The Corrosivity Categories

Tue, 13 Jun 2023
The Corrosivity Categories

ISO 12944 is a globally recognised standard that provides guidelines on the protection of assets from corrosion. It covers the protective paint systems designed for application to abrasive blasted steel, hot-dipped galvanized steel, and thermally sprayed zinc steel.

The classification of the environment is given in this table:

Corrosivity Category

Application Area – Outdoors

Application Area – Indoors

C1 (Very low)

Not Applicable

Inside heated rooms – offices, commercial buildings, schools, hotels

C2 (Low)

Low pollution, mostly rural areas

Unheated buildings where condensation may occur – storage, facilities, sport centres

C3 (Medium)

Urban and industrial areas, moderate pollution, coastal regions with low salt concentration

High humidity rooms with some air pollution – breweries, dairies, food production facilities

C4 (High)

Industrial areas, coastal regions with moderate salt concentration

Chemical plants, swimming pool, boat houses above sea water

C5 – I (Very high)

Industrial areas with high humidity and aggressive atmospheres

Building and areas with ever present condensation and heavy pollution

C5 – M (Maritime)

Coastal and offshore regions with high salt concentration

Buildings and areas with ever present condensation and heavy pollution

The durability categories of corrosion protection are as follow:




Very High

Up to 7 years

7-15 years

15-25 years

More than 25 years

To find out more information, please contact Exnovo’s team of experts to discuss the best surface protection for your transformer needs.

Need more information? Our team is ready to assist you.