Method of measurement of hydrogen permeation and determination of hydrogen uptake and transport in metals by an electrochemical technique (ISO 17081:2014)

ISO 17081:2014 specifies a laboratory method for the measurement of hydrogen permeation and for the determination of hydrogen atom uptake and transport in metals, using an electrochemical technique. The term "metal" as used in ISO 17081:2014 includes alloys.
ISO 17081:2014 describes a method for evaluating hydrogen uptake in metals, based on measurement of steady-state hydrogen flux. It also describes a method for determining effective diffusivity of hydrogen atoms in a metal and for distinguishing reversible and irreversible trapping.
ISO 17081:2014 gives requirements for the preparation of specimens, control and monitoring of the environmental variables, test procedures and analysis of results.
ISO 17081:2014 may be applied, in principle, to all metals for which hydrogen permeation is measurable and the method can be used to rank the relative aggressivity of different environments in terms of the hydrogen uptake of the exposed metal.

Elektrochemisches Verfahren zur Messung der Wasserstoffpermeation und zur Bestimmung von Wasserstoffaufnahme und -transport in Metallen (ISO 17081:2014)

1.1   In dieser Internationalen Norm wird ein elektrochemisches Laboratoriumsverfahren zur Messung der Wasserstoffpermeation und zur Bestimmung der Aufnahme und des Transports von Wasserstoffatomen in Metallen festgelegt. In dieser Internationalen Norm werden mit der Benennung „Metall“ auch Legierungen erfasst.
1.2   Diese Internationale Norm beschreibt ein Verfahren zur Bewertung der Wasserstoffaufnahme in Metallen, das auf der Messung der Wasserstoffströmung (des Wasserstoffflusses) im stationären Zustand beruht. Ferner werden Verfahren zur Bestimmung des effektiven Diffusionsvermögens von Wasserstoffatomen in einem Metall und zur Unterscheidung reversibler und irreversibler Fehlstellen beschrieben.
1.3   In dieser Internationalen Norm werden Anforderungen an die Vorbereitung der Proben, die Kontrolle und Überwachung der Umgebungsvariablen, die Prüfverfahren und die Auswertung der Ergebnisse festgelegt.
1.4   Diese Internationale Norm darf prinzipiell auf alle Metalle, bei denen Wasserstoffpermeation messbar ist, angewendet werden, und das Verfahren kann zur Klassifizierung der relativen Aggressivität unterschiedlicher Umgebungen in Bezug auf die Wasserstoffaufnahme des beanspruchten Metalls angewendet werden.

Méthode de mesure de la perméation de l'hydrogène et détermination de l'absorption d'hydrogène et de son transport dans les métaux à l'aide d'une technique électrochimique (ISO 17081:2014)

L'ISO 17081:2014 spécifie une méthode de laboratoire pour le mesurage de la perméation de l'hydrogène et la détermination de l'absorption et du transport des atomes d'hydrogène dans les métaux à l'aide d'une technique électrochimique. Le terme «métal» utilisé dans la présente Norme internationale comprend les alliages.
L'ISO 17081:2014 décrit une méthode permettant d'évaluer l'absorption d'hydrogène dans les métaux sur la base du mesurage d'un flux stationnaire d'hydrogène. Elle décrit également une méthode permettant de déterminer le coefficient de diffusion effective des atomes d'hydrogène dans un métal et de faire une distinction entre le piégeage réversible et le piégeage irréversible.
L'ISO 17081:2014 fournit des exigences concernant la préparation des éprouvettes, le contrôle et le suivi des variables environnementales, les modes opératoires d'essai et l'analyse des résultats.
L'ISO 17081:2014 peut s'appliquer, en principe, à tous les métaux pour lesquels la perméation de l'hydrogène est mesurable et la méthode peut être utilisée pour classer l'agressivité relative de différents environnements en termes d'absorption d'hydrogène par le métal exposé.

Metoda merjenja prodiranja vodika ter določanje njegovega vpijanja in prenosa v kovinah z elektrokemijsko tehniko (ISO 17081:2014)

Standard EN ISO 17081 določa laboratorijsko metodo merjenja prodiranja vodika ter določanje njegovega vpijanja in prenosa v kovinah z elektrokemijsko tehniko. Pojem »kovina« v tem mednarodnem standardu zajema tudi zlitine. Ta mednarodni standard opisuje metodo za ocenjevanje vpijanja vodika v kovinah, ki temelji na merjenju ustaljene hitrosti pretoka vodika. Prav tako opisuje metodo za določanje učinkovite razprševalnosti vodikovih atomov v kovinah in za razlikovanje med obrnljivim in dokončnim lovljenjem. Ta mednarodni standard določa zahteve za pripravo vzorcev, nadzor in spremljanje okoljskih spremenljivk, preskusnih postopkov in analizo rezultatov. Ta mednarodni standard se lahko načeloma uporablja za vse kovine, pri katerih je mogoče izmeriti prodiranje vodika, metoda pa se lahko uporablja za razvrščanje relativne agresivnosti različnih okolij glede na vpijanje vodika v izpostavljeni kovini.

