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Rust streaks in tanks following passivation

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  • #16
    Thanks for the responses guys. Brian I'll definitely be contacting you to talk further about your chemicals. I've always heard good things.

    As far as our chlorine dioxide, we use 5-star Star-xene, which I've been happy with and prefer over PAA because I don't want the vinegar odor in the brewery and undiluted PAA is much more dangerous than the stabilized ClO2 solution. Producing chlorine gas isn't an issue as long as you're activating it properly, which is not hard to do.

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    • #17
      phosphoric ? Anybody?

      Originally posted by Judd View Post
      Thanks for the responses guys. Brian I'll definitely be contacting you to talk further about your chemicals. I've always heard good things.

      As far as our chlorine dioxide, we use 5-star Star-xene, which I've been happy with and prefer over PAA because I don't want the vinegar odor in the brewery and undiluted PAA is much more dangerous than the stabilized ClO2 solution. Producing chlorine gas isn't an issue as long as you're activating it properly, which is not hard to do.

      Phosphoric Acid seems to me to be the best choice for acid cleaning and passivation. My experience... these stains look similar to me as I left Nitric Acid remains in the tank overnight and did not flush. Here is what we follow for passivation now

      1. Phosphoric acid diluted from 85% to 2 % at 50 C - Check pH 1~2 of the solution
      2. Recirculate for 20 mins
      3. Recollect or discharge from tank
      4. Flush with very hot water - High pressure if possible - 80 C +
      5. Recirculate with Hot water - 15 mins
      6. Flush and check with litmus paper for pH- Flush until neutral i.e Green

      I have used Divosan Activ (PAA) - I am not a fan as well as I was suggested to use it in cold water and chances of contamination are higher. Food grade phosphoric acid does the job for CIP without damaging the tanks and yes I have been using all Chinese.

      Amit

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      • #18
        Please post the remedy

        Judd,

        Please post the remedy that works for you. I too have PBST tanks and the streaks and the rust and use the 5 Star chemicals. ugh.

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        • #19
          Solution?

          What was the solution you came across to solve the streaking problem?

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          • #20
            Phosphoric acid does NOT passivate. Nitric (or if you really must, citric or tartaric acid) does.
            Lots of options on the ASTMS bumf.
            dick

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            • #21
              My solution

              Hey all, thought I'd update on this old thread. The white streaks never went away in the brite. They are embedded in the metal, but the surface isn't rough and I've had no problems using the tank all these years. But the solution to the problem was first, never, ever letting a passivating solution air dry with no rinse. That advice was nothing more than 5 Star's incompetence when it comes to creating products and solutions for professional brewing. Which leads to my second solution, which was to switch chemical suppliers. Unrelated, but I also switched from ClO2 CIP santizing to PAA and haven't looked back. We still do caustic and acid cycles on every tank, every time.

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              • #22
                You never leave acid on a stainless steel surface and allow it to air dry. This recommendation is plain wrong and may lead to corrosion in your equipment. Stainless steel can be passivation using two methods:

                Run a strong Nitric acid based solution ambient for an extended period of time and then rinse. As long as the surface is completely clean, this will chemically create the chromium oxide layer, which is the passive layer. Never leave the acid and allow to dry. This applies for any chemical solution!

                The other method is using citric acid to strip any free metal ions from the surface and then rinse and allow the tank surface to form the passive layer via air exposure. This can take up to two weeks and will likely yield a less permanent passive layer.

                In many cases, you may need to pre-treat the surface with a special chemical to remove any surface contamination prior to chemically passivating the surface.

                You can contact me and I can give you directions on how to get the streaks out, as long as no pitting has taken place.

                Cheers,

                Dirk Loeffler
                Technical Director
                Loeffler Chemical Corporation
                loeffler.dirk@loefflerchemical.com


                Sent from my iPhone using Tapatalk
                Loeffler Chemical Corporation
                (404) 629-0999
                800-769-5020 (US & Canada only)
                www.loefflerchemical.com

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