ISO/DTR 19884-2

Gaseous hydrogen — Pressure vessels for stationary storage — Part 2: Material test data of class A materials (steels and aluminum alloys) compatible to hydrogen service

Hydrogène gazeux — Récipients sous pression pour stockage stationnaire — Partie 2: Données d'essai des matériaux de classe A (aciers et alliages d'aluminium) compatibles avec une utilisation en présence d’hydrogène

General Information

• Status: Not Published
• ICS: 23.020.30 - Pressure vessels, gas cylinders
• ICS: 27.075 - Hydrogen technologies
• Technical Committee: ISO/TC 197 - Hydrogen technologies
• Drafting Committee: ISO/TC 197 - Hydrogen technologies
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 02-Mar-2026
• Completion Date: 02-Mar-2026

Overview

ISO/DTR 19884-2: Gaseous hydrogen - Pressure vessels for stationary storage - Part 2: Material test data of class A materials (steels and aluminum alloys) compatible to hydrogen service provides comprehensive test data and evaluation methods for assessing the hydrogen compatibility of class A materials used in high-pressure hydrogen containers. Developed by ISO/TC 197, this technical report is a critical reference for stakeholders involved in hydrogen storage, safety, and materials engineering, focusing on commonly used steels and aluminum alloys for cylinders and tubes in stationary hydrogen storage systems.

The document addresses the challenges posed by hydrogen embrittlement and highlights standardized test methodologies and material properties crucial for safe and reliable hydrogen storage solutions.

Key Topics

• Hydrogen Compatibility Assessment:
  The standard presents approaches for evaluating materials’ resistance to hydrogen-induced damage, particularly hydrogen embrittlement, which is a key safety concern in high-pressure systems.

• Testing Methods for Hydrogen Service:
  ISO/DTR 19884-2 details three main standardized mechanical tests:

  • Slow Strain Rate Tensile (SSRT) Test: Determines strength and ductility retention in hydrogen environments.
  • Fatigue Crack Growth Rate Test: Measures the acceleration of crack growth under cyclic loading and hydrogen exposure.
  • Fatigue Life (S-N) Test: Assesses endurance under repeated loading both in air and in various hydrogen pressures.

• Material Classes & Properties:

  • Low Alloy Steels (e.g., Cr-Mo steel JIS SCM435, Ni-Cr-Mo steel JIS SNCM439): Typically assessed for yield strength, tensile strength, elongation, and chemical composition.
  • Austenitic Stainless Steels (e.g., SUS316L, SUH660/A286): Noted for their microstructural stability and lower susceptibility to embrittlement.
  • Aluminum Alloys (e.g., A6061-T651): Evaluated for mechanical performance and suitability in hydrogen-rich environments.

• Influence of External Parameters:
  The report underlines the impact of hydrogen pressure, temperature, gas purity, and mechanical stress level on material performance.

Applications

ISO/DTR 19884-2 plays an essential role in guiding industries and regulators on the selection and validation of materials for stationary hydrogen storage vessels. Its primary applications include:

• Hydrogen Storage Facility Design:
  Enables engineers to choose qualified steels and aluminum alloys for the construction of pressure vessels, cylinders, and tubes for equal safety and performance.
• Safety Benchmarking:
  Supports safety authorities and certification bodies by providing vetted test data on hydrogen compatibility and embrittlement risk.
• Hydrogen Infrastructure Development:
  Facilitates the expansion of hydrogen refueling stations, energy storage, and supply chain systems by identifying robust materials for high-pressure applications.
• Materials Research and Development:
  Serves as a foundational dataset for researchers developing new hydrogen-compatible materials or improving testing protocols.

Related Standards

For a comprehensive hydrogen storage safety and materials selection strategy, the following standards are also relevant:

• ISO 19884-1: Gaseous hydrogen - Pressure vessels for stationary storage - Part 1: General requirements
• ASTM G142: Standard Test Method for Determination of Susceptibility to Hydrogen Embrittlement for Metallic Materials
• ASTM E647/E466: Standard Test Methods for Fatigue Crack Growth and Fatigue Life Testing
• CGA G-5.3: Commodity Specification for Hydrogen (purity requirements)
• ISO/IEC 17025: General requirements for the competence of testing and calibration laboratories

By following the guidance and referencing the detailed material data provided in ISO/DTR 19884-2, organizations can enhance the reliability and safety of stationary hydrogen storage systems worldwide. This document is a cornerstone for hydrogen technology standards, fostering safe adoption and innovation within the hydrogen economy.

Standards Content (Sample)

FINAL DRAFT
Technical
Report
ISO/TC 197
Gaseous hydrogen — Pressure
Secretariat: SCC
vessels for stationary storage —
Voting begins on:
2026-03-02
Part 2:
Material test data of class A
Voting terminates on:
2026-04-27
materials (steels and aluminum
alloys) compatible to hydrogen
service
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
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
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.
Reference number
FINAL DRAFT
Technical
Report
ISO/TC 197
Gaseous hydrogen — Pressure
Secretariat: SCC
vessels for stationary storage —
Voting begins on:
Part 2:
Material test data of class A
Voting terminates on:
materials (steels and aluminum
alloys) compatible to hydrogen
service
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.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Terms and definitions . 1
4 Hydrogen compatibility assessment . 2
5 Test method . 3
5.1 SSRT test .3
5.2 Fatigue crack growth test .3
5.3 Fatigue test.4
6 Materials test data . 5
6.1 Low alloy steel .5
6.1.1 Cr-Mo steel (JIS SCM435) .5
6.1.2 Ni-Cr-Mo steel (JIS SNCM439) .16
6.2 Austenitic stainless steel . 29
6.2.1 SUS316L stainless steel . 29
6.2.2 SUH660(SA638) stainless steel . 39
6.3 Aluminum alloy . 46
6.3.1 Materials . 46
6.3.2 SSRT test . 46
6.3.3 Fatigue crack growth test . 48
6.3.4 Fatigue test . 50
6.3.5 Reference .51
Bibliography .52

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 197, Hydrogen technologies.
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.

iv
Introduction
ISO19884-1 allows the use of Class A materials listed in ISO19884-1, Annex B without cycle testing in
hydrogen. In exchange, these materials require test data to demonstrate they are sufficiently hydrogen-
resistant in a high-pressure hydrogen environment. This document provides evaluation test methods used
for hydrogen compatibility assessment, along with published test data.
This document does not provide rules or guidelines for material qualification, but instead presents a
collection of test data on a limited selection (not exhaustive) of materials. However, this allows authorities
and users to review the hydrogen compatibility assessment data of Class A materials, assuring their
performance in hydrogen.
This document presents currently available hydrogen compatibility test methods and test data obtained
from them, but it is not intended to hinder the advancement of new technologies that are presently under
development, in use in the market, or yet to emerge. As these new technologies mature and their design and
testing prove safety, they will be added in future editions.

v
FINAL DRAFT Technical Report ISO/DTR 19884-2:2026(en)
Gaseous hydrogen — Pressure vessels for stationary
storage —
Part 2:
Material test data of class A materials (steels and aluminum
alloys) compatible to hydrogen service
1 Scope
This document provides hydrogen compatibility evaluation methods and test results of Class A materials
used for high-pressure hydrogen containers. This document identifies the safety concerns of materials, and
in particular, hazards and risks caused by hydrogen embrittlement, and describes the metal properties
that are relevant to safety in hydrogen. Detailed safety requirements associated with specific hydrogen
applications are covered in separate International Standards.
2 Terms and definitions
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 terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
displacement rate of crosshead
displacement of a crosshead per unit time
3.2
fatigue crack growth rate
fatigue crack length that progresses with each repetition in a fatigue test
3.3
parallel length
length of the parallel portion of a test specimen with a reduced sectional area
3.4
strain rate
increase in strain of the parallel portion per unit time as calculated from the displacement rate of crosshead
(3.1) and parallel length (3.3) of a test specimen

