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Topic: Please help: Reaction Aluminum + Baking Soda  (Read 11441 times)

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Offline gargarean

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Please help: Reaction Aluminum + Baking Soda
« on: December 19, 2014, 07:12:24 AM »
Dear friends, good day.

Please help me with the following chemical riddle!

I do some homebrewing.

I use a Sodium Bicarbonate solution (NaHCO3 in water) to take labels out easily, leave bottles in the solution for some hours then labels just float up.

I have a large aluminum pot to boil the wort in, to be soon replaced by a stainless steel one.

I had the (bad) idea of using my pot as a receptacle to soak the bottles in the NaHCO3 solution. As I had many bottles to treat I was replacing the ready ones with labeled ones and to make a long story short left the solution in the pot for about a week. After I drained the water I found out to my dismay that the aluminum surface has been covered by a black layer.

I tried to take it out mechanically (scrubbing) but it goes off very slowly and painstakingly. I also tried scrubbing it with weak acid (lemon) but didn't see any big difference.

I was wondering whether I could just fill the pot with ANOTHER solution and leave it overnight and it will just have disappeared in the morning and pot will be shining again!

I had a thought that maybe Al replaced Na in the baking soda and the black stuff is Al(HCO3)3, even tried to find if Aluminum Bicarbonate is black but had no luck with google. And probably it's a stupid idea since Al is more electronegative than Na? Or is it Al(OH)3? But that one seems to be white as per google...

I hope somebody can help with this. Sorry for the long post.

Thank you very much.


Online Hunter2

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Re: Please help: Reaction Aluminum + Baking Soda
« Reply #1 on: December 19, 2014, 07:53:53 AM »
Aluminium will be dissolved in alcaline and acidic solutions. Also baking soda will attack the aluminium. So not a good idea to use a aluminium pot for that. The pot is probaböy made of an alloy, what left the black material.

Offline Enthalpy

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Re: Please help: Reaction Aluminum + Baking Soda
« Reply #2 on: December 19, 2014, 07:27:59 PM »
The black layer may well be much more resistant to chemicals than aluminium is. What about using a rotating hard brush powered by a drill?

Offline billnotgatez

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Re: Please help: Reaction Aluminum + Baking Soda
« Reply #3 on: December 19, 2014, 09:35:12 PM »
http://www.ehow.com/how_8595865_black-out-aluminum-pot.html
maybe this link

They suggest using
2 tbsp. cream of tartar
Spoon
4 tsp. white vinegar
Dishwashing detergent
Nylon mesh scrubber
Kitchen towel
Silver polish
Clean cloths

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