ISO 12944-2-2017 PDF

Full title and description

Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 2: Classification of environments (ISO 12944-2:2017). This part of ISO 12944 defines how to classify the principal environments that expose steel structures to corrosion and describes the corrosivity categories used as a primary input for selecting protective paint systems and required performance levels.

Abstract

ISO 12944-2:2017 establishes atmospheric, immersion (water) and soil corrosivity categories for steel structures. It defines atmospheric-corrosivity categories based on mass loss or thickness loss of standard test specimens, describes typical natural and industrial environments and gives guidance for estimating corrosivity. The standard also identifies special corrosion stresses (for example splash/tidal zones, chemical or biological attack, stray current) that may increase corrosion rates or require more demanding protective systems. The classification is intended to be used together with other parts of ISO 12944 when specifying paint systems, testing and expected durability.

General information

• Status: Published — current (confirmed review in 2023).
• Publication date: 13 November 2017 (Edition 2, 2017).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 87.020 (Paints and varnishes); 91.080.13 (Steel structures).
• Edition / version: Edition 2 (2017).
• Number of pages: 11 pages.

Scope

Specifies classification criteria for environments that affect corrosion of steel structures: atmospheric categories for components exposed to air, categories for components immersed in fresh or seawater or buried in soil, and special cases that impose additional corrosion stresses. The classification is given to support appropriate selection of protective paint systems, and to provide guidance on estimating the corrosivity of a given location or installation.

Key topics and requirements

• Definition of atmospheric corrosivity categories (commonly C1–C5 and the more aggressive CX/extended categories) based on measured mass or thickness loss of standard specimens.
• Categories for immersed and buried environments (Im/Im1–Im4 or equivalent), covering fresh water, seawater/brackish water (with and without cathodic protection) and soil.
• Description of typical natural, urban, industrial and marine exposure examples to assist classification and site assessment.
• Guidance on estimating corrosivity from local conditions (pollution, time-of-wetness, chloride deposition, humidity, temperature, biological activity).
• Identification of special corrosion stresses (splash/tidal zones, cyclic wetting/drying, abrasive or mechanical impact, stray electrical currents, chemical atmospheres) that may require modified protection strategies.
• Requirement that the corrosivity category determined by this part is an essential input to selecting protective paint systems (covered in ISO 12944-5) and to specifying durability levels (ISO 12944-1).
• Tables and examples to map common installations to corrosivity categories for consistent specification and communication between designers, specifiers and contractors.

Typical use and users

Used by corrosion engineers, protective-coating specifiers, structural and civil engineers, asset owners and operators, coating manufacturers, inspectors and maintenance planners to classify environmental exposure, select appropriate paint systems and set inspection/maintenance intervals. Commonly applied in marine/offshore, industrial plants, bridges, buildings, pipelines, ports and infrastructure projects where steel corrosion protection is specified.

Related standards

ISO 12944-2 is one part of the ISO 12944 series. Closely related parts include: ISO 12944-1 (General introduction and durability classes), ISO 12944-3 (Design considerations), ISO 12944-4 (Surface types and surface preparation), ISO 12944-5 (Protective paint systems), ISO 12944-6 (Laboratory performance test methods), ISO 12944-7 (Execution and supervision of paint work), ISO 12944-8 (Development of specifications for new work and maintenance) and ISO 12944-9 (Offshore structures and related laboratory performance methods). National and regional implementations (EN ISO 12944) and other standards on surface condition and test methods are commonly used alongside this part.

Keywords

corrosion classification, corrosivity categories, C1 C2 C3 C4 C5 CX, Im/Im1 Im2 Im3 Im4, atmospheric corrosivity, marine, soil immersion, protective paint systems, steel structures, durability, coating specification, special corrosion stresses

FAQ

Q: What is this standard?

A: ISO 12944-2:2017 is the part of the ISO 12944 series that classifies environments according to their corrosivity for the purpose of selecting and specifying protective paint systems for steel structures.

Q: What does it cover?

A: It covers atmospheric corrosivity categories (examples and criteria), categories for immersion in water and burial in soil, and descriptions of special corrosion stresses that can increase corrosion rates or require higher-performance protection. It provides guidance for estimating the corrosivity of a site.

Q: Who typically uses it?

A: Corrosion engineers, paint/coating specifiers, structural and civil engineers, coating manufacturers, contractors, inspectors and asset owners/operators use it when designing, specifying, applying and maintaining corrosion protection systems for steel.

Q: Is it current or superseded?

A: ISO 12944-2:2017 is the current edition (Edition 2, published 13 November 2017). The standard was reviewed and confirmed in 2023 and remains the valid edition as of 27 February 2026.

Q: Is it part of a series?

A: Yes — it is Part 2 of the ISO 12944 series (parts 1 through 9) that together cover general principles, environment classification, design, surface preparation, protective paint systems, test methods, execution, specification development and offshore-specific requirements.

Q: What are the key keywords?

A: Corrosion classification; corrosivity categories (C1–C5, CX); immersion categories (Im/Im1–Im4); atmospheric exposure; marine and industrial environments; protective paint systems; steel structures; durability; specification.