I have a 1/2 barrel keg that I rescued from the scrap heap. It had several small holes drilled in it(presumably from the mfg to scrap). Welded it up with no problem. The problem I have is that it has red oxide floating around inside that I presume is rusty steel. It was there before I welded it up, so it is not from that.
How do I go about removing this and getting a "clean" interior? Mechanical means are out. I presume some sort of acid bath. What type? How strong? I have easy access to phosphoric acid and can get reasonably strong hydrocholoric without breaking the bank.
I would like to get this to a sanitary status, as I intend to use it as a fermenter for homebrewing.
On 21 Jun 2004 07:39:54 -0700, snipped-for-privacy@yahoo.com (Jeridiah) vaguely proposed a theory ......and in reply I say!:
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hmmm...are you sure you want to get _rid_ of that red stuff?
stainless barrel, red liquid....brewing....
Seriously, I would never...... not _ever_ advise somebody on what to do to get a stained "stainless" keg to "a sanitary status" when they are going to leave stuff in it for any length of time and then consume the product, and had no idea of the history of the
.......(discarded as useless/dangerous and......
_drilled to prevent filling_)
.....barrel.
Jesus! When I buy stuff at auctions and get it from junk piles, I _smell_ it from a distance! And believe me that's learned behaviour. I I once opened a can of "oil" and nearly passed out from the ammoniacal fumes. Still don't know what it was.
One advantage of buying a block of land at the the top of the hill is that nobody can dump _their_ shit on _you_ Joooooookking!
Assuming your barrel is made from one of the 300 series stainless materials, nitric acid should do the trick. Nitric is sold in drums made of stainless, and it is nitric, along with potassium dichromate, that is used to properly passivate 300 series stainless (per MIL specs, anyway). The one problem you may have is in buying it. Unlike HCL, which would not work in this instance, it isn't available at hardware stores. HCL would dissolve the red substance, assuming it is rust, but it would also have a negative affect on the drum. Should you find nitric, keep in mind how aggressively it attacks tissue. It's really hard on eyes. Don't ask. :-)
One thing to consider is that the drum has been used in manufacturing drugs. The red you see may not be rust. I'd go cautiously before using it for anything that you're going to consume.
As others have noted, you should abort this project. Stainless does not rust under normal exposure to beer. That red may very well be some other type of waste, bacteria, etc... Whatever it is you don't want to drink it and it will cost you way more money and effort to properly sanitize the container than to buy a brand new keg.
If you know enough to be tryign to get it snitary for brewing, then you
*SHOULD* know enough that you're never going to make it happen. Lets assume that it is (against all odds... Stainless isn't supposed to rust under anything resembling "normal" conditions) actually rust. That implies that the inner surface is probably pitted to some degree, and those pits are going to provide a haven for "bad news bugs" that'll cheerfully turn your brew, whatever it might be for a particular batch, into garbage.
So, assuming you can "rinse out" the rust somehow, your next problem is going to be filling/sealing/otherwise handling the pits.
I don't even want to go there...
Scrap that thing (this time, damage enough that no poor sap is going to be tempted into wasting time trying to salvage it like you were - may I suggest a fire-axe, applied with great gusto?) and buy a proper keg (or better yet, proper glass carboys) for your fermenter. I'm thinking you'll be *MUCH* better off in the long run, and I'll do everything but give you a guarantee that you'll spend less money in the process.
Significantly more than that. In any case, it came down to the fact that I have it and could repair it. I very seriously doubt it was used for anything other than beer as it has that stale beer smell to it. The concern was the rusting. My guess is that it was drilled with a standard HSS bit and this caused the rusting.
It is 304L stainless.
In any case, maybe it will become a BBQ.
I was a little annoyed when I found the holes. I had taken out the diptube and was preparing to wash it out when I saw the bright spots on the bottom. Looked it over and found about 7 - 1/8" holes drilled into it in various spots.
A carboy is a viable option, but it would take 2 - 6 gallon carboys at ~$25/ea for an equivilant volume so if there was a way to clean this in a reliable manner it was a savings of $50.
Boy you got a lot of negative comments. Is this a Beer keg or was it for something else? I would flush it with a lot of water to get all the loose stuff out. Then inspect it with a light thru the bung and see what the inside looks like. Phosphoric acid would be worth trying. You might also be able to get citric acid from a grocery. That and some sand and tumbling ought to get it clean. If you can get it looking clean, then clorox bleach to sterilize it and more water to flush it out.
