Passivating Stainless Steel Tanks and Equipment


Step 1: Degrease and pre-clean the surface

Before you can passivate, the steel must be clean. Acid cannot reach the iron contaminants if they are hidden under a layer of oil, grease, or leftover food residue.

  • Remove organic soils: Use a high-quality alkaline cleaner (caustic wash, such as PBW Cleaner or Liquid PBW Cleaner) to strip away fats and oils.

  • Scrubbing: If there are stubborn spots, use a non-metallic abrasive pad. Never use steel wool, or you'll be adding the very iron you're trying to remove.

  • Initial Rinse: Thoroughly rinse the tank with water. If the water "beads" on the surface, there is still grease present, if it sheets off evenly, you’re ready for the acid.

Step 2: Acid Treatment

This is the core of the process where we use acid to dissolve free iron and create the protective chromium oxide layer.

  • Select your acid:

    • Acid Cleaner #5: A highly effective, specially formulated chemical used to passivate and repassivate stainless steel. This product is a liquid chemical, drop-shipped directly from the manufacturer.

    • Citric Acid: The modern industry favorite. It’s safer for the environment and operators, and highly effective at removing heavy metals. This product is in a powdered form and shipped directly from us

    • Nitric Acid: The traditional approach. It's faster but much more hazardous and requires stricter disposal protocols. (Please note that we do not carry this product, this is provided for informational purposes only and we recommend avoiding this method if possible)

  • Application: For a large food tank, you will likely use a CIP (Clean-In-Place) system to circulate the solution or a spray wand to ensure 100% coverage of the interior walls.

  • Dwell Time: Allow the solution to sit or circulate for the timeframe recommended by the chemical manufacturer (usually 20 to 60 minutes depending on the temperature and concentration).


    • Acid Cleaner #5 Method: Please visit our product page for instructions and dosage under our product description
    • Citric Acid Method: Use a 4-10% citric acid solution at 120-160°F 49-71°C for 20-30 minutes.

Step 3: Rinse and Air Dry

Once the acid has done its job, you need to return the tank to a food-safe state and ensure the "passive" layer is intact.

  • Final Rinse: Rinse the tank thoroughly with deionized or filtered water until the pH of the rinse water matches the pH of the source water.

  • Air Dry: This is step is crucial to passivation. Oxygen is what actually creates the chromium oxide layer. Let the tank air dry completely before sealing it or putting it back into service.