Questions about citric acid passivation

I'm almost done welding my new kettles and have some citric acid to passivate them. Was hoping someone could answer a few questions.
1) will it harm any other parts like my chugger pumps or sight tubes.
2) I don't have enough to fill my kettles, would it be OK to recirculate it with a CIP while maintaining temp?

I don't know if this helps but....

http://www.bssa.org.uk/topics.php?article=68

That says 4-10% to passivate. Maybe you should just pick up some bar keepers friend. You could us it as directed and just scrub the welded areas really good clean light duty scrub pad. I would use a fresh one so you don't put any detrimental materials into the stainless. I wouldn't think that would screw with your sight glass.

I don't think elevating the temperature of the acid will be beneficial in re-passivating the SS.

I agree with the above, that BKF works great. It contains an acid cleaner as well (oxalic). It comes in a nifty squeeze bottle that contains a cream, so instead of filling your entire keg, just apply to a paper towel and wipe all over the bare metal. 30 minutes later, wipe it off and marvel at the shine.

I was working in a manufacturing facility and our passivation tank was heated. I never thought to ask much about it at the time. I believe I read some place that if you can't heat the solution to the correct temp you need to allow it to sit longer to compensate.

From my understanding, it works best at 160F for 30 minutes. The main thing I'm trying to find out is if there is any risk to the chugger or a polycarbonate sight glass if I recirculate the mixture with the pump and CIP ball

What is the chugger made from? I don't forsee any issues, 10% citric acid does not have a pH much lower than orange juice. And less acidic than coke. Polycarbonate is also fairly inert, but you could test on a cd or dvd, I believe they are polycarbonate.

The pump and sight glass will be fine.

http://www.plasticsintl.com/plastics_chemical_resistence_chart.html

For passivation I heat my citric acid solution to near boiling and then let it cool back down to room temp. The hotter it is the faster it works. You can save and reuse it as well.

Useful link, interesting that acetic acid attacks polycarbonate. Don't get any vinegar on it.

Thanks so much for the info. The people on this forum are the best! Hopefully within a month of my first brew on my new electric brewery and none of it would have been possible without the great people here!

Hey RB,
I know this is an older thread, but I wanted to follow up to see how your citric acid passivation is holding up. I'm getting the rivets on my brew kettle welded since they are leaking, and am debating using citric acid for passivation. I work in a chemical plant that uses nitric acid to passivate their stainless steel due to the fact that citric acid only removes iron, it does not create a chromium oxide layer. I was wondering how your kettle is holding up after using citric. I'm leaning towards that since it's cheaper and safer than nitric acid. What concentration and temperature did you use for your passivation solution? I'm planning on scrubbing my kettle with barkeepers friend and then passivating with a 10% citric acid solution at 140 degF for an hour.

Citric acid passivation works great and is a common alternative to nitric acid.

The ASTM A967 sheet specifies that all you need is 10% w/v citric acid for 15 minutes at 160°F.

I've heard the product "CitriSurf" also works well.

It's worked out very well so far. I only have 1 spot that has shown any signs of rust, and that was where I had left a little pit in a weld. I believe I used a 10% solution at 160F for about 30 minutes. Barkeepers seems to work well for maintaining passivation. I think you'll be fine