The international system: ISO 12944 and the standards around it
The ISO 12944 series is the main international document on the corrosion protection of steel structures by protective paint systems. Client specifications, manufacturers’ technical data sheets and projects with foreign participation refer to it. The series itself sets out the logic: how to describe the environment, what service life to specify, which system to choose and how to substantiate its performance. Surface preparation and the checking of cleanliness, roughness, thickness and adhesion are covered by separate ISO standards on which the series relies. Below we explain what each document covers and which editions are current as of October 2026.
The nine parts of ISO 12944
| Part | Current edition | What it covers | Who needs it most |
|---|---|---|---|
| 1. General introduction | ISO 12944-1:2017 | Scope of the series, basic terms, durability ranges, how to apply the series to a given project | Client, designer |
| 2. Classification of environments | ISO 12944-2:2017 | Atmospheric corrosivity categories, categories for structures immersed in water or buried in soil, special corrosion stresses | Designer |
| 3. Design considerations | ISO 12944-3:2017 | How to design steel members so that they can be properly painted, inspected and maintained | Structural engineer |
| 4. Types of surface and surface preparation | ISO 12944-4:2017 | Preparation of uncoated steel, galvanized and metal-sprayed surfaces, surfaces with prefabrication primer and previously painted surfaces; preparation grades | Designer, contractor |
| 5. Protective paint systems | ISO 12944-5:2019 | Types of paints and systems, guidance on selecting a system for an environment category (except CX and Im4), preparation grade and durability range | Designer, manufacturer |
| 6. Laboratory performance tests | ISO 12944-6:2018 | Laboratory test methods and conditions for systems in categories C2–C5 and Im1–Im3 | Manufacturer, client |
| 7. Execution and supervision | ISO 12944-7:2017 | Execution of paint work in the shop and on site and its supervision | Contractor, inspector |
| 8. Specifications | ISO 12944-8:2017 | Development of specifications for new work and maintenance, reference areas for assessing the quality of work and the performance of the system | Client, designer |
| 9. Offshore and related structures | ISO 12944-9:2018 | Systems and laboratory performance tests for offshore and related structures, categories CX and Im4 | Oil and gas, offshore and coastal facilities |
ISO has decided to revise all nine parts. As of October 2026, the new editions of Parts 1–4, 7 and 8 are at the working draft stage and those of Parts 5 and 6 at the committee draft stage; according to ISO metadata, the drafts of the new Parts 5 and 6 are also intended to replace Part 9. Until the new editions are published, the editions listed above remain current, and a specification should cite them with the year.
Environment categories and durability
ISO 12944-2 divides the atmosphere into corrosivity categories C1–C5 and CX and introduces categories Im1–Im4 for structures in water and soil. The other parts of the series refer to these designations: laboratory testing to Part 6 covers categories C2–C5 and Im1–Im3, while Part 9 covers the offshore atmosphere of category CX and immersion in sea or brackish water (Im4).
A general classification of atmospheric corrosivity for metals is given in a separate standard, ISO 9223:2012: from the first-year corrosion rate of standard specimens, by calculation from climate and pollution data, or from a description of local conditions. ISO 9223 does not characterise the atmospheres of specific industries, such as chemical plants or metallurgical works; for these, ISO 12944-2 gives information on special corrosion stresses, and the decision rests with the designer. A table of categories with examples of environments is given in our corrosion protection guide.
The concept of the durability of a coating system and its ranges are defined in ISO 12944-1. Other documents rely on them: ISO 12944-5 takes the expected durability into account when selecting a system, and ISO 12944-9 and NORSOK M-501 require systems of high durability. A durability range is not a guarantee period — if a guarantee is needed, it is agreed separately.
Why Parts 5, 6 and 9 matter
Part 5 describes the types of paints and paint systems commonly used to protect steel structures and gives guidance on selecting a system for a given environment category, surface preparation grade and expected durability. It is a selection guide, not a list of approved products: the actual materials, number of coats and thicknesses are determined from the manufacturer’s documents and the project requirements.
Part 6 specifies laboratory test methods and test conditions for assessing systems for environments C2–C5 and Im1–Im3 — on uncoated steel, on hot-dip galvanized steel (ISO 1461) and on thermally sprayed metallic coatings (ISO 2063-1 and ISO 2063-2). The standard itself states that test results help in selecting a system but do not give an exact value of durability.
Part 9 replaced ISO 20340:2009. It sets requirements for high-durability systems for offshore and related structures — in a category CX atmosphere and in sea or brackish water (Im4) — together with laboratory tests and the criteria for assessing their results. Its scope is limited; see the page on oil and gas and offshore facilities for details.
The practical consequence: the phrase “the system complies with ISO 12944” says little on its own. Documents for a system should state the environment category, the durability range, the surface preparation grade and the basis for the claim — an example system from Part 5 or test reports to Part 6 or Part 9.
