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Steel Yourself: Why Passivation Is the Secret Weapon for Your Brewery Tanks

Think stainless steel is maintenance-free? Think again. Over time, your brewing equipment can corrode and compromise flavor—even if it looks spotless. Learn how passivation—a simple but essential chemical process—protects your tanks, improves cleaning, and keeps your beer tasting its best. Discover which method is right for your brewery and how to do it safely with Five Star products.

Dana Kapron, Five Star Chemicals (Sponsored) Jun 24, 2025 - 6 min read

Steel Yourself: Why Passivation Is the Secret Weapon for Your Brewery Tanks Primary Image

If you think stainless steel is invincible, I’ve got some slightly corroded news for you.

While stainless steel is a workhorse of modern brewing, keeping it in pristine condition takes more than just a CIP cycle and good intentions. Without proper care, that trusty fermentor or kettle can become a quiet saboteur, slowly introducing corrosion, off-flavors, or worse—causing a batch to go down the drain.

Enter passivation: the slightly scientific, mildly misunderstood, but incredibly important process of chemically conditioning stainless steel to form a protective oxide layer. In short, it helps your tanks do what they do best—stay clean, resist corrosion, and keep making great beer.

What Is Passivation (and Why Should You Care)?

Passivation restores the chromium oxide layer that gives stainless steel its corrosion-resistant properties. This protective film acts as an invisible suit of armor, shielding the steel from the harsh reality of acids, sanitizers, salts, and the CO2 that’s constantly fizzing through your tanks.

Even beer itself—with its low pH and dissolved CO2—over time, can wear down the protective layer on your stainless steel, leading to pitting, rust, and the potential for beer-spoiling contamination.

But My Tanks Look Fine…

Looks can be deceiving. New tanks may arrive from the manufacturer looking spotless, but don’t let the shine fool you—they may be shipped without being fully passivated and may still be carrying machine oils, iron filings, or even rust spots. On older tanks, repeated exposure to chemicals and abrasive cleaning can wear down the passive layer, leaving the surface vulnerable.

Passivation is like resetting the surface—getting back to a clean slate and laying down a protective barrier. It also makes cleaning easier, helps prevent microorganism contamination sites, and keeps your CIP in check.

Old School vs. New School: Choosing Your Passivation Path

The traditional method of passivation uses a high concentration (20–25 percent) of nitric acid, followed by a 24-hour air dry. This creates a durable chromium-oxide film. It’s effective—but handling high-concentration nitric acid isn’t for the faint of heart (or lungs). It’s hazardous, hard on equipment, and time-consuming.

The modern method (popular since the 1990s) offers a safer, quicker approach:

  • Start with a blend of nitric and phosphoric acid.
  • Follow immediately (and without rinsing) with a noncaustic alkaline cleaner containing hydrogen peroxide or sodium percarbonate.
  • Rinse thoroughly with hot water.

This method forms a phosphate/silicate conversion coating that protects the stainless surface and creates a glassy-smooth finish, less prone to harboring beerstone or organic buildup.

A third method is citric-acid passivation. Citric acid is a mild, organic acid that effectively chelates, disabling the free iron elements and rendering them unable to make iron oxide (rust). It’s significantly safer to handle, environmentally friendly, and doesn’t require the same level of personal protective equipment or ventilation as nitric acid. While citric acid doesn't create as thick an oxide layer as nitric, it provides effective corrosion resistance and is particularly useful for smaller breweries, periodic maintenance, or where regulatory or facility limitations make nitric use impractical.

In short:

Nitric Acid = strong oxide layer, but high hazard and downtime.
Nitric/Phos (Conversion Coating) = safer, faster, dual-action cleaning and passivation.
Citric Acid = safest option, ideal for rust removal and periodic surface reconditioning.

The Passivation Playbook Using Five Star Chemicals

With Five Star Chemicals, you’ve got all you need for safer passivation.

For New Tanks:

  1. CIP with 1–2 oz/gal of hot caustic (140–180°F/60–82°C) to remove oils/debris (HD #2 or Super CIP).
  2. Rinse well.
  3. If rust is visible, CIP with 2 oz/gal citric acid at 120–130°F (49–54°C) for 15–30 minutes (Citric Acid).
  4. Rinse again.
  5. CIP with nitric/phosphoric acid blend at 120–135°F (49–57°C) for 15–30 minutes. Do not exceed 140°F (60°C). (Acid #5).
  6. Do not rinse.
  7. CIP immediately with noncaustic alkaline cleaner at 120–140°F (49–60°C) for 15–30 minutes (PBW Powder).
  8. Final hot water rinse until pH is neutral.

For Existing Equipment:

Follow steps 5–8 above every 6–12 months, depending on how hard your water is, tank use, and cleaning chemical exposure.

How Often Should You Passivate?

Most breweries should passivate tanks at least once a year, although breweries with hard water, high-use fermentors, or tanks exposed to acidic/sour beers may need it every three to six months. Anytime a tank undergoes repairs, aggressive scrubbing, or experiences a contamination issue—it’s time to re-passivate.

Final Thoughts

Passivation doesn’t protect just your stainless steel—it protects your beer, your flavor stability, and your bottom line. Whether you’re brewing on a pilot system or running a full-scale production facility, giving your tanks a proper passivation treatment is one of the simplest investments you can make in long-term quality and consistency.

Clean metal. Clean beer. That’s the kind of chemistry we can all get behind.

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