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Steel Structures

High Standards - Coatings for Corrosion Protection

Steel is the most popular building material when high strength is required on relatively thin structures in building construction. Modern sports facilities, residential and administrative buildings, industrial buildings, shopping centres or cultural and event buildings would be unthinkable today without the use of steel structures. But without durable and functional corrosion protection, many steel structures look “pretty old” after only a few years. But it’s not just the appearance that deteriorates; the strength of the structure can also start to suffer. In the worst case, all that remains is the choice between decommissioning or complete refurbishment.

With our coating systems, you can focus on value, durability and aesthetics right from the start.


Since 1998, the corrosion protection of steel structures has been regulated by the international standard EN ISO 12944.

In 2018, the entire standard was adapted to the state of the art with constantly increasing requirements and findings with regard to corrosion protection coatings. In its nine parts, this standard illuminates the following aspects in detail:

  • Basics and environmental influences

  • Surface evaluation and preparation

  • Conception of initial protection and refurbishment

  • Laboratory testing of coating systems

  • Execution and supervision of works

Our high-performance products and systems cover the entire spectrum of the requirements defined there.

Protecting steel against the environmental influences, corrosion protection by coating is the best – and often the only - practicable way. Coatings are specially adapted for the various application scenarios. The selection of the right and suitable coating system is essential. For example, the corrosive atmosphere in an open stadium is higher than in a primary school. In addition, the corrosion rate also increases next to the coast or in tropical climate with high humidity and temperatures.

These environmental influences are regulated by corrosivity categories in the standard for corrosion protection ISO 12944-2.

Further information can also be found in our steel construction brochure.

Corrosivity category

Typical Environments - Indoors

Typical Environments - Outdoors

C1 - very low corrosivity

Heated buildings with a neutral atmosphere

C2 - low

Unheated buildings with risk of condensation

Atmospheres with slight contamination

C3 - moderate

Production rooms with high humidity

Urban and industrial atmospheres

C4 - high

Chemical plants, swimming pools

Industrial areas and coastal areas with moderate salinity

C5 - very high

Buildings with constant condensation

Industrial areas with high humidity and aggressive atmosphere as well as coastal areas

CX - extreme

Industrial sectors with extreme humidity

Offshore areas with high salinity, industrial areas with extreme humidity and tropical atmosphere

Maintenance and repair of the corrosion protection coating systems are important factors for improving environmental protection and economic efficiency regarding steel structures.

The standard EN ISO 12944 also defines the durability of a coating system considering the corrosion load in the environment and the expected time until the first full refurbishment of the selected coating system

The standard divides four time periods for the durability:

  • low for up to 7 years

  • medium for 7 to 15 years

  • high for 15 to 25 years

  • very high for > 25 years.

The technical name “durability” is supposed to help clients to plan or determine repair and refurbishment programs. However, these classes aren’t warranty periods.

Further information can also be found in our steel construction brochure.

Achieving optimal results, surface preparation is extremely important. The type and intensity of the surface preparation should be adapted to the initial state and the expected load. With the right preparation grade, the durability of a coating can be increased. In Part 4 of the standard ISO 12944 the initial state is divided into three grades - rust grade A to rust grade C. This results in the corresponding preparation grades such as Sa 2 1/2.

Further information can also be found in our steel construction brochure.



A / B

Steel surfaces covered with largely firmly adhering mill scale or scale, but essentially free of rust.


Steel surfaces from which mill scale/scale was rusted off or can be scraped off, but which have corrosion pits that are only partially visible to the naked eye.



Manual rust removal

Loose mill scale / loose scale and loose rust are removed with hand tools (wire brush, scraper, etc.) or power tools. Such a condition is suitable for surface-tolerant primers.

Sa 1

Starting from the rust grade A - loose mill scale / scale, rust and coatings are only partially removed.

Sa 2

Starting from rust degree C - almost all mill scale / scale, almost all rust and almost all coatings are removed. Solid residues of mill scale / scale, rust and coatings may remain on the surface only to the extent that there is no longer a contiguous layer.

Sa 2 1/2

Starting from rust grade A – mill scale / scale, rust and coatings are removed to the extent that residues remain visible only as a slight shading due to tinting of pores.

Sa 3

Starting from rust degree A, B or C – mill scale / scale, rust and coatings are completely removed. The surface must have a uniform metallic appearance.

The design of the building structure as well as the colour concept for the object should be considered for the decision of a coating system. With topcoats in attractive RAL colours shades, accents can be set.

Further information can also be found in our steel construction brochure.

Corrosion Protective Coatings for Steel Structures

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Practical coating systems for all important applications according to ISO 12944:2018

Your Advantages
  1. Durability and corrosivity categories
  2. Minimum requirements for coating systems on blasted and hot-dip galvanized steel
  3. Coating systems on steel for various climate conditions
  4. Product features of our primers, intermediate and top coats
Typical Application Areas
Building construction and administration buildings
Industrial buildings
Further brochures
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