IEC 60426:2007

INTERNATIONAL IEC
STANDARD 60426
Second edition
2007-01
Electrical insulating materials –
Determination of electrolytic corrosion
caused by insulating materials –
Test methods
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INTERNATIONAL IEC
STANDARD 60426
Second edition
2007-01
Electrical insulating materials –
Determination of electrolytic corrosion
caused by insulating materials –
Test methods
© IEC 2007 ⎯ Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
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Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
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International Electrotechnical Commission
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– 2 – 60426 © IEC:2007(E)
CONTENTS
FOREWORD.4
INTRODUCTION.6

1 Scope.7
2 Normative references .7
3 Terms and definitions .7
4 General description of the test method .8
5 Test specimens .8
5.1 General .8
5.2 Cut surfaces of rigid materials (blocks, plates, sheets or semi-finished
materials) .9
5.3 Cast, moulding, injection and pressed materials .9
5.4 Cut surfaces of flexible films, foils and thin sheets.9
5.5 Adhesive tapes.10
5.6 Flexible sleeving and tubing .10
5.7 Lacquers and insulating varnishes.10
5.8 Cleanliness of contact surfaces .10
5.9 Number of test specimens .11
6 Test strips .11
6.1 General .11
6.2 Preparation of the test strips .11
6.3 Cleanliness of test strips .12
7 Test device.12
8 Test conditions .14
9 Test procedure .14
10 Evaluation .14
10.1 General evaluation .14
10.2 Visual inspection of the test strips .15
10.3 Tensile strength of test strips .15
11 Evaluation of corrosion on copper strips .16
12 Test report.17

Annex A (normative)  Tables for the evaluation of corrosion on brass and aluminium
strips .18
Annex B (informative) Notes on visual evaluation .20
Annex C (informative) Copper wire tensile strength method .21

Figure 1 – Test specimen of rigid material, for example textile laminate.8
Figure 2 – Test specimen of flexible material, for example flexible films, foils etc.10
Figure 3 – Test strip.12
Figure 4 – Test device for determining electrolytic corrosion.13
Figure C.1 – Apparatus for determining electrolytic corrosion of rigid insulating material .23
Figure C.2 – Apparatus for determining electrolytic corrosion of flexible insulating material .23

60426 © IEC:2007(E) – 3 –
Table 1 – Degrees of corrosion of copper strips .16
Table A.1 – Degrees of corrosion of brass strips.18
Table A.2 – Degrees of corrosion of aluminium strips .19

– 4 – 60426 © IEC:2007(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
ELECTRICAL INSULATING MATERIALS −

DETERMINATION OF ELECTROLYTIC CORROSION CAUSED BY
INSULATING MATERIALS −
TEST METHODS
FOREWORD
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International Standard IEC 60426 has been prepared by IEC technical committee 112:
Evaluation and qualification of electrical insulating materials and systems.
This second edition cancels and replaces the first edition, published in 1973, and constitutes
a technical revision.
The main changes with respect to the previous edition are listed below:
• experience has indicated the need for improved description of the experimental method. It
describes a revised procedure for the visual and tensile strength test method that
overcomes the limitations of the first edition;
• one older method of the first edition has partly been maintained in the informative annex.

60426 © IEC:2007(E) – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
112/45/FDIS 112/55/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A bilingual version of this publication may be issued at a later date.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under “http://webstore.iec.ch” in the
data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
– 6 – 60426 © IEC:2007(E)
INTRODUCTION
Electrical insulating materials at high atmospheric humidity and under influence of electric
stress may cause corrosion of metal parts being in contact with them. Such electrolytic
corrosion is dependent upon the composition of the insulating material and the character of
the metal; it is influenced by temperature, relative humidity, nature of the voltage and the time
of exposure. Direct voltage produces much more rapid and extensive corrosion than alterna-
ting voltage. Corrosion is more pronounced at the positive electrode.
Not only copper but also most other metals, except the noble metals such as platinum or gold,
are subject to electrolytic corrosion. Electrolytic corrosion, however, is usually determined
with insulating materials in contact with copper, brass or aluminium. Copper, however, is a
basic metal and most frequently used in electrotechnical, teletechnical and electronic
equipment, especially for current conducting parts and therefore it was chosen as a basic test
metal. Other metals may be used when needed for special purposes, but the results may
differ from those described in this method.
Electrolytic corrosion may cause open-circuit failure in electrical conductors and devices. It
may promote low resistance leakage path across or through electrical insulation and the
products of corrosion may otherwise interfere with the operation of electrical devices, i.e. may
prevent operation of contacts, etc.
Electronic equipment operating under conditions of high humidity and elevated temperature
may be particula
...