ISO 23449:2020

INTERNATIONAL ISO
STANDARD 23449
First edition
2020-10
Corrosion of metals and alloys —
Multielectrode arrays for corrosion
measurement
Corrosion des métaux et alliages — Assemblages multi-électrodes
pour la mesure de la corrosion
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
4.1 Multielectrode arrays . 3
4.2 Coupled multielectrode array (CMA) . 3
4.3 Multielectrode array with closely packed electrodes for studying spatiotemporal
behaviour of localized corrosion . 4
4.4 Coupled multielectrode array sensor (CMAS) . 5
4.4.1 CMAS for corrosion monitoring . 5
4.4.2 CMAS used without polarization to measure corrosion rate at free
corrosion potential. 6
4.4.3 CMAS used to evaluate the effectiveness of cathodic protection and the
effect of stray current. 6
4.5 Multielectrode arrays for high throughput measurements . 7
4.6 Multielectrode arrays for other applications . 7
5 Instrumentation . 8
5.1 Potential measurement . 8
5.2 Coupling current measurement . 8
5.3 Effective coupling of individual electrodes . 9
5.3.1 Coupling with multichannel ZVA . 9
5.3.2 Coupling with wires and measuring current with a single ZVA .10
6 Fabrication of multielectrode array .10
6.1 Electrode preparation .10
6.2 Number of electrodes .10
6.3 Mounting of electrodes .11
6.4 Surface coating on electrodes for preventing crevice corrosion .11
6.5 Electrode configuration .11
6.6 Size of electrodes .11
6.7 Spacing of electrodes for spatiotemporal studies . .12
6.8 Spacing of electrodes for corrosion monitoring in oil and gas application .12
6.9 Size and spacing of the electrodes for high throughput studies .12
7 Test procedure .12
8 Test report .13
Annex A (informative) Typical results from multielectrode array with closely packed
electrodes for studying spatiotemporal behaviour of localized corrosion .14
Annex B (informative) Typical results from a CMAS for corrosion monitoring .15
Annex C (informative) Example reports.17
Bibliography .18
Foreword
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iv © ISO 2020 – All rights reserved

Introduction
Multielectrode array technology has been used to study electrochemical behaviours and the
[1] to [5]
localized corrosion of metals and alloys since the 1970s . It has been demonstrated that
multielectrode arrays are highly powerful tools for studying the spatiotemporal behaviour of metals
[2] to [16]
in laboratories and for monitoring non-uniform corrosion, especially localized corrosion in
[17]
laboratories and plants . Multielectrode arrays are also used as high throughput probes for studying
[1][18] [19]
the statistical behaviour of metal corrosion and for the evaluation of inhibitors .
This document is designed to outline the requirements and procedures for conducting corrosion
measurements using multielectrode arrays.
The International Organization for Standardization (ISO) draws attention to the fact that it is claimed
that compliance with this document may involve the use of a patent.
ISO takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO that he/she is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In
this respect, the statement of the holder of this patent right is registered with ISO. Information may be
obtained from the patent database available at www .iso .org/ patents.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights other than those in the patent database. ISO shall not be held responsible for identifying
any or all such patent rights.
INTERNATIONAL STANDARD ISO 23449:2020(E)
Corrosion of metals and alloys — Multielectrode arrays for
corrosion measurement
1 Scope
This document specifies the methodology of using multielectrode arrays for the measurement of
the corrosion, especially localized corrosion, of metals and alloys. It can be used as a powerful tool
for studying the initiation and propagation processes of localized corrosion. It is also a useful tool
for long-term corrosion monitoring in the field, especially for localized corrosion, and for obtaining
high throughput results for the evaluation of metals with different compositions and/or physical
properties in different environments and the screening of a large number of inhibitors. Additionally,
the galvanic coupling current and potential distribution of dissimilar metal parings can be assessed
by multielectrode arrays. Multielectrode arrays can be implemented in full-immersion, thin-film, spray
and alternating wet–dry cycle exposures.
This document is not intended to be used for measurements of corrosion caused by a non-electrochemical
mechanism.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 8407, Corrosion of metals and alloys — Removal of corrosion products from corrosion test specimens
ISO 8044, Corrosion of metals and alloys — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8044 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
uneven general corrosion
corrosion that occurs over the whole exposed area of a metal at different rates across the exposed area
Note 1 to entry: It is a type of general corrosion, as defined in ISO 8044, that produces an uneven or wave-like
[20][21]
surface where the thickness reduction at the more corroded areas is significantly larger than the thickness
reduction at the less corroded areas or the average corroded areas.
3.2
non-uniform corrosion
corrosion that occurs at different rates over a metal surface where there is a localized surplus of net
anodic or net cathodic rates such that a localized area does not exhibit charge neutrality and electrons
flow within the metal from the anodic-dominant areas to the cathodic-dominant area
...