3.5
yield strength
stress at which plastic deformation occurs without any increase in force during the test when the metallic
material exhibits a yield phenomenon
Note 1 to entry: Yield strength in this document means the yield point or 0,2 % proof stress. The proof stress is usually
used for austenitic stainless steel which rarely exhibits a clear-cut yield point.
4 Hydrogen compatibility assessment
Hydrogen embrittlement occurs when hydrogen has entered a material after (or simultaneously) exposure
to externally applied stress. There are two types of hydrogen sources: hydrogen gas and corrosion. In a
high-pressure hydrogen gas environment, atomic hydrogen generated by the dissociation of hydrogen gas
enters the material. Gaseous hydrogen embrittlement occurs when a material is concurrently exposed to
stress and gaseous hydrogen, such as in pressured hydrogen systems. The primary difference between
these environments lies in the hydrogen boundary condition; however, in all cases, hydrogen interacts with
the material under the influence of stress.
In general, hydrogen embrittlement in high-pressure hydrogen involves several steps. Gaseous hydrogen
molecules are adsorbed onto the surface of the metal and dissociate into atomic hydrogen. The atomic
hydrogen is then absorbed into the material and diffuses inside the metal. Atomic hydrogen interacts with
inherent defects and stress fields in metals. Although the detailed mechanism is still under discussion,
hydrogen affects mechanical properties, accelerates the propagation of fatigue cracks, and reduces
fracture toughness. The fatigue crack growth rate (3.2) can increase by 10 to 100 times in high-pressure
gaseous hydrogen, and the fracture toughness may decline. For low-alloy steels, the fracture toughness of
high-strength materials is reduced in a high-pressure hydrogen environment. In particular, the fracture
[1]
toughness of materials decreases significantly above TS:915MPa. The degree of embrittlement depends
on the material as well as environmental and mechanical variables that affect hydrogen uptake (adsorption,
absorption, and diffusion), hydrogen distribution in the material, and sensitivity to hydrogen-defect
interactions.
Important material variables are tensile strength, chemical composition, and microstructure, but other
variables may also be important. In particular, high-strength, low-alloy steels tend to be very sensitive
to hydrogen embrittlement when their tensile strength exceeds a certain value. On the other hand, in the
case of austenitic stainless steels, the martensitic transformation induced by deformation has a significant
impact on hydrogen embrittlement sensitivity; therefore, the chemical composition, which determines the
stability of microstructure, is a major factor.
Environmental parameters that affect hydrogen-assisted fatigue and failure include hydrogen pressure,
temperature, and gas impurities. In general, hydrogen embrittlement sensitivity increases with increasing
hydrogen pressure. This is because the amount of hydrogen entering the material is proportional to the
square root of the pressure. Research is underway on the effects of temperature. For example, it is known
that in austenitic stainless steel, the impact of hydrogen becomes significant at -40 °C. Additionally, impurity
gases contained in the hydrogen gas may also affect the sensitivity to hydrogen embrittlement.
Stress is a necessary factor in the hydrogen embrittlement phenomenon, and not only the magnitude of the
stress applied, but also the speed at which the load is applied is important. In general, metals are affected
-5
by strain rate (3.4), and that is why SSRT tests are carried out at the slow strain rate (3.4) of 5,0 x 10 /sec to
investigate the effect of hydrogen. In fatigue, metals are less susceptible to hydrogen-assisted fatigue at high
frequencies.
For the evaluation of hydrogen compatibility of metallic materials under high-pressure hydrogen
[2],[3]
environments, the SSRT test, fatigue test, and fatigue crack propagation test are generally employed.
[4]
The SSRT test in hydrogen is standardized as ASTM G142-98, and tests are conducted under the conditions
provided by the test methods for high-pressure hydrogen vessel materials. Hydrogen compatibility is
evaluated by comparing the strength and ductility in hydrogen and in the atmosphere.
Regarding the fatigue crack propagation test, it is known that the propagation rate of a fatigue crack is
accelerated in high-pressure hydrogen. Depending on the material and conditions, hydrogen can accelerate
the rate of fatigue crack propagation by more than 10 times up to 100 times compared to that in the

atmosphere. As an evaluation method, the effect of hydrogen has been measured by the fatigue crack
propagation rate between hydrogen and the atmosphere.
Regarding fatigue life tests, it is common to use a smooth test specimen and determine hydrogen
compatibility by comparing the test data in the high-cycle region in hydrogen and in the atmosphere.
5 Test method
5.1 SSRT test
Compatibility is determined by material strength and ductility. A steel, which retains sufficiently high
strength, elongation, and reduction of area in high-pressure hydrogen under the service condition in
comparison to those under atmospheric conditions, as determined by the SSRT test, can be deemed hydrogen
compatible. An SSRT test is performed in high-pressure hydrogen and atmospheric environments (air or
inert gases). The test specimens employed in SSRT testing are smooth specimens described in ASTM G142 or
[5]
ASTM E8 as shown in Figure 1. The specimen diameter is between 4 mm and 8 mm, in principle. Specimens
have been processed with a minimum involvement of cold working, and their surface finish conforms to the
finishing method described in ASTM G142. Before the start of testing, it is verified visually or using a x20
magnifying glass that the specimens have no working scars in their circumferential direction. The purity of
[6]
the hydrogen gas used is consistent with CGA G-5.3 grade L or of greater purity. The purity requirements
for CGA G-5.3 grade L are shown in Table 1. The test temperature is in accordance with the actual usage
-5
environment. The strain rate (3.4) does not exceed the 7,0 x 10 /sec given in ASTM G142.
Key
A length of reduced section min.
D diameter
G gage length
R radius of fillet min.
Figure 1 — Shape of SSRT test specimen
Table 1 — Purity requirements for CGA G-5.3 grade L
(ppm)
Hydrogen CO +CO N O Total hydrocarbon content Water
2 2 2
(as methane)
(min.%)
99,999 2 2 1 1 3,5
5.2 Fatigue crack growth test
The fatigue crack growth test is performed in high-pressure hydrogen and atmospheric (air or inert gases)
[7]
environments. The fatigue crack growth test method is in accordance with ASTM E647 as shown in
Figure 2. The frequency of stress is equal to or less than 1 Hz in the hydrogen environment. The purity of the
hydrogen gas used is consistent with CGA G-5.3 grade L or of greater purity.

