Pitting of 301 and 17-4PH Stainless Steel

[csuminski]

Does anyone have information regarding the pitting resistance of 301 half hard SST, 301 High Yield SST and 17-4PH Stainless Steel in a high chloride concentration?

 

[bilge]

ASM's Metals Handbook (volume 3, ninth edition, pages 11-12) shows 17-4 PH to be "resistant" to corrosion in salt water. 301 is not.

 

[mcguire]

None of the materials you mention is immune to pitting corrosion in a saline environment. Don't forget that pH and temperature are factors affecting whether or not pitting will occur, and you didn't mention those. Other factors are sulfur level and surface finish.
Resistance to pitting in stainlesses is proportional to
(%chromium + 3.3X%molybdenum + 13x%nitrogen). Both 17-4 and 301 have about 17% chromium and no molybdenum, so their pitting resistance is equivalent.
These materials are also susceptible to stress corrosion cracking. Consider an high strength, high corrosion resistant duplex like 2205,

 

[CoryPad]

mcguire,

2205 has excellent corrosion resistance, but can it replace the materials mentioned in the original post? 2205 yield strength is ~ 450 - 600 MPa, while 301 half-hard is ~ 760 MPa, 301 full-hard is ~ 965 MPa, and 17-4 can be up to 1170 MPa. If the application requires high strength, 2205 would be unsuitable.

 

[mcguire]

Certainly a design change would be needed, but there is no high strength ferrous material which would not be subject to SCC in a highly saline environment except duplex stainless, so I don't see a realistic alternative. Titanium, perhaps.But,the duplex could also be cold-worked to a higher yield strength, so I still consider it a appropriate material. It doesn't have to be used in the annealed condition.
Your point is well taken, however. I failed to cite its lower yield strength originally.