ISO 16962:2017

Surface chemical analysis — Analysis of zinc- and/or aluminium-based metallic coatings by glow-discharge optical-emission spectrometry

ISO 16962:2017 specifies a glow-discharge optical-emission spectrometric method for the determination of the thickness, mass per unit area and chemical composition of metallic surface coatings consisting of zinc- and/or aluminium-based materials. The alloying elements considered are nickel, iron, silicon, lead and antimony. This method is applicable to zinc contents between 0,01 mass % and 100 mass %; aluminium contents between 0,01 mass % and 100 mass %; nickel contents between 0,01 mass % and 20 mass %; iron contents between 0,01 mass % and 20 mass %; silicon contents between 0,01 mass % and 15 mass %; magnesium contents between 0,01 mass% and 20 mass%; lead contents between 0,005 mass % and 2 mass %, antimony contents between 0,005 mass % and 2 mass %. NOTE Due to environmental and health risks, lead and antimony are avoided nowadays, but this document is also applicable to older products including these elements.

Analyse chimique des surfaces — Analyse des revêtements métalliques à base de zinc et/ou d'aluminium par spectrométrie d'émission optique à décharge luminescente

General Information

• Status: Published
• Publication Date: 23-Feb-2017
• ICS: 71.040.40 - Chemical analysis
• Technical Committee: ISO/TC 201/SC 8 - Glow discharge spectroscopy
• Drafting Committee: ISO/TC 201/SC 8 - Glow discharge spectroscopy
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 15-Jun-2022

Relations

• Revises: ISO 16962:2005 - Surface chemical analysis — Analysis of zinc- and/or aluminium-based metallic coatings by glow-discharge optical-emission spectrometry
• Effective Date: 22-Mar-2014

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 16962
Second edition
2017-02
Surface chemical analysis — Analysis
of zinc- and/or aluminium-based
metallic coatings by glow-discharge
optical-emission spectrometry
Analyse chimique des surfaces — Analyse des revêtements métalliques
à base de zinc et/ou d’aluminium par spectrométrie d’émission
optique à décharge luminescente
Reference number
ISO 16962:2017(E)
©
ISO 2017

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ISO 16962:2017(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
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ISO 16962:2017(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
5.1 Glow-discharge optical-emission spectrometer . 2
5.1.1 General. 2
5.1.2 Selection of spectral lines . 2
5.1.3 Selection of glow-discharge source type . 2
6 Adjusting the glow-discharge spectrometer system settings . 3
6.1 General . 3
6.2 Setting the parameters of a DC source . 4
6.2.1 Constant applied current and voltage . 4
6.2.2 Constant applied current and pressure . 5
6.2.3 Constant voltage and pressure . 5
6.3 Setting the discharge parameters of an RF source . . 6
6.3.1 General. 6
6.3.2 Constant applied power and pressure . 6
6.3.3 Constant applied power and DC bias voltage . 6
6.3.4 Constant effective power and effective RF voltage . 7
6.4 Minimum performance requirements . 7
6.4.1 General. 7
6.4.2 Minimum repeatability . . 7
6.4.3 Detection limit . 8
7 Sampling . 9
8 Calibration . 9
8.1 General . 9
8.2 Calibration samples .10
8.2.1 General.10
8.2.2 Brass calibration samples .10
8.2.3 Zn-Al alloy samples .10
8.2.4 Low alloy iron or steel samples.10
8.2.5 Stainless steel samples .10
8.2.6 Nickel alloy samples . .10
8.2.7 Aluminium-silicon alloy samples .10
8.2.8 Aluminium-magnesium alloy samples.10
8.2.9 High-purity copper and zinc samples .11
8.3 Validation samples and optional RMs for calibration .11
8.3.1 General.11
8.3.2 Zinc-nickel electrolytically coated RM .11
8.3.3 Zinc-iron electrolytically coated RM .11
8.3.4 Zinc-aluminium hot dip coated RM .11
8.3.5 Zinc-iron hot dip coated and annealed RM .11
8.4 Determination of the sputtering rate of calibration and validation specimens .11
8.5 Emission intensity measurements of calibration specimens .13
8.6 Calculation of calibration equations .13
8.7 Validation using reference materials .13
8.7.1 General.13
8.7.2 Checking analytical accuracy using bulk reference materials .13
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ISO 16962:2017(E)

