What is this in my new kettle?

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Belgian Samurai

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Hi,

First time using this new "Mega pot" kettle. I just filled it with 5 gallons of water, albeit, lime heavy tap water and brought to a near boil, before turning of the burner and propane tank to run to the store to get spring water. Upon returning just now, I noticed this in the bottom of my kettle. I tried to scrape it off with my fingernail, but no luck.

What caused this and what is it? I am using a 200,000 btu (20psi hose only tho). The flame was slightly lapping the edge of the side walls.

PXL_20210410_172229969.jpg
PXL_20210410_172219786.jpg

EDIT:
I used a pumice stone and it removed the stain with minimal effort and seemingly no scratching to the stainless steel. Woot woot Moving forward with brew day! (Though, I'd still like 5o know what it was.)
 
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day_trippr

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That is rust. You need to give that pot a citric acid treatment to fry out any exposed iron grains to allow the pot to establish a uniform chromium oxide layer - which won't/can't happen as long as there is exposed surface iron.

4-5% citric acid and water solution (by weight) heated to 150°F and kept there for say 30 minutes should do the job...

Cheers!
 
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Belgian Samurai

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That is rust. You need to give that pot a citric acid treatment to fry out any exposed iron grains to allow the pot to establish a uniform chromium oxide layer - which won't/can't happen as long as there is exposed surface iron.

4-5% citric acid and water solution (by weight) heated to 150°F and kept there for say 30 minutes should do the job...

Cheers!
Thanks!
This make/model of citric acid sounds good; is this what I should purchase?

One further question though: since kegs are also stainless steel, do I also need to perform an acid bath them as well? I recently purchased a 4pk of used kegs and have had craft meister's keg cleaning tablets in one with hot water, which has now sat there for a couple days because I got busy. When I rinse that out with water, should I follow up with citric acid and drip dry it?
 

day_trippr

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That is the same product I buy from Amazon as well. Good pick :)

The need for a "passivation" treatment (likely a misnomer) can usually be determined visually: If you see rust inside an SS vessel, it needs acid frying. Otherwise, let it ride.

If possible, once you have drained the citric acid from the pot the first rinse should be done with uber low ionic content water - eg: either distilled or legit RO water (not the kind that has minerals put back in). After the first rinse subsequent rinses can be done with tap water. The idea here is to avoid acid/mineral reactions that would leave deposits on the very metal you're trying to oxidize...

Cheers!
 
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