C3/C4
- 120 years of experience
- Certified quality
- Sustainable technologies
JAKOB ALBERTSEN KOMPOSIT A/S
Corrosion protection according to C3 and C4
Corrosion classes C3 and C4, as defined in ISO 12944, describe environments with moderate to high corrosion stress. Correct selection of coating system and surface treatment is essential to ensure long service life and reduce maintenance costs in these environments.
What do C3 and C4 corrosion classes mean?
ISO 12944 classifies corrosive environments from C1 (very low corrosion risk) to CX (extremely corrosive environments). C3 and C4 represent intermediate classes covering both indoor and outdoor applications:
- C3 – Moderately corrosive environment
- Outdoors: Urban and industrial environments with moderate air pollution, coastal areas with low salinity.
- Indoors: Production areas with high humidity, such as breweries, dairies and food factories.
- C4 – Highly corrosive environment
- Outdoors: Industrial areas with high humidity and significant air pollution, as well as coastal areas with moderate salt exposure.
- Indoors: Chemical factories, swimming pools, shipyards and areas with frequent condensation.
JAKOB ALBERTSEN KOMPOSIT A/S
Coating systems for C3 and C4 corrosion protection
To achieve certified protection according to ISO 12944-6, the following coating systems are recommended:
C3 – Moderate corrosion protection
Typical systems for C3 environments have a total layer thickness of 120-180 µm and can consist of:
1. Pre-treatment:
- Sandblasting (Sa 2½ according to ISO 8501-1) or chemical cleaning to remove rust and contamination.
- Sponge-Jet blasting of sensitive areas to remove rust and contamination.
2. Coating structure:
- Primer: Epoxy-based zinc-containing primer (50-80 µm) for active corrosion protection.
- Intermediate layer: Epoxy or acrylic-based intermediate coat (50-100 µm) for mechanical strength.
- Topcoat: Polyurethane or polysiloxane (40-60 µm) for UV and chemical resistance.
C4 – High corrosion protection
In C4 environments, a higher total layer thickness of 180-240 µm and more advanced coating systems are required:
1. Pre-treatment:
- Sandblasting to Sa 2½ for optimal surface roughness.
- Sponge-Jet blasting for sensitive areas.
2. Coating structure:
- Primer: Zinc-rich epoxy (80-100 µm) for strong cathodic protection.
- Intermediate layer: High-solids epoxy (80-120 µm) for chemical and mechanical resistance.
- Topcoat: Polyurethane or fluoropolymer (50-80 µm) for optimal weather resistance.
JAKOB ALBERTSEN KOMPOSIT A/S
Lifetime assessment and maintenance
ISO 12944 also specifies the expected service life of coating systems:
- Short (0-5 years) – Minimal protection, requires frequent maintenance.
- Medium (5-15 years) – Standard choice for many industrial applications.
- Long (> 15 years) – Recommended for exposed steel structures with high requirements for service life.
For C3 environments, a medium lifespan system (5-15 years) is often sufficient, while C4 environments require more robust protection, where a long lifespan (> 15 years) can significantly reduce maintenance costs.
Areas of application for C3 and C4 protection
✔ C3 environments: Warehouses, workshops, treatment plants, ventilation systems.
✔ C4 environments: Refineries, bridges, chemical plants, power plants, offshore structures close to the coastline.
At Jakob Albertsen Komposit A/S, we offer custom coating systems according to ISO 12944, ensuring that your structures receive the best possible corrosion protection.
Contact us for professional advice on the right C3 or C4 corrosion protection for your project.
Do you have any questions or would you like a non-binding offer?
Contact us today for competent sparring and advice on your assignment.
JAKOB ALBERTSEN KOMPOSIT A/S
Contact us for advice on tank coating
Do you need professional tank coating in Denmark or internationally? We are ready to provide technical advice, assessment of your ideas and a non-binding offer. You can contact us by calling +45 62 20 20 58 or sending an email to mail@jakob-albertsen.dk .
Certified quality and high operational reliability
Three ISO standards and international accreditations ensure stable, documented quality.
Advanced niche solutions based on 120 years of experience
The combination of historical expertise and modern technology provides technically strong special solutions.
Innovative and sustainable coating technologies
Unique partnerships and a focus on low environmental footprint create effective and future-proof solutions.