How to Fix Corroded Battery Terminals




About: I've always liked pulling things apart - it's the putting back together again that I have some issues with.

Many a time I’ve managed to get my hands on some electronic gizmo only to find that the battery compartment totally corroded. It’s usually one of the main reasons I think that people throw toys and whatever else takes batteries away.

The corrosion is caused by potassium hydroxide which can leak out of alkaline batteries (these are the usual types of batteries you put inside toys etc). All batteries discharge, either through use or just slowly through the production of hydrogen gas which forms pressure in the battery. Eventually that pressure will find a way out through a seal or as the battery ages, through corrosion or rust in the outer shell.

As soon as the first signs of a leak forms, then the best thing to do is to get rid of the battery. if you don’t get to it in time however, then the corrosion can grow and spread out of the battery which causes oxidisation and corrosion of the terminals making your device caput.

This Instructable will go through a couple of ways that you can fix your device to bring it back to life again. The first is the most extreme corrosion where the terminals have to be replaced, the second is a small amount of oxidisation which only needed the potassium hydroxide to be neutralised and the terminals to be cleaned.

You can take precautions though to stop this happening such as not mixing different battery types in the same device, replacing all of the batteries at the same time, storing in a dry place and at room temperature, and removing batteries for storage of devices. I’m inherently optimistic (and also lazy) so I’ve never taken any of these precautions but it’s definitely good practice, especially with expensive electronic goods.

Step 1: Parts and Tools

Your parts are going to be any electronic goods that need terminal cleaning and/or relacing. The following though will come in handy when you are going this type of work


1. Battery Holders. I have a bunch of these lying around which are good for projects. You can also use the terminals from them to repair other electronic goods.

2. You can also just buy these terminals from eBay

2. Small files

3. Vinegar

4. Small paint brush

5. Needle nose pliers

6. Ear cleaners

7. Wire cutters

8. Soldering iron

9. Rubber gloves – to protect your skin from the potassium hydroxide. I have touched it before and it does mildly irritate the skin so it’s best to use gloves when handling.

10. Eye protection – self explanatory

11. Protective mouth and nose mask. Potassium hydroxide can be quite dangerous and breathing it in can be toxic. Better to be safe then sorry.

Step 2: Removing Leaking Batteries

Don’t use your fingers to try and remove the batteries. The potassium hydroxide inside the battery can irritate your skin (I know as I’ve touched it before!). Potassium hydroxide is a caustic agent and is the chemical that corrodes the terminals and destroys the batteries. You may have also seen a feathery crystalline structure forming around the battery and terminal as well. This is potassium carbonate and forms when the potassium hydroxide reacts with carbon dioxide in the air.

For those who want to understand more about the chemical components inside an alkaline battery, please check out the following


1. Place a set of rubber gloves on and some safety glasses

2. Use a small screwdriver to pull the batteries out. The glasses here are very important as it is easy to flick small pieces of the corrosion whist pulling out the batteries.

3. Sometimes that batteries can be so corroded that they virtually weld themselves to the terminals. In this case you will need to use a large screwdriver and maybe some pliers to remove them. You’ll probably rip out the terminals as well so be careful you don’t pull any wires out at the same time

4. Dispose of the batteries in a plastic bag.

Step 3: Removing the Corroded Terminals

Next thing to do is to remove all of the corroded terminals. It can be tricky sometimes to do this if they are severely corroded as bits can break off and the grooves in the battery holder can get clogged-up.


1. Use a small, thin screwdriver and push this between the top of the terminal and the battery holder. This should bend out the terminal

2. With a pair of needle nosed pliers, grab hold of the terminal and pull it out.

3. If the terminal has solder points, make sure you de-solder or cut the wires and cut them away to be able to remove them easily

4. Dispose of the corroded terminals once removed

Step 4: Cleaning the Battery Cover

The battery holder that I fixed came away from the torch so make it easy to wash and clean. However, this might not always be the case as it will depend on what type of electronics you are cleaning.


