Brown Stain in Corny Keg

Brewing Processes
1

Just getting around to cleaning some corny kegs a friend gave me, and I have one with a brownish stain in the bottom that I can’t remove. It is probably a spot where a bit of liquid (assuming beer because he was a brewer but who knows) pooled for a long period of time. It’s not a solid brown spot. It’s more like sort of haphazard rings of various shades of brown and roughly 3" across.

So far I’ve tried PBW, Craft Meister Alkaline Brewery Wash, and StarSan with no luck.

I just want to use this keg for periodic cleaning of beer lines, so I’m not sure if the stain is a big deal. But I would feel better if I could get it cleaned up.

Any ideas?

2

Bar Keeper’s Friend

3

Might be rust.  Passivate the SS with a couple cups of muriatic acid.

4

my bet its in a blemish in the glass…from production. i have one with the same thing…brownish spot on bottom and its clearly in the layer of glass.

throw crap ton of oxyclean in there…if it doesn’t come out its likely in the glass.

5

Glass in a corny keg???

6

haha my bad. i could have sworn i read carboy…only had one beer so far  ::slight_smile:

7

Isn’t Nitric acid used to passivate SS in industrial settings, as it is an oxidizer.

8

I guess it could be rust, but it sure doesn’t look like rust. I can’t imagine what else it could be though that wouldn’t have come off with the cleaners that I’ve tried.

Can I use phosphoric acid? And if yes, how much should I dilute it?

9

Here is advice from a metallurgist named Palmer. Bar Keepers Friend is the source of oxalic acid. You might need someone with skinny arms to reach the bottom to scrub.
http://www.howtobrew.com/appendices/appendixB-1.html

10

Thanks.

11

One of those sponge on one side and scrubby pad on the other and a broom handle can work in place of the skinny arm too.

Paul

12

I keep a toilet bowl brush (never used on a toilet, of course) for keg scrubbing duties.

13

Ha!  I know exactly what you are talking about.  Got my arm caught in one a few weeks back.  Next time I will hold my wife upside down by her legs and let her go in for a good cleaning.

14

My arms are just long and skinny enough to get shoulder deep into a keg allowing me to rest my palm flat on the bottom. Makes my yearly deep clean and rebuild easier.

15

Words to live by.

16

Ha! No doubt!

17

That is an almost sure way to cause rust. Muriatic acid (aka: hydrochloric acid) supplies the chloride ion that is what is needed to cause stainless steel to rust. Don’t ever use muriatic acid on stainless steel.

On a side note, organic stains and deposits can sometimes be dissolved with sodium hydroxide solution (lye). It is very aggressive with organic matter (including your skin), be careful with its use.

18

Martin,
I’m an engineer not a chemist, so I’ll gladly differ to your expertise.  What would be a good, easily obtainable and reasonably safe acid to use to passivate SS?

19

I’m an engineer and not a chemist either. But, I understand the standard for SST passivation is Nitric acid. However as you are probably aware, its not really easily available to regular folks. As a semi-decent alternative, oxalic and citric acids are the active acids in BarKeepers Friend.

20

Thanks, I’ll get some and try it on my boat stainless too.