ISO 23225:2025

International
Standard
ISO 23225
First edition
Corrosion control engineering life
2025-07
cycle in nuclear power plants —
General requirements
Ingénierie du contrôle de la corrosion au cours du cycle de vie
dans les centrales nucléaires — Exigences générales
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Objectives . 2
6 Corrosion sources . 2
7 Materials . 2
8 Technology . 3
9 Design . 3
10 Development . 4
11 Manufacturing . 4
12 Transportation and storage . 5
13 Construction and installation . 5
14 Commissioning and acceptance . 5
15 Operation . 6
16 Testing and inspection . 6
17 Maintenance and repair . 7
18 Life extension and scrapping . 7
19 Documents and records . 7
20 Resource management . 8
20.1 General requirement .8
20.2 General requirement .8
20.3 General requirement .8
20.4 Materials .8
20.5 Procedures .8
20.6 Environment .8
21 Comprehensive assessment . 8
Annex A (informative) Schematic diagrams of the composition of the three main types of
nuclear power plant . 10
Bibliography .12

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys,
Subcommittee SC 1, Corrosion control engineering life cycle.
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International Standard ISO 23225:2025(en)
Corrosion control engineering life cycle in nuclear power
plants — General requirements
1 Scope
This document specifies the general requirements of corrosion control engineering life cycle in nuclear
power plants.
This document applies to the corrosion control engineering in nuclear power plants.
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 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
corrosion control engineering life cycle in nuclear power plants
entire process of identification of the corrosion sources in nuclear power plants to control of corrosion
behaviour
Note 1 to entry: The entire process refers to the systematic engineering of selecting corrosion control materials and
technologies, as well as the design, construction, inspection, assessment and maintenance.
3.2
direct corrosion source
various factors that cause corrosion in direct contact with materials, such as environmental mediums and
acid solutions, alkali solutions and salt solutions
3.3
indirect corrosion source
various factors that cause corrosion without direct contact with materials, such as environmental conditions
and mediums working conditions
4 Principle
This document defines the corrosion control activities conducted throughout the entire engineering life cycle
in nuclear power plants. It identifies all related elements including the objectives, corrosion sources, materials,
technology, development, design, manufacturing, transportation and storage, construction and installation,
commissioning and acceptance, operation, testing and inspection, maintenance and repair, life extension and
scrapping, documents and records, resource management and comprehensive assessment. The requirements
of those elements are specified in accordance with holistic, systematic, coordinated and optimized principles.
The purpose of the requirements is to achieve the objectives (see Clause 5) under the premise of ensuring
public health, lives and property safety, national security and ecological environment safety.

5 Objectives
The corrosion control activities specified in this document aim at controlling corrosion effectively during
the entire engineering life cycle in nuclear power plants, and achieving the optimum benefits of safety, cost-
effectiveness, long-term operation and environmental protection.
6 Corrosion sources
6.1 The corrosion sources of nuclear power plants are classified as follows:
— direct corrosion sources, such as light water, heavy water, liquid metal, helium, boric acid solution, steam,
seawater, fresh water, soil, acid solution, alkali solution and salt solution, waste liquid, atmosphere,
dissolved hydrogen, dissolved oxygen and humidity;
— indirect corrosion sources, such as pressure, temperature, flow rate, radiation, stress field,
microorganisms and their metabolites and other working conditions;
— environmental corrosion sources, such as stray current interference and dissimilar metal contact
resulting in galvanic corrosion current interference;
— corrosion sources generated during corrosion.
6.2 Systematic, comprehensive and accurate investigation and identification should be carried out on the
corrosion sources involved at all stages.
6.3 When identifying corrosion sources, the differences between different reactor types of nuclear power
plant should be taken into account (see Appendix A). This process should cover the normal operating and
accident conditions of equipment and facilities in nuclear power plants.
6.4 Check and recognition of corrosion sources in nuclear power plants should be carried out through the
appropriate procedures.
7 Materials
7.1 Corrosion control materials may include the following:
— metallic materials, such as zirconium alloys, nickel-based alloys, stainless steel, carbon steel, low-alloy
steel, cast iron, copper alloys, titanium alloys and aluminium alloys;
— non-metallic materials, such as rubber, glass fibre reinforced plastics, plastics and coatings;
— composite materials, such as steel-plastic composites.
7.2 Select materials that can resist the corrosion sources identified in Clause 6 to ensure they are
compatible with processes such as design, manufacturing and operation.
7.3 The selection of materials should take into account:
— corrosion resistance, physical properties (such as heat resistance and electrical conductivity), mechanical
properties (such as strength, hardness and plasticity) and processing performance (such as machining,
casting and welding) of the materials;
— the scientific nature, technicality, economy and green environmental protection of the materials;
— materials performance in similar project;

— materials used in irradiation areas have good anti-irradiation and decontamination properties, and
materials in contact with the reactor coolant should be limited elements that can easily lead to increased
radioactive activation.
7.4 Check and validation of the selected materials should be carried out through the appropriate
procedures.
8 Technology
8.1 Select corrosion control technologies that can resist the corrosion sources identified in Clause 6.
8.2 To control corrosion in nuclear power plants, the following may be applied:
— technologies to improve the environmental conditions, such as the addition of corrosion inhibitors and
alkalizers, pH regulation, demineralization, oxygen removal and dehumidification;
— technologies for cover layers providing corrosion protection, such as coating, rubber lining and other
non-metallic covering layer, hot dip galvanizing, thermal spray zinc, thermal spray aluminium and other
metal covering layer, as well as passivation layer, phosphate layer and other surface transformation film;
— technologies for electrochemical protection, such as sacrificial anode protection, impressed current
cathodic protection, and anode protection.
8.3 The selection of corrosion control technologies should take into account the following factors:
— corrosion control technologies should meet the safety design requirements of nuclear power plants;
— corrosion control technologies should be scientific, technical, economic and environmental;
— corrosion control technologies should have successful performance or implementation cases.
8.4 Check and demonstration of the selected corrosion control technology should be carried out through
the appropriate procedures.
9 Design
9.1 Once the corrosion sources
...