8.7.3 Checking analytical accuracy using surface layer reference materials .14
8.8 Verification and drift correction .14
9 Analysis of test specimens .15
9.1 Adjusting discharge parameters .15
9.2 Setting of measuring time and data acquisition rate .15
9.3 Quantifying depth profiles of test specimens .15
10 Expression of results .15
10.1 Expression of quantitative depth profile .15
10.2 Determination of total coating mass per unit area (coating aeric mass) .17
10.2.1 General method . .17
10.2.2 Method for special applications .17
10.3 Determination of average mass fractions .17
11 Precision .17
12 Test report .18
Annex A (normative) Calculation of calibration constants and quantitative evaluation of
depth profiles .19
Annex B (informative) Suggestions concerning suitable spectral lines .31
Annex C (informative) Determination of coating mass per unit area (coating areic mass) .32
Annex D (informative) Additional information on international cooperative tests .38
Bibliography .40
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ISO 16962:2017(E)

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: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 201, Surface chemical analysis,
Subcommittee SC 8, Glow discharge spectroscopy.
This second edition cancels and replaces the first edition (ISO 16962:2005), which has been technically
revised.
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ISO 16962:2017(E)

Introduction
This document is a revision of ISO 16962. Developments in both GD-OES instrumentation and the types
of zinc- and/or aluminium-based metallic coatings currently produced have rendered ISO 16962 partly
obsolete, and this revision is intended to bring it up to date.
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INTERNATIONAL STANDARD ISO 16962:2017(E)
Surface chemical analysis — Analysis of zinc- and/or
aluminium-based metallic coatings by glow-discharge
optical-emission spectrometry
1 Scope
This document specifies a glow-discharge optical-emission spectrometric method for the determination
of the thickness, mass per unit area and chemical composition of metallic surface coatings consisting of
zinc- and/or aluminium-based materials. The alloying elements considered are nickel, iron, silicon, lead
and antimony.
This method is applicable to zinc contents between 0,01 mass % and 100 mass %; aluminium contents
between 0,01 mass % and 100 mass %; nickel contents between 0,01 mass % and 20 mass %; iron
contents between 0,01 mass % and 20 mass %; silicon contents between 0,01 mass % and 15 mass %;
magnesium contents between 0,01 mass% and 20 mass%; lead contents between 0,005 mass % and
2 mass %, antimony contents between 0,005 mass % and 2 mass %.
NOTE Due to environmental and health risks, lead and antimony are avoided nowadays, but this document
is also applicable to older products including these elements.
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 14284, Steel and iron — Sampling and preparation of samples for the determination of chemical
composition
ISO 17925, Zinc and/or aluminium based coatings on steel — Determination of coating mass per unit area
and chemical composition — Gravimetry, inductively coupled plasma atomic emission spectrometry and
flame atomic absorption spectrometry
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Principle
The analytical method described here involves the following processes:
a) preparation of the sample to be analysed, generally in the form of a flat plate or disc of dimensions
appropriate to the instrument or analytical requirement (round or rectangular samples with a
width of more than 5 mm, generally 20 mm to 100 mm, are suitable);
b) cathodic sputtering of the surface coating in a direct current or radio frequency glow-discharge
device;
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ISO 16962:2017(E)

