oSIST prEN ISO 9220:2021

Metallic coatings - Measurement of coating thickness - Scanning electron microscope method (ISO/DIS 9220:2021)

Metallische Überzüge - Messung der Schichtdicke - Verfahren mit Rasterelektronenmikroskop (ISO/DIS 9220:2021)

Dieses Dokument legt ein zerstörendes Verfahren zur Messung der örtlichen Schichtdicke metallischer Überzüge fest (nachstehend sind auch andere anorganische Überzüge gemeint), in dem Querschnitte mit einem Rasterelektronenmikroskop (REM) untersucht werden. Das Verfahren kann für Schichtdicken bis zu mehreren Millimetern angewendet werden, allerdings ist es für solch dicke Schichten üblicherweise praktischer, ein Lichtmikroskop (ISO 1463) zu verwenden, sofern anwendbar. Die untere Dickengrenze hängt von der erreichten Messunsicherheit (siehe Abschnitt 10) ab.

Revêtements métalliques - Mesurage de l'épaisseur de revêtement - Méthode au microscope électronique à balayage (ISO/DIS 9220:2021)

Kovinske prevleke - Merjenje debeline prevleke - Postopek z vrstičnim elektronskim mikroskopom (ISO/DIS 9220:2021)

General Information

• Status: Not Published
• Public Enquiry End Date: 24-May-2021
• ICS: 17.040.20 - Properties of surfaces
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: IPKZ - Protection of metals against corrosion
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 02-Apr-2021
• Due Date: 20-Aug-2021
• Completion Date: 28-May-2021
• Ref Project: prEN ISO 9220 - Metallic coatings - Measurement of coating thickness - Scanning electron microscope method (ISO/DIS 9220:2021)

RELATIONS

• Revised: SIST EN ISO 9220:1999 - Metallic coatings - Measurement of coating thickness - Scanning electron microscope method (ISO 9220:1988)
• Effective Date: 01-May-2021

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN ISO 9220:2021
01-maj-2021
Kovinske prevleke - Merjenje debeline prevleke - Postopek z vrstičnim
elektronskim mikroskopom (ISO/DIS 9220:2021)

Metallic coatings - Measurement of coating thickness - Scanning electron microscope

method (ISO/DIS 9220:2021)
Metallische Überzüge - Messung der Schichtdicke - Verfahren mit
Rasterelektronenmikroskop (ISO/DIS 9220:2021)
Revêtements métalliques - Mesurage de l'épaisseur de revêtement - Méthode au
microscope électronique à balayage (ISO/DIS 9220:2021)
Ta slovenski standard je istoveten z: prEN ISO 9220
ICS:
17.040.20 Lastnosti površin Properties of surfaces
25.220.40 Kovinske prevleke Metallic coatings
oSIST prEN ISO 9220:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 9220:2021
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oSIST prEN ISO 9220:2021
DRAFT INTERNATIONAL STANDARD
ISO/DIS 9220
ISO/TC 107 Secretariat: KATS
Voting begins on: Voting terminates on:
2021-03-24 2021-06-16
Metallic coatings — Measurement of coating thickness —
Scanning electron microscope method

Revêtements métalliques — Mesurage de l'épaisseur de revêtement — Méthode au microscope

électronique à balayage
ICS: 25.220.40
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 9220:2021(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 2021
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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii © ISO 2021 – All rights reserved
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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Instrumentation .................................................................................................................................................................................................... 1

5.1 Scanning electron microscope (SEM) .................................................................................................................................. 1

5.2 Tools to calibrate the length measurement function of the SEM software ......................................... 2

6 Factors influencing the measurement results ....................................................................................................................... 2

6.1 Surface roughness ................................................................................................................................................................................ 2

6.2 Taper of cross-section ....................................................................................................................................................................... 2

6.3 Specimen tilt ............................................................................................................................................................................................. 2

6.4 Coating deformation .......................................................................................................................................................................... 2

