Author Topic: Dark spots, ? beer stones in the bottom of my keg...What to do?  (Read 838 times)

Offline denny

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Re: Dark spots, ? beer stones in the bottom of my keg...What to do?
« Reply #30 on: June 25, 2020, 03:31:53 PM »
There is a lot of misinformation out there about passivating stainless steel. One of being that Bar Keepers Friend will passivate stainless. Even Palmer says it can be passivated with BKF. I used to believe that until I dug deeper into the subject.

BKF contains oxalic acid, which cannot passivate stainless steel. The problem has to do with free iron molecules on the surface of the stainless which prevents chromium from oxidizing, oxalic acid cannot remove this free iron. The layer of chromium oxide is what prevents the iron in the metal from reacting to oxygen and creating iron oxide. It may be possible to create a some passivating to occur naturally after scrubbing with BKF, but it it is not consider passivation by stainless steel manufacturers. Too much free iron is on the surface to create a good layer of chromium oxide.

The only accepted way is to bath the SS in either nitric or citric acid. Citric acid is the preferred acid because not only is it way safer, but it does a better job of creating a deeper layer of chromium oxide. Both acids will remove the free iron. After a soak in the acid solution, the SS needs to be dried and exposed to air for 24-48 hours. Citric acid is available at any place that sells canning supplies for fairly cheap.
idk man, palmer is a metallurgist aka a metal scientist/engineer, if he says bkf will passivate ss i'm gonna have to believe him

Not to mention experience.  I've used BKF to passivate SS several times and it's never failed me.
Life begins at 60.....1.060, that is!

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"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." - Bertrand Russell

Offline Village Taphouse

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Re: Dark spots, ? beer stones in the bottom of my keg...What to do?
« Reply #31 on: June 25, 2020, 04:24:13 PM »
I suppose there could be some variables at play as well.  If you received a very clean [used] keg and your cleaning practices were good and you also happened to have soft water, your keg may stay in very good shape.   Some of my kegs were purchased years ago when AIH was selling used ball-lock Cornelius kegs for $15.  Some looked like they had been stored at the bottom of a lake.  Yes, I cleaned them well but I also have high bicarbonate in my water and shower doors, faucets and the coffee maker all show signs of it.  I am now 50% of the way through my kegs... filled one last night with boiling water and EasyClean and left it until this morning.  A very light scrub with a green pad and it looks brand new now... sparkling clean and no buildup at all. 
Ken from Chicago

Offline HighVoltageMan!

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Re: Dark spots, ? beer stones in the bottom of my keg...What to do?
« Reply #32 on: June 25, 2020, 07:39:51 PM »
There is a lot of misinformation out there about passivating stainless steel. One of being that Bar Keepers Friend will passivate stainless. Even Palmer says it can be passivated with BKF. I used to believe that until I dug deeper into the subject.

BKF contains oxalic acid, which cannot passivate stainless steel. The problem has to do with free iron molecules on the surface of the stainless which prevents chromium from oxidizing, oxalic acid cannot remove this free iron. The layer of chromium oxide is what prevents the iron in the metal from reacting to oxygen and creating iron oxide. It may be possible to create a some passivating to occur naturally after scrubbing with BKF, but it it is not consider passivation by stainless steel manufacturers. Too much free iron is on the surface to create a good layer of chromium oxide.

The only accepted way is to bath the SS in either nitric or citric acid. Citric acid is the preferred acid because not only is it way safer, but it does a better job of creating a deeper layer of chromium oxide. Both acids will remove the free iron. After a soak in the acid solution, the SS needs to be dried and exposed to air for 24-48 hours. Citric acid is available at any place that sells canning supplies for fairly cheap.
idk man, palmer is a metallurgist aka a metal scientist/engineer, if he says bkf will passivate ss i'm gonna have to believe him

Not to mention experience.  I've used BKF to passivate SS several times and it's never failed me.

It may passivate, but there are varying degrees of passivation. Clean SS will have limited passivation  on it's own, but nitric and citric acids will provide the best protection. It's not hard to look it up and discover this is true. If scrubbing and oxalic acid were to work, Coors wouldn't have had to spend a bunch of money looking for an alternative to nitric acid. Not only is citric acid safer, it provides better protection from corrosion.