1. You can neutralise any leftover potassium hydroxide (a caustic agent which acts a little like acid) with some vinegar. Many comments have been made on this in the comments section and initially I also included baking soda as a way to neutralise the alkaline. I've removed this as there is a fair bit of contention if this would actually work or not.

2. Next if possible, wash out the bottom of the battery holder and clean any of the old potassium hydroxide away from the case. If you can’t remove the battery holder, then you are going to have to be a lot more careful when cleaning the area. Use a damp cloth instead of running water and remove any leftover potassium hydroxide residue

3. Next, you may need to remove any pieces of terminal or corrosion that is in-between the grooves that the terminals sit in. Use something thin and sharp to remove anything lodged inside the grooves.

4. Lastly, give the area a clean with some Isopropyl Cleaning Alcohol to remove any last traces of oils, stains etc.

Step 5: Sourcing Some Battery Terminals

In some cases, the corrosion is so bad that you need to replace the terminals inside the battery compartment. One of the easiest places to get these is from old battery holders. You could also grab the terminals out of any old electronic parts.

You can also buy the terminals from eBay and I have put a link in the parts section


1 If your battery terminals have tabs on the back, make sure you lift these up first. You might also need to de-solder any wires on them if you got the terminals out of a toy etc.

2 Next, use a small screwdriver to push them out of the battery holder. Just place the tip of the screwdriver into the bottom of the terminal and lift it out of the battery holder. They are held in place by a couple of grooves in the side of the battery holder so should come out relatively easily.

Step 6: Modifying the Battery Terminals

Chances are you will need to modify the battery terminals so they will fit into the batter holder. You can do this pretty easily with some wire cutters and a dremel if you have one.


1 First, try and fit one of the terminals into the battery holder grooves. If it does fit, then you can probably ignore this step and move onto the next. If not, then you will need to modify it.

2 Trim the sides of the terminal with some wire cutters and try to push into the grooves again in the battery holder

3 I also had to add a small slit into the terminal in order for them to fit which I did with a dremel.

4 Once you have modified, it’s then time to add them to the battery holder

Step 7: Putting the Battery Terminals in Place


1. The first thing to do is to determine the orientation of the terminals. You need to make sure that the spring section on the terminal will be touching the negative part of the battery and the flat section is touching the positive.

2. Usually you can just look on the bottom of the battery holder and there will be images or the orientation. If not, then work out where the positive wire is going to be connected to the terminal and use this as a guide on the orientation of the terminals.

3. Place the terminals into the battery holder grooves and push into place. If they are a little loose then usually the batteries will hold them into place. However, you can slightly bend the terminal and push it back into the grooves which will make the fit a little tighter.

4. Once you have all of the terminals in place, solder the positive and negative wires to the solder points on the terminals

Step 8: Add Some Fresh Batteries and Test


1. Before you screw everything back into place, add some batteries and make sure everything works as it should.

2. If everything works ok – replace the screws and covers and whatever else needs replacing to finish off your part

3. Lastly, give it another test and make sure it works

4. Now if you don’t want to have to do this all over again, go back to the intro and follow the precautions

This is really the most extreme case of having to fix battery terminals. The next sample, I think is more common and is more oxidisation of the terminals due to some leakage of the batteries. It’s easier too to fix!

Step 9: Fixing Oxidised and Minor Corroded Terminals

I found this cool, vintage mike at the dump and wanted to try and get it going again. Initially I tested it not knowing that it needed an AA battery and thought it was probably something to do with the wiring. After un-screwing the case however, I discovered that it needed a AA battery to run. The battery had been in place for some time and the terminals were oxidised and had some minor corrosion damage. I could have replaced the terminals but decided it would be easier just cleaning them


1. Remove the old battery with a screwdriver and dispose of. Even though there was not as much damage and leakage as the first sample, I still made sure that I wore gloves and eye protection. They are considered safe to dispose of in the bin (imagine how many batteries get thrown away each day!) but there might be some local laws that require you to dispose of them in other ways

2. You can see in the images that there is a little corrosion and potassium hydroxide on the end of the terminal but that the terminal itself looks relatively unaffected structurally.