6.5 Rounding of edges of the coating ............................................................................................................................................ 2

6.6 Overplating ................................................................................................................................................................................................. 2

6.7 Etching ........................................................................................................................................................................................................... 3

6.8 Smearing ....................................................................................................................................................................................................... 3

6.9 Poor contrast ............................................................................................................................................................................................ 3

6.10 Magnification ............................................................................................................................................................................................ 3

6.11 SEM imaging parameters ............................................................................................................................................................... 3

7 Preparation of cross-sections ................................................................................................................................................................. 3

8 Calibration of instruments ......................................................................................................................................................................... 4

8.1 General ........................................................................................................................................................................................................... 4

8.2 Photography .............................................................................................................................................................................................. 4

8.3 Measurement ............................................................................................................................................................................................ 4

9 Procedure..................................................................................................................................................................................................................... 4

10 Precision ....................................................................................................................................................................................................................... 4

10.1 General ........................................................................................................................................................................................................... 4

10.2 Repeatability (r) .................................................................................................................................................................................... 4

10.3 Reproducibility limit (R) ................................................................................................................................................................ 5

11 Expression of results ........................................................................................................................................................................................ 5

12 Test report ................................................................................................................................................................................................................... 5

Annex A (informative) General guidance on the preparation and measurement of cross-sections ..7

Annex B (informative) Details on precision ...............................................................................................................................................10

Bibliography .............................................................................................................................................................................................................................12

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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(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 of 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings.

This second edition cancels and replaces the first edition (ISO 9220:1988), which has been technically

revised.
The main changes compared to the previous edition are as follows:
— Addition of two further calibration methods in 5.2, 8.2, and 8.3;

— Deletion of technically outdated content concerning instability of SEMs and analog photos or

concerning the operation of SEMs [removal of old Subclauses 6.11, 6.12, 6.13, 8.4, 9.2.1, 9.2.2, 9.3,

A.2.3, A.3.2, A.3.3, A.3.4, and A.3.7; revision of item e) in Clause 12];

— Discussion of influences of imaging parameters on measurement uncertainty (new Subclause 6.11);

— Revision of Clause 10 and addition of Annex B with precision data from round robin tests;

— Revision of Annex A to (re-) align it with ISO 1463:2021;
— Adding a bibliography with informative references.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2021 – All rights reserved
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oSIST prEN ISO 9220:2021
DRAFT INTERNATIONAL STANDARD ISO/DIS 9220:2021(E)
Metallic coatings — Measurement of coating thickness —
Scanning electron microscope method
1 Scope

This document specifies a destructive method for the measurement of the local thickness of metallic

coatings (hereafter also other inorganic coatings are meant) by examination of cross-sections with a

scanning electron microscope (SEM). The method can be used for thicknesses up to several millimetres,

but for such thick coatings it is usually more practical to use a light microscope (ISO 1463) when

applicable. The lower thickness limit depends on the achieved measurement uncertainty (see Clause 10).

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 1463, Metallic and oxide coatings — Measurement of coating thickness – Microscopical method

ISO 2064, Metallic and other non-organic coatings — Definitions and conventions concerning the

measurement of thickness
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
local thickness

mean of the thickness measurements, of which a specified number is made within a reference area

[SOURCE: ISO 2064:1996, 3.4]
4 Principle

A test specimen is cut, ground, and polished from a crosssection of the coating for metallographic

examination by a scanning electron microscope. The measurement is made on the digital image

generated by the SEM using either the tools of the SEM’s operating software or by importing the image

file together with its calibration data into an image processing software and using that software’s tools.

5 Instrumentation
5.1 Scanning electron microscope (SEM)
Suitable instruments are available commercially.
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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(E)
5.2 Tools to calibrate the length measurement function of the SEM software

Suitable tools are required for the calibration of the length measurement function of the SEM’s

software. Either a stage micrometer, or a graticule, or a piece from a silicon wafer with a regular pattern

of (cylindrical) metallic bumps with a certified distance of the cylinder axes, or spherical polymer

particles of certified diameter in the range of a few tenths of a micrometer to a few micrometers can be

used, all of which are commercially available. They shall have an uncertainty of less than 5 %.

