Stainless question from a non-materials engineer
Stainless question from a non-materials engineer
(OP)
Any thoughts as to corrosion resistance of 17-4 stainless versus 304 SS? This would be for a hydrant rod/stem. The rod might sit in stagnant municipal water at times, and fluctuate between a wet and dry conditions, typically dry though. Temps would be cool, from about freezing to maybe 60 or 70 degrees F.





RE: Stainless question from a non-materials engineer
But that is assuming that both were properly heat treated and cleaned (especially free from any heat tint).
That said 17-4PH even in a lower strength condition (H1150) has a min yield strength of 115ksi min, and to near that with 304 would take some heavily cold worked rod.
I would rather use 17-4PH in the H1150 condition than cold worked 304.
That said there are other options, perhaps a duplex stainless (LDX2101). Even annealed these alloys will have a yield strength of 75ksi which may be enough, and they have better corrosion resistance, and don't require HT or cold work.
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P.E. Metallurgy, Plymouth Tube
RE: Stainless question from a non-materials engineer
RE: Stainless question from a non-materials engineer
RE: Stainless question from a non-materials engineer
That said I have seen stainless trim ones used in places with really bad water.
I am pretty sure that those had NiAl bronze valves in them, not common brass.
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P.E. Metallurgy, Plymouth Tube
RE: Stainless question from a non-materials engineer
Edstainless, your post was 100% over my head. So generally speaking would 17-4 be an appropriate substitute for 304 in terms of corrosion resistance?
RE: Stainless question from a non-materials engineer
One thing to think about is what do these connect to? If the bottom of the rod is frequently wet, and it connects to a steel part, then the stainless will accelerate corrosion of that steel part.
How long do you want these to last? How quickly did the last ones fail? 2 months, 2 years, 20 years?
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P.E. Metallurgy, Plymouth Tube
RE: Stainless question from a non-materials engineer
RE: Stainless question from a non-materials engineer
On option would be to go with steel and double galvanize. But in the high corrosion areas the Zn (galv) will be lost and when it is gone you will just have bare steel again.
The hesitation about SS is that any corrosion will be localized pitting. So 99% of the surface can be perfect and at one place you would have a large pit. In this application that isn't the end of the world so I am not too concerned.
If the existing 17-4PH is on some other heat treat condition it can just be re-aged at 1150F to get into that condition. This material has more toughness and is very resistant to cracking.
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P.E. Metallurgy, Plymouth Tube
RE: Stainless question from a non-materials engineer
RE: Stainless question from a non-materials engineer
RE: Stainless question from a non-materials engineer