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Removing battery corrosion

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).

Reply to
oldschool
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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.

Reply to
default

I recommend swabbing with a solution of sodium bicarbonate to neutralize the acid.

Reply to
Andy

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:

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

Since this layer is alcaline, the best to use an acid ; vinegar for instance.

Reply to
Look165

What acid?

Reply to
default

Yep. The white stuff from an alkaline cell is potassium carbonate and has a pH of about 11 in water: 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: 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: 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.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

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

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

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

Reply to
Jeroen Belleman

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     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

Ammonium chloride

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Reply to
Jasen Betts

Nah! Just part of a high school chemistry course 45 years ago.

Jeroen Belleman

Reply to
Jeroen Belleman

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?

Reply to
oldschool

The older method is the metallic brush and some elbow oil ! It is efficient.

Reply to
Look165

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?

Reply to
default

Under 200 F, I guess?

Reply to
bruce2bowser

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.

Reply to
default

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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Reply to
Jasen Betts

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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Reply to
Jasen Betts

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.

Reply to
default

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