Resistance to Pitting and Crevice Corrosion
HASTELLOY C-22 alloy exhibits very high resistance to chloride-induced pitting and crevice attack, forms of corrosion to which the austenitic stainless steels are particularly prone. To assess the resistance of alloys to pitting and crevice attack, it is customary to measure their Critical Pitting Temperatures and Critical Crevice Temperatures in acidified 6 wt.% ferric chloride, in accordance with the procedures defined in ASTM Standard G 48. These values represent the lowest temperatures at which pitting and crevice attack are encountered in this solution, within 72 hours. For comparison, the values for 316L, 254SMO, 625, C-22 and C-276 alloys are as follows:
| Alloy | Critical Pitting Temperature in Acidified 6% FeCl3 | Critical Crevice Temperaturein Acidified 6% FeCl3 | ||
| – | °F | °F | °F | °F |
| 316L | 59 | 15 | 32 | 0 |
| 254SMO | 140 | 60 | 86 | 30 |
| 625 | 212 | 100 | 104 | 40 |
| C-276 | >302 | >150 | 131 | 55 |
| C-22 | >302 | >150 | 176 | 80 |
Resistance to Stress Corrosion Cracking
One of the chief attributes of the nickel alloys is their resistance to chloride-induced stress corrosion cracking. A common solution for assessing the resistance of materials to this extremely destructive form of attack is boiling 45% magnesium chloride (ASTM Standard G 36), typically with stressed U-bend samples. As is evident from the following results, the three nickel alloys (C-22®, C-276 and 625) are much more resistant to this form of attack than the comparative, austenitic stainless steels. The tests were stopped after 1,008 hours (six weeks).
| Alloy | Time to Cracking |
| 316L | 2 h |
| 254SMO | 24 h |
| 625 | No Cracking in 1,008 h |
| C-276 | No Cracking in 1,008 h |
| C-22® | No Cracking in 1,008 h |
Impact Strength
| Test Temperature | Impact Strength | ||
| °F | °C | ft-lbf | J |
| RT | RT | 419 | 568 |
| -320 | -196 | 346 | 469 |
Hardness
| Form | Hardness, HRBW | Typical ASTM Grain Size |
| Sheet | 88 | 3.5 – 5.5 |
| Plate | 88 | 0 – 4.5 |
| Bar | 84 | 1 – 3.5 |