambers
ASTM E1347, Standard Test Method for Color and Color-Difference Measurement by Tristimulus Colorimetry
...