Overview
ISO 12944-5:2019 - “Paints and varnishes - Corrosion protection of steel structures by protective paint systems - Part 5: Protective paint systems” - describes the common types of paints and complete paint systems used to protect steel from corrosion. It provides guidance for selecting compatible systems for different atmospheric, water and soil corrosivity categories (C1–C5 and Im1–Im3) and links selection to surface preparation and expected durability (see ISO 12944-1, -2 and -4). CX and Im4 corrosivity categories are excluded.
Keywords: ISO 12944-5:2019, protective paint systems, corrosion protection of steel structures, paint systems selection
Key topics and technical requirements
- Types of paints: generic examples included are alkyd (AK), acrylic (AY), ethyl silicate (ESI), epoxy (EP), polyurethane (PUR), polyaspartic (PAS) and polysiloxane (PS).
- Paint system structure: definition and roles of priming coats, intermediate coats, topcoats, tie coats and sealers.
- Compatibility: guidance on using products together successfully as a system without undesirable effects.
- Dry film thickness (DFT): specification concepts such as nominal DFT, maximum DFT and measurement references.
- Durability grading: linking paint-system choice to expected service life (see ISO 12944-1).
- Application contexts: distinctions between new work, total refurbishment and partial refurbishment; shop vs site application; pre-fabrication primers for temporary protection during fabrication.
- Selection aids and tables: prescriptive tables for atmospheric categories C2–C5 and immersion/buried categories Im1–Im3; Annexes with systems for carbon steel, hot-dip galvanised steel, thermal-sprayed metallic coatings, and pre-fabrication primers.
- Minimum requirements: normative requirements and test/measurement references (e.g., film thickness, surface preparation standards).
Practical applications and users
Who uses ISO 12944-5:
- Asset owners and owners’ representatives specifying protective systems for bridges, buildings, offshore and industrial steelwork.
- Design engineers and corrosion consultants selecting coatings to meet durability targets.
- Coating manufacturers and formulators ensuring product compatibility and system designation.
- Contractors and applicators for shop and site painting, surface preparation and quality control.
- Inspectors and certifiers assessing conformity to system specifications.
Practical benefits:
- Streamlines selection of coating systems for given environments and service life goals.
- Promotes consistent communication among stakeholders and reduces corrosion-related risks and lifecycle costs.
Related standards
Relevant cross-references: ISO 12944-1, ISO 12944-2, ISO 12944-4, plus test and surface standards such as ISO 1461, ISO 2063, ISO 2808, ISO 3549, ISO 8501-1, ISO 8503-1, ISO 19840. These provide definitions, environment classification, surface-preparation criteria and measurement methods.
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