General Information

Status
Published
Publication Date
03-Jun-2014
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
04-Jun-2014
Completion Date
04-Jun-2014

RELATIONS

Buy Standard

Standard
EN ISO 17081:2014
English language
26 pages
sale 10% off
Preview
sale 10% off
Preview

e-Library read for
1 day
Draft
FprEN ISO 17081:2014
English language
24 pages
sale 10% off
Preview
sale 10% off
Preview

e-Library read for
1 day

Standards Content (sample)

SLOVENSKI STANDARD
SIST EN ISO 17081:2014
01-september-2014
1DGRPHãþD
SIST EN ISO 17081:2008
0HWRGDPHUMHQMDSURGLUDQMDYRGLNDWHUGRORþDQMHQMHJRYHJDYSLMDQMDLQSUHQRVDY
NRYLQDK]HOHNWURNHPLMVNRWHKQLNR ,62

Method of measurement of hydrogen permeation and determination of hydrogen uptake

and transport in metals by an electrochemical technique (ISO 17081:2014)
Elektrochemisches Verfahren zur Messung der Wasserstoffpermeation und zur
Bestimmung von Wasserstoffaufnahme und -transport in Metallen (ISO 17081:2014)

Méthode de mesure de la perméation de l'hydrogène et détermination de l'absorption

d'hydrogène et de son transport dans les métaux à l'aide d'une technique
électrochimique (ISO 17081:2014)
Ta slovenski standard je istoveten z: EN ISO 17081:2014
ICS:
77.060 Korozija kovin Corrosion of metals
SIST EN ISO 17081:2014 en

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

---------------------- Page: 1 ----------------------
SIST EN ISO 17081:2014
---------------------- Page: 2 ----------------------
SIST EN ISO 17081:2014
EUROPEAN STANDARD
EN ISO 17081
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2014
ICS 77.060 Supersedes EN ISO 17081:2008
English Version
Method of measurement of hydrogen permeation and
determination of hydrogen uptake and transport in metals by an
electrochemical technique (ISO 17081:2014)

Méthode de mesure de la perméation de l'hydrogène et Elektrochemisches Verfahren zur Messung der

détermination de l'absorption d'hydrogène et de son Wasserstoffpermeation und zur Bestimmung von

transport dans les métaux à l'aide d'une technique Wasserstoffaufnahme und -transport in Metallen (ISO

électrochimique (ISO 17081:2014) 17081:2014)
This European Standard was approved by CEN on 13 April 2014.

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-CENELEC 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-CENELEC Management Centre has the same

status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United

Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17081:2014 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 17081:2014
EN ISO 17081:2014 (E)
Contents Page

Foreword ..............................................................................................................................................................3

---------------------- Page: 4 ----------------------
SIST EN ISO 17081:2014
EN ISO 17081:2014 (E)
Foreword

This document (EN ISO 17081:2014) has been prepared by Technical Committee ISO/TC 156 “Corrosion of

metals and alloys” in collaboration with 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 December 2014, and conflicting national standards shall be withdrawn

at the latest by December 2014.

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.

This document supersedes EN ISO 17081:2008.

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, Croatia, Cyprus, Czech

Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,

Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,

Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

Endorsement notice

The text of ISO 17081:2014 has been approved by CEN as EN ISO 17081:2014 without any modification.

---------------------- Page: 5 ----------------------
SIST EN ISO 17081:2014
---------------------- Page: 6 ----------------------
SIST EN ISO 17081:2014
INTERNATIONAL ISO
STANDARD 17081
Second edition
2014-06-01
Method of measurement of hydrogen
permeation and determination of
hydrogen uptake and transport
in metals by an electrochemical
technique
Méthode de mesure de la perméation de l’hydrogène et détermination
de l’absorption d’hydrogène et de son transport dans les métaux à
l’aide d’une technique électrochimique
Reference number
ISO 17081:2014(E)
ISO 2014
---------------------- Page: 7 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2014

All rights reserved. Unless otherwise specified, 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
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2014 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(E)
Contents Page

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

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

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

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

4 Symbols .......................................................................................................................................................................................................................... 2

5 Principle ........................................................................................................................................................................................................................ 3

6 Samples .......................................................................................................................................................................................................................... 4

6.1 Dimensions ................................................................................................................................................................................................. 4

6.2 Preparation ................................................................................................................................................................................................ 5

7 Apparatus ..................................................................................................................................................................................................................... 6

8 Test environment considerations ....................................................................................................................................................... 8

9 Test procedure ........................................................................................................................................................................................................ 9

10 Control and monitoring of test environment .......................................................................................................................11

11 Analysis of results.............................................................................................................................................................................................11

11.1 General ........................................................................................................................................................................................................11

11.2 Analysis of steady-state current ............................................................................................................................................11

11.3 Analysis of permeation transient .........................................................................................................................................12

12 Test report ................................................................................................................................................................................................................14

Annex A (informative) Recommended test environments for specific alloys .........................................................16

Bibliography .............................................................................................................................................................................................................................19

© ISO 2014 – All rights reserved iii
---------------------- Page: 9 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(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 meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers

to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 156, Corrosion of metals and alloys.

This second edition cancels and replaces the first edition (ISO 17081:2004), of which it constitutes a

minor revision. Figure 1 has been corrected and Figure 2 made language independent.

iv © ISO 2014 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 17081:2014
INTERNATIONAL STANDARD ISO 17081:2014(E)
Method of measurement of hydrogen permeation and
determination of hydrogen uptake and transport in metals
by an electrochemical technique
1 Scope

1.1 This International Standard specifies a laboratory method for the measurement of hydrogen

permeation and for the determination of hydrogen atom uptake and transport in metals, using an

electrochemical technique. The term “metal” as used in this International Standard includes alloys.

1.2 This International Standard describes a method for evaluating hydrogen uptake in metals, based

on measurement of steady-state hydrogen flux. It also describes a method for determining effective

diffusivity of hydrogen atoms in a metal and for distinguishing reversible and irreversible trapping.

