Alloy Resistant to Bleach 1

[swall]

We supply a 17-7 stainless tension spring for an application involving a chlorine bleach type disinfectant (specifically,sodium dichloro S tirazinetrione). We are getting corrosion fatigue failures in a matter of a couple of weeks.Anybody got ideas on a more resistant alloy?

 

[unclesyd]

Can you post a little more information.

Is this a dry powder exposure?
Is this a solution, give details?
Any other information will help.
What are the quantities needed

There are several materials that will be better but getting a spring is a different story.

 

[rnd2]

Consider treating the spring by coating it with a tough and flexible corrosion resistant material. There are plenty out there.

 

[EdStainless]

It depends, are is the corrosion primarialy pitting or is it chloride stress corrosion cracking?
What strength level do you need?
I hate to say it, but you do need to look at coatings. An alloy solution will be expensive. Give us some more details and we'll come up with some specific suggestions.

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Corrosion never sleeps, but it can be slowed down.

 

[swall]

Tension spring,.050" wire, 17-7 CH900 condition. Fracture occuring in hook after a few days to a week in service, which equates to 12k-30k cycles.Single point of initiation, transverse fracture.No pitting;no evidence of scc. Appears to be corrosion fatigue. The chloro tabs are used in aqueous solution, approx. 10% at 250F, then steam/hot water rinse.Coating would be a problem, since this is a close wound tension spring.Also, this is used in a food service application (disinfecting plastic liners for boxed wine).

 

[moltenmetal]

Have you considered Elgiloy? It's a frequently-used alloy spring material in devices like pressure regulators etc. I don't have any corrosion data on it personally so I can't comment on how well it would work for your application. I would appreciate links in regard to its corrosion resistance properties from anyone who has them.

 

[metengr]

moltenmetal;
The following web site is for a Trent tube publication that does list Elgiloy (page 13) with corrosion resistance in several environments. I did not know that this is a spring material used in bioengineering functions.

http://www.trenttube.com/Trent/downloads/StainlessSteel&Alloy_PDFs/

trent.pdf

Other spring material options include a Carpenter alloy MP35N, or Inconel 718, which has high fatigue strength and is used for spring applications.

 

[metengr]

Bad link;
try this

http://www.trent-tube.com/Trent/literature.htm

go to the the downloads link and open the Stainless Steel and Alloy Tubular Products Handbook

 

[unclesyd]

Multiphase: MP-35N or MP-19 like think would also be a good candidate as stated by metengr.
I don't like 718 as I seen several references to having problems with corrosion fatigue.
Several other alloys are possible, like 625 and 825 but will be hard to get springs.
If anyone has some older literature from Dupont or SPS there was some information on the Multiphase Alloys. My literature shows MP-35N to have outstanding resistance to stress corrosion and cracking and fatigue in salt water.

This material (sodium dichloro S tirazinetrione)is so common there should be data available all over the place, but I don’t seem to find it. Has anyone got an up to date reference on Ti vs this material. A common trade name is "Dichlor" and a chemical trade name is "sodium dichloroisocynurate"

Here is a supplier of all springs needed.

http://www.dracospring.com/index.html

 

[TVP]

Steve,

Elgiloy, Alloy 718, MP35N, or a titanium alloy would be good candidates. Beta C or the new Timet LCB (low cost beta) would be my suggestions for suitable titanium alloys. Contact Allvac or Dynamet about the Beta C, and Timet or Perryman about LCB. I am curious about the relative costs of these alloys. It would be great if you or someone else could share some data on this. Good luck.

 

[EdStainless]

Stay away from 718. C-276 would work, so would 625 and X-750. Elgiloy and MP35N would be great, but they are going to be very hard to find.
I would worry about Ti if there is caustic used in cleaning. Ti only likes oxidizing conditions and caustics will eat it up.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be slowed down.

 

[swall]

Thanks guys, for the tips so far.I've got a call into Elgiloy (I remembered that I know the wire metallurgist over there).At this point, the only suggested alloys I'm leery of are the Inconels. I had a failure a couple of years ago with a swimming pool vacuum cleaner spring made of Inconel 600. Torsion spring. Over 30 I.D. cracks in it within a short time from the chlorinated swimming pool water.

 

[swall]

Elgiloy came back with recommendations for Nitronic 50 and Elgiloy, the Nitronic being the lower cost of the two. At this point, I get to hand this off to product engineering and see what they want to do.

 

[rmw]

Metengr,

I made the link work by copying and pasting into the url address bar, and taking out the space between the slash, and the word trent.pdf if that will help.

rmw

 

[unclesyd]

The link I posted has the alloys mentioned for the springs and they make they might make small lots to test if the spring design is straight forward.

We had some cracking problems Aquamet 22 (22-13-5/ Nitronic 50)in a case where there was around 200 ppm Cl. This was on an agitator shaft at around 200° F. Runs good on the boat in salt water.

I would stay with Elgiloy if the cost don’t bite you. This should get you out of trouble will you test other materials.

 

[EdStainless]

Nit 50 is an austenitic stainless, it will not resist cracking in a chloride environment. It works on boats because it is cathodicly protected by other parts of the structure.
Don't be afriad of C-276, 625 or X-750. They have good corrosion resistance. Your experience with 600 is not unexpected. It has little pitting resistance and micro pits make great stress concentrators. I would expect 800 and 825 to fail under similar conditions.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be slowed down.