Offline denny

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Re: Dark spots, ? beer stones in the bottom of my keg...What to do?
« Reply #33 on: June 25, 2020, 07:58:21 PM »
There is a lot of misinformation out there about passivating stainless steel. One of being that Bar Keepers Friend will passivate stainless. Even Palmer says it can be passivated with BKF. I used to believe that until I dug deeper into the subject.

BKF contains oxalic acid, which cannot passivate stainless steel. The problem has to do with free iron molecules on the surface of the stainless which prevents chromium from oxidizing, oxalic acid cannot remove this free iron. The layer of chromium oxide is what prevents the iron in the metal from reacting to oxygen and creating iron oxide. It may be possible to create a some passivating to occur naturally after scrubbing with BKF, but it it is not consider passivation by stainless steel manufacturers. Too much free iron is on the surface to create a good layer of chromium oxide.

The only accepted way is to bath the SS in either nitric or citric acid. Citric acid is the preferred acid because not only is it way safer, but it does a better job of creating a deeper layer of chromium oxide. Both acids will remove the free iron. After a soak in the acid solution, the SS needs to be dried and exposed to air for 24-48 hours. Citric acid is available at any place that sells canning supplies for fairly cheap.
idk man, palmer is a metallurgist aka a metal scientist/engineer, if he says bkf will passivate ss i'm gonna have to believe him

Not to mention experience.  I've used BKF to passivate SS several times and it's never failed me.

It may passivate, but there are varying degrees of passivation. Clean SS will have limited passivation  on it's own, but nitric and citric acids will provide the best protection. It's not hard to look it up and discover this is true. If scrubbing and oxalic acid were to work, Coors wouldn't have had to spend a bunch of money looking for an alternative to nitric acid. Not only is citric acid safer, it provides better protection from corrosion.

I have no doubt that's true, but for my purposes BKF worked great.  Took the rust off a poorly cut keg and it has not returned after 8 years.
Life begins at 60.....1.060, that is!

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The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

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Online erockrph

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Re: Dark spots, ? beer stones in the bottom of my keg...What to do?
« Reply #34 on: June 25, 2020, 08:37:06 PM »
There is a lot of misinformation out there about passivating stainless steel. One of being that Bar Keepers Friend will passivate stainless. Even Palmer says it can be passivated with BKF. I used to believe that until I dug deeper into the subject.

BKF contains oxalic acid, which cannot passivate stainless steel. The problem has to do with free iron molecules on the surface of the stainless which prevents chromium from oxidizing, oxalic acid cannot remove this free iron. The layer of chromium oxide is what prevents the iron in the metal from reacting to oxygen and creating iron oxide. It may be possible to create a some passivating to occur naturally after scrubbing with BKF, but it it is not consider passivation by stainless steel manufacturers. Too much free iron is on the surface to create a good layer of chromium oxide.

The only accepted way is to bath the SS in either nitric or citric acid. Citric acid is the preferred acid because not only is it way safer, but it does a better job of creating a deeper layer of chromium oxide. Both acids will remove the free iron. After a soak in the acid solution, the SS needs to be dried and exposed to air for 24-48 hours. Citric acid is available at any place that sells canning supplies for fairly cheap.
idk man, palmer is a metallurgist aka a metal scientist/engineer, if he says bkf will passivate ss i'm gonna have to believe him

Not to mention experience.  I've used BKF to passivate SS several times and it's never failed me.

It may passivate, but there are varying degrees of passivation. Clean SS will have limited passivation  on it's own, but nitric and citric acids will provide the best protection. It's not hard to look it up and discover this is true. If scrubbing and oxalic acid were to work, Coors wouldn't have had to spend a bunch of money looking for an alternative to nitric acid. Not only is citric acid safer, it provides better protection from corrosion.
No doubt Coors has a lot more invested in their brewhouse and it sees a lot more use than the typical homebrewer. While oxalic acid passivation may not be up to ASM standards, it is certainly good enough for most homebrewers.

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