Stainless Passivation

[MX1]

Looking to make sure I have the math right, but my plan is to add about 2 tablespoons of Citric acid per gallon of water to get just above a 5% solution to use in my new kettle and fermenter.

Sound right?

I have read that stars can be used but at 1oz per gallon, that cost way to much..

Also, can I reuse the solution? If I start in fermentor, then rack it over to the brew kettle will that be ok? Will it damage my hoses?

Tim

 

[Rev2010]

Never used Citric Acid, only ever used StarSan, so can't answer that one, but yes you can reuse the solution and no it won't damage your tubing, just rinse them with water after the transfer..


Rev.

 

[Nokt]

What about Bar Keepers Friend?

 

[schematix]

Hot citric acid is amazing. I did 10% at 180F. If you do it right your resulting water will be bright green or orange. You can reuse the heck out of the solution.

Starsan and BKF don’t really passivate.

Also you can buy a 5lb bag of citric acid for a little over $10 on amazon.

 

[Cavpilot2000]

Hot citric acid is amazing. I did 10% at 180F. If you do it right your resulting water will be bright green or orange. You can reuse the heck out of the solution.

Starsan and BKF don’t really passivate.

Also you can buy a 5lb bag of citric acid for a little over $10 on amazon.

WHat he said.
Plus, BKF leaves residue that has to be washed off more aggressively than simply rinsing, which is fine for a kettle, but not so good for valves, fittings, and stuff with surfaces you can't wipe off.

 

[MX1]

How did you measure out your solution

 

[MaxStout]

Interesting about Starsan not being effective. The instructions for the Brewbucket I bought called for 1oz/gallon Starsan. Took almost half the damn bottle of Starsan for this.

I haven't used the BB yet, might try the citric method first.

 

[Rev2010]

Interesting about Starsan not being effective. The instructions for the Brewbucket I bought called for 1oz/gallon Starsan.

Not sure I believe the comment that it doesn't really passivate as Phosphoric Acid, which is the highest concentration of ingredient in StarSan, is very well known to passivate. Also, at the strength of concentration of 1oz per gallon how could it not? Has worked fine for all my stainless gear.


Rev.

 

[schematix]

How did you measure out your solution

Used sight glass in BK to measure water.
Converted to mass. Used my brewing ingredient scale to measure the citric acid. Easy peasy.

My brewing vessels looking absolutely flawless when complete. I had done the BKF “passivation” on one of the 3 vessels before this one and uh, the color of the resulting water told me all I needed to know about BKF. It does a great job on my stainless sink though.

 

[hedgie57]

I've never passivated.J use kept the very thing clean and haven't had any problems

 

[schematix]

It’s important in low oxygen brewing because iron is a big contributor to Fenton reactions. A poorly passivated vessel has a lot of free surface iron that wort will dissolve into it. Passivating strips it away so a new protective oxide layer can form.

 

[SpikeBrewing]

A lot of misinformation about passivation. We've actually worked with one of the local universities on this topic. See our knowledgebase article which touches on the subject and has a link to a study touching specifically on stainless steel passivation.

https://spikebrewing.freshdesk.com/...-do-i-need-to-passivate-my-kettle-before-use-

 

[MaxStout]

Not sure I believe the comment that it doesn't really passivate as Phosphoric Acid, which is the highest concentration of ingredient in StarSan, is very well known to passivate. Also, at the strength of concentration of 1oz per gallon how could it not? Has worked fine for all my stainless gear.


Rev.

I was skeptical too, but another poster mentioned it and I wanted to investigate it further. It seems to me that a more concentrated solution of Starsan would provide enough acid to remove free-iron deposits. SS Brewtech suggests either Starsan, BKF or citric will work.

Thank you to @SpikeBrewing for the linked information. Maybe we've been over-thinking this.

 

[schematix]

I think the point here is that not all stainless has been perfectly treated before it gets to you. I know I have a dozen fittings with rust on them and they claim to be 304 or 316.

So yah stainless does auto oxidize - in fact you let it air dry after using the chemicals. But that doesn’t mean it isn’t otherwise contaminated or completely free of surface defects.

It’s certainly a process that’s not for everyone.

 

[MX1]

I will still put my gear through the process at the concentration I stated in the OP if for no other reason than cleaning

 

[Cavpilot2000]

I have found that letting a normal concentration of STar-San solution sit for a few days at room temp in my BK will make it bright and fresh-looking.
But citric acid is cheaper and more friendly to work with and, with heat, can do the job in under an hour.

 

[LarMoeCur]

I think the point here is that not all stainless has been perfectly treated before it gets to you. I know I have a dozen fittings with rust on them and they claim to be 304 or 316.

So yah stainless does auto oxidize - in fact you let it air dry after using the chemicals. But that doesn’t mean it isn’t otherwise contaminated or completely free of surface defects.

It’s certainly a process that’s not for everyone.

I’d bet those rust marks are pieces of steel left over from the tooling process. Most fitting parts are cast and then machine finished with steel carbide cutters. Kettles are pressed into steel molds using heat and a hydraulic steel ram. These industrial processes can leave carbide/steel pieces embedded in surface of the stainless. Those impurities may not immediately rust but over time will start to show. A good acid bath should dissolve those less hard/acid resistant pieces of non-stainless. Clean stainless will instantly passivate when exposed to oxygen.

 

[Bilsch]

Not sure I believe the comment that it doesn't really passivate as Phosphoric Acid, which is the highest concentration of ingredient in StarSan, is very well known to passivate.
Rev.

