Yes. Under the wrong conditions, any stainless steel can corrode or rust. Aggressive environments containing acids or chlorides, such as seawater, increase the likelihood and extent of corrosion, as does contamination of the working fluid, surface damage, poor surface preparation or welding. "Stainless" is a better description than "stain-free".
There is a wide variety of austenitic stainless steels. The more common grades, 304 and 316, have a pitting resistance equivalent number (PREN) of between 20 and 25. Higher-performance grades such as Fermonic® 50 (XM-19, UNS S20910, 1.3964) have a PREN of around 34, a significant uplift in pitting resistance.
There are also super austenitic grades, with higher molybdenum and nickel, such as Alloy 254 (6Mo, 254SMO, F44, UNS S31254, 1.4547), which reaches a PREN of 43, just above that of super duplex stainless steels.
| Grade | PREN |
|---|---|
| 304 / 316 | 20-25 |
| Fermonic® 50 (XM-19, UNS S20910) | 34 |
| Alloy 254 (6Mo, UNS S31254) | 43 |