H2SO4

More information, please.

What is your application?

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

Is upper limit really 100% H[sub]2[/sub]SO[sub]4[/sub] or perhaps only 93 or 96 or 98%?

High-purity H[sub]2[/sub]SO[sub]4[/sub]?

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

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.

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...

How about using a ceramic/polymer composite coating?

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

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.

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.