ISO 22910:2020

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 22910
ISO/TC 156
Corrosion of metals and alloys —
Secretariat: SAC
Measurement of the electrochemical
Voting begins on:
2020­05­13 critical localized corrosion
temperature (E-CLCT) for Ti
Voting terminates on:
2020­07­08
alloys fabricated via the additive
manufacturing method
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OF ANY RELEVANT PATENT RIGHTS OF WHICH
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Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 22910:2020(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
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LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. ISO 2020

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ISO/FDIS 22910:2020(E)

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© ISO 2020
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ii © ISO 2020 – All rights reserved

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ISO/FDIS 22910:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Main contents and limitations of existing standards . 1
4.1 Application coverage of ISO 17864 . 1
4.2 Limitations of ISO 17864 . 1
4.3 Scope of ISO 18089. 2
4.4 Limitations of ISO 18089 . 2
5 Principle . 2
6 Apparatus . 4
7 Test solutions . 6
8 Test specimens. 6
9 Procedure. 6
9.1 Preparation of reference electrodes . 6
9.2 Preparation of Ti alloy specimen . 6
9.3 Preparation of solution . 6
9.4 Setting up the E­CLCT test . . 6
9.5 Ending test . 7
10 Evaluation of test results . 7
11 Test report . 7
Annex A (informative) Relationship between applied potential and localized corrosion of
AM Ti-alloys with temperature . 9
Bibliography .10
© ISO 2020 – All rights reserved iii

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ISO/FDIS 22910:2020(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
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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).
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/FDIS 22910:2020(E)

Introduction
Ti alloys such as Ti-6Al-4V are considered the most promising engineering materials. Due to a unique
combination of high strength-to-density ratio and increased mechanical and corrosion resistance,
their applications are growing in a wide range of industries, e.g. aerospace, automobile, marine and
biomedical fields.
Ti alloys are conventionally produced by wrought or cast processes, which are subtractive
manufacturing (SM) methods. The recent emergence of a new additive manufacturing (AM) method
known as “3D printing” has gained worldwide attention as a way to cut costs and improve efficiency for
small quantity, batch productions.
Additively manufactured Ti alloys are extensively investigated for their usage in aerospace and medical
applications. When AM is compared with conventional manufacturing, the buy-to-fly ratio is known
to be around 15:1 (conventional). In terms of mechanical viewpoints, both the strength and ductility
of Ti alloys such as Ti-6Al-4V fabricated via AM are comparable to or superior to those developed
via conventional manufacturing methods, because of their unique microstructure based on laser or
electron beam technologies. However, the characteristics of additively manufactured alloys are highly
dependent upon the geometric and processing conditions (and there are over 130 variables) such as
layer formation (imbedded or sprayed), size and quality of powder or wire, dimension, input energy,
layer orientation and surface conditions, and tolerance in the CAD process, which converts the data
into additive layers for building parts. The differences in layer orientation and the porosity generated
by crossing hatches during the layer-by-layer fabrication process can result in differences in both
mechanical and electrochemical properties in AM materials. Heat treatment controls the porosity or
the microstructure derived from rapid melting and quenching; however, it cannot eliminate interlayers,
which contribute to the differences in the mechanism of localized corrosion in AM materials. The
resistance to corrosion of Ti alloys produced via AM is similar to that of conventionally manufactured
Ti alloys. The mechanisms of corrosion also differ. Therefore, since the conventional testing methods
have shown limited ability for evaluation of those properties, the new test method measuring
electrochemical critical localized corrosion temperature (E­CLCT) has been developed to evaluate
pitting and crevice corrosion in alloys generated via AM. E-CLCT is defined as the lowest temperature
on the surface of the AM specimen on which localized corrosion to both pitting and crevice corrosion is
initiated under specified test conditions.
This document specifies a procedure for evaluation of the resistance to localized corrosion on the
AM alloys by measuring their E-CLCT, providing an efficient method for a qualitative evaluation or
comparison of corrosion properties between AM materials or their heats with altered process variables.
This test method demonstrates the quality of heat treatment, bonding integrities between layers, and
effective control of variables for AM materials, providing a qualitative tool for long-term application.
Furthermore, this document can extend its use from AM Ti-alloys to other AM alloys, such as Ni alloys
by modifying the concentration of test solutions or the applied potentials. This document also provides
important clues to evaluate other types of localized corrosion such as corrosion cracking and erosion-
corrosion. Related documents can be developed and followed up based on the results of this test.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 22910:2020(E)
Corrosion of metals and alloys — Measurement of the
electrochemical critical localized corrosion temperature
(E-CLCT) for Ti alloys fabricated via the additive
manufacturing method
1 Scope
This document specifies procedures for testing the resistance to localized corrosion of Ti alloys
fabricated via additive manufacturing (AM) method. This document regulates the electrochemical
critical localized corrosion temperature (E­CLCT) of the AM Ti materials for a comparative evaluation
of resistance to localized corrosion.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
electrochemical critical localized corrosion temperature
E-CLCT
lowest temperature on the surface of the AM Ti alloy specimen at which stable localized corrosion,
including both pitting and crevice corrosion, occurs under specified test conditions
3.2
temperature ramp rate
rate at which the surface temperature of the specimen increases during the test
4 Main contents and limitations of existing standards
4.1 Application coverage of ISO 17864
The test method in ISO 17864 determines the critical pitting temperature (CPT) using a potentiostatic
technique with a temperature scan. The current is monitored during the temperature scan, and CPT
is defined as the temperature at which the current increases rapidly, which for practical reasons is
2
defined as the temperature at which the current density exceeds 100 µA/cm for 60 s. Pitting on the
specimen is confirmed visually after the test.
4.2 Limitations of ISO 17864
ISO 17864 is useful to measure the resistance of pitting corrosion for stainless steel and related alloys.
This method applies to wrought or cast products. However, this method cannot be used for Ti alloys
© ISO 2020 – All rights reserved 1

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ISO/FDIS 22910:2020(E)

fabricated via
...