corrosion resistance

[marcrhod]

I am looking for recommendations on a corrosion resistant metal suitable for immersion in a process water with 130000 ppm chlorides, pH 5.5, salinity as NaCl 212967 ppm.

This material must be workable for small hardware parts, be strong for gears and large shafts.

I have been given the suggestion of 6XN but wish to confirm and get other recomendations.

Thanks

 

[Metalguy]

I think I'd use something like Alloy 718 instead.

 

[CoryPad]

Titanium and its alloys essentially are immune to chloride corrosion attack. There are processes such as nitrogen diffusion hardening that can harden selectively the surface for wear-resistance applications like gears. Timet is a good supplier:

http://www.timet.com

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[stanweld]

There are a number of materials available, but selection must also be based on temperature. What is the temp. range of operation?

 

[JimMetalsCeramics]

You might try Monel.

 

[Rusty1]

Contrary to CoryPad's post, titanium is not immune to chloride attack. Titanium can suffer from pitting and crevice corrosion from chlorides if the conditions are right. It has happened many times on gasket surfaces. I recommend you use a nickel/moly alloy, Inconel or Hastelloy, just about any variety should work, such as Inconel 625 or 686 or Hastelloy C276 if they are strong enough. The ultimate in strength and corrosion resistance can be found by using Inconel 725 or Carpenter 625Plus. Both are precipitation hardening nickel alloys with very high strength and excellent corrosion resistance. The draw back is they can be difficult to machine.

 

[CoryPad]

Rusty1,

Thanks for your information. Of course, there are few guarantees in life, that is why I used "essentially" in my original post. The fact remains that titanium and its alloys are used extensively in chloride containing environments due to its (usual) inertness. One reason to consider it over the other alloys mentioned is its strength/density ratio - it can have around the same strength as the nickel alloys at about half the density. This can make for low mass items (good performance in moving parts like shafts, etc.), and reduce the amount of material that must be purchased (a good thing when considering the cost of the alloys mentioned in this thread).





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