Unremovable stains after stainless steel passivation

[happyduke]

Hi guys,

So I've found one of these passivation methods on the internet which includes using a higher ratio of Bar Keeper's Friend. You basically make a paste using 1:2 water to BKF ratio (I might've used kinda 1:3, not sure though). I've used this method on my electric brewery (local-made, very similar to Anvil or Robobrew) and a keg. While the keg turned out ok except posts being a bit darker now, the brewery has covered with cloudy stains which I was unable to wash out. Unlike keg, there was distinct smell when BKF reacted with the metal. I still brewed with that stains (well, don't know how the beer will turn out) and after cleaning it with OxiClean-TSP solution the stains turned kinda yellowish and bluish color (see the pictures below).

Any ideas on how to fix this? Did I just ruin my brewery? =(
Also, interested in how it could have affected the beer I just brewed.
Thanks!

 

[RPh_Guy]

I'm not really an expert on this, but I'd suggest using BKF as directed on the package.

It makes my stainless shiny like new. I spray on some water, sprinkle the powder, scrub with a soft wet sponge, and then rinse. Contact time should be short, like a minute.

 

[augiedoggy]

The smell from the BKF is normal. it is not harming the stainless. the rust stains are likely from machining contamination on the surface of the stainless but it could just also be the stainless rusting depending on quality. I use BKF with a rag or sponge and scrub the surface with it as its mild abrasives will remove the stains and the acid will passivate which should aid in preventing the rust from reappearing but if it comes back the contamination is deeper in the surface.

In any case your brewery is still fully functional and fine..

 

[happyduke]

Forgot to mention, the brewery is almost new so the rusting isn't something to expect at this stage. Anyway, will try BKF again but in normal dosages.

 

[augiedoggy]

Forgot to mention, the brewery is almost new so the rusting isn't something to expect at this stage. Anyway, will try BKF again but in normal dosages.

stainless rusting has nothing to do with age. Its not supposed to rust. but this is actually a common thing Ive seen reported on all sorts of brands of equipment including blichmann and ss brewtech..

 

[happyduke]

I see, thanks! So I tried BKF as per instruction and the rust stains have turned cloudy again:

I'm afraid it will become rusty again after my next brew. Maybe I should re-passivate it with StarSan or something? Or I don't know... I mean it was shiny before my "passivation" :|

 

[augiedoggy]

I see, thanks! So I tried BKF as per instruction and the rust stains have turned cloudy again:

I'm afraid it will become rusty again after my next brew. Maybe I should re-passivate it with StarSan or something? Or I don't know... I mean it was shiny before my "passivation" :|

just curious, are you using the liquid bar keepers friend polish or the powder? maybe you have unpolished the stainless somehow. Ive used both and the liquid bkf seems to work better to polish.

 

[happyduke]

Powder, like this one.

 

[augiedoggy]

Powder, like this one.

they make a liquid which has finer abrasives and leaves a shinier finish when used.. it honestly looks like you havent scrubbed enough to remove the stains though.

 

[happyduke]

Ok, thanks for your help, I'll try the liquid one and will scrub harder.

 

[RPh_Guy]

@augiedoggy Thanks! I always learn from your posts.

 

[ZmannR2]

Bought me a Spike conical fermenter recently and came with paperwork saying passivation of Stainless has become a "buzz word" lately and really isn't needed....Thoughts?

 

[day_trippr]

I dunno, if I started seeing rust spots on my new conical, kettle or bucket, I'd be highly concerned.
It shouldn't happen, period...

Cheers!

 

[RPh_Guy]

Bought me a Spike conical fermenter recently and came with paperwork saying passivation of Stainless has become a "buzz word" lately and really isn't needed....Thoughts?

My limited understanding is that no, it's not necessary. I haven't ever actively passivated my stainless equipment.

 

[Bilsch]

Just do it the right way with a 4% citric acid solution at 160-180 degrees for about an hour. You spent a lot of money on your stainless kit.. whats a few more bucks to passivate it correctly.

 

[augiedoggy]

My limited understanding is that no, it's not necessary. I haven't ever actively passivated my stainless equipment.

me either.. then again ive read that the simple act of boiling water in it would passivate it so..

to be honest, In the first photo it kinda looks like the ring sitting in the channel in the top of the kettle may be made of a dissimiliar lower grade of stainless and rusting where its sitting against the kettle and moisture is trapped in there? either that or the tool that was used to press that channel into the top lip of that kettle had some ferrous metal contamination or intself was made of ferrous metal which left contamination in the surface thats causing the staining.. theres lots of possibilities here but I have seen white cloudy stains like this on my 3bbl boil kettle on the outside which I have always been able to polish out with BKF even though it would take a lot of scrubbing.

 

[augiedoggy]

You spent a lot of money on your stainless kit..

Exactly, and for that kind of money it really should already be done if needed.