Key
W W
A recommended thickness: ≤≤B
20 4
B suggested Min. dimensions: W2 5mm(1.0in) a = 02, 0 W
n
Figure 2 — Example of crack growth rate test specimen
5.3 Fatigue test
The fatigue test is performed in high pressure hydrogen and atmospheric (air or inert gases) environments.
[8]
Test specimens are smooth and round tension specimens in conformance to ASTM E466 with the diameter
in section L (see Figure 3 below) being equal to or more than 5 mm, and have been processed with a minimum
involvement of cold working in accordance with the processing method described in ASTM E466, Appendix
XI. Before the start of testing, it is verified visually or using a x20 magnifying glass that the specimens have
no processing scars in their circumferential direction. The frequency of stress is equal to or less than 1 Hz
6 6
during 0 to 10 cycles and equal to or less than 10 Hz exceeding 10 cycles. The purity of the hydrogen gas
used is consistent with CGA G-5.3 grade L or of greater purity.
Key
D diameter
L length
R radius of fillet
Figure 3 — Example of fatigue life specimen

6 Materials test data
6.1 Low alloy steel
6.1.1 Cr-Mo steel (JIS SCM435)
6.1.1.1 Materials
The chemical composition and mechanical properties of SCM435 materials used in this test are shown in
Table 2 and Table 3. Heat J and K were used for the SSRT test, the fatigue crack growth test and the fatigue
test and heat T was used for the SSRT test and the fatigue crack growth test.
Table 2 — Chemical composition of material used
(mass%)
Heat C Si Mn P S Cr Mo
J 0,36 0,18 0,78 0,013 0,005 1,04 0,20
K 0,37 0,22 0,84 0,012 0,005 1,15 0,24
T 0,37 0,21 0,77 0,012 0,007 1,07 0,28
Table 3 — Mechanical Properties of material used
Heat 0,2 % proof stress Tensile strength Elongation
(MPa)
(MPa) (%)
J 681 838 23
K 683 820 22
T 780 943 17
6.1.1.2 SSRT test conditions
SSRT test conditions and the test specimen are shown in Table 4 and Figure 4.
Table 4 — SSRT test conditions
-3
Actuator speed 1,5×10 mm/sec
Environment 106 MPa or115 MPa H : -45 °C, RT, 120 °C
115 MPa N2: -40 °C. RT, 120 °C
Gas purity Hydrogen gas: 99,999 % (5 N)

Dimensions in mm
Figure 4 — Dimensions of SSRT test specimen

SSRT test data are shown in Figures 4 to 10. There is no significant difference in yield strength (3.5)
between the hydrogen environment and the atmospheric environment. The specimens of material J and K
in the hydrogen environment did not break before reaching the maximum load point of the SSRT test in
atmospheric environment, but the specimen of material T whose tensile strength is 943 MPa broke before
reaching the maximum load point in the hydrogen environment at -45 °C and at room temperature.
(a-1) -45 °C, 106 MPa H (a-2) RT, 115 MPa H
2 2
(a-3) 120 °C, 115 MPa H
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat J(600 °C T) in 106 MPa hydrogen gas at -45 °C
2 large-sized, SCM435, heat J(600 °C T) in 115 MPa hydrogen gas at RT
3 large-sized, SCM435, heat J(600 °C T) in 115 MPa hydrogen gas at 120 °C
Figure 5 — SSRT test data of SCM435 steel material J in H environment
(a-1) -45 °C, 0,1 MPa N (a-2) RT, air
(a-3) 120 °C, air
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat J(600 °C T) in 1,0 MPa nitrogen gas at -45 °C
2 large-sized, SCM435, heat J(600 °C T) in air at RT
3 large-sized, SCM435, heat J(600 °C T) in air at 120 °C
Figure 6 — SSRT test data of SCM435 steel material J in air or N environment
(b-1) -40 °C, 115 MPa H (b-2) RT, 115 MPa H
2 2
(b-3) 120 °C, 115 MPa H
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat K(630 °C T) in 115 MPa hydrogen gas at -40 °C
2 large-sized, SCM435, heat K(630 °C T) in 115 MPa hydrogen gas at RT
3 large-sized, SCM435, heat K(630 °C T) in 115 MPa hydrogen gas at 120 °C
Figure 7 — SSRT test data of SCM435 steel material K material in H environment
(b-1) -40 °C, 0,1 MPa N (b-2) RT, air
(b-3) 120 °C, air
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat K(630 °C T) in 0,1 MPa nitrogen gas at -40 °C
2 large-sized, SCM435, heat K(630 °C T) in air at RT
3 large-sized, SCM435, heat K(630 °C T) in air at 120 °C
Figure 8 — SSRT test data of SCM435 steel material K in air or N environment
(c-1) -45 °C, 106 MPa H (c-2) RT, 115 MPa H
2 2
(c-3) 120 °C, 115 MPa H
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat T(560 °C T) in 106 MPa hydrogen gas at -45 °C
2 large-sized, SCM435, heat T(560 °C T) in 115 MPa hydrogen gas at RT
3 large-sized, SCM435, heat T(560 °C T) in 115 MPa hydrogen gas at 120 °C
Figure 9 — SSRT test data of SCM435 steel material T in H environment
(c-1) -40 °C, 0,1 MPa N (c-2) RT, air
(c-3) 120 °C, air
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat T(560 °C T) in 0,1 MPa nitrogen gas at -45 °C
2 large-sized, SCM435, heat T(560 °C T) in air at RT
3 large-sized, SCM435, heat T(560 °C T) in air at 120 °C
Figure 10 — SSRT test data of SCM435 steel material T in air or N environment
6.1.1.3 Fatigue crack growth rate test
Fatigue crack growth rate (3.2) test conditions and the test specimen are shown in Table 5 and Figure 11.
These tests were performed on a single specimen both in hydrogen and in the atmosphere.
Table 5 — Fatigue test conditions
Type of test Uniaxial, Sinusoidal (R=0,1)
Frequency 0,001-20 Hz
Environment 10-115 MPa H : RT,
Laboratory air: RT
Gas purity Hydrogen gas: 99,999 % (5 N)

Dimensions in mm
Figure 11 — Dimensions of fatigue crack growth rate test specimen
Fatigue crack growth rate (3.2) test data are shown in Figures 12 to 14. The fatigue crack growth rate (3.2) of
material T, which has a tensile strength of 943 MPa, was higher than those of other materials.
Key
1/2
X stress intensity factor range, K()MPam
Y crack growth rate, da/dN (m/cycle)
∆P constant
∆K increasing
115 MPa hydrogen gas
air
1 large-sized, SCM435, heat J R=0,1
Figure 12 — Fatigue crack growth curve of SCM435 steel material J

Key
1/2
X stress intensity factor range, K()MPam
Y crack growth rate, da/dN (m/cycle)
∆P constant
∆K increasing
115 MPa hydrogen gas
45 MPa hydrogen gas
10 MPa hydrogen gas
air
1 large-sized, SCM435, heat K R=0,1
Figure 13 — Fatigue crack growth curve of SCM435 steel material K
(c-1) dda/ N versus∆K
Key
1/2
X stress intensity factor range, K()MPam
Y crack growth rate, da/dN (m/cycle)
∆P constant
∆K increasing
90 MPa hydrogen gas
air
1 large-sized, SCM435, heat T R=0,1
Figure 14 — Fatigue crack growth curve of SCM435 steel material T
6.1.1.4 Fatigue test
Fatigue test conditions are shown in Table 6 and Figure 15.
Table 6 — Fatigue test conditions
Type of test Uniaxial
Loading condition Constant stress amplitude test under zero mean stress (R=-1)
Waveform Sinusoidal
Frequency 0,01 – 1 Hz
Environment 115 MPa H : RT,
Laboratory air: RT,
Gas purity Hydrogen gas: 99,999 % (5 N)

Dimensions in mm
Figure 15 — Dimensions of fatigue test specimen
Fatigue test data are shown
...