Where did you find the very well known sources that state phosphoric acid will passivate, i.e. remove iron and enrich the chromium layer? Because I can find no incidences in the metal finishing industry where H3PO4 is used for this purpose. It is sometimes used as a pickle but that's a different process.

While this idea keeps popping up on homebrew sites, the reality is that Starsan (phosphoric acid) does not passivate stainless.

 

[Rev2010]

Where did you find the very well known sources that state phosphoric acid will passivate.

I don't keep a log of all the sources I've read from when I initially was looking to passivate stainless years ago. But a simple Google search yields this as an top result example:

https://www.bssa.org.uk/topics.php?article=32

"Phosphoric acid is used as a chemical-cleaning agent for stainless steels.
It is used in commercially available stainless steel cleaning preparations and so if used in accordance with the manufacturers / suppliers instructions will not etch or corrode the steel surface.
Phosphoric acid is not considered to be a 'passivating' acid but the clean surface left after treatment should allow the stainless steel to naturally self passivate."

Also the came up which included Phosphoric in the test: http://astropak.com/wp-content/uploads/2015/01/Comparison-Of-Passivation-Modalities.pdf

"Conclusion
All three passivation modalities provided enhanced corrosion resistance on the 304L stainless
steel test coupons. The citric acid passivation proved to be the most efficacious surface
treatment tested"

Whether it's right or wrong I don't seem to have any issues with my stainless equipment that I used StarSan in high concentration with.


Rev.

 

[Bilsch]

My problem is that your initial post makes it sound as if phosphoric is commonly used at a passivating acid. These two links are hardly constitute "well known" in the industry. One even says quite clearly that phosphoric is not considered a passivating acid. Used as a cleaning acid certainly, but as I said is not used in the metal finishing industry for passivation. There is a reason no one uses it.

 

[MX1]

My problem is that your initial post makes it sound as if phosphoric is commonly used at a passivating acid. These two links are hardly constitute "well known" in the industry. One even says quite clearly that phosphoric is not considered a passivating acid. Used as a cleaning acid certainly, but as I said is not used in the metal finishing industry for passivation. There is a reason no one uses it.

Well the team at SS Brew Tech seem to think Starsan can be used to passivate it.....

and this thread is not about Starsan, it is about the amount of CA I plan to use

 

[Bilsch]

Use 4% citric at 160f to 180f for an hour or two.

 

[user 246304]

I was very surprised to find one of my vessel's inside bottom hit pretty heavily with rust one morning. I was concerned I was making a bonehead move by keeping them on my mild steel (and rusting, by design, really) frame. But even to my inept-technically mind, it seemed weird the oxidation would move through the metal from the ss contact with the stainless. Never had this issue before. Not knowing other methods (actually, never had the need with other builds, either), I used BKF and rinsed off like crazy.

Perhaps I'm blowing it by keeping the vessels on the frame? I always hot rinse, wash with PBW after a session, rinse again (all through a pumped recirc), and carefully dry the vessels, FWIW.

 

[MX1]

I was very surprised to find one of my vessel's inside bottom hit pretty heavily with rust one morning. I was concerned I was making a bonehead move by keeping them on my mild steel (and rusting, by design, really) frame. But even to my inept-technically mind, it seemed weird the oxidation would move through the metal from the ss contact with the stainless. Never had this issue before. Not knowing other methods (actually, never had the need with other builds, either), I used BKF and rinsed off like crazy.

Perhaps I'm blowing it by keeping the vessels on the frame? I always hot rinse, wash with PBW after a session, rinse again (all through a pumped recirc), and carefully dry the vessels, FWIW.

has it rusted again after BKF?

 

[user 246304]

has it rusted again after BKF?

No - or at least I think not. Kind of sucks, but we had to move and my brewery is at a garage my friend is lending me, so far without water, though there is electrical. All my lab/propagation stuff is here at home. So cannot easily get over there as often to see the vessel condition. Hope not! Had never seen rust like this on s/s, before, so I guess I was broadsided a bit.

 

[augiedoggy]

I have a stainless meat slicer we bought for our brewpub at an auction that has rusted spots starting all over (my guess is someone used steel wool). I tried BKF twice and even left a film of it and the rust still comes back. I will try citric acid next.

it did always seem to work on my brewing kettles though.

 

[Cavpilot2000]

Looking to make sure I have the math right, but my plan is to add about 2 tablespoons of Citric acid per gallon of water to get just above a 5% solution to use in my new kettle and fermenter.

Sound right?

Tim

Not sure about 2T/gal.
5% is around 6.5 oz.
Not sure how much a T of citric weighs, but I don't think 2T will get 6.5 oz.
I made 10 gallons of 5% yesterday which, unless my math is way off, was 4 lb of citric acid.

 

[MX1]

maybe your right, but it seemed to work out, it was really just another step in the cleaning process.
SS really does not need to be passivated at our level (IMHO) but every little bit helps

 

[Cavpilot2000]

maybe your right, but it seemed to work out, it was really just another step in the cleaning process.
SS really does not need to be passivated at our level (IMHO) but every little bit helps

I also question whether the heat is necessary for the process, but rather speeds the process. I strongly suspect that a room temp soak for, say, 24-48 hours, will do the same thing.

 

[Bilsch]

I think there were some charts in the NASA write up with temperature as a variable. My take on it was to use heat.