Passivation Procedure for 300-Series Stainless Steels
Step 2. Apply the passivating solution to the complete surface. Cover all areas several times. Keep the surface wet with the acid solution for about 1 h. With a small vessel (15 gal or less), it is easiest simply to fill the vessel with the passivating solution and let it soak. When dealing with larger vessels, passivation via a spray-ball system is very effective.
Step 3. Rinse the vessel thoroughly with clean, warm water to remove all traces of acid. Wipe with a clean cloth (wet or dry). If no discoloration appears on the cloth, the surface is conditioned and ready to use.
Passivation is not a permanent treatment. Stainless steel surfaces can become recontaminated and corroded if proper care is not taken.