1.3 This International Standard gives requirements for the preparation of specimens, control and

monitoring of the environmental variables, test procedures and analysis of results.

1.4 This International Standard may be applied, in principle, to all metals for which hydrogen permeation

is measurable and the method can be used to rank the relative aggressivity of different environments in

terms of the hydrogen uptake of the exposed metal.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 17475, Corrosion of metals and alloys — Electrochemical test methods — Guidelines for conducting

potentiostatic and potentiodynamic polarization measurements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
charging

method of introducing atomic hydrogen into the metal by exposure to an aqueous environment under

galvanostatic control (constant charging current), potentiostatic control (constant electrode potential),

free corrosion or by gaseous exposure
3.2
charging cell

compartment in which hydrogen atoms are generated on the sample surface, including both aqueous

and gaseous charging
3.3
decay current

decay of the hydrogen atom oxidation current, after attainment of steady state, following a decrease in

charging current
© ISO 2014 – All rights reserved 1
---------------------- Page: 11 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(E)
3.4
Fick’s second law

second-order differential equation describing, in this case, the concentration of atomic hydrogen in the

sample as a function of position and time
2 2

Note 1 to entry: The equation is of the form ∂C (x, t)/t = D∂ C(x, t)/∂x for lattice diffusion in one dimension where

diffusivity is independent of concentration. See Table 1 for an explanation of the symbols.

3.5
hydrogen flux
amount of hydrogen passing through the metal sample per unit area per unit time
3.6
hydrogen uptake
atomic hydrogen absorbed into the metal as a result of charging
3.7
irreversible trap

microstructural site at which the residence time for a hydrogen atom is infinite or extremely long

compared to the time-scale for permeation testing at the relevant temperature
3.8
mobile hydrogen atoms

hydrogen atoms in interstitial sites in the lattice (lattice sites) and reversible trap sites

3.9
oxidation cell
compartment in which hydrogen atoms exiting from the metal sample are oxidized
3.10
permeation current
current measured in oxidation cell associated with oxidation of hydrogen atoms
3.11
permeation flux
hydrogen flux exiting the test sample in the oxidation cell
3.12
permeation transient

variation of the permeation current with time, from commencement of charging to the attainment of

steady state, or modification of charging conditions
3.13
recombination poison

chemical within the test environment in the charging cell which enhances hydrogen absorption by

retarding the recombination of hydrogen atoms on the metal surface
3.14
reversible trap

microstructural site at which the residence time for a hydrogen atom is greater than that for the lattice

site but is small in relation to the time to attain steady-state permeation
4 Symbols
Table 1 gives a list of symbols and their designations.
2 © ISO 2014 – All rights reserved
---------------------- Page: 12 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(E)
Table 1 — Symbols and their designations and units
Symbol Designation Unit
A Exposed area of sample in the oxidation cell m

C(x, t) Lattice concentration of hydrogen as a function of position and time mol·m

C Sub-surface concentration of atomic hydrogen in interstitial lattice sites on the mol·m

charging side of the sample

C Summation of the sub-surface concentration of hydrogen in interstitial lattice sites mol·m

and reversible trap sites on the charging side of the sample
2 −1
D Lattice diffusion coefficient of atomic hydrogen m ·s
2 −1

D Effective diffusion coefficient of atomic hydrogen based on elapsed time correspond- m ·s

eff
ing to J (t)/J = 0,63
−1 −1
F Faraday’s constant (F = 96 485 C·mol ) C·mol
−2 −1

J (t) Time-dependent atomic hydrogen permeation flux as measured on the oxidation side mol·m s

of the sample
−2 −1

J Atomic hydrogen permeation flux at steady-state as measured on the oxidation side mol·m s

of the sample
J (t)/J Normalized flux of atomic hydrogen 1
I (t) Time-dependent atomic hydrogen permeation current A·m
I Steady-state atomic hydrogen permeation current A·m
L Sample thickness m
t Time elapsed from commencement of hydrogen charging s

t Elapsed time measured by extrapolating the linear portion of the rising permeation s

current transient
t Time to achieve a value of J (t)/J = 0,63 s
lag ss
x Distance in sample measured in the thickness direction m
τ Normalized time (D t/L ) 1
τ Normalized time to achieve a value of J (t)/J = 0,63 1
lag ss
5 Principle

5.1 The technique involves locating the metal sample of interest between the charging and oxidation

cells, where the charging cell contains the environment of interest. Hydrogen atoms are generated on the

sample surface exposed to this environment.

5.2 In gaseous environments, the hydrogen atoms are generated by adsorption and dissociation of the

gaseous species. In aqueous environments, hydrogen atoms are produced by electrochemical reactions.

In both cases, some of the hydrogen atoms diffuse through the metal sample and are then oxidized to

hydrogen cations on exiting from the other side of the metal in the oxidation cell.

A palladium coating is sometimes applied to one or both sides of the membrane following initial removal

of oxide films. A palladium coating on the charging face of the membrane affects the sub-surface

hydrogen concentration in the substrate and the measured permeation current. It is important to verify

that the calculated diffusivity is not influenced by the coating. Palladium coating is particularly useful

for gaseous charging.

5.3 The environment and the electrode potential on the oxidation side of the membrane are selected

so that the metal is either passive or immune to corrosion. The background current established prior to

hydrogen transport is steady, and small compared to the hydrogen atom oxidation current.

© ISO 2014 – All rights reserved 3
---------------------- Page: 13 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(E)

5.4 The electrode potential of the sample in the oxidation cell is controlled at a value sufficiently positive

to ensure that the kinetics of oxidation of hydrogen atoms are limited by the flux of hydrogen atoms, i.e.

the hydrogen atom oxidation current density is transport limited.

