304 Stainless Corrosion Resistance

[BugHunter]

I've recently started culturing sour beers, but I do have one question about storing them once their done. I'll keep it simple: Can you safely (for the container) store low pH sour beer in a keg?

I'm not terribly familiar with the corrosion resistance specifications of 300-series stainless so I'm not sure if kegs can handle prolonged contact with such an acidic media without either developing liquid/air interface pitting or otherwise corroding. Any thoughts?

 

[foltster]

I don't know about beer kegs but the common colas both have ph levels below 3 so corny kegs that used to hold soda should be pretty safe.

soda ph chart:
http://www.selah.k12.wa.us/soar/sciproj2005/Graphs/MarshalN.pdf

 

[BugHunter]

You know, I didn't even consider that these things used to be used for soda... Good point. And this is why I picked up a career staring through a microscope and not working in a welding shop. ;-). Thanks for clearing that up.

 

[mnick12]

304 generally has good corrosion resistance to acidic enviroments, the only case where I would be concerned is saline solutons, like a gose.

In that case I would be worried. Otherwise most sours are probably OK

 

[foltster]

Since many breweries are putting gose beers and other very sour beers into SS kegs, I think there really is nothing to worry about here.

 

[mnick12]

Well it really does depend on the situation. Even though breweries may use 304l for their gose, does not mean its ok for long term storage. 304 is tolerant of up to 1000ppm Cl @ 10C, but at 30C its down to around 400ppm. This doesnt take into consideration the pH, which would surely lessen the chloride tolerance. Under these conditions steel including stainless is highly vulnerable to stress corrossion cracking.

So I would say if you are just using a keg to store sours for a long time, you should be ok. However if you are planning on storing a gose long term, I would consider the final pH and the amount of salt you used.