Material selection for Boiling concentrated Sulfuric acid? 2

[nalmeter]

I am trying to develope a process that involves boiling sulfuric acid, 91% Sulfuric acid at 260°C. I am curious if anyone else has had any success in finding a material of construction capable of taking these harsh conditions. the material would be used to construct the reactor vessel. So far I have found that a glass-lined reactor is possible, however, gasketing material (normally PTFE/graphite) may degrade releasing HF and corroding the glass.
Any metals worth while???

 

[IRstuff]

Should check with semiconductor wet processing suppliers. Hot sulfuric was used for removing photoresist from semiconductor wafers in the past.

TTFN

FAQ731-376

 

[EdStainless]

I don't have my curves with me, but 91% sounds too low for metals to handle.
I know that alloy 20 and G30 will not handle this service.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[strider6]

look at these isocorrosion curves.

http://www.sulphuric-acid.com/TechManual/Corrosion/corrosion.htm#Corrosion Charts

hope this help

S.

http://www.corrosionist.com

 

[moltenmetal]

It's too hot for glass and conventional non-metallics and too dilute for most alloys. Tantalum cladding is about your only choice at these conditions, but you'd have to check for sure whether even Ta can handle this. Gasketing is going to be a struggle too.

 

[nalmeter]

I have looked into Tantalum and there appears to be some potential success, however, 260° seems to be a limitation due to hydrogen embrittlement. Pfaudler makes a high temperature glass that supposedly can handle this sulfuric, but testing really has to be done. I also agree that gasketing is truly going to be difficult.

Does anyone have any familiarity with Silicon Iron for this service?

 

[IRstuff]

Here's an article describing using sulfuric to remove photoresist as a replacement for plasma ashing. Gotta love that, I remember when plasma ashing was the rage, since it got rid of the wet sulfuric processing:

http://www.semiconductor.net/article/CA6433057.html

These guys advertise hot pots, so they might be able to help:

http://www.fabtronics.co.uk/about.shtml

TTFN

FAQ731-376

 

[tonyowens]

I've used both virgin and 30% glass-fibre-filled Teflon stock to make fluid-handling parts for sulphuric acid service at all concentrations and fast-ramping temperatures up to 300C w/o problems apart from handling accelerated creep and enormous thermal expansion.
Going that way trades corrosion problems for mechanical design (sealing preload control and dimensional accuracy) ones. SiC-coated steel pipe is another potential route.

 

[nalmeter]

Tonyowens, I am interested in this application, perhaps you can pass along some additional information for me to research. Have you had any floropolymer degredation at temps close to 300°C? I'll check into SiC-coated steel pipes, I was unaware of that; I'm sure there are some special thermal expansion designs especially for large bore pipes...say 10"-14". I appreciate your input. Have you had any luck with Silicon Iron? I also wonder if any of these materials are used in valves?

 

[PLANTRON]

I have a requirement to find historical information that will provide possible rate of corrosion for small bore glass lined pipe - service is seawater, providing cooling water for an alternator cooler on offshore, North Sea.

Known that the seawater in itself is not filtered, this poses an erosion potential for small bore pipe.

Any takers, please???