First edition
ISO/TC 197
Secretariat: SCC
Date: 2026-02-13
Gaseous hydrogen — Pressure vessels for stationary storage - —
Part 2:
Material test data of class A materials (steels and aluminum alloys)
compatible withto hydrogen service for cylinders and tubes for
stationary storage
Hydrogène gazeux — Données d’essai des matériaux de classe A (aciers et alliages d’aluminium) compatibles
avec l’hydrogène pour bouteilles et tubes de stockage fixe

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Fax: + 41 22 749 09 47
E-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2025 – All rights reserved

Contents
Introduction . vii
1 Scope . 1
2 Terms and definitions . 1
3 Hydrogen compatibility assessment . 2
4 Test method . 3
4.1 SSRT test . 3
4.2 Fatigue crack growth test . 4
4.3 Fatigue test . 5
5 Materials test data . 5
5.1 Low alloy steel . 5
5.1.1 Cr-Mo steel (JIS SCM435) . 5
5.1.2 Ni-Cr-Mo steel (JIS SNCM439) . 17
5.2 Austenitic stainless steel . 28
5.2.1 SUS316L stainless steel . 28
5.2.2 SUH660(SA638) stainless steel . 36
5.3 Aluminum alloy . 43
5.3.1 Materials . 43
5.3.2 SSRT test . 43
5.3.3 Fatigue crack growth test . 45
5.3.4 Fatigue test . 47
5.3.5 Reference . 48

Foreword . vii
Introduction . viii
1 Scope . 1
2 Terms and definitions . 1
3 Terms and definitions . 1
4 Hydrogen compatibility assessment . 2
5 Test method. 3
6 Materials test data . 6
Bibliography . 91

iv © ISO 2025 – All rights reserved

FIGURE 1 — SHAPE OF SSRT TEST SPECIMEN 4
FIGURE 2—EXAMPLE OF CRACK GROWTH RATE TEST SPECIMEN 4
FIGURE 3 — EXAMPLE OF FATIGUE LIFE SPECIMEN 5
FIGURE 4 — DIMENSIONS OF SSRT TEST SPECIMEN (UNIT: MM) 6
FIGURE 5 — SSRT TEST DATA OF SCM435 STEEL MATERIAL J IN H2 ENVIRONMENT 7
FIGURE 6 — SSRT TEST DATA OF SCM435 STEEL MATERIAL J IN AIR OR N2 ENVIRONMENT 8
FIGURE 7— SSRT TEST DATA OF SCM435 STEEL MATERIAL K MATERIAL IN H2 ENVIRONMENT 9
FIGURE 8 — SSRT TEST DATA OF SCM435 STEEL MATERIAL K IN AIR OR N2 ENVIRONMENT 10
FIGURE 9 — SSRT TEST DATA OF SCM435 STEEL MATERIAL T IN H ENVIRONMENT 11
FIGURE 10 — SSRT TEST DATA OF SCM435 STEEL MATERIAL T IN AIR OR N ENVIRONMENT 12
FIGURE 11 — DIMENSIONS OF FATIGUE CRACK GROWTH RATE TEST SPECIMEN (UNIT: MM) 13
FIGURE 12 — FATIGUE CRACK GROWTH CURVE OF SCM435 STEEL MATERIAL J 14
FIGURE 13 — FATIGUE CRACK GROWTH CURVE OF SCM435 STEEL MATERIAL K 14
FIGURE 14 — FATIGUE CRACK GROWTH CURVE OF SCM435 STEEL MATERIAL T 15
FIGURE 15 — DIMENSIONS OF FATIGUE TEST SPECIMEN (UNIT: MM) 15
FIGURE 16 — S-N DIAGRAM OF SCM435 STEEL MATERIAL J IN AIR AND 115 MPA HYDROGEN GAS AT RT 16
FIGURE 17 — S-N DIAGRAM OF SCM435 STEEL MATERIAL K IN AIR AND 115 MPA HYDROGEN GAS AT RT 16
FIGURE 18 — DIMENSIONS OF SSRT TEST SPECIMEN (UNIT: MM) 17
FIGURE 19 — SSRT TEST DATA OF SNCN439 STEEL MATERIAL L IN H ENVIRONMENT 18
FIGURE 20 — SSRT TEST DATA OF SNCN439 STEEL MATERIAL L IN AIR OR N ENVIRONMENT 19
FIGURE 21 — SSRT TEST DATA OF SNCN439 STEEL MATERIAL E IN H ENVIRONMENT 20
FIGURE 22 — SSRT TEST DATA OF SNCN439 STEEL MATERIAL E IN AIR OR N2 ENVIRONMEN 21
FIGURE 23 — SSRT TEST DATA OF SNCN439 STEEL MATERIAL R IN H2 ENVIRONMENT 22
FIGURE 24 — SSRT TEST DATA OF SNCN439 STEEL MATERIAL R IN AIR OR N2 ENVIRONMENT 23
FIGURE 25 — DIMENSIONS OF FATIGUE TEST SPECIMEN (UNIT: MM) 24
FIGURE 26 — FATIGUE CRACK GROWTH CURVE OF SNCM439 STEEL MATERIAL L 25
FIGURE 27 — FATIGUE CRACK GROWTH CURVE OF SNCM439 STEEL MATERIAL E 25
FIGURE 28 — FATIGUE CRACK GROWTH CURVE OF SNCM439 STEEL MATERIAL R 26
FIGURE 29 — DIMENSION OF FATIGUE TEST SPECIMEN (UNIT: MM) 26
FIGURE 30 — S-N DIAGRAM OF SNCM439 STEEL MATERIAL C IN AIR AND IN 115 MPA HYDROGEN GAS AT
RT 27
FIGURE 31 — S-N DIAGRAM OF SNCM439 STEEL MATERIAL H IN AIR AND IN 115 MPA HYDROGEN GAS AT
RT 27
FIGURE 32 — DIMENSIONS OF SSRT TEST SPECIMEN (UNIT: MM) 29
FIGURE 33 — SSRT TEST DATA OF SUS316L STAINLESS STEEL MATERIAL M IN H2 ENVIRONMENT 29
FIGURE 34 — SSRT TEST DATA OF SUS316L STAINLESS STEEL MATERIAL M IN AIR OR N ENVIRONMENT
FIGURE 35 — SSRT TEST DATA OF SUS316L STAINLESS STEEL MATERIAL P IN H ENVIRONMENT 31
FIGURE 36 — SSRT TEST DATA OF SUS316L STAINLESS STEEL MATERIAL P IN AIR OR N ENVIRONMENT 32
FIGURE 37 — DIMENSIONS OF FATIGUE TEST SPECIMEN (UNIT: MM) 33
FIGURE 38 — FATIGUE CRACK GROWTH CURVE OF SUS316L STAINLESS STEEL MATERIAL C 34
FIGURE 39 — DIMENSION OF FATIGUE TEST SPECIMEN (UNIT: MM) 34
FIGURE 40 — S-N DIAGRAM OF SUS316L STAINLESS STEEL MATERIAL M IN AIR AND HYDROGEN GAS AT -
45℃ 35
FIGURE 41 — S-N DIAGRAM OF SUS316L STAINLESS STEEL MATERIAL M IN AIR AND HYDROGEN GAS AT
RT 35
FIGURE 42 — S-N DIAGRAM OF SUS316L STAINLESS STEEL MATERIAL P IN AIR AND HYDROGEN GAS AT RT
FIGURE 43 — DIMENSIONS OF SSRT TEST SPECIMEN FOR MATERIAL C (UNIT: MM) 37
FIGURE 44 — DIMENSIONS OF SSRT TEST SPECIMEN FOR MATERIAL E (UNIT: MM) 38
FIGURE 45 — SSRT TEST DATA OF SUH660(A286) STAINLESS STEEL MATERIAL C 38
FIGURE 46 — SSRT TEST DATA OF SUH660(A286) STAINLESS STEEL MATERIAL E 39
FIGURE 47 — DIMENSIONS OF FATIGUE TEST SPECIMEN (UNIT: MM) 40
FIGURE 48 — FATIGUE CRACK GROWTH CURVE OF SUH660(A286) STAINLESS STEEL MATERIAL C 41
FIGURE 49 — DIMENSION OF FATIGUE TEST SPECIMEN (UNIT: MM) 41
FIGURE 50 — S-N DIAGRAM OF SUH660(A286) IN AIR AND 115 MPA HYDROGEN GAS AT RT 42
FIGURE 51 — DIMENSIONS OF SSRT TEST SPECIMEN (UNIT: MM) 43
FIGURE 52 — SSRT TEST DATA OF A6061-T651 ALUMINUM ALLOY IN H2 ENVIRONMENT 44
FIGURE 53 — SSRT TEST DATA OF A6061-T651 ALUMINUM ALLOY IN N2 ENVIRONMENT 45
FIGURE 54 — DIMENSIONS OF FATIGUE TEST SPECIMEN (UNIT: MM) 46
FIGURE 55 — FATIGUE CRACK GROWTH CURVE OF A6061-T651 ALUMINUM ALLOY 47
FIGURE 56 — DIMENSION OF FATIGUE TEST SPECIMEN (UNIT: MM) 47
FIGURE 57 — S-N DIAGRAM OF A6061-T651 ALUMINIUM ALLOY 48

