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Rust streaks in tanks following passivation

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  • Rust streaks in tanks following passivation

    So I'm having this weird issue with my tanks. I first noticed it after about 6 months of use in my brite and more recently on a brand new tank after the very first caustic/acid/passivation cycle. I use Five Star acid cleaner #5(phosphoric/nitric acid blend) and follow the passivation instructions, which calls for a stronger that usual concentration(5oz acid/gallon) and then allow to air dry. So on this brand new, unused tank I ran the passivation cycle(after a good caustic clean first) and left it to air dry overnight. When I came in the next morning this is what it looked like inside the tank.
    Click image for larger version

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    It is hard to tell from the pic but those streaks are a nasty looking rust color. It doesn't come off with a rinse, even hot water, and scrubbing with scotch brite will get rid of the rust color, but whitish streaks remain. It looks like as the acid runs down the tank walls after the cycle is finished, as it is air drying, it causes the tank to rust where the acid sits for a while.

    Now I have had this happen previously on my original brite tank as well, and beer after beer, cleaning after cleaning, these white streaks never come off and seem to be getting worse.
    Click image for larger version

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    I have passivated this tank several times, originally thinking that it would get rid of the streaks, but after every time it made them even worse.

    As you can see in this last pic, the streaks in the brite are white and as you can tell from my scouring scratches with scotch brite, they do not come off with scrubbing which leads me to believe that it is IN the metal.
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    I would really like to know what is going on here and what I can do about it. FYI, my cleaning routine after every beer that goes through is: Hot rinse, ~160F caustic cycle for 30-60mins, hot rinse, ~120F acid cycle for 10-20 mins, hot rinse, cold rinse. Oh and I use Star-xene(ClO2) to sanitize. I have also tried the "reverse clean" method of doing acid first then caustic with no rinse in between, and saw no benefit.

  • #2
    Wow. That looks nasty.

    My best guess is that you need to eliminate the ClO2 sanitizer--chlorine and SS aren't a good mix. We use heat to sanitize, and haven't had any problems. Our sanitize rinse is about 193-195 F, followed by a flush and pressurization with CO2.
    Timm Turrentine

    Brewerywright,
    Terminal Gravity Brewing,
    Enterprise. Oregon.

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    • #3
      I would highly recommend talking to either Dirk Loeffler at Loeffler Chemical or Dana Johnson at Birko. They are the most knowledgable guys I have met on this issue. Talk to either, or both, of them, tell them what you have.. forward the pics even. They are good guys and won't steer you wrong. I had a nasty, rusty looking uni once and Dirk gave me a specific course of action, all chemical, that cleared the thing up beautifully. The knowledge those guys possess will be helpful to you across the board, not just with this single issue.

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      • #4
        Originally posted by TGTimm View Post
        Wow. That looks nasty.

        My best guess is that you need to eliminate the ClO2 sanitizer--chlorine and SS aren't a good mix. We use heat to sanitize, and haven't had any problems. Our sanitize rinse is about 193-195 F, followed by a flush and pressurization with CO2.
        But plenty of breweries use ClO2 with no issues and as long as you are activating it properly, there should be nowhere near enough free chlorine to damage the stainless. Besides, this new tank has never been sanitized yet. Hot water sanitizing isn't an option for us and I dislike paracetic acid.

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        • #5
          Chlorine dioxide is a fine sanitizer with no issues regarding free chloride intergranular stress crack corrosion. Stick with it, that's not your problem. Air drying might be the problem. Passivation requires a RINSE after the acid wash. NOT AIR DRYING. Look up other threads on this site regarding this issue and read the relevant standards to understand exactly how to passivate. Anyone who tells you to air dry is (after extensive research and in my opinion) sadly misguided. To those who cling to this method, please prove me wrong and cite a source other than urban brewing legend. I'd love to know where this method came from. I've had pickling paste (which is close to the same thing) cause streaking if not immediately rinsed clean from the stainless. Another issue is that your tanks might be made from less than excellent metal. Made in China? Dirk and Dana are great sources of information. This issue falls squarely in the metallurgy camp. Perhaps you could find a thirsty metallurgist in your area? Good luck!
          Phillip Kelm--Palau Brewing Company Manager--

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          • #6
            Originally posted by gitchegumee View Post
            Chlorine dioxide is a fine sanitizer with no issues regarding free chloride intergranular stress crack corrosion. Stick with it, that's not your problem. Air drying might be the problem. Passivation requires a RINSE after the acid wash. NOT AIR DRYING. Look up other threads on this site regarding this issue and read the relevant standards to understand exactly how to passivate. Anyone who tells you to air dry is (after extensive research and in my opinion) sadly misguided. To those who cling to this method, please prove me wrong and cite a source other than urban brewing legend. I'd love to know where this method came from. I've had pickling paste (which is close to the same thing) cause streaking if not immediately rinsed clean from the stainless. Another issue is that your tanks might be made from less than excellent metal. Made in China? Dirk and Dana are great sources of information. This issue falls squarely in the metallurgy camp. Perhaps you could find a thirsty metallurgist in your area? Good luck!
            I definitely plan on talking to Dirk soon. As far as the air drying for passivation, besides hearing it from other brewers, it is exactly what the instructions on the bottle of Five Star Acid Cleaner #5 say to do. But it certainly couldn't hurt to try it again without air drying.