3. The brown streaks you can see running through the middle of the battery holder is actually glue that has discoloured over time, not corrosion

4. The next step is to neutralise the alkaline from the potassium hydroxide.

Step 10: Neutralise the Acid

Next thing to do is to neutralise any residual potassium hydroxide left of the terminals. There have been many comments left on how best to neutralise the corrosives from the potassium hydroxide. As potassium hydroxide is a strong base, then an acid like vinegar or lemon juice is probably the best thing to use when neutralising an alkaline like potassium hydroxide.

Here's a little more information on acids and bases for those who are interested and how to neutralising.


1. First thing to do is to add the vinegar to a small container like a bottle cap lid.

2. Next, add a little to each terminal with a small paint brush or something similar.

3. Wipe off any excess from the terminals and leave to dry

4. Now that the potassium hydroxide has been neutralised, it’s time to clean-up the terminals

Step 11: Cleaning Up the Terminals

You need to remove any oxidisation and corrosion from the terminals. I find that the best thing to use is a small file but you could use sandpaper or an emery board or nail file as well.


1. Use a small, fine file on the terminal until the oxidisation and any corrosion is removed. You may not be able to get it all off but sure you get as much as possible.

2. Once you have removed the oxidisation, give the terminals a clean with some isopropyl alcohol. You can also add some non-oxidising grease to help stop any further oxidisation.

3. You can sometimes remove the terminals from the grooves without having to undo any screws or removing any wires. It can make it easier to file if you can do this – just be careful that you don’t break any wires etc.

Step 12: Add a Fresh Battery and Test


1. Once the terminals are clean and back into place, you can add a battery/s and test.

2. As before, it’s best to test before you screw everything back into place

That’s it! Hopefully you have managed to bring something back to life again with only a little bit of work.

Do you have any other tips? Let me know in the comments



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112 Discussions


3 months ago

Hi All,

Thanks for the comments. I have updated the section in the Instructable on what to use to neutralise the Potassium Hydroxide that can be produced in Alkaline batteries.


2 months ago

I have been using a very simple method for 65 years and my parents used this method before me, so I don't know how many years this has been common knowledge. I have never failed to permanently restore even the most corroded terminals on vehicle batteries or any other battery-dependent item. It is a three-step process: take some regular cold, very strong black tea, pour it on the terminals as you scrub with an old toothbrush. Let it dry, and then coat terminals heavily with vaseline. Put your new batteries back in. I have never had to dismantle any mechanism, and have had 100% success using this very simple method.

2 replies

Reply 4 weeks ago

Hentyharp hasn't come across some of the vehicle terminals I've seen! Black tea won't replace lost metal. I'm curious to see how it performs on less radical cases, though. Great to see so many fellow 'rescuers' on here. I do hate the bin it & buy new culture.


2 months ago on Step 4

Potassium hydroxide is ALKALINE and can be neutalized with an acid. ACIDS can be neutralized with sodium bicarbonate. There is some confusion about this in the text. An alkaloid is not the same as an alkaline substance either, it is a group of agents from plants containing nitrogen and can be acids and neutral too. I might be a bit picky here but there are several errors in the otherwise useful text.

2 replies

Reply 4 weeks ago

Nothing picky where correct information is needed. There was a famous murder case, here in Britain, where the culprits tried to get rid of the body by putting it in a bath of acid and caustic soda!
If only they'd had your knowledge, or not.


Reply 2 months ago

Thanks for the information. I have updated the 'ible.


Question 3 months ago

Can heat insulation be increased by using aluminium foil over the usual 8 cm deep lagging under the loft floorboards, please? Is it save to have insulation between the roof rafters?

