Corrosion categories acc. ISO 12944-5

Be aware that your steel is to be addressed to the correct corrosion category

It is requirement to life span in a concrete environment that determines the choice of the corrosion category a given steel structure to be treated for.

Steel structures must be used/placed under different climatic conditions:

Low corrosion categories of protected environments such as indoor use
High corrosion categories of vulnerable and coastal surroundings

Corrosion categories are divided into 6 different categories according to ISO 12944-5, by their scope:

Category	Outdoor	Indoor
C1: Very low		Heated buildings with production, such as offices, shops, schools, hotels, etc.
C2: Low	Environments with low levels of polution. Mainly rural setting	Unheated buildings where condensation can occur. For example, warehouses, depots, sport facilities and similar.
C3: Medium	City and industrial environments with moderate sulfur dioxide pollution. Coastal areas with low salinity	Production areas with high humidity and some air pollution. For example, industrial plants, laundries, breweries, food production, etc.
C4: High	Industrial areas and coastal areas with moderate salinity	Chemical industry, ship- and boat yard.
C5I: Very high	Industrial areas with high humidity and aggressive environment	Buildings and areas with almost permanent condensation and with high pollution impact.
C5M: Maritime	Coastal environment and off-shore installations with high salt content	Buildings and areas with a high degree of condensation and with high impact of pollution.