TABLE 1 PURITY REQUIREMENTS FOR CGA G-5.3 GRADE L 4
TABLE 2 CHEMICAL COMPOSITION OF MATERIAL USED 5
TABLE 3 MECHANICAL PROPERTIES OF MATERIAL USED 5
TABLE 4 SSRT TEST CONDITIONS 6
TABLE 5 FATIGUE TEST CONDITIONS 13
TABLE 6  FATIGUE TEST CONDITIONS 15
TABLE 7 CHEMICAL COMPOSITION OF MATERIAL 17
TABLE 8  MECHANICAL PROPERTIES OF MATERIAL 17
TABLE 9 SSRT TEST CONDITIONS 17
TABLE 10 FATIGUE CRACK GROWTH RATE TEST CONDITIONS 24
TABLE 11 FATIGUE TEST CONDITIONS 26
TABLE 12 CHEMICAL COMPOSITION OF MATERIAL USED 28
TABLE 13 MECHANICAL PROPERTIES OF MATERIAL USED 28
TABLE 14 SSRT TEST CONDITIONS 28
TABLE 15 FATIGUE TEST CONDITIONS 33
TABLE 16 FATIGUE TEST CONDITIONS 34
TABLE 17 CHEMICAL COMPOSITION OF MATERIAL USED 37
TABLE 18 MECHANICAL PROPERTIES OF MATERIAL USED 37
TABLE 19 SSRT TEST CONDITIONS 37
TABLE 20  FATIGUE CRACK GROWTH RATE TEST CONDITIONS 40
TABLE 21 FATIGUE TEST CONDITIONS 41
TABLE 22  CHEMICAL COMPOSITION OF MATERIAL USED 43
TABLE 23 MECHANICAL PROPERTIES 43
TABLE 24 SSRT TEST CONDITIONS 43
TABLE 25  FATIGUE TEST CONDITIONS 45
TABLE 26 FATIGUE TEST CONDITIONS 47

vi © ISO 2025 – All rights reserved

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 documentsdocument 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).
Field Code Changed
Attention is drawnISO draws attention to the possibility that some of the elementsimplementation
of this document may beinvolve the subjectuse of (a) patent(s). ISO takes no position concerning the
evidence, validity or applicability of any claimed patent rights. in respect thereof. As of the date of
publication of this document, ISO had not received notice of (a) patent(s) which may be required to
implement this document. However, implementers are cautioned that this may not represent the
latest information, which may be obtained from the patent database available at
www.iso.org/patents. 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 onof the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT)), see the
following URL: www.iso.org/iso/foreword.html.
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This document was prepared by Technical Committee [or Project Committee] ISO/TC 197, Hydrogen
technologies.
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.
Field Code Changed
Introduction
The proposed draft of ISO19884-1 allows the use of Class A materials listed in itsISO19884-1,
Annex B without cycle testing in hydrogen. In exchange, these materials require test data to
demonstrate they are sufficiently hydrogen-resistant in a high-pressure hydrogen environment. This
document provides evaluation test methods used for hydrogen compatibility assessment, along with
published test data.
This document does not provide rules or guidelines for material qualification, but instead presents a
collection of test data on a limited selection (not exhaustive) of materials. However, this allows
authorities and users to review the hydrogen compatibility assessment data of Class A materials,
assuring their performance in hydrogen.

This document presents currently available hydrogen compatibility test methods and test data
obtained from them, but it is not intended to hinder the advancement of new technologies that are
presently under development, in use in the market, or yet to emerge. As these new technologies
mature and their design and testing prove safety, they will be added in future revisions of this
International Standard. Since these emerging technologies are developing rapidly, ISO Technical
Committee 197 Hydrogen Technologies will monitor the technology trend to prepare for further
revision.
viii © ISO 2025 – All rights reserved

editions.
ix
Gaseous hydrogen — Pressure vessels for stationary storage —
Part 2:
Material test data of class A materials (steels and aluminum alloys)
compatible withto hydrogen service for cylinders and tubes for
stationary storage
1 Scope
This Technical Reportdocument provides hydrogen compatibility evaluation methods and test results of Class
A materials used for high-pressure hydrogen containers. ItThis document identifies the safety concerns of
materials, and in particular, hazards and risks caused by hydrogen embrittlement, and describes the metal
properties that are relevant to safety in hydrogen. Detailed safety requirements associated with specific
hydrogen applications are covered in separate International Standards.
2 Terms and definitions
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 terminologicalterminology databases for use in standardization at the following
addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
2.13.1
displacement rate of crosshead
displacement of a crosshead per unit time
2.23.2
2.3
fatigue crack growth rate
fatigue crack length that progresses with each repetition in a fatigue test
2.43.3
parallel length
length of the parallel portion of a test specimen with a reduced sectional area
2.53.4
strain rate
increased amount ofincrease in strain of the parallel portion per unit time as calculated from the displacement
rate of crosshead (2.1)3.1) and parallel length (2.3)3.3) of a test specimen
2.63.5
yield strength
stress at which plastic deformation occurs without any increase in force during the test when the metallic
material exhibits a yield phenomenon
Note 1 to entry 1: : Yield strength in this Technical Reportdocument means the yield point or 0.,2 % proof stress. The proof
stress is usually used for austenitic stainless steel which rarely exhibits a clear-cut yield point.

