430 has good resistance to a wide variety of corrosive media including nitric acid and some organic acids. It attains its maximum corrosion resistance when in the highly polished or buffed condition. In general its resistance to pitting and crevice corrosion resistance is close to that of grade 304. Stress corrosion cracking resistance of Grade 430 is very high, as it is for all ferritic grades.
Like other high-sulphur free machining grades 430F has much reduced resistance to pitting and crevice corrosion compared to its non-free machining equivalent, particularly in the cross-section direction.
1.Aqueous
| Temperature oC |
20 |
80 |
| Concentration, % mass |
1 5 10 20 80 100 |
1 5 10 20 80 100 |
| Sulphuric Acid |
2 2 2 2 2 1 |
2 2 2 2 2 2 |
| Nitric Acid |
0 0 0 0 1 2 |
0 0 0 1 1 2 |
| Phosphoric Acid |
0 0 2 2 1 0 |
0 0 2 2 1 1 |
| Acetic Acid |
0 0 1 1 1 0 |
0 2 2 2 2 0 |
Key: 0 = resistant - corrosion rate less than 100 m/year
1 = partly resistant - corrosion rate less than 1000 m/year
2 = non resistant - corrosion rate more than 1000 m/year
2 Atmospheric
The performance of 430 compared with other metals in various environments is shown in the following table. The corrosion rate is based on a 10 year exposure.
| Environment |
Corrosion Rate (um/year) |
| SX 430 |
Aluminium-3S |
Mild Steel |
| Rural |
0.0025 |
0.028 |
4.3 |
| Marine |
0.0381 |
0.424 |
25.7 |
| Marine-Industrial |
0.0406 |
0.546 |
37.1 |