 

[happyduke]

Exactly, and for that kind of money it really should already be done if needed.

Yeah, but even if you pay extra for that high-end equipment the manufactures still recommend doing that. Suppose there should be a reason for that...

 

[augiedoggy]

Yeah, but even if you pay extra for that high-end equipment the manufactures still recommend doing that. Suppose there should be a reason for that...

I bought my 3bbl system new and there was no mention of passivation.. As mentioned above spike is saying its not needed on their stuff..

 

[Bilsch]

me either.. then again ive read that the simple act of boiling water in it would passivate it so..

I’ve read that starsan will passivate stainless but that isn’t true either so...

 

[TheMadKing]

Agreed, with the above posts that passivation should not be needed. It said specifically on my spike+ system that it's not required, which makes sense because passivation is the formation of an oxide layer on the surface of metal that prevents corrosion and stainless is typically dipped in nitric as part of the manufacturing process after welding, then exposed to air to allow the oxide to form evenly.

Looking at your photos I think you may have received a cheap/bad alloy of stainless, or even worse just nickel plated steel. Can you contact the manufacturer and ask what grade of stainless he used? It should be 304 or 316. If it's 200 series, that is prone to rusting, and if it's only nickel plated, or stainless clad then I'm afraid you might have eaten through the corrosion resistant cladding but I really hope not

Edit: apparently you can save a cheap grade of stainless by redoing the passivation from scratch, but you need to immerse the pot in enough citric/nitric/phosphoric acid to completely remove the chromium oxide layer evenly over the entire surface and then let it immediately air dry overnight (not rinse). That will only work if it's truly stainless and not if it's simply a cladding or electroplating

 

[augiedoggy]

I’ve read that starsan will passivate stainless but that isn’t true either so...

ahh found the confusion... boiling water in an aluminum pot will passivate it.

 

[happyduke]

Agreed, with the above posts that passivation should not be needed. It said specifically on my spike+ system that it's not required, which makes sense because passivation is the formation of an oxide layer on the surface of metal that prevents corrosion and stainless is typically dipped in nitric as part of the manufacturing process after welding, then exposed to air to allow the oxide to form evenly.

Looking at your photos I think you may have received a cheap/bad alloy of stainless, or even worse just nickel plated steel. Can you contact the manufacturer and ask what grade of stainless he used? It should be 304 or 316. If it's 200 series, that is prone to rusting, and if it's only nickel plated, or stainless clad then I'm afraid you might have eaten through the corrosion resistant cladding but I really hope not

Edit: apparently you can save a cheap grade of stainless by redoing the passivation from scratch, but you need to immerse the pot in enough citric/nitric/phosphoric acid to completely remove the chromium oxide layer evenly over the entire surface and then let it immediately air dry overnight (not rinse). That will only work if it's truly stainless and not if it's simply a cladding or electroplating

Thanks, this's actaully what I thought as well. Ordered a citric acid, it's cheap and safe for metal. I've read about 40g per 1l of water ratio, 180F for 30 min, going to try that. Will update on the results.

 

[Bilsch]

For everyone who thinks passivizing your stainless isn't necessary...
The citric acid in solution (RO water) starts out perfectly clear then you get this color after about an hour.

Quiz: What is the color of Iron (III) Citrate in a acidic solution?

 

[RPh_Guy]

What is the color of Iron (III) Citrate in a acidic solution?

Green at pH > 2.0.
I cheated.

Passivation pulls off surface iron atoms, preventing Fenton reactions. Right now I'm using a copper CFC, so removing a little iron hardly seems worth the effort. What do you think? I use BtB in the mash and boil.

 

[happyduke]

Ok guys, so I've used a citric solution (4% for 30-40 mins) and the cloudy strains didn't go away but overall it looks shiny. I'm pretty glad with results anyway because my recent batch with this brewery turned out very tasty. Taking into account all that's being said I wouldn't do the passivation anymore because it caused me more bad than good so I would recommend to take all such info with a grain of salt.

 

[MaxStout]

Maybe those remaining cloudy stains are due to physical abrasion from the BKF, rather than chemical. A little too much elbow grease and too much BKF being rubbed into it.

 

[Bilsch]

Taking into account all that's being said I wouldn't do the passivation anymore because it caused me more bad than good so I would recommend to take all such info with a grain of salt.

The problem in your case was not with passivation, it was with passivating the wrong way. BKF is meant for abrasive cleaning of smaller areas and stuck on crud while providing chromium enrichment for the areas it abraded. Brewing gear should be done with citric or nitric soak without rubbing and grit.

 

[Bilsch]

Green at pH > 2.0.
I cheated.

What do you think? I use BtB in the mash and boil.

No way to say, each system is different and every piece of stainless in your kit is as well and how it’s been treated. Personally I do what ever I can reasonably to reduce Fe, Mn and Cu in my brewery.