In 1998, the International Organization for Standardization (ISO) introduced ISO12944 (Corrosion Protection of Steel Structure Protective Coating Systems), which is an international common standard. ISO12944-2017 is a reference provided by the International Organization for Standardization for global anti-corrosion technicians and units.

The atmospheric environment is divided into six levels of atmospheric corrosiveness:

C1 has very low corrosiveness

Low corrosiveness of C2

C3 moderate corrosiveness

C4 high corrosiveness

C5 has very high corrosiveness

CX extreme corrosiveness

Immersion in water or buried in soil is classified into four levels:

Im1 freshwater

Im2 seawater or brackish water without cathodic protection

Im3 soil

Im4 seawater or brackish water with cathodic protection