ISO 3651-3:2017

Determination of resistance to intergranular corrosion of stainless steels — Part 3: Corrosion test for low-Cr ferritic stainless steels

ISO 3651-3:2017 specifies the determination of the intergranular corrosion susceptibility of low-Cr [less than 16 % Cr, less than 0,3 % Ni, less than 0,3 % Ti and less than 0,3 % Nb, less than 0,3 % (Ti + Atomic weight ratio Nb)] ferritic stainless steels in the 0,5 % sulfuric acid/copper sulfate test. It also specifies the purposes which may be assigned to the test. The method is applicable to stainless steels supplied in the form of rolled sheets and welded tubes and intended for use in a mildly oxidizing acid medium. It is important to note that the result of the corrosion test is only strictly valid for the corrosive medium used in the test. It constitutes a basis for estimating the resistance to intergranular corrosion but cannot be used to check resistance to other forms of corrosion (general corrosion, pitting, stress corrosion, etc.). It is important for the user to adapt the specified corrosion test where steels are used. This test is, in no case, considered as an absolute criterion of the quality of the metal.

Détermination de la résistance à la corrosion intergranulaire des aciers inoxydables — Partie 3: Essai de corrosion pour les aciers inoxydables ferritiques à faible teneur en chrome

General Information

• Status: Published
• Publication Date: 09-May-2017
• ICS: 77.060 - Corrosion of metals
• Technical Committee: ISO/TC 156 - Corrosion of metals and alloys
• Drafting Committee: ISO/TC 156/WG 5 - Intergranular corrosion
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 07-Dec-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 3651-3
First edition
2017-05
Determination of resistance to
intergranular corrosion of stainless
steels —
Part 3:
Corrosion test for low-Cr ferritic
stainless steels
Détermination de la résistance à la corrosion intergranulaire des
aciers inoxydables —
Partie 3: Essai de corrosion pour les aciers inoxydables ferritiques à
faible teneur en chrome
Reference number
ISO 3651-3:2017(E)
©
ISO 2017

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ISO 3651-3:2017(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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ii © ISO 2017 – All rights reserved

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ISO 3651-3:2017(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Preparation of test specimens . 1
4.1 Principle . 1
4.2 Dimensions . 2
4.3 Welded test pieces . 4
4.4 Sensitization heat treatment . 4
4.5 Mechanical preparation . 4
4.6 Degreasing and drying . 4
5 Test methods . 4
6 Evaluation by metallographic examination. 6
7 Test report . 6
Bibliography . 7
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ISO 3651-3:2017(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
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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).
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URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.
A list of all parts in the ISO 3651 series can be found on the ISO website.
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ISO 3651-3:2017(E)

Introduction
The term “intergranular corrosion test” denotes the corrosion test carried out by means of preferential
attack of the grain boundaries.
The low-Cr [less than 16 % Cr, less than 0,3 % Ni, less than 0,3 % Ti and less than 0,3 % Nb, less than
0,3 % (Ti + Atomic weight ratio Nb)] ferritic stainless steels may be subject to such attack when they
have been exposed to a temperature between about 500 °C to 1 300 °C. This heat cycle, which may
provoke sensitization to intergranular corrosion, may occur during rolling or welding operation.
Low-Cr ferritic stainless steels may show high risks to uniform corrosion rates and copper deposit
when tested by the methods given by ISO 3651-1 and ISO 3651-2 since the electrochemical potential
difference between the matrix and the Cr depletion for low-Cr ferritic stainless steels is much less
than that of medium-Cr ferritic stainless steels. These risks should be considered in selecting this test
method. Application of this standard test to the other stainless steels out of the above specifications
should be made based on the specific agreement between the interested parties.
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INTERNATIONAL STANDARD ISO 3651-3:2017(E)
Determination of resistance to intergranular corrosion of
stainless steels —
Part 3:
Corrosion test for low-Cr ferritic stainless steels
1 Scope
This document specifies the determination of the intergranular corrosion susceptibility of low-Cr [less
than 16 % Cr, less than 0,3 % Ni, less than 0,3 % Ti and less than 0,3 % Nb, less than 0,3 % (Ti + Atomic
weight ratio Nb)] ferritic stainless steels in the 0,5 % sulfuric acid/copper sulfate test. It also specifies
the purposes which may be assigned to the test.
The method is applicable to stainless steels supplied in the form of rolled sheets and welded tubes and
intended for use in a mildly oxidizing acid medium.
It is important to note that the result of the corrosion test is only strictly valid for the corrosive medium
used in the test. It constitutes a basis for estimating the resistance to intergranular corrosion but cannot
be used to check resistance to other forms of corrosion (general corrosion, pitting, stress corrosion,
etc.). It is important for the user to adapt the specified corrosion test where steels are used. This test is,
in no case, considered as an absolute criterion of the quality of the metal.
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 8044, Corrosion of metals and alloys — Basic terms and definitions
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8044 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Preparation of test specimens
4.1 Principle
Depending on the purpose of the test and agreement between supplier and purchaser, the test pieces
shall be prepared as specified in 4.2, 4.3 or 4.4. The thickness of the test specimen can be the same as
the original samples.
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ISO 3651-3:2017(E)

4.2 Dimensions
2 2
A specimen having a total surface area of 5 cm to 20 cm is recommended. It should include welded
zone, heat-affected zone and unaffected base metal.
Dimensions in millimetres
Key
1 no sampling area (avoid weld defects)
2 sampling area
3 welding sample
4 no sampling area
Figure 1 — Test piece for plates and strips with welded butt joint
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ISO 3651-3:2017(E)

Key
1 welding sample
2 welding sample
3 sampling area
Figure 2 — Test piece for plates and strips with crossing welded butt joint
Key
1 sampling area
2 welding samples
Figure 3 — Longitudinal test piece for tubes with welded butt joint
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ISO 3651-3:2017(E)

Key
1 sampling area
2 welding samples
Figure 4 — Circumferential test piece for tubes with welded butt joint
4.3 Welded test pieces
Welded test pieces are prepared according to Fig
...