Corrosion Protection - Offshore Structures: Design, Construction and Maintenance - page 403

TABLE 6.7 Atmospheric Corrosivity Categories and Examples of Typical Environments

Mass Loss per Unit Surface/Thickness Loss
(After First Year of Exposure) Typical Environments in a Temperate Climate

Low-Carbon Steel Zinc

Corrosivity
Category

Mass Loss
(g/m 2 )

Thickness
Loss (

Mass Loss
(g/m 2 )

Thickness
Loss (

μ m) μ m) Exterior Interior

C1 very low ≤ 10 ≤ 1.3 ≤ 0.7 ≤ 0.1 Heated buildings with clean atmo-

spheres, such as offices, shops,
schools or hotels

C2 low > 10 - 200 > 1.3 - 25 > 0.7 - 5 > 0.1 - 0.7 Atmospheres with low levels of

pollution, mostly rural areas

Unheated buildings where conden-
sation may occur (e.g., depots,
sports halls)

C3 medium > 200 - 400 > 25 - 50 > 5 - 15 > 0.7 - 2.1 Urban and industrial atmospheres,

moderate sulfur dioxide pollution;
coastal area with low salinity

Production room with high humidity
and some air pollution (e.g., food-
processing plant)

C4 high > 400 - 650 > 50 - 80 > 15 - 30 > 2.1 - 4.2 Industrial area and coastal area with

low salinity

Chemical yards, swimming pools,
coastal shipyards and boatyards

C5.I very high
(industrial)

> 650 - 1500 > 80 - 200 > 30 - 60 > 4.2 - 8.4 Industrial areas with high humidity

and aggressive atmosphere

Buildings or areas with almost per-
manent condensation and with high
pollution

C5.M very high
(marine)

> 650 - 1500 > 80 - 200 > 30 - 60 > 4.2 - 8.4 Coastal and offshore areas with high

salinity

Buildings or areas with almost per-
manent condensation and with high
pollution