NOTE Palladium coating of the oxidation side of the sample can enhance the rate of oxidation and thereby

enable attainment of transport-limited oxidation of hydrogen atoms at less positive potentials than for the

uncoated sample.

5.5 The oxidation current is monitored as a function of time. The total oxidation current comprises the

background current and the permeation current.

5.6 The thickness of the sample, L, is usually selected to ensure that the measured flux reflects volume

(bulk) controlled hydrogen atom transport.

NOTE Thin specimens may be used for evaluation of the effect of surface processes on hydrogen entry

(absorption kinetics or transport in oxide films).

5.7 In reasonably pure metals with a sufficiently low density of microstructural trap sites, atomic

hydrogen transport through the material is controlled by lattice diffusion.

5.8 The effect of alloying and of microstructural features such as dislocations, grain boundaries,

inclusions, and precipitate particles is to introduce traps for hydrogen atoms, which retard hydrogen

transport.

The rate of hydrogen atom transport through the metal during a first permeation test can be affected

by both irreversible and reversible trapping. At steady-state, all of the irreversible traps are occupied.

If the mobile hydrogen atoms are then removed and a subsequent permeation test conducted on the

sample, the difference between the first and second permeation transients may be used to evaluate the

influence of irreversible trapping on transport.

For some environments the conditions on the charging side of the sample may be suitably altered to

induce a decay of the oxidation current after attainment of steady-state. The rate of decay is determined

by diffusion and reversible trapping only and hence can also be used to evaluate the effect of irreversible

trapping on transport during the first transient.

NOTE 1 Reversible and irreversible traps can both be present in a particular metal.

NOTE 2 Comparison of repeated permeation transients with those obtained for the pure metal can be used, in

principle, to evaluate the effect of reversible trapping on atomic hydrogen transport.

NOTE 3 The technique is suitable for systems in which hydrogen atoms are generated uniformly over the

charging surface of the sample. It is not usually applicable to corroding systems in which pitting attack occurs,

unless the charging cell environment is designed to simulate the localized pit environment and the entire metal

surface is active.

5.9 The method may be used for stressed and unstressed samples but testing of stressed samples

requires loading procedures to be taken into consideration.
6 Samples
6.1 Dimensions

Samples shall be in the form of plate or pipe. The dimensions shall be such as to enable analysis of the

permeation transient based on one-dimensional diffusion, e.g. for plates with a circular exposed area,

the radius exposed to the solution should be sufficiently large relative to thickness.

A ratio of radius to thickness of 10:1 or greater is recommended. This condition may be made less

stringent if the exposed area on the oxidation side is smaller than that on the charging side. A ratio of

4 © ISO 2014 – All rights reserved
---------------------- Page: 14 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(E)

radius to thickness of 5:1 or greater is recommended if the radius of the exposed area on the oxidation

side is reduced to 90 % of the area of the charging side.

For pipes, the ratio of the outer radius to the inner radius shall be less than 1,1:1 if the experimental

results are to be analysed based on planar one-dimensional diffusion.
6.2 Preparation

6.2.1 As hydrogen atom permeation can be influenced by microstructural orientation, the form of the

original material shall be recorded (e.g. bar) as well as the location and orientation of the sample relative

to that of the original material (see Clause 12).
6.2.2 Samples shall be prepared using one of the following methods:
a) electrochemical discharge machining (EDM) plus final machining;
b) mechanical cutting.

EDM is particularly useful for preparing thin sheets of material but can introduce hydrogen into the

metal. Although hydrogen atoms dissolved in lattice sites or reversible trap sites are gradually lost

subsequent to EDM, hydrogen atoms can be retained in irreversible trap sites. The amount of hydrogen

generated and the extent of ingress into the metal depend on the details of the EDM process and the

material characteristics but sufficient material should be removed by subsequent machining to ensure

that all residual hydrogen atoms are removed.

NOTE 1 Careful consideration should be given to the method of manufacture of sheet samples.

NOTE 2 The preferred method for the preparation of thin sheets of material is fine mechanical cutting.

6.2.3 Sheet samples shall be machined to the required thickness. Care shall be taken in machining to

minimize surface damage.

6.2.4 The thickness of the sample in the region of interest shall be as uniform as possible with a

maximum variation no greater than ± 5 %.

6.2.5 The oxidation side of the sample shall be mechanically ground or polished to a repeatable finish.

The charging side may be similarly treated or used as for an intended service application.

NOTE Electropolishing of samples may also be employed in appropriate cases.

6.2.6 After polishing, traces of polishing chemicals shall be removed by an appropriate cleaning

procedure.

NOTE Rinsing with distilled water, followed by alcohol and a non-chlorinated solvent, is adequate for most

cases.

6.2.7 The final thickness shall be measured in at least five locations in the exposed region of the

membrane. The sample shall then be degreased and the specimen stored in a dry environment.

Palladium coating of the sample may be undertaken at this stage. Electrochemical methods of forming

the coating can introduce hydrogen atoms into the material and can influence the subsequent permeation

measurements. Argon etching of the surface followed by sputter coating with palladium can avoid this

problem.

6.2.8 A suitable electrical connection shall be made to the sample remote from the active areas.

© ISO 2014 – All rights reserved 5
---------------------- Page: 15 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(E)

6.2.9 The sample shall be uniquely identified. Stamping or scribing on the sample remote from the

active areas is recommended.
7 Apparatus

Two-compartmental environmental cell consisting of separate charging and oxidation cells (e.g. as

shown in Figure 1) constructed from inert materials, with reference electrodes and auxiliary electrodes

(usually platinum).

