Electrical insulating materials - Determination of electrolytic corrosion caused by insulating materials - Test methods

This standard determines the ability of insulating materials to produce electrolytic corrosion on metals being in contact with them under the influence of electric stress, high humidity and elevated temperature. The effect of electrolytic corrosion is assessed in one test by using consecutively two methods: visual semi-quantitative method consisting in comparing visually the corrosion appearing on the anode and cathode metal strips, with those given in the reference figures. This method consists of the direct visual assessment of the degree of corrosion of two copper strips, acting as anode and cathode respectively, placed in contact with the tested insulating material under a d.c. potential difference at specified environmental conditions. The degree of corrosion is assessed by visually comparing the corrosion marks on the anode and cathode metal strips with those shown in the reference figures; quantitative method, which involves the tensile strength measurement, carried out on the same anode and cathode metal strips after visual inspection. An additional quantitative test method for determining electrolytic corrosion, which involves tensile strength measurement of copper wire, is described in the informative Annex C.

Elektroisolierstoffe - Prüfungen zur Bestimmung der elektrolytischen Korrosionswirkung von Isoliermaterialien

Matériaux isolants électriques - Détermination de la corrosion électrolytique en présence de matériaux isolants - Méthodes d'essais

La CEI 60426:2007 détermine la capacité des matériaux isolants à produire une corrosion électrolytique sur des métaux en contact avec eux, sous l'influence de contraintes électriques, d'une forte humidité et de températures élevées. L'effet de la corrosion électrolytique est apprécié d'après un seul essai, en utilisant successivement les deux méthodes suivantes: - une méthode visuelle semi-quantitative qui consiste à comparer visuellement la corrosion qui apparaît sur les bandes métalliques pour l'anode et la cathode, à celles des figures de référence. Cette méthode consiste en l'appréciation visuelle directe du degré de corrosion de deux lames de cuivre, servant respectivement d'anode et de cathode, mises en contact avec le matériau isolant en essai et soumises dans des conditions d'environnement spécifiées à une différence de potentiel en courant continu. Le degré de corrosion est évalué en comparant visuellement les marques de corrosion constatées sur les bandes métalliques anode et cathode, à celles des figures de référence; - une méthode quantitative, qui met en jeu des mesures de résistance à la traction, effectuées sur les mêmes bandes métalliques pour l'anode et la cathode, après inspection visuelle. Une méthode d'essai quantitative supplémentaire en vue de déterminer la corrosion électrolytique, qui met en jeu des mesures de la résistance à la traction de fils de cuivre, est décrite dans l'Annexe informative C.

Električni izolacijski materiali - Ugotavljanje elektrolitske korozije, ki jo povzročajo izolacijski materiali – Preskuševalne metode (IEC 60426:2007)

General Information

Status
Published
Publication Date
25-Oct-2007
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
17-Oct-2007
Due Date
22-Dec-2007
Completion Date
26-Oct-2007

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SLOVENSKI STANDARD
SIST EN 60426:2007
01-december-2007

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Electrical insulating materials - Determination of electrolytic corrosion caused by

insulating materials - Test methods (IEC 60426:2007)

Elektroisolierstoffe - Prüfungen zur Bestimmung der elektrolytischen Korrosionswirkung

von Isoliermaterialien (IEC 60426:2007)

Matériaux isolants électriques - Détermination de la corrosion électrolytique en présence

de matériaux isolants - Méthodes d'essais (IEC 60426:2007)
Ta slovenski standard je istoveten z: EN 60426:2007
ICS:
17.220.99 Drugi standardi v zvezi z Other standards related to
elektriko in magnetizmom electricity and magnetism
29.035.01 Izolacijski materiali na Insulating materials in
splošno general
SIST EN 60426:2007 en,de

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

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD
EN 60426
NORME EUROPÉENNE
February 2007
EUROPÄISCHE NORM
ICS 17.220.99; 29.035.01
English version
Electrical insulating materials -
Determination of electrolytic corrosion caused by insulating materials -
Test methods
(IEC 60426:2007)
Matériaux isolants électriques - Elektroisolierstoffe -
Détermination de la corrosion Prüfungen zur Bestimmung
électrolytique en présence der elektrolytischen Korrosionswirkung
de matériaux isolants - von Isoliermaterialien
Méthodes d'essais (IEC 60426:2007)
(CEI 60426:2007)

