ISO 22500:2026

• Abstract:

  This document specifies a magnetic flux leakage (MFL) testing method and evaluation of results for in-use equipment made of ferromagnetic materials. This document is mainly applicable for the detection of volume defects such as corrosion and mechanical damage on the test surface and the opposite surface of plate and tubular structures. A coating with a maximum thickness of 6 mm is allowed on the test surface. This document applies to external MFL testing of in-use ferromagnetic seamless steel pipes and base metal of pressure vessel shells with an outer diameter of not less than 38 mm and a wall thickness of not more than 20 mm. This document is also applicable to MFL testing of base metal of pressure vessels and storage tank bottom plates with a wall thickness of not more than 20 mm.

• Status: Published
• Publication Date: 28-Jun-2026
• ICS: 77.040.20 - Non-destructive testing of metals
• Technical Committee: ISO/TC 135/SC 2 - Surface methods
• Drafting Committee: ISO/TC 135/SC 2 - Surface methods
• Current Stage: 6060 - International Standard published
• Start Date: 29-Jun-2026
• Due Date: 05-Sep-2026
• Completion Date: 29-Jun-2026

Overview

ISO 22500:2026 specifies requirements and procedures for magnetic flux leakage (MFL) testing to detect corrosion and mechanical defects in in-service equipment made from ferromagnetic materials, such as steel plates and steel pipes. As a critical standard for non-destructive testing (NDT), ISO 22500:2026 ensures safe and efficient evaluation of metal loss caused by corrosion or damage, aiding industries in reliable asset integrity management.

This document is particularly valuable for operators of pressure vessels, seamless steel pipes, and storage tanks, focusing on base metals with specific dimensional criteria. The standard also permits MFL testing through coatings up to 6 mm thick, making it suitable for real-world applications where protective coatings are present.

Key Topics

• Magnetic Flux Leakage Testing Method: Outlines principles, system components (magnetization device, sensors, scanning device), and performance criteria.
• Detection Capability: Supports identification of volumetric defects (such as corrosion and mechanical damage) on both accessible and opposite surfaces.
• Applicable Equipment: External testing of ferromagnetic seamless steel pipes and pressure vessel shells (outer diameter ≥ 38 mm, wall thickness ≤ 20 mm), and storage tank bottom plates (wall thickness ≤ 20 mm).
• Personnel Qualification: Test personnel must be certified and competent, following ISO 9712 requirements.
• Site and Testing Preparation: Describes preliminary information collection, site investigation, and removal of interfering materials like rust or debris.
• Testing Procedures: Specifies systematic approach to scanning, sensitivity checks, and adjustments for optimal accuracy.
• Data Evaluation: Provides guidance for interpreting test results, setting defect thresholds, and marking findings.
• Recommended Actions: Suggests follow-up inspections (visual, hammer, ultrasonic) based on MFL findings.
• Documentation: Details required structure and content of test instructions, test records, and test reports for traceability and repeatability.

Applications

Magnetic flux leakage testing according to ISO 22500:2026 is highly relevant for a variety of sectors relying on the integrity of steel infrastructure, including:

• Oil & Gas Pipelines: Routine inspection of pipelines for corrosion and mechanical damage, minimizing the risk of leaks and failures.
• Pressure Vessel Maintenance: Ensures the safe operation of vessels under pressure by detecting subsurface and surface defects before serious issues occur.
• Storage Tank Bottom Plates: Supports the evaluation of tank bottoms, critical for environmental protection and regulatory compliance.
• Chemical Processing Plants: Ongoing monitoring of process equipment where corrosion or wear poses operational risks.
• Power Generation: Inspection and maintenance planning for boilers and steam pipelines in power plants.

The method can be applied to both manually and automatically operated scanning systems, with adjustments for coated and uncoated surfaces. By implementing this standard, organizations can improve maintenance forecasting, extend asset service life, and comply with industry safety requirements.

Related Standards

ISO 22500:2026 refers to and aligns with several foundational and complementary standards in the field of non-destructive testing:

• ISO 9712: Non-destructive testing - Qualification and certification of NDT personnel
• ISO 12707: Non-destructive testing - Magnetic particle testing - Vocabulary
• ISO 12718: Non-destructive testing - Eddy current testing - Vocabulary
• ISO 16809: Non-destructive testing - Ultrasonic thickness determination

Other closely associated standards and guidelines:

• ASME BPVC Section V, Article 16 (Magnetic Flux Leakage Examination)
• SAC standards for atmospheric storage tanks and pressure equipment

By adhering to ISO 22500:2026, engineers and inspectors ensure high standards of reliability in corrosion detection and contribute to the overall safety and longevity of critical steel infrastructure.

