SIST EN ISO 12732:2008

Corrosion of metals and alloys - Electrochemical potentiokinetic reactivation measurement using the double loop method (based on Cihal's method) (ISO 12732:2006)

This International Standard specifies the method for measuring the degree of sensitization (DOS) in stainless steel and nickel-based alloys using the Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) test (based on Cihal's method). The method may be used for the quantitative assessment of deleterious thermal effects resulting in the formation of alloy-element-depleted zones at grain boundaries or in the matrix. How ever, attention should be paid when testing heat-affected weld zones, due to possible non-uniform distribution of sensitized zones along the fusion lines. The results of the test can be used as an index to identify the potential susceptibility of stainless steel and nickel-based alloys to intergranular corrosion, pitting corrosion, and intergranular-stress corrosion cracking, but prediction of these corrosion modes depends on complementary specific testing. This International Standard describes the general methodology and, in Annex C, gives examples of suitable test exposure conditions for specific alloys.

Korrosion von Metallen und Legierungen - Verfahren für die elektrochemische potentiodynamische Reaktivierungsmessung mit dem Double-loop-Verfahren (Čihal-Verfahren) (ISO 12732:2006)

Diese Internationale Norm legt das Verfahren zum Messen des Sensibilisierungsgrades (DOS) für nichtrostenden Stahl und Nickelbasislegierungen fest, indem eine elektrochemische potentiodynamische Reaktivierung nach dem Double Loop Verfahren (DL EPR Prüfung) angewendet wird (Čihal Verfahren).
Das Verfahren kann zur quantitativen Beurteilung ungünstiger thermischer Einflüsse angewendet werden, die zur Bildung von Zonen führen, in denen eine Abreichung (Konzentrationsverminderung) des Legierungs¬elements an Korngrenzen oder in der Matrix auftritt. Wärmeeinflusszonen von Schweißungen sollten jedoch wegen der möglichen ungleichmäßigen Verteilung der sensibilisierten Zonen entlang der Schmelzlinien besonders aufmerksam geprüft werden.
Die Ergebnisse der Prüfung können als Index zur Bestimmung der möglichen Anfälligkeit von nichtrostendem Stahl und Nickelbasislegierungen für interkristalline Korrosion, Lochkorrosion und interkristalline Spannungsrisskorrosion verwendet werden, wobei eine genauere Vorhersage für das Auftreten dieser Korrosionsarten jedoch weitere spezifische Prüfungen erfordert.
Diese Internationale Norm beschreibt die allgemeine Methodologie und gibt in Anhang C Beispiele für geeignete Beanspruchungsbedingungen für die Prüfung spezifischer Legierungen.

Corrosion des métaux et alliages - Mesurage de la réactivation électrochimique potentiocinétique par la méthode de la double boucle (dérivée de la méthode de Cihal) (ISO 12732:2006)

L'ISO 12732:2006 spécifie une méthode permettant de mesurer le degré de sensibilisation (DOS) des aciers inoxydables et des alliages à base de nickel par réalisation de l'essai de réactivation électrochimique potentiocinétique double boucle (DL-EPR) (dérivée de la méthode Cihal).
Cette méthode peut être employée pour évaluer quantitativement les effets thermiques néfastes qui génèrent des zones appauvries en éléments d'alliage au niveau des joints de grain ou dans la matrice. Il convient cependant de faire particulièrement attention lors des essais relatifs aux zones de soudure affectées par la chaleur en raison de la répartition non uniforme des zones sensibilisées le long des lignes de fusion.
Les résultats de l'essai peuvent aussi servir d'indice pour qualifier la tendance potentielle de l'acier inoxydable et des alliages à base de nickel à la corrosion intergranulaire, à la corrosion par piqûres, et à la fissuration par corrosion sous contrainte intergranulaire, mais la prédiction de ces modes de corrosion dépend d'essais spécifiques supplémentaires.
L'ISO 12732:2006 décrit la méthodologie générale et donne des exemples de conditions d'essai adaptées pour des alliages spécifiques.

Korozija kovin in zlitin - Merjenje elektrokemične potenciokinetične reaktivacije z uporabo metode z dvojno zanko (na osnovi Cihalove metode) (ISO 12732:2006)