6 Factors influencing the measurement results
6.1 Surface roughness

If the coating or its substrate is rough relative to the coating thickness, one or both of the interfaces

bounding the coating cross-section may be too irregular to permit accurate measurement of the average

thickness in the field of view. In this case it can be helpful to use software solutions, which can identify

the boundary lines of the coating and either determine its area and divide it by the image width or place

automatically e. g. 100 measurement lines in order to calculate an average coating thickness.

6.2 Taper of cross-section

If the plane of the cross-section is not perpendicular to the plane of the coating, the measured thickness

will be greater than the true thickness. For example, an inclination of 10° to the perpendicular will

contribute a 1.5 % error.

NOTE This source of error is also known as cosine error in the small-angle approximation.

6.3 Specimen tilt

Any tilt of the specimen (plane of cross-section) with respect to the SEM beam may result in an

inaccurate measurement.

NOTE 1 If the tilt of the test specimen is different from that used for calibration, inaccuracies may result.

NOTE 2 This source of error is also known as cosine error in the small-angle approximation.

6.4 Coating deformation

Detrimental deformation of the coating can be caused by excessive temperature or pressure during the

mounting and preparation of cross-sections of soft coatings or coatings that melt at low temperatures,

and by excessive abrasion of brittle materials during preparation of cross-sections.

6.5 Rounding of edges of the coating

If the edge of the coating cross-section is rounded, i.e. if the coating cross-section is not completely flat

up to its edges, the observed thickness may differ from the true thickness. Edge rounding can be caused

by improper mounting, grinding, polishing, or etching (see 6.6 and A.1).
6.6 Overplating

Overplating of the test specimen serves to protect the coating edges during preparation of cross-

sections and thus to prevent an inaccurate measurement. Removal of the coating material during

surface preparation for overplating can cause a low thickness measurement.
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oSIST prEN ISO 9220:2021
ISO/DIS 9220:2021(E)
6.7 Etching

Optimum etching will produce a clearly defined and narrow dark line at the interface between the two

materials. A wide or poorly defined line can result in an inaccurate measurement.

NOTE Etching is usually applied for the microscopic method (ISO 1463) and can be useful for relatively thick

coatings in the SEM, too, especially when individual layers from the same material need to be distinguished and

there is no or too weak material contrast in the back scattered electron image (6.9). For (very) thin coatings

etching has often a negative effect on the measurement uncertainty.
6.8 Smearing

Polishing may leave smeared metal that obscures the true boundary between two metals and results

in an inaccurate measurement. This may occur with soft metals like indium or gold. To help identify

whether or not there is smearing, repeat the polishing, etching, and measurement several times. Any

significant variation in readings is an indication of possible smearing.
6.9 Poor contrast

The visual contrast between metals in an SEM is poor when their atomic numbers are close together. For

example, bright and semi-bright nickel layers may not be discriminable unless their common boundary

can be brought out sufficiently by appropriate etching (6.7) and SEM techniques.
6.10 Magnification

For a given coating thickness, measurement errors tend to increase with decreasing magnification.

If practical, the magnification should be chosen so that the field of view is between 1.5 and 3 times

the coating thickness. For very thin coatings this is often not practicable; then choose the maximum

magnification at which the image of the coating and its boundaries appears still “sharp”.

6.11 SEM imaging parameters

The acceleration voltage of the SEM can influence the appearance of the coating in the image. For

example, a higher acceleration voltage causes a higher depth from which the signal is collected and can

lead to not clearly discernible edges, e. g. at a metal to polymer (e. g. molding resin) interface.

High probe currents can improve the brightness and contrast of
...