Specifications
- Commercial: CRF & CRC
- EN: Euro Codes 1-4
Guidelines for the selection of the correct stainless steel grade in structural applications according to the service environment: Euro Codes 1 to 4 provide a procedure for selecting the appropriate grade of stainless steel for the service environment of structural members. The environment is assessed using Corrosion Resistance Factor (CRF) and the stainless grades are placed in Corrosion Resistance Classes (CRC) I, I, III, IV & V according to CRF value.
Calculation of Corrosion Resistance Factor (CRF)
The Corrosion Resistance Factor is comprised of three elements: F1, F2 & F3.
- F1 rates the risk of exposure to chlorides from salt water/sea water or de-icing salts
- F2 rates the risk of exposure to Sulphur Dioxide
- F3 rates the cleaning regime or exposure to washing by rain
Calculation of F1: Risk of Exposure to Chlorides
| F1 Value | Description |
| 1 | Internal, Controlled Environment |
| 0 | Low Risk of Exposure: M.10km or S>0.1km |
| -3 |
Medium Risk of Exposure: 1km |
| -7 |
High Risk of Exposure: 0.25km |
| -10 | Very High Risk of Exposure: Road Tunnels where de-icing salts used |
| -10 | Very High Risk of Exposure: M<0.25km: North Sea Coast of Germany & All Baltic Coastal Areas |
| -15 | Very High Risk of Exposure: M<0.25km - Incl All other European/UK Coastal Areas |
M is distance from sea. S is distance from roads where de-icing salts are used
Calculation of F2: Risk of Exposure to Sulphur Dioxide
| F2 Value | Description |
| 0 | Low Risk of Exposure: 10 average deposition |
| -5 | Medium Risk of Exposure: 10-90 average deposition |
| -10 | High Risk of Exposure: 90-250 average deposition |
Note: In European coastal environments the SO2 value is usually low. For inland environments the value is either low or medium. High values are usually associated with heavily industrialised locations or specific environments such as tunnels. In the table the deposition values are given in the units micro-grams per m3.
Calculation of F3: Cleaning or Rain Washing
| F3 Value | Description |
| 0 | Fully Exposed to Washing by Rain |
| -2 | Specified Cleaning Regime |
| -7 | No Washing by Rain or Specified Cleaning Regime |
For Cold rolled stainless steel the old BS1449 standard has been replaced by two EN Standards:
Calculation of CRC
The Corrosion Resistance Class (CRC) required for the given environment is given by first calculating the Corrosion Resistance Factor (CRF) through adding F1+F2+F3.
Corrosion Resistance Class (CRC)
| CRF | CRC |
| 1 | I |
| 0 to under -7 | II |
| -7 to under -15 | III |
| -15 to under -20 | IV |
| Over -20 | V |
An appropriate stainless steel grade for the environment can now be chosen from the table below showing the CRC for the various commonly available grades.
CRC By Grade
| CRC Class | Grades |
| I (Ferritic) | 1.4003, 1.4016 (430), 1.4512 (409) |
| II (Standard 18/8 Austenitic) | 1.4301 (304), 1.4307 (304L), 1.4311, 1.4541, 1.4318, 1.4306, 1.4567, 1.4482 |
| III (Mo-Austenitic & Lean Duplex) | 1.4410, 1.4404, 1.4435, 1.4571, 1.4429, 1.4432, 1.4578, 1.4462, 1.4362, 1.4062, 1.4162 |
| IV (Super-Austenitic & Duplex) | 1.4439, 1.4539, 1.4462 |
| V (Super-Austenitic & Duplex) | 1.4565, 1.4529, 1.4547, 1.4410, 1.4501, 1.4507 |