Sealed oxidation cells, in which an additional membrane (usually palladium) is clamped against the

test sample and the flux exiting this additional membrane is measured, may be used provided that it is

demonstrated that the introduction of this additional interface has no effect on the calculated diffusivity.

A Luggin capillary should be used for more accurate measurement of potential where the current is

large. In order to avoid shielding effects, the tip of the Luggin should be no closer to the surface than

twice the diameter of the tip. Typically the distance is 2 mm to 3 mm.
Non-metallic materials are recommended for cell construction.

At temperatures above 50 °C leaching from the cell material (e.g. silica dissolution from glass) can modify

the solution chemistry and may influence hydrogen permeation. Polytetrafluoroethylene is an example

of a suitable material for elevated temperatures up to about 90 °C.

Where metallic chambers are necessary, the materials chosen shall have a very low passive current to

ensure minimal effect on the solution composition, and shall be electrically isolated from the membrane.

When testing at elevated temperatures the O-ring material shall be selected to minimize possible

degradation products from the seals and contamination of the solution.

The choice of reference electrode depends on the particular exposure conditions. Saturated calomel

electrodes (SCE) or silver/silver chloride electrodes are often used, although use of the former is no

longer permitted in some countries because of environmental concerns. The chloride concentration in

the latter shall be specified. The solution contained in the reference electrode shall not contaminate the

test solution.
6 © ISO 2014 – All rights reserved
---------------------- Page: 16 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(E)
Key
A charging cell 1 reference electrode Gas in.
B oxidation cell 2 counter electrode Gas out.
3 test sample

Figure 1 — Hydrogen permeation cell (constructed of polytetrafluoroethylene) with double

junction electrodes
© ISO 2014 – All rights reserved 7
---------------------- Page: 17 ----------------------
SIST EN ISO 17081:2014
ISO 17081:2014(E)

Contamination may be avoided by the use of double junction reference electrodes or by remote

monitoring using a solution conductivity b
...

SLOVENSKI STANDARD
kSIST FprEN ISO 17081:2014
01-februar-2014
0HWRGDPHUMHQMDSURGLUDQMDYRGLNDWHUGRORþDQMHQMHJRYHJDYSLMDQMDLQSUHQRVDY
NRYLQDK]HOHNWURNHPLMVNRWHKQLNR ,62)',6

Method of measurement of hydrogen permeation and determination of hydrogen uptake

and transport in metals by an electrochemical technique (ISO/FDIS 17081:2013)
Elektrochemisches Verfahren zur Messung der Wasserstoffpermeation und zur
Bestimmung von Wasserstoffaufnahme und -transport in Metallen (ISO/FDIS
17081:2013)

Méthode de mesure de la perméation de l'hydrogène et détermination de l'absorption

d'hydrogène et de son transport dans les métaux à l'aide d'une technique
électrochimique (ISO/FDIS 17081:2013)
Ta slovenski standard je istoveten z: FprEN ISO 17081
ICS:
77.060 Korozija kovin Corrosion of metals
kSIST FprEN ISO 17081:2014 en,de

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

---------------------- Page: 1 ----------------------
kSIST FprEN ISO 17081:2014
---------------------- Page: 2 ----------------------
kSIST FprEN ISO 17081:2014
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 17081
ISO/TC 156
Method of measurement of hydrogen
Secretariat: SAC
permeation and determination of
Voting begins on:
2013-12-12 hydrogen uptake and transport in
metals by an electrochemical technique
Voting terminates on:
2014-02-12
Méthode de mesure de la perméation de l’hydrogène et détermination
de l’absorption d’hydrogène et de son transport dans les métaux à
l’aide d’une technique électrochimique
Please see the administrative notes on page iii
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 SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 17081:2013(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2013
---------------------- Page: 3 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2013

All rights reserved. Unless otherwise specified, 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
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved
---------------------- Page: 4 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)
ISO/CEN PARALLEL PROCESSING

This final draft has been developed within the International Organization for Standardization (ISO), and pro­

cessed under the ISO-lead mode of collaboration as defined in the Vienna Agreement. The final draft was

established on the basis of comments received during a parallel enquiry on the draft.

This final draft is hereby submitted to the ISO member bodies and to the CEN member bodies for a parallel

two­month approval vote in ISO and formal vote in CEN.
Positive votes shall not be accompanied by comments.
Negative votes shall be accompanied by the relevant technical reasons.
© ISO 2013 – All rights reserved iii
---------------------- Page: 5 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

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

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

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

4 Symbols .......................................................................................................................................................................................................................... 2

5 Principle ........................................................................................................................................................................................................................ 3

6 Samples .......................................................................................................................................................................................................................... 4

6.1 Dimensions ................................................................................................................................................................................................. 4

6.2 Preparation ................................................................................................................................................................................................ 5

7 Apparatus ..................................................................................................................................................................................................................... 6

8 Test environment considerations ....................................................................................................................................................... 8

9 Test procedure ........................................................................................................................................................................................................ 9

10 Control and monitoring of test environment .......................................................................................................................11

11 Analysis of results.............................................................................................................................................................................................11

11.1 General ........................................................................................................................................................................................................11

11.2 Analysis of steady-state current ............................................................................................................................................11

11.3 Analysis of permeation transient .........................................................................................................................................12

12 Test report ................................................................................................................................................................................................................14

Annex A (informative) Recommended test environments for specific alloys .........................................................16

Bibliography .............................................................................................................................................................................................................................19

iv © ISO 2013 – All rights reserved
---------------------- Page: 6 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(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 meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers

to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 156, Corrosion of metals and alloys.