34 Hydrogen compatibility assessment
Hydrogen embrittlement occurs when hydrogen has entered a material after (or simultaneously) exposure to
externally applied stress. There are two types of hydrogen sources: hydrogen gas and corrosion. In a high-
pressure hydrogen gas environment, atomic hydrogen generated by the dissociation of hydrogen gas enters
the material. Gaseous hydrogen embrittlement occurs when a material is concurrently exposed to stress and
gaseous hydrogen, such as in pressured hydrogen systems. The primary difference between these
environments lies in the hydrogen boundary condition; however, in all cases, hydrogen interacts with the
material under the influence of stress.
In general, hydrogen embrittlement in high-pressure hydrogen involves several steps. Gaseous hydrogen
molecules are adsorbed onto the surface of the metal and dissociate into atomic hydrogen. The atomic
hydrogen is then absorbed into the material and diffuses inside the metal. Atomic hydrogen interacts with
inherent defects and stress fields in metals. Although the detailed mechanism is still under discussion,
hydrogen affects mechanical properties, accelerates the propagation of fatigue cracks, and reduces fracture
toughness. The fatigue crack growth rate (2.2)(3.2) can increase by 10 to 100 times in high-pressure gaseous
hydrogen, and the fracture toughness may decline. For low-alloy steels, the fracture toughness of high-
strength materials is reduced in a high-pressure hydrogen environment. In particular, the fracture toughness
of materials decreases significantly above TS:915MPa. (1).[1] The degree of embrittlement depends on the
material as well as environmental and mechanical variables that affect hydrogen uptake (adsorption,
absorption, and diffusion), hydrogen distribution in the material, and sensitivity to hydrogen-defect
interactions.
Important material variables are tensile strength, chemical composition, and microstructure, but other
variables may also be important. In particular, high-strength, low-alloy steels tend to be very sensitive to
hydrogen embrittlement when their tensile strength exceeds a certain value. On the other hand, in the case of
austenitic stainless steels, the martensitic transformation induced by deformation has a significant impact on
hydrogen embrittlement sensitivity; therefore, the chemical composition, which determines the stability of
microstructure, is a major factor.
Environmental parameters that affect hydrogen-assisted fatigue and failure include hydrogen pressure,
temperature, and gas impurities. In general, hydrogen embrittlement sensitivity increases with increasing
hydrogen pressure. This is because the amount of hydrogen entering the material is proportional to the square
root of the pressure. Research is underway on the effects of temperature. For example, it is known that in
austenitic stainless steel, the impact of hydrogen becomes significant at -40 °C. Additionally, impurity gases
contained in the hydrogen gas may also affect the sensitivity to hydrogen embrittlement.
Stress is a necessary factor in the hydrogen embrittlement phenomenon, and not only the magnitude of the
stress applied, but also the speed at which the load is applied is important. In general, metals are affected by
-5
strain rate (2.43.4), and that is why SSRT tests are carried out at the slow strain rate (2.43.4) of 5.,0 x 10 /sec
to investigate the effect of hydrogen. In fatigue, metals are less susceptible to hydrogen-assisted fatigue at high
frequencies.
For the evaluation of hydrogen compatibility of metallic materials under high-pressure hydrogen
environments, the SSRT test, fatigue test, and fatigue crack propagation test are generally employed
,
(2,3).[2] [3] The SSRT test in hydrogen is standardized as ASTM G142-98(4),,[4] and tests are conducted
under the conditions provided by the test methods for high-pressure hydrogen vessel materials. Hydrogen
compatibility is evaluated by comparing the strength and ductility in hydrogen and in the atmosphere.
2 © ISO 20252026 – All rights reserved
Regarding the fatigue crack propagation test, it is known that the propagation rate of a fatigue crack is
accelerated in high-pressure hydrogen. Depending on the material and conditions, hydrogen can accelerate
the rate of fatigue crack propagation by more than 10 times up to 100 times compared to that in the
atmosphere. As an evaluation method, the effect of hydrogen has been measured by the fatigue crack
propagation rate between hydrogen and the atmosphere.
Regarding fatigue life tests, it is common to use a smooth test specimen and determine hydrogen compatibility
by comparing the test data in the high-cycle region in hydrogen and in the atmosphere.
45 Test method
4.15.1 SSRT test
Compatibility is determined by material strength and ductility. A steel, which retains sufficiently high strength,
elongation, and reduction of area in high-pressure hydrogen under the service condition in comparison to
those under atmospheric conditions, as determined by the SSRT test, can be deemed hydrogen compatible. An
SSRT test is performed in high-pressure hydrogen and atmospheric environments (air or inert gases). The test
specimens employed in SSRT testing are smooth specimens described in ASTM G142 or ASTM E8 (5)[5] as
shown in Figure 1.0. The specimen diameter is between 4 mm and 8 mm, in principle. Specimens have been
processed with a minimum involvement of cold working, and their surface finish conforms to the finishing
method described in ASTM G142. Before the start of testing, it is verified visually or using a x20 magnifying
glass that the specimens have no working scars in their circumferential direction. The purity of the hydrogen
gas used is consistent with CGA G-5.3 grade L (6)[6] or of greater purity. The purity requirements for CGA G-
5.3 grade L are shown in Table 1.0. The test temperature is in accordance with the actual usage environment.
-5
The strain rate (2.43.4) does not exceed the 7.,0 x 10 /sec given in ASTM G142.
given in ASTM G142, as expressed by the following equation:
Strain rate (2.4) = (displacement rate of crosshead((2.1)/ (parallel length (2.3))

Key
A: Length of reduced section min.

Key
A length of reduced section min.
D: Diameter diameter
G: Gage gage length
R: Radius radius of fillet min.

Figure 1 1 — Shape of SSRT test specimen

Table 1 1 — Purity requirements for CGA G-5.3 grade L
(ppm)
Hydrogen CO +CO N O Total hydrocarbon content Water
2 2 2
(as methane)
(min.%)
99.,999 2 2 1 1 3.,5
4.25.2 4.2 Fatigue crack growth test
The fatigue crack growth test is performed in high-pressure hydrogen and atmospheric (air or inert gases)
environments. The fatigue crack growth test method is in accordance with ASTM E647(7)[7] as shown in
Figure 2.0. The frequency of stress is equal to or less than 1 Hz in the hydrogen environment. The purity of
the hydrogen gas used is consistent with CGA G-5.3 grade L or of greater purity.

4 © ISO 20252026 – All rights reserved
Key
W W
A recommended thickness: ≤ B≤
20 4
B suggested Min. dimensions: W≃ 25 mm (1.0 in) a =0,20 W
n
Figure 2— 2 — Example of crack growth rate test specimen

4.35.3 4.3 Fatigue test
The fatigue test is performed in high pressure hydrogen and atmospheric (air or inert gases) environments.
Test specimens are smooth and round tension specimens in conformance to ASTM E466(8)[8] with the
diameter in section L (see Figure 30 below) being equal to or more than 5 mm, and have been processed with
a minimum involvement of cold working in accordance with the processing method described in ASTM E466,
Appendix XI. Before the start of testing, it is verified visually or using a x20 magnifying glass that the
specimens have no processing scars in their circumferential direction. The frequency of stress is equal to or
6 6
less than 1Hz1 Hz during 0 to 10 cycles and equal to or less than 10 Hz exceeding 10 cycles. The purity of
the hydrogen gas used is consistent with CGA G-5.3 grade L or of greater purity.

Key
D: Diameter diameter
L: Length length
R: Radius radius of fillet
Figure 3 3 — Example of fatigue life specimen

56 Materials test data
5.16.1 Low alloy steel
5.1.16.1.1 Cr-Mo steel (JIS SCM435)
5.1.1.11.1.1.1 Materials
6.1.1.1 Materials
The chemical composition and mechanical properties of SCM435 materials used in this test are shown in Table
2 and Table 3.0 and 0. Heat J and K were used for the SSRT test, the fatigue crack growth test and the fatigue
test and heat T was used for the SSRT test and the fatigue crack growth test.

