Nitric acid/hydrogen peroxide 1

[enmax]

Does anyone have experience of or could point me to a reference on the corrosion of austenitic stainless steel (304L and 316L) in 40% nitric acid/30%hydrogen peroxide mixture at 50 deg C? My instinct is that, as these are both oxidisers , the stainless steel would be OK but I'd would prefer to see a definitive reference if one's available.

http://uk.linkedin.com/pub/terry-roberts/28/a9a/a10

 

[Guest102023]

I have no direct experience, but the Nickel Institute is an excellent online resource.

http://www.nickelinstitute.org

 

[EdStainless]

Here is another good source:

http://tools.outokumpu.com/spt/corrosion/corrstart.asp

While 304 should hold up fine I have some concerns, specifically about the welds.
Any residual delta ferrite in the welds will be attacked fast.
You might consider using overalloyed filler, such as 310 to minimize ferrite in the welds.
You will need to watch out for the rick of hot tearing.

Is there any risk of chlorides in this system? Even in the low ppm levels 304 and 316 would be at risk.

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Plymouth Tube

 

[GHartmann]

My own experience for nitric acid alone, is that 304L is the preferred material.

Not sure what adding hydrogen peroxide does to the corrosion properties.

 

[enmax]

Thanks for your replies. I had previously checked the Outokumpu and Nickel Institute (as well as the Kreysa & Schutze Corrosion Handbook, the NACE Corrosion Database and a few other sources but couldn't find nitric acid/ hydrogen peroxide mixtures - either chemical on its own is OK at the relatively low temperature of 50C but no information on what happens in a mixture of the two. Perhaps the only way would be to do some corrosion tests (on welded samples in view of what Edstainless says!) Edstainless - why is the delta ferrite in the weld susceptible? Galavanic corrosion between the two pahses perhaps? Can you recommend a reference source that I could read up on? The use of 310 would produce a ferrite free deposit and would be expected to be more corrosion resistant because of its higher alloy content but I'm still left with no information on its performance in the mixture.

Regards

http://uk.linkedin.com/pub/terry-roberts/28/a9a/a10

 

[EdStainless]

I have seen as-welded samples etch on the welds in straight nitric (fixtures in our passivation tanks)

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Plymouth Tube

 

[jwhit]

If you stick with 304, unless there is another reason for it, I would use 304L filler or as was suggested a fully austenitic such as 310. It would also be a good idea to Post Weld Solution Anneal to further reduce precipitated carbides in the weld and HAZ. That should significantly reduce the chance of IGC occurring. The solution anneal will reduce the amount of ferrite in the weld in addition to cleaning up any carbides.

 

[cloa]

Have you tried contacting the Nickel Institute? See if they can link you to at least some scholarly articles. I tried Google Scholar but that's hopeless.