International
Standard
ISO 22500
First edition
Non-destructive testing — Magnetic
2026-06
flux leakage testing — Corrosion
of steel plates and steel pipes of in-
service equipment
Essais non destructifs — Essai de fuite de flux magnétique —
Corrosion des plaques et tuyaux en acier des équipements en
service
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ISO copyright office
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Phone: [phone]
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General principles . 2
5 Qualification of test personnel . 3
6 Safety requirements. 3
7 Equipment . 4
7.1 MFL testing system .4
7.1.1 Overview .4
7.1.2 Magnetization device and probe .4
7.1.3 Channels .4
7.1.4 Scanning device .4
7.1.5 Signal display . .4
7.1.6 Maintenance .4
7.1.7 System verification . . .4
7.1.8 Functional check .4
7.2 Blocks .4
7.2.1 System verification block .4
7.2.2 Reference block . .5
7.2.3 Fabrication requirements.5
7.3 Shim .5
8 Testing procedure . 5
8.1 Preliminary information .5
8.2 Site investigation .5
8.3 Test conditions .5
8.4 Scanning mode .6
8.5 Testing system adjustment .6
8.5.1 General .6
8.5.2 Sensitivity check .6
8.6 Testing .6
9 Evaluation and recommended actions . 6
9.1 Evaluation of test data .6
9.2 Recommended further action of relevant indications .7
10 Documentation . 7
10.1 General .7
10.2 Test instructions .7
10.3 Test records .8
10.4 Test report .8
Annex A (Informative) Examples of reference blocks of MFL testing . 9
Bibliography .13

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing, Subcommittee SC
2, Surface methods.
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
Industrial applications of magnetic flux leakage (MFL) testing for steel pipelines, pressure vessels and
atmospheric storage tanks have been gaining wider usage alongside marked improvement of MFL testing
technologies. The effectiveness of any application of MFL testing depends upon proper and correct use of the
MFL testing instruments and test techniques.
There is currently a lack of relevant International Standards for MFL testing, and this document provides
requirements for the testing equipment, testing procedures and evaluation method of test results for MFL
testing for corrosion of steel plates and steel pipes of in-service equipment.

v
International Standard ISO 22500:2026(en)
Non-destructive testing — Magnetic flux leakage testing
— Corrosion of steel plates and steel pipes of in-service
equipment
1 Scope
This document specifies a magnetic flux leakage (MFL) testing method and evaluation of results for in-use
equipment made of ferromagnetic materials. This document is mainly applicable for the detection of volume
defects such as corrosion and mechanical damage on the test surface and the opposite surface of plate and
tubular structures. A coating with a maximum thickness of 6 mm is allowed on the test surface.
This document applies to external MFL testing of in-use ferromagnetic seamless steel pipes and base metal
of pressure vessel shells with an outer diameter of not less than 38 mm and a wall thickness of not more
than 20 mm. This document is also applicable to MFL testing of base metal of pressure vessels and storage
tank bottom plates with a wall thickness of not more than 20 mm.
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 9712, Non-destructive testing — Qualification and certification of NDT personnel
ISO 12707, Non-destructive testing — Magnetic particle testing — Vocabulary
ISO 12718, Non-destructive testing — Eddy current testing — Vocabulary
ISO 16809, Non-destructive testing — Ultrasonic thickness determination
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12707, ISO 12718 and the following
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
defect equivalent
value characterizing a defect, determined by analysis of signal features obtained during MFL testing
3.2
channel
combination of a magnetic field sensor and associated signal acquisition unit within a magnetic flux leakage
testing probe
Note 1 to entry: A probe can comprise multiple magnetic field sensors.

4 General principles
Figure 1 shows the basic principle of MFL testing method. The magnetizer excites magnetic field in the
ferromagnetic component. If any corrosion or mechanical damage exist on the component, magnetic flux
will leak out, and forms a leakage magnetic field near the surface. The leakage magnetic field can be detected
by the magnetic field sensors, (Hall elements or magnetoresistive elements are commonly used), which are
placed in the middle of the magnetizer. Intensity of the magnetic flux leakage field is related to the size
and depth of defects, therefore the features of defects on the component can be obtained by analysing the
leakage magnetic field signals. Figure 2 shows the typical MFL signals. Figure 2 a) and b) show the tangential-
component and normal-component of the MFL signals when a sensor scans along the x-axis direction as
shown in Figure 1, respectively.
Key
1 sensor
2 magnetizer
3 magnetic flux
4 test object
5 defect
Figure 1 — Schematic of MFL testing
a) Tangential component of MFL signal

b) Normal component of MFL signal
Key
D scan distance along the x-axis direction, expressed in millimetres
V output of sensor, expressed in Volts
Figure 2 — Typical MFL signals
5 Qualification of test personnel
It is assumed that MFL testing is performed by competent personnel. In order to ensure that this is the case,
personnel shall demonstrate understanding of the basics of electromagnetics by qualification in MT-FL in
accordance with ISO 9712 or equivalent.
6 Safety requirements
This document does not list all safety requirements for testing and further applicable safety and health
guidelines can exist.
If permanent magnets are used, protection measures shall be taken to avoid the impact of strong magnetism
on personal safety, equipment, instruments and environment during the transportation, storage and
handling of the magnetization device.
The basic safety requirements during testing are as follows:
a) The inspectors shall comply with the safety requirements of the site, wear protective work clothes and
relevant protective equipment as required;
b) Attention shall be paid to avoid personal injury and equipment damage caused by magnetic field suction
during handling and testing, due the risk of being pressed or flattened between the magnet and a steel
object;
c) Attention shall be paid to the influence of magnetic field on o
...