Table 2 2 — Chemical composition of material used
(mass%)
Heat C Si Mn P S Cr Mo
J 0.,36 0.,18 0.,78 0.,013 0.,005 1.,04 0.,20
K 0.,37 0.,22 0.,84 0.,012 0.,005 1.,15 0.,24
T 0.,37 0.,21 0.,77 0.,012 0.,007 1.,07 0.,28

Table 3 3 — Mechanical Properties of material used
Heat 0.,2 % proof stress Tensile strength Elongation
(MPa)
(MPa) (%)
J 681 838 23
K 683 820 22
T 780 943 17
5.1.1.26.1.1.2 SSRT test conditions
SSRT test conditions and the test specimen are shown below.in 0 and 0.
Table 4 4 — SSRT test conditions
-3
Actuator speed 1.,5×10 mm/sec
o o
Environment 106 MPa or115MPaor115 MPa H2: -45 C °C, RT, 120 C °C
o o
115MPa115 MPa N2: -40 C40 °C. RT, 120 C °C
Gas purity Hydrogen gas: 99.,999% (5N % (5 N)
6 © ISO 20252026 – All rights reserved
Dimensions in mm
Figure 4 4 — Dimensions of SSRT test specimen (unit: mm)

SSRT test data are shown below.in 0 to 0. There is no significant difference in yield strength (2.53.5) between
the hydrogen environment and the atmospheric environment. The specimens of material J and K in the
hydrogen environment did not break before reaching the maximum load point of the SSRT test in atmospheric
environment, but the specimen of material T whose tensile strength is 943MPa943 MPa broke before reaching
o
the maximum load point in the hydrogen environment at -45 C45 °C and at room temperature.

Figure 5 — SSRT test data of SCM435 steel material J in H environment
8 © ISO 20252026 – All rights reserved
Figure 6 — SSRT test data of SCM435 steel material J in air or N environment
Figure 7—SSRT test data of SCM435 steel material K material in H environment
10 © ISO 20252026 – All rights reserved
Figure 8 — SSRT test data of SCM435 steel material K in air or N environment
Figure 9 — SSRT test data of SCM435 steel material T in H environment
12 © ISO 20252026 – All rights reserved
Figure 10 — SSRT test data of SCM435 steel material T in air or N2 environment

5.1.1.3 Fatigue crack growth rate test

Fatigue crack growth rate (2.2) test conditions and the test specimen are shown below.
These tests were performed on a single specimen both in hydrogen and in the atmosphere.

Table 5 Fatigue test conditions
Uniaxial, Sinusoidal (R=0.1)
Type of test
Frequency(a-1) -45 °C, 106 MPa H 0.001-20 Hz(a-2) RT, 115 MPa H
2 2
10-115MPa H : RT,
Laboratory air: RT
Environment
Gas purity(a-3) 120 °C, 115 MPa H Hydrogen gas: 99.999% (5N)
14 © ISO 20252026 – All rights reserved
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat J(600 °C T) in 106 MPa hydrogen gas at -45 °C
2 large-sized, SCM435, heat J(600 °C T) in 115 MPa hydrogen gas at RT
3 large-sized, SCM435, heat J(600 °C T) in 115 MPa hydrogen gas at 120 °C
Figure 5 — SSRT test data of SCM435 steel material J in H environment
(a-1) -45 °C, 0,1 MPa N (a-2) RT, air
(a-3) 120 °C, air
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat J(600 °C T) in 1,0 MPa nitrogen gas at -45 °C
2 large-sized, SCM435, heat J(600 °C T) in air at RT
3 large-sized, SCM435, heat J(600 °C T) in air at 120 °C
Figure 6 — SSRT test data of SCM435 steel material J in air or N environment
(b-1) -40 °C, 115 MPa H2 (b-2) RT, 115 MPa H2

(b-3) 120 °C, 115 MPa H2
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat K(630 °C T) in 115 MPa hydrogen gas at -40 °C
2 large-sized, SCM435, heat K(630 °C T) in 115 MPa hydrogen gas at RT
3 large-sized, SCM435, heat K(630 °C T) in 115 MPa hydrogen gas at 120 °C
Figure 7 — SSRT test data of SCM435 steel material K material in H environment
16 © ISO 20252026 – All rights reserved
(b-1) -40 °C, 0,1 MPa N (b-2) RT, air
(b-3) 120 °C, air
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat K(630 °C T) in 0,1 MPa nitrogen gas at -40 °C
2 large-sized, SCM435, heat K(630 °C T) in air at RT
3 large-sized, SCM435, heat K(630 °C T) in air at 120 °C
Figure 8 — SSRT test data of SCM435 steel material K in air or N environment
(c-1) -45 °C, 106 MPa H (c-2) RT, 115 MPa H
2 2
(c-3) 120 °C, 115 MPa H2
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat T(560 °C T) in 106 MPa hydrogen gas at -45 °C
2 large-sized, SCM435, heat T(560 °C T) in 115 MPa hydrogen gas at RT
3 large-sized, SCM435, heat T(560 °C T) in 115 MPa hydrogen gas at 120 °C
Figure 9 — SSRT test data of SCM435 steel material T in H environment
18 © ISO 20252026 – All rights reserved
(c-1) -40 °C, 0,1 MPa N (c-2) RT, air
(c-3) 120 °C, air
Key
X stroke (mm)
Y nominal stress (MPa)
1 large-sized, SCM435, heat T(560 °C T) in 0,1 MPa nitrogen gas at -45 °C
2 large-sized, SCM435, heat T(560 °C T) in air at RT
3 large-sized, SCM435, heat T(560 °C T) in air at 120 °C
Figure 10 — SSRT test data of SCM435 steel material T in air or N environment
6.1.1.3 Fatigue crack growth rate test
Fatigue crack growth rate (3.2) test conditions and the test specimen are shown in 0 and 0. These tests were
performed on a single specimen both in hydrogen and in the atmosphere.
11 Table 5 — Fatigue test conditions
Type of test Uniaxial, Sinusoidal (R=0,1)
Frequency 0,001-20 Hz
Environment 10-115 MPa H : RT,
Laboratory air: RT
Gas purity Hydrogen gas: 99,999 % (5 N)

Dimensions in mm
Figure 11 — Dimensions of fatigue crack growth rate test specimen (unit: mm)

Fatigue crack growth rate (2.2)(3.2) test data are shown below. in 0 to 0. The fatigue crack growth rate
(2.2)(3.2) of material T, which has a tensile strength of 943MPa943 MPa, was higher than those of other
materials.
20 © ISO 20252026 – All rights reserved
Key
1/2
X stress intensity factor range, 𝛥𝐾(MPa⋅ m )
Y crack growth rate, da/dN (m/cycle)
𝛥𝑃 constant
𝛥𝐾 increasing
115 MPa hydrogen gas
air
1 large-sized, SCM435, heat J R=0,1
Figure 12 12 — Fatigue crack growth curve of SCM435 steel material J

Key
1/2
X stress intensity factor range, 𝛥𝐾(MPa⋅ m )
Y crack growth rate, da/dN (m/cycle)
𝛥𝑃 constant
𝛥𝐾 increasing
115 MPa hydrogen gas
45 MPa hydrogen gas
10 MPa hydrogen gas
air
1 large-sized, SCM435, heat K R=0,1
Figure 13 13 — Fatigue crack growth curve of SCM435 steel material K

22 © ISO 20252026 – All rights reserved
(c-1) d𝑎/d𝑁 versus 𝛥𝐾
Key
1/2
X stress intensity factor range, 𝛥𝐾(MPa⋅ m )
Y crack growth rate, da/dN (m/cycle)
𝛥𝑃 constant
𝛥𝐾 increasing
90 MPa hydrogen gas
air
1 large-sized, SCM435, heat T R=0,1
Figure 14 14 — Fatigue crack growth curve of SCM435 steel material T
5.1.1.46.1.1.4 Fatigue test
Fatigue test conditions are shown below.in 0 and 0.
Table 6  6 — Fatigue test conditions
Type of test Uniaxial
Loading condition Constant stress amplitude test under zero mean stress (R=-1)
Waveform Sinusoidal
Frequency 0.,01 – 1 Hz
Environment 115MPa115 MPa H : RT,
Laboratory air: RT,
Gas purity Hydrogen gas: 99.,999% (5N % (5 N)

Dimensions in mm
Figure 15 15 — Dimensions of fatigue test specimen (unit: mm)
Fatigue test data are shown below.in 0 and 0. There is no significant difference between the hydrogen and
atmospheric environments in high cycle region.