I would really like to know what it was used for before using it. If I couldn't find out what it was originally used for, I might still use it if I felt lucky. You could put some water in it for a few days and then get the water tested.
Don't give up on the keg just yet. Stainless Steel can and will rust. Check out this section of the online book "How to Brew" by John Palmer. Appendix B is about Metallurgy and the page 'B.1' is about SS. The whole section is a good read and might help you in your mission. Other parts of Appendix B talk about SS also.
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BTW, John Palmer is a Metallurgist as well as a beer brewer and author. His book is one of the best out there.
I think I need to clarify this a little bit after re-reading my post and the several negative comments I recieved. The red oxide is/was pretty much limited to the edges of the drilled holes. I cleaned them as well as possible from the outside, but that wasn't terribly much. I purged the interior with argon before welding and patched the holes up.
As I mentioned elsewhere, I concluded the rust was contamination from the drilling process, not some other foreign entity.
I have had some phosphoric acid in the bottom of the keg for about a week. I looked into it again last night, and the welds look "clean". They look like discolored SS, but are basically smooth and proper looking. Not a lot of carbide precipitation or anything to that effect.
They are not shiny and smooth, and I can't think of a good way to get in there and grind/smooth them off.
As I understand it, the process of passivation is not well understood. The accepted concept (at least where I came from) is that there is a given amount of "free" iron on the surface of stainless, and this free iron is what rusts. When you machine, or otherwise work on stainless, if you expect it to remain rust free, the passivation process is required. Nitric acid and potassium dichromate, along with distilled water and a slightly elevated temperature (about 130 degrees F as I recall) is all that is required to remove the free iron, which is what rusts. Once it's gone, either by rusting or by passivation, the process ceases. By using phosphoric acid, it is not removed, but converted to a compound of phosphorus, better known by many as Parkerizing. I don't know that it makes all that much difference, for it, too, may be a stable surface.
Given that you suggest the rust is only around the holes that were drilled, I'd consider that to be a normal reaction for stainless that is subjected to the elements but has not been passivated. I have components on my custom built mail box that have done a like thing, pieces that were bead blasted before mounting. In order to remain rust free, they will require passivation. All in good time!
Good luck with your keg! Didn't mean to imply that it shouldn't be used, just to exercise caution if it had an abundance of rust, which might have been a deposit of some chemical, not really rust. Apparently not.
Citric acidisoften used toremove freeiron from 300 series stainless steel. This is much safer than the other acids listed. Searc the web for Citric Acid and Passivate. and you may find some supplier however it can be purchased at many drugstores.
The process is actually fairly well understood. The acid used for passivation preferentailly acts on ferritic iron (which is why nitric works so well for passivating, etching grain boundries of a weld, for removing broken taps from aluminum, etc) leaving the chromium and nickel.
Also, the process (ideally) promotes the oxidation of the chromium. This forms a hard barrier surface to protect the underlying metal from further chemical action. Similar, conceptually, to aluminum being protected by aluminum oxide (the nemesis of the Al welder; also known as saphire) Note that chromium (and nickel?) are happily attacked by hydrochloric acid, and many stainlesses are sensitive to chlorine containing compounds, like hypochlorites (as in bleach) especialy at higher temperatures. HCl is also aggreessive on aluminum, removing the protective oxide and reacting with the underlying metal.
You probably don't want to do this to a surface that will come in contact with food.
Cheapest way to get a keg: go to the store and buy a keg of cheap beer. Eat the $20 deposit (OK... in some states its more than $20 but still less than a new one)
I believe this was true in the '40s and '50s. Then liquid fuelled rocketry became important, and a _whole_ lot of studying rapidly went into passivation.
Sort of showing my age, eh? It was in the late 50's and ealry 60's that I worked in the missile facility where all the stainless components got passivated.
We had an engineer at our company that is considered an expert in passivation of stainless steel. He said that it was possible to passivate small stainless pieces in a dishwasher charged with "Tang" beverage concentrate. The citric acid and elevated temperatures are the important elements here.
Pretty cool, cheap, & easy method.
Also, chorine compounds are the enemy of stainless steel. I *never* use bleach to sanitize stainless equipment. Iodophor is prefered.
A friend of mine used to brine meat in a stainless stock pot. One day the thing literally just split down the middle. Now he uses a giant tupperware.
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