Surface preparation: ISO 8501, 8502, 8503 and 8504
The four series look at steel preparation from different angles: ISO 8501 covers visual cleanliness, ISO 8502 invisible contaminants and conditions before painting, ISO 8503 roughness after blast cleaning, and ISO 8504 the preparation methods themselves.
| Standard | Edition | What it covers |
|---|---|---|
| ISO 8501-1 | 2007 | Rust grades and preparation grades of uncoated steel and of steel after overall removal of previous coatings, including Sa 2½ and Sa 3; reference photographs |
| ISO 8501-2 | 1994 | Preparation grades after localized removal of previous coatings — for maintenance painting |
| ISO 8501-3 | 2025 | Three preparation grades for welds, edges and areas with surface imperfections; replaced the 2006 edition |
| ISO 8501-4 | 2020 | Water jetting: initial surface conditions, preparation grades and flash rust grades |
| ISO 8502-3, 8502-4 | 2017 | Residual dust by the pressure-sensitive tape method; estimating the probability of condensation before painting |
| ISO 8502-6, 8502-9 | 2020 | Extraction of water-soluble contaminants with a cell (Bresle method) and field determination of total soluble salts by conductivity |
| ISO 8502-2, 8502-5 | 2017, 2025 | Chloride: a laboratory method and a field method using ion detection tubes |
| ISO 8503-1 … 8503-5 | 2012; Part 5 — 2017 | Surface profile: profile comparators, focusing microscope, stylus instrument, replica tape |
| ISO 8504-1 … 8504-5 | 2018–2024 | Preparation methods: general principles, abrasive blast cleaning, hand and power tools, acid pickling, water jet cleaning |
| ISO 11124, ISO 11126 | by part | Metallic and non-metallic blast-cleaning abrasives |
The visual cleanliness grade is not the only criterion of a surface being ready for painting: ISO 8501-4 explicitly refers to ISO 8502 for invisible contaminants and to ISO 8503 for the profile, and assessment with a comparator to ISO 8503-2 applies only to surfaces cleaned to Sa 2½ or Sa 3. The standards provide the methods, while the limits — the amount of salts, the profile, the dust class — are set by the project specification and the material’s technical data sheet.
Thickness, adhesion, porosity and defects
| What is checked | Standard | Points to note |
|---|---|---|
| Wet and dry film thickness | ISO 2808:2019 | Overview of methods and the field of application of each |
| Dry film on rough steel | ISO 19840:2012 | Instrument adjustment, inspection areas, sampling plan, acceptance criteria; not applicable to nominal thicknesses below 40 µm |
| Thickness gauges | ISO 2178:2016, ISO 2360:2017 | Magnetic method for coatings on steel; eddy-current method on non-magnetic metals |
| Pull-off adhesion | ISO 4624:2023; acceptance — ISO 16276-1:2025 | The required value and the type and manufacturer of the test equipment are specified in advance: results from different instruments are not comparable |
| Cross-cut and X-cut | ISO 2409:2020; acceptance — ISO 16276-2:2025 | ISO 2409 is an empirical test, not a measurement of adhesion; not suitable for coatings thicker than 250 µm |
| Porosity (pinholes) | ISO 29601:2026 | The type of instrument is chosen according to the thickness of the non-conductive coating |
| Assessment of defects | ISO 4628, Parts 1–8 and 10 | A common system for designating blistering, rusting, cracking, flaking, chalking and corrosion around a scribe |
| Laboratory resistance | ISO 9227:2022, ISO 6270, ISO 2812 | Salt spray, humidity, liquids; ISO 9227 is not intended for ranking materials or predicting long-term durability |
New editions of ISO 4624, ISO 16276-1, ISO 16276-2 and ISO 29601 were published in 2023–2026; older specifications still refer to the previous ones, which is worth checking when a document is updated.
Metallic coatings and duplex systems
Hot-dip galvanizing of articles is covered by ISO 1461:2022, guidance on zinc coatings by ISO 14713-1:2017 and ISO 14713-2:2019, and thermal spraying of zinc and aluminium by ISO 2063-1:2019 and ISO 2063-2:2017. ISO 1461 does not cover painting over zinc: the preparation of such surfaces is described in ISO 12944-4, and laboratory testing of systems over zinc and thermally sprayed metal in ISO 12944-6.
Applicability in Uzbekistan
Under the Law “On Standardization” (ZRU-800), international standards apply in Uzbekistan on a par with national ones on the basis of a decision by the national standardization body to put them into effect. We have not found national standards adopting ISO 12944, ISO 8501-1, ISO 2409 or ISO 4624 in official sources. The ISO 12944 series has been adopted with modifications (MOD) as interstate standards GOST 34667.1–34667.9: Uzbekistan voted for the adoption of Parts 1–7 and 9 and joined Part 8 later. ISO 19840 (GOST 35271-2025), ISO 2808 (GOST 31993-2024), ISO 4624 (GOST 32299-2025) and ISO 2409 (GOST 31149-2014) have been adopted in the same way. The current design code for corrosion protection, ShNK 2.03.11-24, does not refer to ISO 12944, so ISO requirements enter a project through the contract and the client’s specification. See Corrosion protection standards in Uzbekistan for details.
Information on the editions and status of ISO standards is based on ISO Open Data (iso_deliverables_metadata dataset, ODC-By 1.0) as of October 2026. Check the current edition before use.
Need ISO 12944 requirements drawn up for your facility? We will define the environment categories by zone and select the system, thicknesses and inspection procedure. Phone, WhatsApp, Telegram: +998 94 094 52 27. E-mail: info@ognezashita.uz.