c) excitation of the analyte atoms in the plasma formed in the glow-discharge device;
d) spectrometric measurement of the intensities of characteristic emission spectral lines of the
analyte atoms and ions as a function of sputtering time (qualitative depth profile);
e) conversion of the depth profile in units of intensity versus time to mass fraction versus depth by means
of calibration functions (quantification). Calibration of the system is achieved by measurements on
calibration samples of known chemical composition and measured sputtering rate.
5 Apparatus
5.1 Glow-discharge optical-emission spectrometer
5.1.1 General
The required instrumentation includes an optical-emission spectrometer system consisting of a
[1]
Grimm type or similar glow-discharge source (direct current or radio frequency powered) and a
simultaneous optical spectrometer as described in ISO 14707, capable of providing suitable spectral
lines for the analyte elements. It is also common to combine this with a sequential spectrometer
(monochromator), allowing the addition of an extra spectral channel to a depth profile measurement.
An array-type detector, such as a charge coupled device (CCD) or a charge injection device (CID) can
also be used for simultaneous detection to cover a wide spectral range of the analytical lines.
The inner diameter of the hollow anode of the glow-discharge source should be in the range 2 mm to
8 mm. A cooling device for thin specimens, such as a metal block with circulating cooling liquid, is also
recommended, but not strictly necessary for implementation of the method.
Since the principle of determination is based on continuous sputtering of the surface
layer, the spectrometer shall be equipped with a digital readout system for time-resolved
measurement of the emission intensities. A system capable of a data acquisition speed of at least
300 measurements/second per spectral channel is recommended, but for a large number of applications
speeds of > 50 measurements/second per spectral channel are acceptable. In practice, it has been
established that 10 to 100 measurements/second per spectral channel are suitable.
5.1.2 Selection of spectral lines
For each analyte to be determined, there exist a number of spectral lines which can be used. Suitable
lines shall be selected on the basis of several factors, including the spectral range of the spectrometer
used, the analyte mass fraction range, the sensitivity of the spectral lines and any spectral interference
from other elements present in the test specimens. For applications where several of the analytes
of interest are major elements in the specimens, special attention shall be paid to the occurrence of
self-absorption of certain highly sensitive spectral lines (so-called “resonance lines”). Self-absorption
causes non-linear calibration curves at high analyte mass fraction levels, and strongly self-absorbed
lines should therefore be avoided for the determination of major elements. Suggestions concerning
suitable spectral lines are given in Annex B. Spectral lines other than those listed may be used, so long
as they have favourable characteristics.
5.1.3 Selection of glow-discharge source type
5.1.3.1 Anode size
Most GD-OES instruments on the market are delivered with options to use various anode diameters,
2 mm, 4 mm and 8 mm being the most common. Some older instruments have one anode only, usually
8 mm, while the most commonly used anode in modern instruments is 4 mm. A larger anode requires
larger specimens and higher power during analysis; therefore, the specimen is heated to a greater
extent. On the other hand, a larger anode gives rise to a plasma of larger volume that emits more light,
resulting in lower detection limits (i.e. higher analytical sensitivity). Furthermore, a larger anode helps
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ISO 16962:2017(E)