General Information

• Status: Published
• Publication Date: 20-May-2008
• ICS: 77.060 - Corrosion of metals
• Technical Committee: IPKZ - Protection of metals against corrosion
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 07-May-2008
• Due Date: 12-Jul-2008
• Completion Date: 21-May-2008
• Ref Project: EN ISO 12732:2008 - Corrosion of metals and alloys - Electrochemical potentiokinetic reactivation measurement using the double loop method (based on Cihal's method) (ISO 12732:2006)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 12732:2008
01-julij-2008
.RUR]LMDNRYLQLQ]OLWLQ0HUMHQMHHOHNWURNHPLþQHSRWHQFLRNLQHWLþQHUHDNWLYDFLMH]
XSRUDERPHWRGH]GYRMQR]DQNRQDRVQRYL&LKDORYHPHWRGH,62
Corrosion of metals and alloys - Electrochemical potentiokinetic reactivation
measurement using the double loop method (based on Cihal's method) (ISO
12732:2006)
Corrosion des métaux et alliages - Mesurage de la réactivation électrochimique
potentiocinétique par la méthode de la double boucle (dérivée de la méthode de Cihal)
(ISO 12732:2006)
Ta slovenski standard je istoveten z: EN ISO 12732:2008
ICS:
77.060 Korozija kovin Corrosion of metals
SIST EN ISO 12732:2008 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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EUROPEAN STANDARD
EN ISO 12732
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2008
ICS 77.060

English Version
Corrosion of metals and alloys - Electrochemical potentiokinetic
reactivation measurement using the double loop method (based
on Cihal's method) (ISO 12732:2006)
Corrosion des métaux et alliages - Mesurage de la Korrosion von Metallen und Legierungen - Verfahren für die
réactivation électrochimique potentiocinétique par la elektrochemische potentiodynamische
méthode de la double boucle (dérivée de la méthode de Reaktivierungsmessung mit dem Double-loop-Verfahren
Cihal) (ISO 12732:2006) (Cihal-Verfahren) (ISO 12732:2006)
This European Standard was approved by CEN on 21 March 2008.
CEN 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 CEN Management Centre or to any CEN 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 CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12732:2008: E
worldwide for CEN national Members.

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EN ISO 12732:2008 (E)
Contents Page
Foreword.3

2

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EN ISO 12732:2008 (E)
Foreword
The text of ISO 12732:2006 has been prepared by Technical Committee ISO/TC 156 “Corrosion of metals and
alloys” of the International Organization for Standardization (ISO) and has been taken over as EN ISO
12732:2008 by Technical Committee CEN/TC 262 “Metallic and other inorganic coatings” the secretariat of
which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by October 2008, and conflicting national standards shall be withdrawn at
the latest by October 2008.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 12732:2006 has been approved by CEN as a EN ISO 12732:2008 without any modification.

3

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INTERNATIONAL ISO
STANDARD 12732
First edition
2006-09-15

Corrosion of metals and alloys —
Electrochemical potentiokinetic
reactivation measurement using the
double loop method (based on Čihal's
method)
Corrosion des métaux et alliages — Mesurage de la réactivation
électrochimique potentiocinétique par la méthode de la double boucle
(dérivée de la méthode de Čihal)





Reference number
ISO 12732:2006(E)
©
ISO 2006

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ISO 12732:2006(E)
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ii © ISO 2006 – All rights reserved

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ISO 12732:2006(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 1
4 Principle. 2
5 Apparatus. 3
6 Test solutions. 5
7 Test specimen preparation . 5
8 Procedure. 5
9 Metallographic inspection. 6
10 Evaluation of results. 6
11 Test report. 7
Annex A (informative) Flushed port cell and flushed electrode holder. 9
Annex B (informative) Potential of selected reference electrodes at 25 °C with respect to the
standard hydrogen electrode (SHE) . 12
Annex C (informative) Suggested method for sensitizing test specimens . 13
Annex D (informative) Correlation of I /I with the degree of grain-boundary sensitization, P
r p a
(ASTM G108), Q and Q . 14
GBA GBL

© ISO 2006 – All rights reserved iii

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ISO 12732:2006(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.
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.
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.
ISO 12732 was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.

iv © ISO 2006 – All rights reserved

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INTERNATIONAL STANDARD ISO 12732:2006(E)

