Alternatives for 316 Crevice Corrosion
Alternatives for 316 Crevice Corrosion
(OP)
I am attempting to solve a crevice corrosion problem on an instrument that my company manufactures. The instrument was designed for use in fresh water up to 250 ft deep and is made of 316 stainless steel. Ideally it should have a life of 5 years or more. The design of the case has several o-ring grooves and one press fit. It works great in fresh water, but in salt water it is ideal for crevice corrosion and my testing has demonstrated failure (leaks) after a few months in moving salt water with moderate bio-fouling.
I am very price sensitive so I am very reluctant to switch to titanium. Can you recommend an alternative (machineable) material that will not suffer the effects of crevice corrosion but is a bit less expensive? Marine bronze? Certain grades of aluminum? or do I need to switch to something like Inconel 625 or AL-6XN?
Alternatively, is it possible to protect the device by attaching a sacrificial metal such as a zinc? Does cathodic protection work for crevice corrosion?
Thank you,
Nick
I am very price sensitive so I am very reluctant to switch to titanium. Can you recommend an alternative (machineable) material that will not suffer the effects of crevice corrosion but is a bit less expensive? Marine bronze? Certain grades of aluminum? or do I need to switch to something like Inconel 625 or AL-6XN?
Alternatively, is it possible to protect the device by attaching a sacrificial metal such as a zinc? Does cathodic protection work for crevice corrosion?
Thank you,
Nick





RE: Alternatives for 316 Crevice Corrosion
Don't waste money on 625 unless you need high temp strength. For simple Cl corrosion resistance 622 or 59 willb e the same price and have better crevice corrosion resistance.
Could you use a non-metalic? I don't see good options for metals if you can't afford something that is 3x the price.
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Corrosion never sleeps, but it can be managed.
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RE: Alternatives for 316 Crevice Corrosion
What about adding a zinc? Does that protect from crevice corrosion or only general surface corrosion?
RE: Alternatives for 316 Crevice Corrosion
RE: Alternatives for 316 Crevice Corrosion
1 - all materials are subject to crevice corrosion, given a sufficiently suvere crevice.
2 - galvanic corrosion (or the inverse - cathodic protection) is ever present.
With these in mind, here's a suggestion that may or may not be cost effective (you'll need to decide): consider cladding a thin layer of a more crevice-corrosion resistent material where the o-ring seats. This new material will also be cathodically protected by the bulk 316-CRES in the area.
RE: Alternatives for 316 Crevice Corrosion
When I used to coat equipment for continious exposure like yours, we assembled it then sprayed with Monel, and then sealed with epoxy or urethane (depending on temp).
The sealer had a very nice rough surface to bond to, and if the surface was damaged all that was exposed was Monel, not the underlying stainless.
This makes units un-servicable, but it works. You can't coat of seal only a portion becuase the edges will be subject to crevice attack.
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Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Alternatives for 316 Crevice Corrosion
RE: Alternatives for 316 Crevice Corrosion
I also have a similar concern as "we" gradually shift piping materials to more corrosion resistent materials; we are aimultaneously increasing the problems of galvanic corrosion of the "last piece" of the previous material.
RE: Alternatives for 316 Crevice Corrosion
RE: Alternatives for 316 Crevice Corrosion
RE: Alternatives for 316 Crevice Corrosion
Do you have any inforamtion regarding depth in fresh water when stainless steel crevice corrosion would occur?
thanks,
bob
RE: Alternatives for 316 Crevice Corrosion
What I really need is a better understaning of the relative resistance of various materials to crevice corrosion. What is the relative resistance of 316 SS versus titanium versus AL6XN versus silicon bronze? There must be a standard test for crevice corrosion in salt water with a table listing the relative resistance. Can anyone point me towards this information?
RE: Alternatives for 316 Crevice Corrosion
There are a number of publications available from the Ni Institute concerning material selection for saline waters, brines and such. I have a few of them and none that I have list crevice corrosion limits for all of the potential alloys. I am sure that it is there somewhere, just not in my sources.
One reason that this info is not common is htat each alloy system (stainless, Ti Cu based) have different weaknesses. Because of this they tend to have different standard tests.
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Corrosion never sleeps, but it can be managed.
http://www.trenttube.com/Trent/tech_form.htm
RE: Alternatives for 316 Crevice Corrosion
I don't know of a single listing; but I know the first place I would look for data: the Handbook of Corrosion Data by ASM International.
If you want a relatively decent yet concise description of CC testing, I recommend ASM Handbook Volume 13 - Corrosion.
RE: Alternatives for 316 Crevice Corrosion
http://www.hpalloy.com/2551.htm
RE: Alternatives for 316 Crevice Corrosion
Are you sure it's crevice corrosion and not SCC?
RE: Alternatives for 316 Crevice Corrosion
http:/www.alleghenyludlum.com/ludlum/documents/al6xn.pdf
It may be of some assistance.
RE: Alternatives for 316 Crevice Corrosion
2205 will even give 317LMN a run in terms of pitting resistance.
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Corrosion, every where, all the time.
Manage it or it will manage you.
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RE: Alternatives for 316 Crevice Corrosion
We changed the critical parts to either Ti or NiAlBronze. Both to good effect.