How to remove rust from the inside of a cornelius keg

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SiHoltye

How to remove rust from the inside of a cornelius keg

Post by SiHoltye » Sun Jul 18, 2010 11:54 am

I've got rust on the inside of 2 of my kegs (one shown below).

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To remove this I'm thinking of using a stainless steel scrubber to remove the rust and allowing a day for the oxide layer to reform. All this should be done dry so as not to create rust promoting conditions during the process.

Any advise much appreciated.

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Aleman
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Re: How to remove rust from the inside of a cornelius keg

Post by Aleman » Sun Jul 18, 2010 12:06 pm

Fine wet and dry used wet, Green Scrubby, Dry well . . . Conc Nitric acid . . . rinse . . . sorted

boingy

Re: How to remove rust from the inside of a cornelius keg

Post by boingy » Sun Jul 18, 2010 4:51 pm

Or use Barkeepers Friend, rinse, dry and let it form a new protective layer.

SiHoltye

Re: How to remove rust from the inside of a cornelius keg

Post by SiHoltye » Fri Jul 30, 2010 7:54 pm

What a PITA that is, will be more gentle with the long dip tube from now on. Scrubbed away the rust spots with 160grit 'sand paper' then a non-stick scrubby smooth it a bit. Rinsed and dried with kitchen roll. Currently in the 32°C airing cupboard until I fill it on Monday.
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Subsonic

Re: How to remove rust from the inside of a cornelius keg

Post by Subsonic » Fri Jul 30, 2010 9:49 pm

I am glad I am not the only one who is so obsessed with his kegs :D I can't spell that word after my IPA... Stainless often rusts when scrubbed with wire wool, its fatal to use steel wool on stainless. Someone may have used a wire wool scrubber before you. The best scrubbers for us are shiney nrop ones lol. Subsonic.

gav_k

Re: How to remove rust from the inside of a cornelius keg

Post by gav_k » Sat Jul 31, 2010 3:39 pm

how did you get to reach the bottom? i cant my arm in past my elbow! any advice on how i could do this

Cliff-R

Re: How to remove rust from the inside of a cornelius keg

Post by Cliff-R » Wed Aug 11, 2010 4:22 pm

Yes to the abrasive. Yes to letting the chrome oxide develop, which it'll do all by itself so long as the chrome is about 12% or better.
Problem is, you got pits. You can't get the abrasive action down into those pits and removing them means removing all the adjacent metal.

The easiest cheapest and best solution for pits is Citric Acid. It won't fill 'em but it will strip the ferritic material away leaving the chrome behind which will produce a passivated layer. The result is exactly the same as if you went through the rather cumbersome process of passivation using nitric acid. Just way easier cheaper and with none of the mess to deal with when you are done.
You can use citric in pretty much any form whether pure crystals in water (my preferred method) or just dump some lemon juice in there, or grab a few Vitamin C tabs grind 'em up and mix with a little water.
If you are using lemon juice you can add heat to accelerate the effect.

That'll take care of the rust in the pits plus it'll increase the passive layer's density.

Bribie

Re: How to remove rust from the inside of a cornelius keg

Post by Bribie » Thu Aug 12, 2010 5:23 am

For future reference, from dear old Wikipedia

Rust removal

Phosphoric acid may be used as a "rust converter", by direct application to rusted iron, steel tools, or surfaces. The phosphoric acid converts reddish-brown iron(III) oxide (rust) to black ferric phosphate, FePO4.

"Rust converter" is sometimes a greenish liquid suitable for dipping (in the same sort of acid bath as is used for pickling metal), but it is more often formulated as a gel, commonly called naval jelly. It is sometimes sold under other names, such as "rust remover" or "rust killer". As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces.

After treatment, the black ferric-phosphate coating can be scrubbed off, leaving a fresh metal surface. Multiple applications of phosphoric acid may be required to remove all rust. The black phosphate coating can also be left in place, where it will provide moderate further corrosion resistance. (Such protection is also provided by the superficially similar Parkerizing and blued electrochemical conversion coating processes.)


Phosphoric acid is fairly safe to use, it's in Coca Cola :shock: - and a lot of brewers use it to wash yeast to kill bacteria as well, so should be available without too much hunting around.

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Re: How to remove rust from the inside of a cornelius keg

Post by Wozboy » Sat Apr 03, 2021 10:59 am

gav_k wrote:
Sat Jul 31, 2010 3:39 pm
how did you get to reach the bottom? i cant my arm in past my elbow! any advice on how i could do this
Did you ever get an answer? I'm trying to remotely remove rusty from the bottom of my kegs and I'm facing exactly the same problem couple with a general lethargy to get in and do the job mainly due to conflicting advice on cleaning agents and removal of said rust!

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Re: How to remove rust from the inside of a cornelius keg

Post by Carnot » Wed Apr 07, 2021 7:28 pm

This topic has been covered a number of times. Here is a link of how to passivate SS.
https://bssa.org.uk/bssa_articles/passi ... ss-steels/
There is no better source than this that I know of. The classic way is with nitric acid AND chromates which are very hazardous. The easy way is citric acid and you need to use enough . A lemon is not enough and Vitamin C tablets are whimsical .Vitamin C is ascorbic acid, which is actually quite good as an oxygen scavenger but you could never afford enough to apssivate SS.
If there is rust it is highly likely that wire wool has been used which is an absolute No-No. Never use wire wool or another type of stainless steel abrasive as it may induce corrosion. Polishing requires the proper material and 240 grit abrasives are too aggressive. 1200 grit is about as much as you should use, preferebaly even higher. Better use a proper stainless steel polishing kit such you can find here.
https://www.metalpolishingsupplies.co.uk/
240 grit will leave ridges like a ploughed field and could induce corrosion - self passivation is slow and not always successful which is why chemical passivation is better. Buy some citric acid and soak your kegs. You will need AT least 60 g per litre and fill the keg which means a lot of citric acid. You can re-use the citric acid.

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