Saturated NaCl Solution 1

[alexit]

I am looking for a recommendation for materials for long-term direct contact with saturated NaCl. While 316 is "compatabile" I am wondering about long (3-5yrs) contact. We could coat or otherwise improve the surface but the costs must be considered. Any suggestions?

 

[kenvlach]

1) What is the application???
2) 316 SS is incompatible with saturated NaCl solution. Maybe titanium, PVC, polypropylene...

 

[alexit]

It will be a housing for mounting magnetic detectors and associated electronics. One surface will be in direct contact with the solution, while the others will be exposed only to air. Titanium or Hastelloy-C are possible but I was hoping for a less expensive option.
The tables I have show 316 as an option but who knows for how long.

Thanks,
Alex

 

[EdStainless]

Is it at room temp? How hot can it get?
If it isn't too hot then maybe a 6%Mo stainless would work. But given the cost and risk I would just use a C type alloy.
If it doesn't need to be metal than plastic is an even better option. You could even use a high grade amterial (PPS or PEEK) to get strength and corrosion resistance.

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[arunmrao]

A curious question. An Indian common salt manufacturing company in its advertisement shows all the equipments and parts including stairs,railings motor casings etc are made in 316 alloy. what is the frequency of replacement in such an environment.

 

[metengr]

arunmrao;
Probably it would never need replacement, as long as there is no contact with water or excessive humidity.

 

[geoffthehammer]

We routinely use saturated NaCl at temperatures between 0 and +40 Celsius. We use to use 316 but it corroded within days so we had to upgrade from 316 to Titanium and we also use Nickel Aluminium Bronze which seems to stand up quite well.
Surface finish and crevice corrosion were big problems with any SS

 

[EdStainless]

There are a number of stainless grades, as well as Ni alloys, that can be used in wet NaCl applications with very long lives.
I have some 316 tube that lasted less than a month in service as overhead air lines in a salt plant. The exxternal CSCC is clasic.

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[alexit]

The fluid can be between 0 and +70 degrees celsius, though normal conditions would be 0 to 15 degrees celsius. Because of heat transfer requirements plastics are not on option.

Would you suggest 2205?

The part is minimal loaded, we are looking for 1-2 bar differential pressure integrity only when you say 316 tube failed I am thinking you were at 5-6 bar? Was it a minimal leak or catastrophic split?

 

[EdStainless]

No, I don't see 2205 as an option. It would escape CSCC but it would pit quickly in this service.

The 316 that failed was from salt dust settling on the tube and then becoming wet from condensation. It was a 2 bar system. The tubing is literally coming apart.

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Rust never sleeps
Neither should your protection

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[unclesyd]

If you could use an inhibitor you could use steel and galvanized steel as the old block ice plants used throughout the process.
The process used NH3 refrigeration to cool a brine solution that circulated around the cans where the block ice was formed. the large tanks we steel and cans holding the ice were galvanized. The ammonia piping was a combination of both CS and Galvanized.

 

[EdStainless]

Syd, at low temp galv would be a good option. All of the equipment in salt mines is simply galv.
In a warmer system I don't think that it would hold up long enough.

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Rust never sleeps
Neither should your protection

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[alexit]

Ed,

What would be the upper temp limit your recommend for galvanized? Would that be better than a stainless at the same temperature range?

Thanks,
Alex

 

[EdStainless]

I have never seen galvanized used for brine contact above 40F.

You are going to need to use a high Ni alloy or a good engineered plastic.

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Rust never sleeps
Neither should your protection

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[unclesyd]

After the introduction of the "Turbo" ice plants the "Block" ice plants would run several weeks and then go idle for several weeks at which time the brine would approach 100F in the ice house. I can't recall ever hearing that this caused any problems.

I think that the traveling ice shows and some stationary ice rinks still use brine and the heat transfer medium.