            And yes, the tanks are from China, like most of the world's stainless.

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            • #7
              I somehow missed the air dry mention in the original post... yeah, rinse after your acid step

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              • #8
                Originally posted by Bham Brewer View Post
                I somehow missed the air dry mention in the original post... yeah, rinse after your acid step
                But like I said, that is what the instructions specifically say to do in order to properly passivate. I have also read it from multiple sources.

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                • #9
                  Lifted from another thread on this site that deals with passivation...

                  According to ASTM A380-06, section A2.10:

                  "... To minimize staining, surfaces must not be permitted to dry between successive steps of the acid cleaning or passivation and rinsing procedure. Thorough drying should follow the final water rinse."

                  http://discussions.probrewer.com/sho...-the-scratches

                  Again, if you want to know about passivation, then get the ASTM standard. What sources can anyone else cite for air drying?
                  Phillip Kelm--Palau Brewing Company Manager--

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                  • #10
                    Originally posted by gitchegumee View Post
                    According to ASTM A380-06, section A2.10:

                    "... To minimize staining, surfaces must not be permitted to dry between successive steps of the acid cleaning or passivation and rinsing procedure. Thorough drying should follow the final water rinse."

                    http://discussions.probrewer.com/sho...-the-scratches

                    Again, if you want to know about passivation, then get the ASTM standard. What sources can anyone else cite for air drying?

                    Interesting. I guess I should call Five Star and tell them to change their product instructions. Thanks for the info. Hopefully I can re-passivate(properly) and get rid of the stains.

                    Comment


                    • #11
                      It's possible that 5-Star isn't doing much passivation with this dilute solution. Or perhaps it's a different concentration/approach to "passivation". But you are correct in their assessment: From 5-Star Acid #5:
                      "Drain vessel and allow to air dry. The vessel must air dry to achieve successful passivation."
                      Would love to hear their response to this apparent conflict. In the meantime, I'm with ASTM who represent a collective wisdom in metallurgy far beyond any one cleaning chemical manufacturer. No offense to 5-Star; I've used many, many manufacturers' cleaning chemicals over the years. But 5-Star is in my brewery today. And I've found zero references in respected sources that are contrary to the rinse after acid approach. Only from brewers who have repeated the status quo to the extent of an urban legend.
                      Phillip Kelm--Palau Brewing Company Manager--

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                      • #12
                        This looks like a 100% PBST tank. I, too, have the same issues. however, my streaks are not rusted, just white. I used some BRU-R-EZ on the vessel not to long ago and that took care of a lot of this. I bet PBW would do the same...

                        Comment


                        • #13
                          Looks like our PBST brite. 5 star recommended a particular product to remove this that worked. Not at the brewery to check but you could call Charlie and ask. Ill try and remember to post it once I take a look. I believe Charlie suspected that the problem came from the factory using finishing tools of a (grinders/wire wheels?) of a lower grade stainless than the tank which causes the rust spots. I also had issues finding the right gasket for the bottom of our tank as it is an oddball 7" Triclamp. Even Dwight at Brewery Gaskets didnt have one and had to fab me a flat gasket.

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                          • #14
                            I have never air dried a tank as part of passivation cycle. I have one PBST tank, two Premieres and a mess of others made in the USA. The only interesting thing I saw inside the PBST tanks was the size 5 bare foot prints from where I can only guess they were grinding the inside with no shoes on.
                            Joel Halbleib
                            Partner / Zymurgist
                            Hive and Barrel Meadery
                            6302 Old La Grange Rd
                            Crestwood, KY
                            www.hiveandbarrel.com

                            Comment


                            • #15
                              Originally posted by wailingguitar View Post
                              I would highly recommend talking to either Dirk Loeffler at Loeffler Chemical or Dana Johnson at Birko. They are the most knowledgable guys I have met on this issue. Talk to either, or both, of them, tell them what you have.. forward the pics even. They are good guys and won't steer you wrong. I had a nasty, rusty looking uni once and Dirk gave me a specific course of action, all chemical, that cleared the thing up beautifully. The knowledge those guys possess will be helpful to you across the board, not just with this single issue.
                              I worked with Dirk Loeffler for many years. He is very knowledgeable and honest. You can google Loeffler Chemical Corporation and e mail him from the site or you can call him at 1-404-629-0999 ext. 15

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