H2SO4

[venoma]

hi guys,

I am in the process of making a selection between devices of various vendors (made of exposed parts of titanium (alloy), SS 420, tungsten carbide ?, hardmetal Co/WC, phosphor bronze). Also one gives Hastelloy as an option.

exposure to: 1 - 100% H2SO4, temperature 20 - 80 degrees C...

I guess you guys would go for the Hastelloy option. But what is your opinion and ranking (based on the limited info) on the H2SO4 corrosion resistance of the other materials ?

many thanks

 

[kenvlach]

More information, please.

What is your application?

Any reason not to use glass or PTFE as material or liner?

Is upper limit really 100% H₂SO₄ or perhaps only 93 or 96 or 98%?

High-purity H₂SO₄?

 

[venoma]

thanks kenvlach !

OK, you're right, let's say 98% H2SO4 is the upper limit. (I read that corrosion rates are often maximum around 70%).

Sorry, I should have been more specific. I am talking about rheometers, so the material has also to be tough, hard and abrasion resistant. PTFE and glass are indeed excellent in terms of corrosion resistance for H2SO4, but I guess they are no real options in this application (glass = brittle, PTFE is not hard enough). They are at least not given as an option by vendors. Hope to have made things more clear.

thanks again

 

[rsmallwood]

The selection of a suitable metal depends upon how much corrosion that you can accept. Hastelloy C-276 and Hastelloy B-4 will corrode up to 10 to 20 mills per year (mpy) under some conditions that you listed e.g 0-99 % and 20 to 80 degrees C. Other than glass and PTFE (Teflon), the only materials with corroion rates below 1 mpy throughout the entire range of conditions are high silicon iron (Durion), tantalum, gold and platinum; of these materials tantalum is probaly the most practical or least costly.

 

[venoma]

rsmallwood thanks for your comments

Of course corrosion prevention in a rheometer application is quite critical as a slight change in dimensions easily yields fully wrong measurements. I have now found product info on various Hastelloy alloys and believe that they should be able to do the job. I guess minimization of contact time to these acids and also good washing after measurements are important. Will also look into Tantalum possibilities...

 

[Hush]

How about using a ceramic/polymer composite coating?

 

[twalicia]

Zirconium is a good alternative to Ta and is cheaper. It is slightly more expensive than Hast alloys but better corrosion resistant.

Try this link

http://www.alleghenytechnologies.com/wahchang/pages/products/data/zirconium/zrsulf2.htm

 

[tomwalz]

ceramics?

Call
Scott Pyle
High Performance Alloys
444 Wilson St.
P.O. Box 40
Tipton, Indiana 46072
800 472-5569

he can help you with alloy choices.

 

[JTreglio]

You may want to consider adding a ZrN coating. It will increase your corrosion resistance and is pretty much impervious to scratching (hardness off the Rockwell C scale, around 2600 Hv).

Jim Treglio
Molecular Metallurgy, Inc.