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.
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.
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.
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.
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.
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.
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.
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