Coating and Protection Classes

1. The right corrosion protection for your application

Corrosion is a silent threat that can significantly reduce the lifespan and safety of metal structures. To combat this, surfaces are protected using specialized coating systems tailored to the surrounding environment. The protection classes C2 through C5-M serve as guidelines for determining the level of protection required. In this article, you’ll learn what each class means, how the coatings are applied, where they’re used, and the benefits they offer.

2. C2 – Low corrosion exposure

Typical environment:

Indoor spaces with a controlled climate, such as offices or dry storage facilities.

Coating system:

1. Single-layer or thin two-layer system
2. Dry film thickness: approx. 80–100 µm
3. Usually primer + topcoat

Benefits:

1. Cost-effective protection
2. Sufficient for clean, dry indoor environments

Typical applications:

1. Shelving systems
2. Machine housings used indoors
3. Lightweight steel structures

3. C3 – Medium corrosion exposure

Typical environment:

Indoor spaces with high humidity or outdoor areas with low air pollution.

Coating system:

1. Two-layer system (primer + topcoat)
2. Dry film thickness: approx. 120–160 µm
3. Sometimes includes zinc phosphate coating or adhesion promoter

Benefits:

1. Reliable protection for changing conditions
2. Good balance between cost and performance

Typical applications:

1. Industrial buildings
2. Exterior walls in rural areas
3. Ventilation systems

4. C4 – High corrosion exposure

Typical environment:

Industrial areas or coastal regions with moderate salt exposure.

Coating system:

1. Three-layer system (zinc primer + intermediate coat + topcoat)
2. Dry film thickness: approx. 200–240 µm
3. High resistance to mechanical and chemical stress

Benefits:

1. Durable protection under demanding conditions
2. Reduces maintenance intervals

Typical applications:

1. Outdoor steel structures
2. Bridges
3. Offshore-ready equipment

5. C5-I – Very high corrosion exposure (Industrial)

Typical environment:

Industrial zones with high humidity and aggressive atmospheres (e.g., chemical plants).

Coating system:

1. Three- to four-layer system
2. Dry film thickness: approx. 240–320 µm
3. Uses highly resistant epoxy and polyurethane coatings

Benefits:

1. Maximum service life
2. Protection from chemicals and moisture

Typical applications:

1. Industrial facilities
2. Pipelines
3. Chemical processing plants

6. C5-M – Very high corrosion exposure (Marine)

Typical environment:

Coastal and offshore areas with high salt exposure and humidity.

Coating system:

1. Three- to four-layer system
2. Dry film thickness: approx. 280–350 µm
3. Special marine-grade coatings with high salt resistance

Benefits:

1. Extremely resistant to saltwater
2. Minimizes corrosion in maritime environments

Typical applications:

1. Port facilities
2. Offshore platforms
3. Shipbuilding

7. Conclusion: How to choose the right protection class

The right protection class depends on the environmental conditions, desired service life, and expected maintenance effort. A C2 coating might be sufficient for a warehouse, while a C5-M coating is essential for a port facility.

If you’re unsure which class is right for your project, seek expert advice — choosing the wrong protection level can lead to costly consequences in the long run.