ISO 12944-2:2017

Overview

ISO 12944-2:2017 - part of the ISO 12944 series on paints and varnishes - defines how to classify the environments that cause corrosion of steel structures. The standard describes the corrosivity of atmospheres, water and soil, explains how environmental stresses affect corrosion rates, and identifies special cases (micro-environments and unusual stressors) that can increase demands on protective paint systems. It provides a foundation for selecting appropriate protective paint systems by linking environmental classification to required corrosion protection measures.

Key topics

• Atmospheric-corrosivity categories
  Defines classification of outdoor and indoor atmospheres based on measured mass loss (or thickness loss) of standard specimens and gives guidance for estimating local corrosivity.
• Environmental parameters that drive corrosion
  Time of wetness, relative humidity, condensation, pollutants (for example sulfur dioxide and salts), temperature and micro-environment effects are identified as principal drivers of atmospheric corrosion.
• Immersion and burial environments
  Describes categories for structures immersed in water (fresh, brackish, salt) and buried in soil, and differentiates immersion zones: underwater, intermediate (fluctuating level), and splash zone. Soil corrosivity factors (mineral/organic content, aeration, ground water) are discussed qualitatively.
• Special corrosion stresses
  Notes special cases and local conditions (e.g., poor ventilation, sheltered corrosion spots, biological growth, mechanical wear, stray current) that can significantly increase corrosion rates and affect paint-system performance.
• Terminology and measurement basis
  Uses standardized terms (corrosivity, time of wetness, micro-environment) and bases categories on measurable corrosion loss to ensure consistent estimation.

Applications

ISO 12944-2:2017 is used to:

• Assess site-specific environmental corrosivity for new or existing steel structures
• Inform the selection and specification of protective paint systems (in conjunction with other ISO 12944 parts)
• Guide maintenance planning and life‑cycle corrosion management
• Support contract specifications, inspection planning and risk assessment for bridges, buildings, offshore structures, pipelines, tanks and industrial installations

Typical users include owners, structural engineers, corrosion specialists, coating manufacturers, applicators, and inspectors.

Related standards

ISO 12944-2 is part of the ISO 12944 series. Relevant companion documents include:

• ISO 12944-1 (General introduction)
• ISO 12944-3 (Design considerations)
• ISO 12944-4 (Surface preparation)
• ISO 12944-5 (Protective paint systems)
• ISO 12944-6, -7, -8, -9 (testing, execution, specifications, offshore systems)

By classifying environments and outlining the corrosion stresses that govern paint performance, ISO 12944-2:2017 provides the essential environmental input for specifying durable corrosion protection for steel structures.