to mask inhomogeneity within a surface layer. This may or may not be an advantage, depending on
the application. In a large number of applications, the 4 mm anode is a good compromise. However,
in surface analysis applications, it is rather common to encounter problems of overheating of the
specimens due to surface layers of poor heat conductivity and/or very thin specimens, for example. In
such cases, a smaller anode (typically 2 or 2,5 mm) is preferable, even if there is some loss of analytical
sensitivity.
5.1.3.2 Type of power supply
The glow-discharge source can be either a type powered by a direct current (DC) power supply or a radio
frequency (RF) type. The most important difference is that the RF type can sputter both conductive
and non-conductive specimens; hence, this is the only type that can be used for polymer coatings and
insulating oxide layers, for example. On the other hand, it is technically simpler to measure and control
the electrical source parameters (voltage, current, power) of a DC type. Several commercially available
GD-OES systems can be delivered with the option to switch between DC and RF operation, but RF-only
systems are becoming increasingly common. In short, there are a very large number of applications
where DC or RF sources can be used and several where only an RF source can be used.
5.1.3.3 Mode of operation
Both DC and RF sources can be operated in several different modes with respect to the control of the
electrical parameters (current, voltage, power) and the pressure. There are several reasons for this:
— “historical” reasons (older instruments have simpler but functional power supplies, while the
technology has evolved, so newer models have more precise and easier-to-operate source control);
— different manufacturers have chosen different solutions for source control;
— there are some application-related issues where a particular mode of operation is to be preferred.
This document gives instructions for optimizing the source parameters based on several available
modes of operation. The most important reason for this is to make these instructions comprehensive
so as to include several types of instruments. In most applications, there is no major difference
between these modes in terms of analytical performance, but there are other differences in terms of
practicality and ease of operation. For instance, a system equipped with active pressure regulation will
automatically be adjusted to the same electrical source parameters every time a particular analytical
method is used. Without this technology, some manual adjustment of the pressure to achieve the
desired electrical source parameters is normally required.
[2][3][4][7]
NOTE In this context, what is known as the emission yield forms the basis for calibration and
quantification as described in this document. The emission yield has been found to vary with the current, the
[4][7]
voltage and, to a lesser extent, the pressure . It is impossible in practice to maintain all three parameters
constant for all test specimens, due to variations in the electrical characteristics of different materials. In several
instrument types, the electrical source parameters (the plasma impedance) can therefore be maintained constant
by means of automatic systems that vary the pressure during analysis. Alternatively, there exist methods to
[4][7]
correct for impedance variations by means of empirically derived functions , and this type of correction is
implemented in the software of commercially available GD-OES systems.
6 Adjusting the glow-discharge spectrometer system settings
6.1 General
Follow the manufacturer’s instructions or locally documented procedures for preparing the instrument
for use.
For the optical system, the most important preparation step is to check that the entrance slit to the
spectrometer is correctly adjusted, following the procedure given by the instrument manufacturer.
This ensures that the emission intensities are measured on the peaks of the spectral lines for optimum
signal-to-background ratio and good reproducibility. For further information, see ISO 14707.
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The most important step in developing a method for a particular application is to optimize the
parameters of the glow-discharge source. The source parameters shall be chosen to achieve three aims:
a) adequate sputtering of the test specimen, to reduce the analysis time without overheating the
specimen;
b) good crater shape, for good depth resolution;
c) constant excitation conditions in calibration and analysis, for optimum accuracy.
Trade-offs are often necessary among the three specified aims. More detailed instructions on how to
adjust the source parameters are given in 6.2 and 6.3.
The settings of the high voltage for the detectors depend on the source parameters, but the procedure
is the same for all modes of operation of the source. This procedure is therefore only described for the
first mode of operation.
Similarly, the steps to adjust and optimize the source settings in terms of signal stability and sputter
crater shape are also similar in principle for all modes of operation. Therefore, these procedures are
only described in detail for the first mode of operation.
NOTE There is no difference between DC and RF concerning the possibilities to measure the pressure.
However, there are large pressures differentials in a Grimm type source, and pressure readings obtained depend
on the location of the pressure gauge. Some instrument models have a pressure gauge attached to measure the
actual pressure in the plasma, while others have a pressure gauge located on a “low pressure” side of the source
closer to the pump. Therefore, the pressure readings can, for several instruments, just be used to adjust the source
parameters of that particular instrument, not as a measure of the actual operating pressure in the plasma.
6.2 Setting the parameters of a DC source
6.2.1 Constant applied current and voltage
6.2.1.1 General
The two control parameters are the applied current and the applied voltage. Set the power supply for
the glow-discharge source to constant current/constant voltage operation (current set by the power
supply, voltage adjusted by pressure/gas flow regulation). Then, set the current and voltage to the
typical values recommended by the manufacturer. Alternatively, set the power supply to constant
voltage/constant current operation (voltage set by the power supply, current adjusted by pressure/gas
flow regulation). If no recommended values are available, set the voltage to 700 V and the current to
a value in the range 5 mA to 10 mA for a 2 mm or 2,5 mm anode, 15 mA to 30 mA for a 4 mm anode
or 40 mA to 100 mA for a 7 mm or 8 mm anode. If n
...