This European Standard was approved by CENELEC on 2007-02-01. CENELEC members are bound to comply

with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard

the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on

application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other

language made by translation under the responsibility of a CENELEC member into its own language and notified

to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the

Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,

Sweden, Switzerland and the United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60426:2007 E
---------------------- Page: 2 ----------------------
EN 60426:2007 - 2 -
Foreword

The text of document 112/45/FDIS, future edition 2 of IEC 60426, prepared by IEC TC 112, Evaluation

and qualification of electrical insulating materials and systems, was submitted to the IEC-CENELEC

parallel vote and was approved by CENELEC as EN 60426 on 2007-02-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2007-11-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2010-02-01
Annex ZA has been added by CENELEC.
__________
Endorsement notice

The text of the International Standard IEC 60426:2007 was approved by CENELEC as a European

Standard without any modification.
__________
---------------------- Page: 3 ----------------------
- 3 - EN 60426:2007
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.

NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD

applies.
Publication Year Title EN/HD Year
IEC 60068-3-4 2001 Environmental testing – EN 60068-3-4 2002
Part 3-4: Supporting documentation and
guidance - Damp heat tests
IEC 60454-2 - Specifications for pressure-sensitive adhesive - -
tapes for electrical purposes –
Part 2: Methods of test
At draft stage.
---------------------- Page: 4 ----------------------
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.

International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland

Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch

PRICE CODE
Commission Electrotechnique Internationale U
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
---------------------- Page: 5 ----------------------
– 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

---------------------- Page: 6 ----------------------
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

---------------------- Page: 7 ----------------------
– 4 – 60426 © IEC:2007(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
ELECTRICAL INSULATING MATERIALS −
DETERMINATION OF ELECTROLYTIC CORROSION CAUSED BY
INSULATING MATERIALS −
TEST METHODS
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

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.

---------------------- Page: 8 ----------------------
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.
---------------------- Page: 9 ----------------------
– 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 particularly subjected to failure from electrolytic corrosion. Therefore, the selection of

insulating materials, which do not produce electrolytic corrosion, is important for such

applications.

The test method described in this second edition replaces two separate methods of the first

edition – visual and tensile strength method. The former tensile strength method of the first

edition, using copper wires, has been maintained in an informative annex. It must be

emphasized that the advantage of this new method is that the same strip used for visual

inspection is next used for the tensile strength test in opposite to the method described in the

first edition. Therefore the correlation between tensile strength and visual examination is more

obvious.
---------------------- Page: 10 ----------------------
60426 © IEC:2007(E) – 7 –
ELECTRICAL INSULATING MATERIALS −
DETERMINATION OF ELECTROLYTIC CORROSION CAUSED BY
INSULATING MATERIALS −
TEST METHODS
1 Scope

This standard determines the ability of insulating materials to produce electrolytic corrosion

on metals being in contact with them under the influence of electric stress, high humidity and

elevated temperature.

The effect of electrolytic corrosion is assessed in one test by using consecutively two

methods:

• visual semi-quantitative method consisting in comparing visually the corrosion appearing

on the anode and cathode metal strips, with those given in the reference figures.

This method consists of the direct visual assessment of the degree of corrosion of two

copper strips, acting as anode and cathode respectively, placed in contact with the tested

insulating material under a d.c. potential difference at specified environmental conditions.

The degree of corrosion is assessed by visually comparing the corrosion marks on the

anode and cathode metal strips with those shown in the reference figures;

• quantitative method, which involves the tensile strength measurement, carried out on the

same anode and cathode metal strips after visual inspection.

An additional quantitative test method for determining electrolytic corrosion, which involves

tensile strength measurement of copper wire, is described in the informative Annex C.

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.

