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Old 15th Jun 2006, 12:25 pm   #1
boiss
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Default Battery acid corrosion

What is the best way to stop corrosion of an aluminium chassis caused by acid from dry cells? I have tried cleaning and soaking in a bicarb solution but after a couple of days the white deposit returns.
Cheers,
Boiss
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Old 15th Jun 2006, 1:13 pm   #2
Geoff G4ICD
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Default Re: Battery acid corrosion

Try, Hammerite rust remover it is excellent! Goeff
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Old 15th Jun 2006, 4:51 pm   #3
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Default Re: Battery acid corrosion

I have a recollection that Aluminium is attacked by caustic soda. It might well react with other alkalis as well.
This could explain the white deposit. Incidentally do the dry cells have an acid electrolyte? If it is alkaline, then vinegar may help. I seem to remember that boiling fruit in an aluminium saucepan makes it nice and shiny.
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Old 15th Jun 2006, 6:14 pm   #4
boiss
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Default Re: Battery acid corrosion

The problem was started by acid from old dry cells ( Sal Ammoniac?) I cleaned the chassis with a wire brush and dremel etc and then left it in a bicarbonate of soda solution for a couple of days. Then washed it with warm soapy water. After about 2 days there were signs of white deposits again. I have now soaked it in WD40 but I am not convinced that this will cure it. the copper and brass bits are fine after the bicarb treatment. They were not put in the solution together and the solution used was not very strong.
I was wondering if anodising it might be a better long term cure.
Cheers,
Boiss.
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Old 15th Jun 2006, 6:19 pm   #5
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Default Re: Battery acid corrosion

Freshly cleaned aluminium forms a thin oxide film within minutes (seconds?) of being exposed to air. Anodising is the process of thickening this film by an electrolytic process. Ali actually corrodes very readily. It's only the oxide film that stops it corroding away to nothing.

I suspect that the white deposit is a carbonate or chloride. I'm afraid my chemistry runs out about there.
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Old 15th Jun 2006, 8:34 pm   #6
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Default Re: Battery acid corrosion

Quote:
Originally Posted by boiss
What is the best way to stop corrosion of an aluminium chassis caused by acid from dry cells? I have tried cleaning and soaking in a bicarb solution but after a couple of days the white deposit returns.
Cheers,
Boiss
You have to neutralise it first.You should not use bicarb ,you will make it worse.!You can only use this on ACID. For dry cells use vinegar or lemon juice which is ACID (to kill the ALKALI)
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Old 16th Jun 2006, 12:14 am   #7
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Default Re: Battery acid corrosion

I have used vinegar on a cotton bud or toothbrush. I suspect Tomato Ketchup would work well too( very good for cleaning coins).
Take care to wash the vinegar off afterwards and tin the contacts.
Cheers
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Last edited by Darren-UK; 2nd Sep 2007 at 12:46 pm. Reason: Relevant typo corrected.
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Old 16th Jun 2006, 5:47 am   #8
John M0GLN
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Default Re: Battery acid corrosion

Quote:
Originally Posted by boiss
the copper and brass bits are fine after the bicarb treatment.
Hi,
Are these copper and brass bits in physical contact with the aluminium? If so, that could be a cause, they form a galvanic cell, and aluminium being the most electro-negative of the two will corrode away.
Regards
John.
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Old 16th Jun 2006, 1:57 pm   #9
Sideband
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Default Re: Battery acid corrosion

Quote:
Originally Posted by Tim
I have used vinegar on a cotton bud or toothbrush.

Take care to wash the vinegar off afterwards and tin the contacts.
Cheers
Tim
I keep a bottle of the clear vinegar in the workshop and find it ideal for cleaning all sorts of things and it should work well on battery corrosion but with aluminium, it must be washed off completely.


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Old 21st Jun 2006, 6:38 pm   #10
boiss
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Default Re: Battery acid corrosion

OK, Thanks for the help, the vinegar appears to work a treat. That was a bad mistake putting it in bicarb solution. If it had been left another year or two it would have been unuseable (just powder.) I will lacquer the chassis part in an attempt to halt any further corrosion.

Thanks again,
Boiss

Last edited by Darren-UK; 2nd Sep 2007 at 12:47 pm. Reason: Reference to non-existent image removed.
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