Be sure to check to read our Before Using Your Equipment: Cleaning Guide first!
Please review dosage and disposal requirements for all chemicals before use.
Do I need to force passivation? Can't I just let the air naturally passivate my tank on its own?
Passivation is the forming of a non-reactive (passive) chromium oxide layer to protect stainless steel.
"If you clean the surface well, then the chromium on the surface will certainly passivate into chromium oxide. However, at best that will only give [~]20% coverage since there’s typically only that much [or less] chromium in the alloy. A proper acid passivation bath increases the surface coverage of the chromium by removing the surface iron, resulting in improved corrosion resistance. -Citrisurf.com
Once you REMOVE the manufacturing residues and oils (via TSP) it can take up to 48 hours to form a passive oxide layer over the entire surface, provided that steel is in an isolated, clean space without any airborne or surface contaminants (loose iron particles, dust, humidity, etc). Since these are common factors in homes and garages, we recommend using acids to induce chemical passivation so you know it's a strong and even coating. Plus this way you can get right to brewing without having to wait.
What if I don't chemically passivate?
Then you aren't doing everything you can to make the best beer. We understand that for most brewers, purchasing stainless steel gear is an investment in making the best beverage they can. We only recommend this step to help ensure that your gear is well taken care of and will last for a long time. Taking care of your investment just makes sense to us.
What acid do you recommend for passivation?
We recommend using citric acid or a citric acid blend like Citrisurf. Citric acid is the most readily available passivation acid for homebrewers in most regions. It is environmentally friendly and not as dangerous for home use as other products for passivation.
What about using Nitric Acid? Isn't that better?
Nitric acid is more hazardous to use in the home environment and isn't always easy to get. Citric acid can easily be picked up in the grocery store, homebrew shop, or from online retailers in almost any region. Citric acid emits no harmful fumes and vapors that can be harmful to the atmosphere. Nitrogen oxides aid in the production of smog and acid rain, citric acid is naturally occurring and does not. In addition to removing free iron, nitric also can remove nickel, chromium, or other heavy metals from steel.
In the words of a NASA published report on citric acid passivation* - "citric acid passivation process performs as well as, or better than, the nitric acid passivation ... The citric acid process also exhibits environmental, safety, and cost benefits in preference to passivation via the traditional nitric acid procedure."
Can I use Bar Keepers Friend or other Oxalic Acids?
Yes, it technically can but we do not recommend it in most cases. Oxalic acid is naturally occurring and simply is nitric acid that has been oxidized with sugar. Bar Keepers Friend or other oxalic acids will clean off loose irons from the surface of the steel (including surface rust!) and will buff out minor scratches in your steel. However, it can also take off your etched gallon markings or logos because those etchings use an oxidization process as well and Bar Keeper's Friend will fade them rapidly. Bar Keeper's Friend should ONLY be used in a very localized and tactical fashion.
Can I use Star San to passivate?
While Star San is readily available for homebrewers and primarily contains two acids (phosphoric acid and dodecylbenzenesulphonic acid) recent studies have shown these to be less effective than other acids for chemical passivation. We recommend keeping Star San for sanitation or descaling calcium deposits and no longer recommend it for passivation.
How often do I need to passivate?
It’s good practice to periodically passivate all stainless-steel equipment with an acid-based solution to establish a uniform passive oxide layer that will maximize corrosion resistance. We recommend passivating immediately after pre-cleaning new gear with TSP. Moving forward, for best stainless performance, passivation should be performed anytime you believe you may have inadvertently scratched the surface. If you are a frequent brewer, we recommend passivating annually.
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*https://ntrs.nasa.gov/api/citations/20110001362/downloads/20110001362.pdf
*https://ntrs.nasa.gov/api/citations/20140002809/downloads/20140002809.pdf
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