This second edition cancels and replaces the first edition (ISO 17081:2004), of which it constitutes a

minor revision. Figure 1 has been corrected and Figure 2 made language independent.

© ISO 2013 – All rights reserved v
---------------------- Page: 7 ----------------------
kSIST FprEN ISO 17081:2014
---------------------- Page: 8 ----------------------
kSIST FprEN ISO 17081:2014
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 17081:2013(E)
Method of measurement of hydrogen permeation and
determination of hydrogen uptake and transport in metals
by an electrochemical technique
1 Scope

1.1 This International Standard specifies a laboratory method for the measurement of hydrogen

permeation and for the determination of hydrogen atom uptake and transport in metals, using an

electrochemical technique. The term “metal” as used in this International Standard includes alloys.

1.2 This International Standard describes a method for evaluating hydrogen uptake in metals, based

on measurement of steady-state hydrogen flux. It also describes a method for determining effective

diffusivity of hydrogen atoms in a metal and for distinguishing reversible and irreversible trapping.

1.3 This International Standard gives requirements for the preparation of specimens, control and

monitoring of the environmental variables, test procedures and analysis of results.

1.4 This International Standard may be applied, in principle, to all metals for which hydrogen permeation

is measurable and the method can be used to rank the relative aggressivity of different environments in

terms of the hydrogen uptake of the exposed metal.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 17475, Corrosion of metals and alloys — Electrochemical test methods — Guidelines for conducting

potentiostatic and potentiodynamic polarization measurements
3 Terms a nd definiti ons
For the purposes of this document, the following terms and definitions apply.
3.1
charging

method of introducing atomic hydrogen into the metal by exposure to an aqueous environment under

galvanostatic control (constant charging current), potentiostatic control (constant electrode potential),

free corrosion or by gaseous exposure
3.2
charging cell

compartment in which hydrogen atoms are generated on the sample surface, including both aqueous

and gaseous charging
3.3
decay current

decay of the hydrogen atom oxidation current, after attainment of steady state, following a decrease in

charging current
© ISO 2013 – All rights reserved 1
---------------------- Page: 9 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)
3.4
Fick’s second law

second-order differential equation describing, in this case, the concentration of atomic hydrogen in the

sample as a function of position and time
2 2

Note 1 to entry: The equation is of the form ∂C (x, t)/t = D∂ C(x, t)/∂x for lattice diffusion in one dimension where

diffusivity is independent of concentration. See Table 1 for an explanation of the symbols.

3.5
hyd r o g en f lu x
amount of hydrogen passing through the metal sample per unit area per unit time
3.6
hydrogen uptake
atomic hydrogen absorbed into the metal as a result of charging
3.7
irreversible trap

microstructural site at which the residence time for a hydrogen atom is infinite or extremely long

compared to the time­ scale for permeation testing at the relevant temperature
3.8
mobile hydrogen atoms

hydrogen atoms in interstitial sites in the lattice (lattice sites) and reversible trap sites

3.9
oxidation cell
compartment in which hydrogen atoms exiting from the metal sample are oxidized
3.10
permeation current
current measured in oxidation cell associated with oxidation of hydrogen atoms
3.11
p er me at ion f lu x
hydrogen flux exiting the test sample in the oxidation cell
3.12
permeation transient

variation of the permeation current with time, from commencement of charging to the attainment of

steady state, or modification of charging conditions
3.13
recombination poison

chemical within the test environment in the charging cell which enhances hydrogen absorption by

retarding the recombination of hydrogen atoms on the metal surface
3.14
reversible trap

microstructural site at which the residence time for a hydrogen atom is greater than that for the lattice

site but is small in relation to the time to attain steady-state permeation
4 Symbols
Table 1 gives a list of symbols and their designations.
2 © ISO 2013 – All rights reserved
---------------------- Page: 10 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)
Table 1 — Symbols and their designations and units
Symbol Designation Unit
A Exposed area of sample in the oxidation cell m

C(x, t) Lattice concentration of hydrogen as a function of position and time mol·m

C Sub-surface concentration of atomic hydrogen in interstitial lattice sites on the mol·m

charging side of the sample

C Summation of the sub-surface concentration of hydrogen in interstitial lattice sites mol·m

and reversible trap sites on the charging side of the sample
2 −1
D Lattice diffusion coefficient of atomic hydrogen m ·s
2 −1

D Effective diffusion coefficient of atomic hydrogen based on elapsed time correspond­ m ·s

eff
ing to J (t)/J = 0,63
−1 −1
F Faraday’s constant (F = 96 485 C·mol ) C·mol
−2 −1

J (t) Time-dependent atomic hydrogen permeation flux as measured on the oxidation side mol·m s

of the sample
−2 −1

J Atomic hydrogen permeation flux at steady-state as measured on the oxidation side mol·m s

of the sample
J (t)/J Normalized flux of atomic hydrogen 1
I (t) Time-dependent atomic hydrogen permeation current A·m
I Steady-state atomic hydrogen permeation current A·m
L Sample thickness m
t Time elapsed from commencement of hydrogen charging s

t Elapsed time measured by extrapolating the linear portion of the rising permeation s

current transient
t Time to achieve a value of J (t)/J = 0,63 s
lag ss
x Distance in sample measured in the thickness direction m
τ Normalized time (D t/L ) 1
τ Normalized time to achieve a value of J (t)/J = 0,63 1
lag ss
5 Principle

5.1 The technique involves locating the metal sample of interest between the charging and oxidation

cells, where the charging cell contains the environment of interest. Hydrogen atoms are generated on the

sample surface exposed to this environment.