IEC 60068-3-4:2001, Environmental testing – Part 3-4: Supporting documentation and

guidance – Damp heat tests

IEC 60454-2:⎯, Pressure-sensitive adhesive tapes for electrical purposes – Part 2: Methods

of test
3 Terms and definitions
For the purposes of this document the following terms and definitions apply:
3.1
electrolytic corrosion

kind of galvanic corrosion caused by joint action of external source of d.c. potential and some

substances included in some organic materials in presence of high humidity and elevated

temperature
—————————
To be published
---------------------- Page: 11 ----------------------
– 8 – 60426 © IEC:2007(E)
3.2
test strip
a) positive

a metal strip connected with positive pole of direct current source which forms the anode

in the contact system: metal – insulating material
b) negative

a metal strip connected with negative pole of direct current source which forms the

cathode in the contact system: metal – insulating material
3.3
surface of contact
a) of tested material

part of insulating material specimen which is in direct contact with metal strips

b) of metal strip

part of metal strip (positive or negative) which is in direct contact with insulating material

specimen
4 General description of the test method

The test consists of applying specified environmental conditions and a d.c. potential

difference to two parallel copper strips 3 mm apart, acting as the anode and the cathode

respectively. The insulating material under test (test specimen) is placed across these two

strips. In order to obtain a good and uniform contact between the metal strips and the material

under test, the test specimen is pressed to the strips by a cylindrical loading tube.

5 Test specimens
5.1 General

The preparation of the specimens depends on the type of material and the form in which it is

supplied. The shape and dimensions of the test specimen are shown in Figure 1. Procedures

for the preparation of the test specimen are reported beneath (5.2 to 5.7).
Dimensions in millimetres
Surface of contact
4,0 ± 0,1
40 ± 1
IEC 122/07
Figure 1 – Test specimen of rigid material, for example textile laminate
10,0 ± 0,5
---------------------- Page: 12 ----------------------
60426 © IEC:2007(E) – 9 –

5.2 Cut surfaces of rigid materials (blocks, plates, sheets or semi-finished materials)

The test specimens shall be cut out or machined from the tested material to a thickness of

4 mm, by means of a dry method without the use of cutting oils or lubricants and without

overheating or damaging them. It is recommended to take several test specimens from

various layers of the product.

It is permissible to use the test specimens of thickness smaller than 4 mm, but not smaller

than 2 mm.

The contact surface of the test specimen shall be smoothed using abrasive paper. Care

should be taken to keep parallelism of the opposite surfaces of the test specimen, in order to

assure a good contact of the test specimen to the metal strips. The surface of contact should

not show any flaws, cracks, inclusions or bubbles.

The abrasive paper shall not contain any contaminations causing a bad corrosion index, for

example halogen components.
5.3 Cast, moulding, injection and pressed materials

From insulating materials delivered in the form of liquid resin, moulding powder or granules,

the test specimens shall be made in shapes and dimensions as shown in Figure 1. The

specimens shall be made by casting or pressing in a special mould, following exactly the

technological instruction recommended by the manufacturer of the tested material.

The test specimen and surface of contact shall be prepared as given in 5.2.
5.4 Cut surfaces of flexible films, foils and thin sheets

Test specimens of these products shall be made up in layers to form small packs placed

between suitable holding plates of insulating material not causing electrolytic corrosion itself,

for example polymethylmethacrylate (Plexiglas® ). The preferred thickness of holding plates

is 1 mm ± 0,2 mm.

The thickness of a pack should be approximately of 4 mm or 2 mm, depending on the

thickness of the tested foils. The value of 4 mm is recommended in the case of the single foil

thickness being less than 2 mm and more than 0,5 mm, whereas that one of 2 mm is
recommended if the single foil thickness is less than 0,5 mm.

These test blocks shall be compressed with screws made of the same material as holding

plates and then machined to the appropriate shape as shown in Figure 2. The material to be

tested should protrude 0,2 mm to 0,5 mm beyond the holding plates.
—————————

Plexiglas® is an example of a suitable product available commercially. This information is given for the

convenience of users of this document and does not constitute an endorsement by IEC of this product.

---------------------- Page: 13 ----------------------
– 10 – 60426 © IEC:2007(E)
Dimensions in millimetres
Holding plates
Surface of contact
1,0 ± 0,2
2 or 4
40 ± 1
IEC 123/07

Figure 2 – Test specimen of flexible material, for example flexible films, foils etc.