Corrosion of metals and alloys — Electrochemical
potentiokinetic reactivation measurement using the double loop
method (based on Čihal's method)
WARNING — This International Standard may involve hazardous materials, operations and equipment.
It is the responsibility of whoever uses this standard to consult and establish appropriate safety and
health practices, and determine the applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies the method for measuring the degree of sensitization (DOS) in stainless
steel and nickel-based alloys using the Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR)
test (based on Čihal's method).
The method may be used for the quantitative assessment of deleterious thermal effects resulting in the
formation of alloy-element-depleted zones at grain boundaries or in the matrix. However, attention should be
paid when testing heat-affected weld zones, due to possible non-uniform distribution of sensitized zones along
the fusion lines.
The results of the test can be used as an index to identify the potential susceptibility of stainless steel and
nickel-based alloys to intergranular corrosion, pitting corrosion, and intergranular-stress corrosion cracking,
but prediction of these corrosion modes depends on complementary specific testing.
This International Standard describes the general methodology and, in Annex C, gives examples of suitable
test exposure conditions for specific alloys.
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 8044:1999, Corrosion of metals and alloys — Basic terms and definitions
ISO 643:2003, Steels — Micrographic determination of the apparent grain size
3 Terms and definitions
For the purposes of this document, the terms and definitions in ISO 8044 and the following apply.
3.1
integrated charge
Q
charge measured during passivation (Q ) and reactivation (Q ), given by the time integral of current below the
p r
passivation and reactivation peak of the curve
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ISO 12732:2006(E)
4 Principle
Heat treatment (including welding) of corrosion-resistant alloys can lead to formation of particles, such as
chromium carbide in the case of 304 SS or σ-phase (FeCrMo) in duplex stainless steels. This will lead to local
depletion of alloying elements, unless replenished by matrix diffusion, the extent of which will be temperature
dependent. This process is commonly referred to as sensitization, because depleted zones have an intrinsic
lower resistance to localized corrosion and, where appropriate, to stress corrosion cracking. The extent to
which these damage mechanisms develop and propagate will depend on the extent of depletion and the
density of depleted zones. There was a need for a simple laboratory test to rapidly identify potentially
deleterious thermal effects on stainless steels and nickel-based alloys. The EPR test was developed for that
purpose. Although two methods have been used in laboratory testing, the single loop and the double loop, the
former, which involves polarization scanning from the passive to the active state, has the disadvantage that
the method can be sensitive to surface finish. The EPR test may also be applied to in-field testing, provided
some adaptation be made to the cell and assembly.
The double loop version of this method is preferred. Here, the specimen is immersed in an acid solution such
that it is in the active state under freely corroding conditions, but then anodically polarized into the passive
domain. As surface features are dissolved during initial immersion under active corrosion conditions, the
likelihood of surface preparation having an impact diminishes. From the passive state, the specimen is
polarized at a controlled scan rate in the cathodic direction. A schematic illustration is shown in Figure 1. In
the absence of active depleted zones, the passive film can become unstable as the potential becomes less
positive and can start to dissolve (e.g. by reductive dissolution). However, the rate of dissolution is small and,
with the sweep rate employed, the anodic current is not able to rise substantially, so that only a modest anodic
peak current is measured. The process of anodic dissolution during the cathodic scan is referred to as
reactivation. Occasionally, the current may go transiently cathodic on lowering the potential, as the passive
current density may be less than the cathodic current at the potentials of relevance.
When a depleted zone is present, the passive film is locally less protective and is more easily reduced. Hence,
active dissolution of the depleted zones will occur more readily whilst adjacent material still retains some
passive film, albeit a gradually thinning passive film. Thus significant active dissolution occurs. The reason for
the gradual rise in current is probably a reflection of the spread in activity associated with a spread of the
extent of depletion and corresponding variations in the passive film properties (some sections reduced at
higher potentials and some at lower potentials). Gradually, as the activity of all the sites build up, this begins to
be counteracted by the decrease in potential reducing the current of the active regions because of Tafel
behaviour; thus a reactivation peak is observed. The peak in the current density, and the charge passed
associated with that peak, depend on the extent of alloy depletion.
The ratio of the reactivation peak to the activation peak, or the reactivation charge to the activation charge,
when compared with the values for the solution-annealed specimen, gives an index of sensitization. However,
for sensitized grain boundaries, these values have to be normalized to the grain size. At the end of the test,
the specimen is examined to confirm the nature of the localized corrosion process.
2 © ISO 2006 – All rights reserved

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ISO 12732:2006(E)

Key
X potential
Y log of current
1 anodic scan
2 reactivation scan
Figure 1 — Schematic polarization curves of the double loop EPR test method
5 Apparatus
The apparatus necessary for obtaining EPR data consists of electronic instruments and a test cell. The
electronic instruments may be integrated into one instrument package or may be individual components.
Either form of instrumentation can provide acceptable data.
5.1 Scanning potentiostat
The potentiostat should be capable of controlling the potential to within ± 1 mV accuracy, over the range of
potential and current encountered in the EPR measurements. The potentiostat should have a potential range
of −2 000 to +2 000 mV and a current range of 1 µA to 1 A.
5.2 Electrode potential-measuring instrument
11 14
The electrode potential-measuring circuit should have a high input impedance of the order of 10 Ω to 10 Ω,
to minimize current drawn from the system during measurements. Such circuits are provided with most
potentiostats. Instruments should have sufficient sensitivity and accuracy to detect a change of 1,0 mV over a
potential range between −2 000 and +2 000 mV.
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ISO 12732:2006(E)
5.3 Current-measuring instruments
The current in the circuit is evaluated from the potential drop measured across a known resistor. In many
potentiostats, this measurement is made internally but measurements can also be made externally by locating
a resistor in the current line from the counter electrode to the auxiliary connection on the potentiostat. The
–2 –2
current intensities enc
...