5.2 In gaseous environments, the hydrogen atoms are generated by adsorption and dissociation of the

gaseous species. In aqueous environments, hydrogen atoms are produced by electrochemical reactions.

In both cases, some of the hydrogen atoms diffuse through the metal sample and are then oxidized to

hydrogen cations on exiting from the other side of the metal in the oxidation cell.

A palladium coating is sometimes applied to one or both sides of the membrane following initial removal

of oxide films. A palladium coating on the charging face of the membrane affects the sub-surface

hydrogen concentration in the substrate and the measured permeation current. It is important to verify

that the calculated diffusivity is not influenced by the coating. Palladium coating is particularly useful

for gaseous charging.

5.3 The environment and the electrode potential on the oxidation side of the membrane are selected

so that the metal is either passive or immune to corrosion. The background current established prior to

hydrogen transport is steady, and small compared to the hydrogen atom oxidation current.

© ISO 2013 – All rights reserved 3
---------------------- Page: 11 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)

5.4 The electrode potential of the sample in the oxidation cell is controlled at a value sufficiently positive

to ensure that the kinetics of oxidation of hydrogen atoms are limited by the flux of hydrogen atoms, i.e.

the hydrogen atom oxidation current density is transport limited.

NOTE Palladium coating of the oxidation side of the sample can enhance the rate of oxidation and thereby

enable attainment of transport-limited oxidation of hydrogen atoms at less positive potentials than for the

uncoated sample.

5.5 The oxidation current is monitored as a function of time. The total oxidation current comprises the

background current and the permeation current.

5.6 The thickness of the sample, L, is usually selected to ensure that the measured flux reflects volume

(bulk) controlled hydrogen atom transport.

NOTE Thin specimens may be used for evaluation of the effect of surface processes on hydrogen entry

(absorption kinetics or transport in oxide films).

5.7 In reasonably pure metals with a sufficiently low density of microstructural trap sites, atomic

hydrogen transport through the material is controlled by lattice diffusion.

5.8 The effect of alloying and of microstructural features such as dislocations, grain boundaries, inclusions,

and precipitate particles is to introduce traps for hydrogen atoms, which retard hydrogen transport.

The rate of hydrogen atom transport through the metal during a first permeation test can be affected

by both irreversible and reversible trapping. At steady-state, all of the irreversible traps are occupied.

If the mobile hydrogen atoms are then removed and a subsequent permeation test conducted on the

sample, the difference between the first and second permeation transients may be used to evaluate the

influence of irreversible trapping on transport.

For some environments the conditions on the charging side of the sample may be suitably altered to

induce a decay of the oxidation current after attainment of steady-state. The rate of decay is determined

by diffusion and reversible trapping only and hence can also be used to evaluate the effect of irreversible

trapping on transport during the first transient.

NOTE 1 Reversible and irreversible traps can both be present in a particular metal.

NOTE 2 Comparison of repeated permeation transients with those obtained for the pure metal can be used, in

principle, to evaluate the effect of reversible trapping on atomic hydrogen transport.

NOTE 3 The technique is suitable for systems in which hydrogen atoms are generated uniformly over the

charging surface of the sample. It is not usually applicable to corroding systems in which pitting attack occurs,

unless the charging cell environment is designed to simulate the localized pit environment and the entire metal

surface is active.

5.9 The method may be used for stressed and unstressed samples but testing of stressed samples

requires loading procedures to be taken into consideration.
6 Samples
6.1 Dimensions

Samples shall be in the form of plate or pipe. The dimensions shall be such as to enable analysis of the

permeation transient based on one­ dimensional diffusion, e.g. for plates with a circular exposed area,

the radius exposed to the solution should be sufficiently large relative to thickness.

A ratio of radius to thickness of 10:1 or greater is recommended. This condition may be made less

stringent if the exposed area on the oxidation side is smaller than that on the charging side. A ratio of

4 © ISO 2013 – All rights reserved
---------------------- Page: 12 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)

radius to thickness of 5:1 or greater is recommended if the radius of the exposed area on the oxidation

side is reduced to 90 % of the area of the charging side.

For pipes, the ratio of the outer radius to the inner radius shall be less than 1,1:1 if the experimental

results are to be analysed based on planar one-dimensional diffusion.
6.2 Preparation

6.2.1 As hydrogen atom permeation can be influenced by microstructural orientation, the form of the

original material shall be recorded (e.g. bar) as well as the location and orientation of the sample relative

to that of the original material (see Clause 12).
6.2.2 Samples shall be prepared using one of the following methods:
a) electrochemical discharge machining (EDM) plus final machining;
b) mechanical cutting.

EDM is particularly useful for preparing thin sheets of material but can introduce hydrogen into the

metal. Although hydrogen atoms dissolved in lattice sites or reversible trap sites are gradually lost

subsequent to EDM, hydrogen atoms can be retained in irreversible trap sites. The amount of hydrogen

generated and the extent of ingress into the metal depends on the details of the EDM process and the

material characteristics but sufficient material should be removed by subsequent machining to ensure

that all residual hydrogen atoms are removed.

NOTE 1 Careful consideration should be given to the method of manufacture of sheet samples.

NOTE 2 The preferred method for the preparation of thin sheets of material is fine mechanical cutting.

