Question on new still and corrosion

Simple pot still distillation and construction with or without a thumper.

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tauren58
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Question on new still and corrosion

Post by tauren58 »

Here is my new set up. I posted this at another spot, but I think that was the wrong spot. It’s stainless steel, from an old pool filter can. I have not tried it yet, I will be doing a vinegar run this weekend hopefully. It’s 25 gallons with a removable head. One question I wanted to ask is this..

I had my friend do the welding. He used TIG stainless welds, but the backsides of the welds, inside the tank, were unshielded and he thinks the chromium in the stainless welding was burned out. He said it might corrode because the chromium gives the stainless, the corrosion resistance.

Anyone have experience with this? Wondering if it will be okay to use and run? I hope so cause it’s costing me a fair bit for the work;-)

Thanks
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Tauren
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TwoSheds
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Re: Question on new still and corrosion

Post by TwoSheds »

I'm sure others will respond but what you want to search for is 'passivating' or 'passivation' on this site or the internet at large.

Likely your friend is at least partly right and scrubbing away the rust, or the right amount of acid for the right amount of time will beat back the rust and expose enough chromium to protect it again.

Good luck!
tauren58
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Re: Question on new still and corrosion

Post by tauren58 »

Thanks I will do some looking into that. Seemslike I could use some powdered citric acid or something like that to clean it.
Setsumi
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Re: Question on new still and corrosion

Post by Setsumi »

Polish it with citric acid paste.
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Ben
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Re: Question on new still and corrosion

Post by Ben »

It will rust, he should have back gassed or used a paste designed for that type of work. On a home distiller scale it isn't likely to hurt anything though. Stomach acid will turn it to iron, which your body uses. It wouldn't pass a food grade inspection, but also isn't likely to rust through on you. I would recommend storing dry though.
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tauren58
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Re: Question on new still and corrosion

Post by tauren58 »

I’ve been doing a bit of reading on this site and some other stuff about passivation. I thought that I just need to give it a scrub and a wash with some citric acid solution to restore the oxized coding and should be good to go. Maybe I need to do that after every run I don’t know yet. Storing it dry makes good sense.
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squigglefunk
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Re: Question on new still and corrosion

Post by squigglefunk »

i used bar keepers friend on my welds and other rust spots, it seems to work well. I made a paste and applied overnite then scrubbed clean. Seems to stop the rust from returning
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Ben
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Re: Question on new still and corrosion

Post by Ben »

Talking about 2 separate things here. Using BKF or whatever is a process to convert rust to something else. The active ingredient in BKF is oxalic acid, and the cleanser part is a mild abrasive. The conversion of rust by oxalic acid creates ferric oxalate, which does have some solubility in water. You would be better off to use a phosphoric acid (active ingredient in star-san) based converter, that leaves you with iron phosphate which is insoluble and what is used in the food industry.

Passivation uses an acid to remove oils and free iron from the surface, it is done with any new stainless vessel used in the food industry, and should be done any time you abrade your stainless. Phosphoric acid will passivate as well, so a treatment with hp3o4 is your best option for your initial clean up of the vessel. Periodic use may be required.

You have to have stainless steel in order to passivate. When your welder left the back side of the weld open to the atmosphere he allowed oxides into the surface the chromium in the stainless will not be able to creep to the surface and seal. You have to treat that as it is just plain steel.
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still_stirrin
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Re: Question on new still and corrosion

Post by still_stirrin »

Ben wrote: Fri Oct 15, 2021 7:04 am… Phosphoric acid … hp3o4
It should be H3PO4.
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Re: Question on new still and corrosion

Post by Ben »

Yep, excuse the typo.
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Demy
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Re: Question on new still and corrosion

Post by Demy »

I remember that tank. Sincerely, for our uses, I believe that a cleaning with citric acid is fine ..... we must not insert a food liquid that will be drunk directly (like a fruit juice) but it will be distilled, for me just keep clean, moreover You not can do much more after the welding was made.
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