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Corrosivity class

Compilation of the various corrosivity classes commonly used.

Corrosivity class

Corrosivity class Corrosivity of the environment Outside Inside
C1 Very low - Heated buildings with clean air such as offices, shops, schools etc.
C2 Low Atmosphere with low level of pollution eg rural areas. Unheated buildings where condensation can occur such as depots and sports halls.
C3 Moderate Urban and industrial air with medium high sulfur dioxide content, and coastal areas with low salinity. Production room with high humidity and some pollutants eg food production premises, laundry facilities, breweries, dairies etc.
C4 High Industrial areas and coastal areas with medium salinity. Chemical plants, bathhouses, boat yards or the like.
C5-I (Industrial) Very high Industrial areas with high humidity with an aggressive atmosphere. Buildings or areas of almost permanent condensation and high levels of pollution.
C5-M (Marine) Very high Coastal and marine areas with high salinity Buildings or areas of almost permanent condensation and high levels of pollution.

Each class above can also be divided into different levels as below.

Durability Years
Låg 2-5
Medel 5-15
Hög >15

Water and soil categories.

Category Enviroment Examples of environments and buildings.
lm1 Fresh water River installations, hydropower plants etc
lm2 Sea or brackish water Port areas with buildings such as locks, bridges, sea platforms etc
lm3 Earth Excavated tanks, steel columns, steel pipes etc

Rust level.

Classification according to ISO Classification according to ASTM Rust surface
Ri 0 10 0
Ri 1 9 0,05
Ri 2 7 0,5
Ri 3 6 1
Ri 4 4 8
Ri 5 1 - 2 40-50


Corrosivity class

Indicates the degree of corrosion or corrosion per unit of time that can be expected depending on the environment.

Another name for corrosivity class that was previously used is environmental class.

Water and soil categories.

Applies to buildings that are submerged in water or buried in soil.


One way to define different rust protection within a corrosivity class and how long it takes to reach rust level Ri 3.

Rust level

A rating of how much of the surface is affected by rust.


ASTM or "American Society for Testing and Materials" is an American classification of the surface area affected by rust.