Apart from this, the particulars given in 5.2 apply.
5.5 Adhesive tapes
For adhesive tapes the method of Clause 7 of IEC 60454-2 is recommended.
5.6 Flexible sleeving and tubing

Sleeving and tubing (both varnished fabric and extruded) are slit open, so as to make flat

sheets, which can then be prepared as for films (see 5.4).
5.7 Lacquers and insulating varnishes

The lacquer or insulating varnish to be tested shall be applied in the manner recommended by

the manufacturer to the surface of a test specimen of shape as shown in Figure 1 and

described in 5.2. The base material of the test specimen shall be a corrosion free plastic such

as polymethylmethacrylate.

In case of solvent incompatibility or a baking temperature being too high for the base material,

another suitable base material such as cast, hot cured corrosion free epoxy resin or glass

shall be used. If the lacquer or insulating varnish is designed to contribute freedom from

corrosion to another material, a test specimen of that material shall be used.

The tested lacquer or varnish shall be sprayed, dipped or otherwise coated to the desired

thickness and baked, if necessary, as specified or according to the directions of the

manufacturer.

If the thickness of coating is not determined by specification or direction of the manufacturer,

it shall be of (30 ± 10) μm.
5.8 Cleanliness of contact surfaces

When preparing and handling the test specimens, any soiling of the test surfaces, for example

by perspiration from the hands, shall be avoided. The specimens shall be touched only with a

pair of tweezers or with protecting gloves made of materials free from corrosion (e.g.

polyethylene). After the test specimens have been machined or cut, their surfaces shall be

cleaned with a soft brush. Before cleaning, the brush shall be rinsed in ethanol (96 %) and

then dried.
10,0 ± 0,5
0,2 to 0,5
---------------------- Page: 14 ----------------------
60426 © IEC:2007(E) – 11 –

After the cleaning procedure, the surface of contact shall not show any foreign particles,

residues of oil or grease, no mould residues, etc.
5.9 Number of test specimens

At least five test specimens made from the same material shall be tested at the same time.

A specific sampling procedure may be desired. If necessary, such a sampling procedure

should be specified and used.
6 Test strips
6.1 General

The test strips shall be made of 0,1 mm thick, semi-hard copper of purity 99,9 Cu. Their

dimensions are 10 mm wide and 200 mm long. The test strips shall be flat, without bends and

burrs at the edges as well as any other mechanical defects or impurities on the test surface,

which may have influence on the test results.
NOTE Test strips of brass or aluminium can be made in the same way.
6.2 Preparation of the test strips

From each new reel of strip (sold as a semi-finished product) the first several decimetres of

the strip shall be rejected and then the suitable number of strip segments, each 200 mm long,

shall be cut-off.

Copper strips shall be degreased with a low boiling point organic solvent (e.g. acetone or

hexane) and then etched. Etching shall be carried out at laboratory temperature, with a

solution of the following composition: sulphuric acid (1,82) with a mass fraction of 73 %, nitric

acid (1,33) with a mass fraction of 26 %, sodium chloride with a mass fraction of 0,5 % and

hard carbon black with a mass fraction of 0,5 %. The time of etching shall be between 20 s to

60 s. All strips, which are destined for one set of testing, shall be etched at the same time.

The coarseness of the strip surface can be controlled by adjustment of the etching time until

the copper strip has an even dull sheen. The strips shall then be washed in distilled water,

then dipped in ethanol and dried with blotting paper.

NOTE Unevenness of the surface of the strip may influence the discolouration and may lead to a wrong

evaluation. A surface, which is evenly dull, shows a discolouration of greater intensity than a surface, which is

slightly corroded, semi-dull or brilliant.

After degreasing and etching, both ends of the strip shall be reeled loose to the shape as

shown in Figure 3.

So prepared test strips shall be immediately (within 20 min) mounted in the test device, ready

for the test procedure, as shown in Figure 4.
---------------------- Page: 15 ----------------------
– 12 – 60426 © IEC:2007(E)
Dimensions in millimetres
...

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