Removing battery corrosion

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I got an old AM-FM pocket transistor radio which looked good and clean
till I opened the battery compartment. Very corroded carbon zinc
batteries were in it. After removing them, I cleaned off as much of the
corrosion as possible by scraping with a plastic stick, and scrubbing
with q-tips and rubbing alcohol. That got rid of most of it, and I was
surprised to find the battery clips are not badly damaged, but I had to
use a fingernail file (sandpaper strip) on the ends of the springs.  

Better yet, the radio works perfectly.

But there is still a little of that battery corrosion still in there. In
all the years I've worked on electronics, I have never found a perfect
way to clean up leaked batteries. Is there some sort of spray or a
chemical that will dissolve or deactivate that crap?  

Of course it has to be safe for the circuit board and components too. I
use the 91% isopropyl alcohol, so it evaporates quickly and leaves
little water residue behind. (Then leave it dry well before use).  


Re: Removing battery corrosion
On Sun, 11 Feb 2018 04:52:51 -0600, snipped-for-privacy@tubes.com wrote:

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I like dish detergent and a soak in very hot water then scrub with a
toothbrush and let dry in a warm oven, for hours.  But with unsealed
potentiometers, or those poly insulated tuning caps they used back in
the day, I wouldn't recommend it.

WD-40 seems to work well in electronics.  Good for noisy pots and can
help keep out moisture.

Re: Removing battery corrosion
On Sunday, February 11, 2018 at 6:59:23 AM UTC-6, default wrote:
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I recommend swabbing with a solution of sodium bicarbonate to neutralize the acid.  

Re: Removing battery corrosion
On Sun, 11 Feb 2018 05:53:28 -0800 (PST), Andy

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What acid?

Re: Removing battery corrosion
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Ammonium chloride


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Re: Removing battery corrosion

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Ah, good point.

I looked up Joy dishwashing liquid for the hell of it and the MSDS
gives the ph as 9 in a 10% solution.

So it will neutralize acids, and isn't unique in that respect.  (most
household cleaners are alkaline in nature, from what I'm reading on
the subject)

AND 10%?  does it really take that much Joy to do dishes, and have I
been doing it wrong all these years?

Re: Removing battery corrosion
On Sunday, February 11, 2018 at 7:59:23 AM UTC-5, default wrote:
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Under 200 F, I guess?

Re: Removing battery corrosion
On Tue, 13 Feb 2018 00:44:32 -0800 (PST), snipped-for-privacy@gmail.com
wrote:

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Too hot that I want to keep my hands on it, but can't say I ever
measured the temperature.  I'm a hobbyist these days and bake a lot of
bread so have a good feel for how my oven behaves. I use a baking
sheet under the electronics to shield them from direct radiation from
the element, then put them on a paper towel or newsprint, preheat the
oven then put the stuff in.

When I was working in lab we had vacuum ovens and that would be my
first choice for drying electronics.  An hour under vacuum at maybe
50C and it would be bone dry.

I once used my pressure cooker (with all the sealing reversed) to pull
a vacuum on molten wax to impregnate an induction coil secondary that
I was building.  That's a technique used in line frequency
transformers with varnish to draw the varnish into the windings (or,
more correctly, pull out the air/moisture) and laminations to stop
buzzing.  

Re: Removing battery corrosion
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capacitor electrolyte boils hotter than water does, so if the plastics
and adhesives in the radio can stand it you can go hotter


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Re: Removing battery corrosion

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Yeah, but he's dealing with old stuff, germanium transistors and
phenolic or paper-epoxy circuit boards, etc..  It would be too easy to
wreck stuff.

Re: Removing battery corrosion
On Sun, 11 Feb 2018 04:52:51 -0600, snipped-for-privacy@tubes.com wrote:

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I use 409 spray cleaner, a plastic scraper, and a paint brush.  For
alkaline cells, scrape off as much of the white powder as possible.
Clean what you can with the small paint brush.  Then attack with the
409 spray.  It will evaporate dry in about an hour.  If you have an
air compressor, you can blow out the excess liquid and it will dry
quicker.

It's been so long since I've seen any equipment that uses a carbon
zinc cell, that I don't recall how it's cleaned.  Probably some
alkaline cleaner.

The most common problem I see are corroded battery springs and
contacts.  Once the plating is gone, it's difficult to keep them from
corroding again.  Grease helps, but makes a mess.  So, I replace them
with similar or identical spring contacts purchased on eBay and other
online vendors:
<https://www.ebay.com/sch/i.html?_nkw=battery+spring+contact


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Re: Removing battery corrosion
Since this layer is alcaline, the best to use an acid ; vinegar for  
instance.


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Re: Removing battery corrosion
wrote:

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<https://en.wikipedia.org/wiki/Alkaline_battery#Leaks
Yep.  The white stuff from an alkaline cell is potassium carbonate and
has a pH of about 11 in water:
<https://en.wikipedia.org/wiki/Potassium_carbonate
Vinegar works, but citric acid (lemon juice) smells better.  If the
cleaner produces gas bubbles, it's working.  However, I don't think it
matters much.  I use 409 household cleaner which has a pH of 9 to 11.5
depending on concentration:
<http://www.gjfood.com/pdf/msds/79_820040.pdf
It produces some bubbles, does a good job of cleaning, and smells ok.

The white stuff that leaks out of carbon zinc battery is the zinc
chloride electrolyte:
<https://en.wikipedia.org/wiki/Zinc%E2%80%93carbon_battery#Durability
<https://en.wikipedia.org/wiki/Zinc_chloride
Zinc chloride in water is very acidic with a pH of 2.0 to 3.0
depending on concentration.  It's very soluble in water so any water
based alkaline cleaner, such as houshold ammonia, should work.



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Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Removing battery corrosion
wrote:

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Oops.  Zinc chloride is the crud that leaks out of the battery.  The
electrolyte is ammonium chloride.

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Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Removing battery corrosion
On 11/02/18 23:38, Jeff Liebermann wrote:
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Zinc chloride actually attracts so much water that it dissolves in it,
as I found out when I tried to crystallize the stuff.

Jeroen Belleman

Re: Removing battery corrosion
On Mon, 12 Feb 2018 00:31:54 +0100, Jeroen Belleman

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What were you trying to make?  Soldering flux (usually a mix of zinc
chloride and hydrochloric acid)?  Don't use it on electronics as it's
conductive.

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Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Removing battery corrosion
Jeff Liebermann wrote:
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Nah! Just part of a high school chemistry course 45 years ago.

Jeroen Belleman

Re: Removing battery corrosion
wrote:

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That's acid plumbing solder for copper pipes.

But you brought up a question. Electrical solder is rosin. What exactly
is roisn and how does it work for a flux? Is it the same thing used for
playing a violin, which as far as I know, is made from pine tree sap?


Re: Removing battery corrosion
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yes that's the stuff.

what it does is when heated decompose into acids which dissolve oxides,  
and into hydrocarbons which reduce oxides back to clean metal, all of
which which helps the molten solder to wet the metal.  

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Re: Removing battery corrosion
The older method is the metallic brush and some elbow oil !
It is efficient.



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