Cleaning Corrosion Off Battery Terminals

[DavePEI]

Hi Folks:

While Tom and Carol Black were visiting the museum yesterday, I noticed the signals on my military switchboard, a Vietnam era SB-22/PT weren't working.

Last year I had been thinking I should change the batteries in it, but due to procrastination, it never happened.

The SB-22 has its 4 D cell batteries in a long aluminum tube which plugs into circular contacts within the board. Each side screws off for access to two batteries each. Talk voltage and signal voltages come off each pair of batteries. This corrosion was on  the signal side. I will later treat the clean talk side just to neutralize any potential corrosive. Then the two tubes screw together to become one unit.

I took the first (talk) side off and the batteries were just starting to corrode. The other side (signal) was a whole different matter! It was seized solid. Thankfully, the battery tube has a link in the middle which allows the removal of each side as well.

With difficulty, I finally got that side loose, and the severely corroded batteries out, revealing some serious corrosion inside the tube.

Now, I have done this before, but I thought I would see if anyone else had any, possibly better ideas.

In the past, I have used both baking soda solution (a base) and also vinegar (a weak acid) to remove this corrosion. Seeing as the corrosion from normal  D cells is potassium hydroxide (an alkali), I decided to use the vinegar to neutralize it. After soakng it for a half an hour, it was possible to  use a toothbrush in the vinegar solution to remove the corrosion completely. After ten minutes soaking, the phenolic end cap would again unscrew.

If you look carefully at the photo below, you will see bits of the corrosion breaking loose as it soaks in the vinegar.

When done, I will soak the holder in water for a while, use some vaseline on the battery contacts and threads, then re-assemble the holder.

I have removed batteries from most items in the museum to prevent this from happening, and will likely devise a way to power the board without using batteries to avoid this in the future..

I just wanted to post it so we can share other ways of taking care and restoring items from battery corrosion!

Dave

[ESalter]

I've always used the same methods as you Dave, baking soda paste or white vinegar depending on what the corrosion was from.  I've always had great luck with those two.  My dad has a large Maglite flashlight, a couple weeks ago I went to use it and it wouldn't turn on.  Come to find out the batteries were dead and were corroded solid inside of it.  It takes 4 D cell batteries, it took probably 10 minutes of beating on the end of this flashlight with a rubber mallet before I got all 4 of them out.  To clean it, I set it in a bread pan with vinegar overnight.  The next morning there appeared to be no result.  So, I rinsed it with water and let it dry.  The next day about half of the corrosion was falling off it.  I scrubbed it out with a toothbrush and put it in vinegar again.  I had to cycle between vinegar, water, and dry about 3 times before all of it came out, but it did eventually get all of it.

---Eric

[DavePEI]

I've always used the same methods as you Dave, baking soda paste or white vinegar depending on what the corrosion was from.  I've always had great luck with those two.  My dad has a large Maglite flashlight, a couple weeks ago I went to use it and it wouldn't turn on.  Come to find out the batteries were dead and were corroded solid inside of it.  It takes 4 D cell batteries, it took probably 10 minutes of beating on the end of this flashlight with a rubber mallet before I got all 4 of them out.  To clean it, I set it in a bread pan with vinegar overnight.  The next morning there appeared to be no result.  So, I rinsed it with water and let it dry.  The next day about half of the corrosion was falling off it.  I scrubbed it out with a toothbrush and put it in vinegar again.  I had to cycle between vinegar, water, and dry about 3 times before all of it came out, but it did eventually get all of it.

---Eric

Hi Eric:

Well, I am glad I didn't leave it longer - nipped it in the bud, so to speak - the tube and the terminals are back to shiny aluminum again, but I am going to leave it soaking for a couple more hours to make sure it is all neutralized before putting it back together. At least the contacts on this, being military are solid enough they can handle a bit of corrosion. But, as long as contacts haven't been eaten out by the corrosion, this usually works... Thank goodness, as I am sure I wouldn't be able to find another original battery holder for it!

Dave

[G-Man]

Dave and Eric ...

Thanks for providing this much needed tutorial regarding the removal and neutralization of the byproducts of battery corrosion.

You might want to consider posting it on the other telephone collecting listserves as well since I am sure a number of people will find it of use.

[DavePEI]

Dave and Eric ...

Thanks for providing this much needed tutorial regarding the removal and neutralization of the byproducts of battery corrosion.

You might want to consider posting it on the other telephone collecting listserves as well since I am sure a number of people will find it of use.

Yes, I will, as there is nothing more heartbreaking than to find a fine piece of equipment destroyed due to battery corrosion. Sadly, one often notices it too late, when the corrosion has eaten through the battery terminals, but if you catch it on time, and neutralize it, you can save the equipment.

I should note: If your equipment was damaged by a lead-acid battery, use the baking soda to neutralize it. Alkaline batteries require the vinegar, as the corrosion caused by it is a base. If unsure, and you have litmus paper, test the corrosion to see whether it is acid or base. Use the opposite to neutralize it.

I normally test all battery equipment with batteries, but I power the board up so seldom that I completely forgot about it. Last night, I realized I will have to check my TA-33 field phone as well - hopefully it isn't badly corroded. Today's project!

The best option if you have battery equipment you don't use daily, is to remove the batteries when you aren't using it - my battery operated test equipment is used often enough I notice the batteries getting low, but other less used items I normally store without batteries. I simply forgot in this case, and never wouldn't have thought of it had I not tried to demonstrate the board the other day!

As I think I mentioned above, a light coating of petroleum jelly (vaseline) will also help for keep corrosion from spreading once it has been cleaned off and neutralized.

All these little tidbits can help others - if you think of anything which may help others, please post it to the forum. Sometimes, it seems, about half of my posts are of this type, but then that is what the forum is about, sharing knowledge. I just hope every time that I post something like this, that it will help someone!

Dave

[DavePEI]

One other thing I thought should be mentioned. Often as a result of battery or other corrosion, particularily where rivets are used to connect terminals to a board, the corrosion will end up insulating the rivet from the board.

Although mentioned somewhere on the forum, a good example of this is inside the electro-luminescent panels used on some AE phones. This can be repaired quite easily as follows:

Go to Canadian Tire, NAPA, Auto Zone or any of the big auto parts store and get a rear window defroster repair kit. One commonly available brand is Permatex. This contains a conductive epoxy paint and masking materials. You can also use colloidal silver paint.

Clean around the offending rivet, and then place a drop of the paint over the end of the rivet where it can soak onto the contact area of the board. In 99% of cases, this will return the panel to operation.

The same product may also be used to repair missing or damaged traces on printed circuit boards - much better than trying to solder bits of wire on the board to repair it. Simply mask the area where the open is, than put several layers of conductive paint on it.

I mention this in this thread, because often corrosion effects rivets where battery corrosion has insulated them from the board. This will fix this problem in most cases.

Dave