Smaller scale passivation with citric acid

[Onebadsc]

Been doing a bunch of searching and about to try it, but just wanted to see what people thought of my procedure. I have a Psycho Brew kettle, and 55 gallon drums for my hlt and mlt.

All kettles have been cleaned with tsp, bkf and pbw (in no particular order).

1. Fill the hlt with a few gallons of water and heat to about 150, add citric acid to make a 5% solution.

2. Pump solution to BK via spray ball until hlt is empty (I can not recirculate since my kettle's outlets are too small)

3. Pump it back and forth between all the kettles a few times via spray ball.

4. Empty citric acid.

5. Rinse out kettles and leave to air dry.

Any suggestions or comments on any of this would be greatly appreciated!

Thanks!

[jebzter]

Why not just get five star acid #5 and follow their instructions. The main thing is that you do not do a water rinse, you need to let it air dry to form the oxide layer.

[Onebadsc]

I've read some people say that I need to rinse the acid off or it will stain, then let it air dry. I'm pretty sure it was in a thread here somewhere.

[Onebadsc]

Has anyone had an issue with stainless being stained or ruined by not rinsing off citric acid? I'm kind of leaning towards using a weaker solution of citric or just not passivating at all.

[gitchegumee]

Rinse, baby, Rinse!

Need to rinse. Air drying without rinsing is a myth. Plenty threads on this topic here already. There are slightly different procedures for parts vs. systems, but I didn't see much of a difference.

[bcofresi]

i got staining on the underside of my new "Chronical" lid, (we bought it as a yeast propagator), just from the yeast/foam of first use. passivation with citric acid gel and a magic eraser subsequent, has not cleaned it up much. Still looks like kinda-sorta damascus steel. I'm thinking... cheap stainless steel = not so stainless

[rdcpro]

i got staining on the underside of my new "Chronical" lid, (we bought it as a yeast propagator), just from the yeast/foam of first use. passivation with citric acid gel and a magic eraser subsequent, has not cleaned it up much. Still looks like kinda-sorta damascus steel. I'm thinking... cheap stainless steel = not so stainless

Passivation won't remove stains, and doesn't work well unless the part is already very clean. All it does is remove the free iron from the surface of the stainless, down to the grain boundaries. Rinsing should be done with de-ionized water. Then the air drying part of the process actually forms the chromium oxide layer.

But you're totally right about cheap stainless. If it's got a lot of sulfides (to improve machinability) or other impurities, it's not so stainless. And who knows if cheap "304" stainless is actually close to the correct alloy or not. 304 does tarnish, though. It's a kind of yellow color.

Regards,
Mike Sharp