ISO 12944 Certified Coating Systems
(C1–C2–C3–C4 & C5)
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Corrosion Protection You Can Rely On
Designed to Perform in C1–C5 Environments
What Are ISO 12944 Coating Systems?
ISO 12944 is the international standard for corrosion protection of steel structures using protective paint systems. It classifies environments based on their corrosivity and defines the appropriate coating systems required to achieve a specific durability.
The main categories include:
- C1 (Very Low) – Heated buildings with clean atmospheres
- C2 (Low) – Rural or low pollution environments
- C3 (Medium) – Urban and light industrial areas
- C4 (High) – Industrial areas or coastal locations with moderate salinity
- C5 (Very High) – Offshore, marine, or highly aggressive industrial environments
Each system is designed with a defined lifespan, such as:
- Low durability (Up to 7 years)
- Medium durability (From 7-15 years)
- High durability (15-25 years)
- Very high durability (more than 25 years)
ISO 12944 Corrosivity Categories C1 to C5
ISO 12944-2 sorts environments into corrosivity categories. The category your steel sits in decides how robust the coating system needs to be. Choosing the right one at the start avoids paying for a system that is either over-specified or fails early.
| Category | Corrosivity | Typical exterior environments | Typical interior environments |
|---|---|---|---|
| C1 | Very low | Not applicable | Heated buildings with clean air, such as offices, shops and schools |
| C2 | Low | Low pollution, mostly rural areas | Unheated buildings where condensation can occur, such as depots and sports halls |
| C3 | Medium | Urban and industrial areas with moderate pollution, coastal areas with low salinity | Production areas with high humidity and some pollution, such as food processing, laundries and breweries |
| C4 | High | Industrial areas and coastal areas with moderate salinity | Chemical plants, swimming pools, coastal boatyards |
| C5 | Very high | Industrial areas with high humidity and aggressive atmosphere, coastal areas with high salinity | Buildings with almost permanent condensation and high pollution |
| CX | Extreme | Offshore and extreme industrial environments | Industrial areas with extreme humidity and aggressive atmosphere |
Durability. ISO 12944 also sets out how long a system is designed to last before its first major maintenance: low (up to 7 years), medium (7 to 15 years), high (15 to 25 years) and very high (more than 25 years). Durability is a planning figure for specifying the system, not a guarantee period.
Not sure which category applies? We assess the environment at survey or work to the category in your specification. Read our guide to ISO 12944 coating systems for more detail.
Our Approach
- Detailed assessment of environment and exposure level
- Identification of required ISO category (C1–C5)
- Specification of correct coating system and build-up
- Surface preparation to required standards
- Professional spray application using approved materials
- Final inspection to ensure compliance with specification
Where These Systems Are Used
ISO 12944 coating systems are used across a wide range of sectors, including:
- Structural steel frameworks
- Warehouses and industrial units
- Car parks and multi-storey structures
- Bridges and infrastructure
- External plant and equipment
- Coastal and marine environments
Why Use ISO 12944 Certified Coatings?
- Ensures compliance with recognised international standards
- Provides predictable lifespan and performance
- Protects against corrosion, weathering, and environmental damage
- Reduces long-term maintenance and repair costs
- Suitable for both new build and refurbishment projects
Why Choose Spray Chroma?
We understand that ISO 12944 systems are not just about applying paint – they require correct specification, preparation, and application to perform as intended.
Our team works closely with clients to ensure:
- The correct system is selected for the environment
- Application meets required standards
- Disruption on site is kept to a minimum
- The final result is both protective and visually consistent
ISO 12944 Coating Projects
ISO 12944 Coating London
Read how our ISO 12944 coating project in London delivered a C5-grade system using a 2-part polyurethane coating, applied on-site to meet strict requirements.
On Site ISO 12944 Coating Leicestershire
See how we applied an ISO 12944 C3 protective coating to machinery components on site in Leicestershire, avoiding additional transport costs.
ISO 12944 Coating & Intumescent Paint Spraying Watford
Our ISO 12944 coating and intumescent paint spraying project in Watford protected structural steel from corrosion and 60-minute passive fire protection for a underground car park.
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Our ISO 12944 Coating Application Process
Thorough Inspection:
We assess the structure, environment, and level of exposure to determine the correct ISO classification and coating requirements.
Customised Specification:
We specify a tailored ISO 12944 compliant system, including full coating build-up and durability requirements (e.g. C3 Low, Medium, or High systems).
High-Quality On-Site Application:
Our team applies coatings using professional equipment, ensuring consistent coverage, correct film thickness, and protection of surrounding areas.
Certified Project Completion:
We carry out a final inspection to confirm the coating system meets the required specification and performance standards.
Accreditations
Our paint spraying teams are fully qualified and accredited by a range industry bodies, demonstrating the professional level of our on site spraying and coating services and why you should trust in Spray Chroma to deliver commercial paint spraying solutions of a high scale.
Choosing Spray Chroma for Your ISO 12944 Coating Requirements
You’re investing in a compliant coating system designed to protect your structure and extend its lifespan. Contact us today to find out how we can deliver a solution tailored to your environment and performance requirements.