passivating tanks

[777dvr]

Anybody got the breakdown for passivating 7bbl brewhouse and tanks using citric acid powder,
Mixture,temp of solution and timeof circulation, and how many tanks can I do before I mix up
a new batch. Equipment is used but has been in storage for 9 years

[dick murton]

Passivating means recreating the chromium dioxide layer on stainless. As far as I am aware, citric is not an oxidising agent and therefore will not passivate.

Degrease and use nitric acid to passivate. Lots of discussions about this, including one dealing with rust spots.

[gitchegumee]

Hey Dick! Sorry to contradict you, but the US method of passivating according to ASTM includes a citric acid option. Not sure what the equivalent document/technique is where you are. 777dvr, do a search on "passivate" here on Probrewer for lots of discussion on this topic. And find those relevant standards and read them. You'll be glad you did. Many folks in this industry learned OTJ along with the bad habits & practices associated with older techniques that are NOT grounded in science. Don't trust your brewery to a practice that cannot be backed up with solid reasoning. Good luck!

[dick murton]

Hi Phillip

OK, thanks

Stand corrected. Guess that is my big brewery experience where we have only ever used nitric acid (or hydrofluoric for pickling welds).