24 © ISO 20252026 – All rights reserved
Key
X number of cycles to failure, N
f
Y stress amplitude, 𝜎 (MPa)
a
in air, f = 1 Hz
in air, f = 0,5 Hz
in air, f = 0,2 Hz
in 115 MPa hydrogen, f = 1 Hz
in 115 MPa hydrogen, f = 0,5 Hz

in 115 MPa hydrogen, f = 0,2 Hz

1 large-sized, SCM435, heat J R=-1
Figure 16 16 — S-N diagram of SCM435 steel material J in air and 115 MPa hydrogen gas at RT

Key
X number of cycles to failure, Nf
Y stress amplitude, 𝜎 (MPa)
a
in air, f = 1 Hz
26 © ISO 20252026 – All rights reserved
in air, f = 0,1 Hz
in 115 MPa hydrogen, f = 1 Hz
in 115 MPa hydrogen, f = 0,1 Hz

in 115 MPa hydrogen, f = 0,01 Hz

1 large-sized, SCM435, heat K R=-1
Figure 17 17 — S-N diagram of SCM435 steel material K in air and 115 MPa hydrogen gas at RT
5.1.1.56.1.1.5 Reference
Hydrogenius Database No. C57
Database of slow-strain-rate test (SSRT) properties of JIS-SCM435 Low-Alloy Steel in 115-MPa-hydrogen gas
(2015)
Hydrogenius Database, No. B58
Database of long, fatigue crack-growth properties of JIS-SCM435 Chromium Molybdenum Steel in 115-MPa-
hydrogen gas (2015)
-
Hydrogenius Database and No. B60. [9] [11]
Database of fatigue strength properties of JIS-SCM435 Low-Alloy Steel in 115-MPa-hydrogen gas (2015)

5.1.26.1.2 Ni-Cr-Mo steel (JIS SNCM439)
5.1.2.16.1.2.1 Materials
The chemical composition and mechanical properties of SNCM439 materials used in this test are shown
below.in 0 and 0. Heat L, E and R were used for the SSRT test and the crack growth rate test, and heat C and H
were used for the fatigue test.
Table 7 7 — Chemical composition of material
(mass%)
Heat C Si Mn P S Ni Cr Mo
L 0.,39 0.,22 0.,80 0.,016 0.,002 1.,80 0.,84 0.,26
E 0.,42 0.,22 0.,82 0.,016 0.,002 1.,81 0.,86 0.,26
R 0.,39 0.,22 0.,82 0.,015 0.0024,0 1.,81 0.,85 0.,26
02 4
C 0.,42 0.,22 0.,82 0.,015 0.,002 1.,80 0.,85 0.,25
H 0.,39 0.,22 0.,79 0.,016 0.,002 1.,81 0.,84 0.,26

Table 8  8 — Mechanical properties of material
Heat 0.,2 % proof stress Tensile strength (MPa) Elongation
(MPa) (%)
L 755 875 21
E 739 860 25
R 748 870 22
C 738 867 22
H 746 873 23
5.1.2.26.1.2.2 SSRT test
SSRT test conditions are shown below.in 0 and 0.
Table 9 9 — SSRT test conditions
-3 -3
Actuator speed 1.,5×10 mm/sec, 2.,0×10 mm/sec
o o
Environment 0.,7 - 115MPa115 MPa H2: -40 C °C, RT, 120 C °C
Laboratory air: RT
o o
0.1MPa,1 MPa N2: -40 C °C, RT, 120 C °C
Gas purity Hydrogen gas: 99.,999% (5N % (5 N)

Dimensions in mm
Figure 18 18 — Dimensions of SSRT test specimen (unit: mm)
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SSRT test data are shown below.in 0 to 0. There is no significant difference in strength between hydrogen
environment and the atmospheric environment, and the specimens in the hydrogen environment did not
break before reaching the maximum load point of the SSRT test in the atmospheric environment.

Figure 19 — SSRT test data of SNCN439 steel material L in H environment
Figure 20 — SSRT test data of SNCN439 steel material L in air or N environment
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Figure 21 — SSRT test data of SNCN439 steel material E in H environment
Figure 22 — SSRT test data of SNCN439 steel material E in air or N environment
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Figure 23 — SSRT test data of SNCN439 steel material R in H environment
Figure 24 — SSRT test data of SNCN439 steel material R in air or N environment
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5.1.2.3 Fatigue crack growth rate test
Fatigue crack growth rate (2.2) test conditions and the test specimen are shown below.
These tests were performed on a single specimen both in hydrogen and in the atmosphere.

Table 10 Fatigue crack growth rate test conditions
Uniaxial, Sinusoidal (R=0.1)
Type of test
Frequencya) In 106 MPa hydrogen gas at -45 °C 1 Hzb) In 115 MPa hydrogen gas at RT
115MPa H : RT,
Laboratory air: RT
Environment
Gas purityc) In 115 MPa hydrogen gas at 200 °C Hydrogen gas: 99.999% (5N)

Key
X stroke (mm)
Y nominal stress (MPa)
1 SNCM439, heat L in 106 MPa hydrogen gas at -45 °C
2 SNCM439, heat L in 115 MPa hydrogen gas at RT
3 SNCM439, heat L in 115 MPa hydrogen gas at 200 °C
Figure 19 — SSRT test data of SNCN439 steel material L in H2 environment

a) In 0,1 MPa nitrogen gas at -45 °C b) In air at RT
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c) In air at 200 °C
Key
X stroke (mm)
Y nominal stress (MPa)
1 SNCM439, heat L in 0,1 MPa nitrogen gas at -45 °C
2 SNCM439, heat L in air at RT
3 SNCM439, heat L in air at 200 °C
Figure 20 — SSRT test data of SNCN439 steel material L in air or N environment
a) In 106 MPa hydrogen gas at -45 °C b) In 115 MPa hydrogen gas at RT
c) In 115 MPa hydrogen gas at 200 °C
Key
X stroke (mm)
Y nominal stress (MPa)
1 SNCM439, heat E in 106 MPa hydrogen gas at -45 °C
2 SNCM439, heat E in 115 MPa hydrogen gas at RT
3 SNCM439, heat E in 115 MPa hydrogen gas at 200 °C
Figure 21 — SSRT test data of SNCN439 steel material E in H environment
a) In 0,1 MPa nitrogen gas at -45 °C b) In air at RT
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c) In air at 200 °C
Key
X stroke (mm)
Y nominal stress (MPa)
1 SNCM439, heat E in 0,1 MPa nitrogen gas at -45 °C
2 SNCM439, heat E in air at RT
3 SNCM439, heat E in air at 200 °C
Figure 22 — SSRT test data of SNCN439 steel material E in air or N environment
a) In 106 MPa hydrogen gas at -45 °C b) In 115 MPa hydrogen gas at RT
c) In 115 MPa hydrogen gas at 200 °C
Key
X stroke (mm)
Y nominal stress (MPa)
1 SNCM439, heat R in 106 MPa hydrogen gas at -45 °C
2 SNCM439, heat R in 115 MPa hydrogen gas at RT
3 SNCM439, heat R in 115 MPa hydrogen gas at 200 °C
Figure 23 — SSRT test data of SNCN439 steel material R in H environment
a) In 0,1 MPa nitrogen gas at -45 °C b) In air at RT
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c) I
...