6.2.3 Sheet samples shall be machined to the required thickness. Care shall be taken in machining to

minimize surface damage.

6.2.4 The thickness of the sample in the region of interest shall be as uniform as possible with a

maximum variation no greater than ± 5 %.

6.2.5 The oxidation side of the sample shall be mechanically ground or polished to a repeatable finish.

The charging side may be similarly treated or used as for an intended service application.

NOTE Electropolishing of samples may also be employed in appropriate cases.

6.2.6 After polishing, traces of polishing chemicals shall be removed by an appropriate cleaning procedure.

NOTE Rinsing with distilled water, followed by alcohol and a non-chlorinated solvent, is adequate for most cases.

6.2.7 The final thickness shall be measured in at least five locations in the exposed region of the

membrane. The sample shall then be degreased and the specimen stored in a dry environment.

Palladium coating of the sample may be undertaken at this stage. Electrochemical methods of

forming the coating can introduce hydrogen atoms into the material and can influence the subsequent

permeation measurements. Argon etching of the surface followed by sputter coating with palladium

can avoid this problem.

6.2.8 A suitable electrical connection shall be made to the sample remote from the active areas.

6.2.9 The sample shall be uniquely identified. Stamping or scribing on the sample remote from the

active areas is recommended.
© ISO 2013 – All rights reserved 5
---------------------- Page: 13 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)
7 Apparatus

Two­ compartmental environmental cell consisting of separate charging and oxidation cells (e.g. as

shown in Figure 1) constructed from inert materials, with reference electrodes and auxiliary electrodes

(usually platinum).

Sealed oxidation cells, in which an additional membrane (usually palladium) is clamped against the

test sample and the flux exiting this additional membrane is measured, may be used provided that it is

demonstrated that the introduction of this additional interface has no effect on the calculated diffusivity.

A Luggin capillary should be used for more accurate measurement of potential where the current is

large. In order to avoid shielding effects, the tip of the Luggin should be no closer to the surface than

twice the diameter of the tip. Typically the distance is 2 mm to 3 mm.
Non­ metallic materials are recommended for cell construction.

At temperatures above 50 °C leaching from the cell material (e.g. silica dissolution from glass) can modify

the solution chemistry and may influence hydrogen permeation. Polytetrafluoroethylene is an example

of a suitable material for elevated temperatures up to about 90 °C.

Where metallic chambers are necessary, the materials chosen shall have a very low passive current to

ensure minimal effect on the solution composition, and shall be electrically isolated from the membrane.

When testing at elevated temperatures the O-ring material shall be selected to minimize possible

degradation products from the seals and contamination of the solution.

The choice of reference electrode depends on the particular exposure conditions. Saturated calomel

electrodes (SCE) or silver/silver chloride electrodes are often used, although use of the former is no

longer permitted in some countries because of environmental concerns. The chloride concentration in

the latter shall be specified. The solution contained in the reference electrode shall not contaminate the

test solution.
6 © ISO 2013 – All rights reserved
---------------------- Page: 14 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)
Key
A charging cell 1 reference electrode Gas in.
B oxidation cell 2 counter electrode Gas out.
3 test sample

F i g u r e 1 — Hyd r o g en p er me at ion c el l (c on s t r uc t e d of p ol y t e t r a f luor o e t hy lene) w it h double

junction electrodes
© ISO 2013 – All rights reserved 7
---------------------- Page: 15 ----------------------
kSIST FprEN ISO 17081:2014
ISO/FDIS 17081:2013(E)

Contamination may be avoided by the use of double junction reference electrodes or by remote

monitoring using a solution conductivity bridge arrangement with inert materials.

A standard resistor and a digital voltmeter should be used for recording of oxidation current (and, as

appropriate, charging current), or a current monitoring device used for direct measurement, all traceable

to appropriate national standards and calibrated on a regular basis, typically once per year. The resistor

should be positioned in series in the auxiliary electrode line.

The potentiostats used for each cell shall be configured such that they do not have a common earth.

8 Test environment considerations

8.1 The test environment shall be chosen on the basis of one of the following criteria:

a) relevance to the intended service application;
b) ease and reliability of measurement.
NOTE Suggestions for suitable systems for item b) are given in Annex A.

8.2 The environments in the oxidation cell and in the charging cell shall be of sufficient purity for the

intended purpose.

8.3 The environment in the oxidation cell shall be prepared using analytical grade chemicals and

distilled or deionized water of purity sufficient to avoid unintentional contamination.

8.4 Where the environment in the charging cell is aqueous, the solution shall be either that directly used

in service or a laboratory environment prepared with the purity as indicated in 8.3. Gaseous environments

shall simulate those for the intended applications.

In some cases for which higher purity of the charging solution is desirable, the solution may be prepared

by using appropriate high purity analytical grade chemicals or by pre-electrolysis. Pre-electrolysis may

be used to remove certain cationic contaminants by cathodic deposition and usually involves applying a

voltage difference between two platinum electrodes in the solution of interest. The area of the cathode

should be as large as is reasonable in order to enhance the rate of removal of contaminants.

8.5 The ratio of volume of solution (in millilitres) to metal area (in square centimetres) in the oxidation

chamber shall be greater than 20:1.

NOTE A large volume of solution in the oxidation chamber is not necessary as the extent of the reaction is

usually relatively small.

8.6 The solution composition in the charging cell shall be maintained constant during the experiment.

The volume of solution in the charging cell depends on the particular choice of environment and the

extent of reaction on the specimen. Recombination poisons added to enhance hydrogen entry may be

consumed w
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.