According to ISO 12944-2
| Category | Examples, I=interior, E=exterior | Screw recommendation |
| C1 Very low |
I = Warm, ventilated indoor spaces E = – |
Carbon steel, zinc coated Carbon steel + Ruspert |
| C2 Low |
I = Unheated buildings E = Clean rural climate |
Carbon steel + Ruspert AISI 410 + Ruspert |
| C3 Medium |
I = High humidity, some air pollution E = City and industry, moderate sulphur dioxide pollution |
(AISI 410 + Ruspert) A2 |
| C4 High |
I = Chemical plants, swimming pools, shipyards E = Industrial and coastal areas, moderate salinity |
A4 |
| C5-I Very high, industrial |
I = Permanent condensation, high pollution E = Industrial areas – high humidity, aggressive atmosphere |
Clarified case-by-case |
| C5-M Very high, marine |
I = Permanent condensation, high pollution E = Marine climate, high salinity |
Clarified case-by-case |