1 answer

Answer 2 months ago

You generally do not want the roof Rafters insulated if you live in a cold climate. in fact you want the Loft area ventilated. What you don't want is heat building up under the roof melting snow near the Apex which runs down as water and refreezes at your eaves. This causes ice daming which damages the roof. The insulation underneath your Loft floor is to keep the house heat inside the house and out from under the roof. I suppose you could add a second loft floor, but it would really depend on the method used to construct your house.


3 months ago

1- WD40 helps to fix even broken hearts... I use it to protect guitar strings from hands sweat, and playing guitar is good to forget broken hearts...

2- Don't use Duracell batteries. I've seen many that leaks even in unopened blisters and still in warranty...

3 replies

Reply 2 months ago

As WD-40 is a degreaser which evaporates, it should not be used where grease or light oil is the proper lubricant. Like bicycles chains and door hinges. Its a good cleaning solvent, but you need to apply the proper lubrication after its use.


Reply 3 months ago

I have an unopened package of Duracell AAA batteries that are going back to Costco. Sad, they used to put out a decent product.


3 months ago

FULLY DETAILED PROCEDURE, (long post warning):

OK, this has been said MANY times already in different and sometimes confusing ways, but it needs to be stated simply and clearly (chemists please refrain from correcting the details I am ignoring... this is a broad-brush SIMPLE explanation):

1) Alkaline batteries do *NOT* contain ACID, but non-chemistry people will almost always use that term for what leaks out (and be wrong!).

2) To neutralize ALKALINE (also referred to as a BASE), you *MUST USE* an acid.

3) Vinegar is an ACID, baking soda is an ALKALINE substance (but **much** 'weaker' than the alkaline substance in alkaline batteries).

4) IPA (Isopropyl alchohol) is not either an acid NOR a base, but a solvent. For this purpose use nothing less than 98% (99.9% preferred!). This can be hard to find as grocery stores/pharmacies seem to be selling mostly water these days (60% or 70%) instead of IPA.

With all that in mind, we can first excuse the author for referring to the 'leaking stuff' as "acid" since most non-chemists do this too. Hopefully this clears things up, at least for those who read the comments this far ).

The idea for a proper process is to convert bad stuff to less bad stuff in as few steps as possible, then finally convert to stuff that is easily rinsed away, then a drying substance to get the water out.


Here's my method for decontaminating the corrosive alkaline substance from alkaline batteries, based on solid cemistry principles (the instructable is close, so you can follow it (*mostly*). Lots of words of explanation here, but once you do it you will find it is easy and fast!:

0) **MAKE SURE** you have *all* materials, tools, water, canned air, whatever, ready and a place to do this *before you start*. I like to do some of this outside in the driveway, so I am prepared for that too.

1) Remove as much of the crusty stuff as practical, brush and shake the crumbs off and try to not let it spread into other parts of the device. I will use a can of air to blow it out if necessary (I do this outside).

2) CAREFULLY, put vinegar on all areas contaminated (note: vinegar will corrode things too! So be ready for the next steps as we won't be wasting time neutralizing the vinegar right away!). Try really hard to not get vinegar on parts that don't need it, but pay attention to everywhere the vinegar goes so you can neutralize it next. The vinegar is strong enough to chemically change the alkaline into something that can easily wash off and stop it from corroding further.

3) Let it fizz a bit to allow it to fully neutralize the alkaline material.

4) RINSE THOROUGHLY with clean water, avoid some well waters that are hard or have high alkali levels, use bottled water if you have poor water. Don't worry TOO much if water goes in areas not intended, but avoid letting it get into switches and parts that you can internally clean easily. Rinse more than once if you need to. I do this outside on the driveway, too.

5) if the contamination is severe, you may need to repeat the vinegar and rinse (steps 2, 3, 4).

6) Put baking soda everywhere the vinegar solution may have reached (note this will likely be a much larger area than you started with... it's important to neutralize the leftover vinegar at this time). I just use the powdered baking soda directly, especially since the device should still be wet from the rinsing at this point.

7) Let it fizz a bit if you see that happening.

8) Rinse it slightly... the intent is to introduce just a little water so the baking soda can get to the tiny places where the dry powder may not have reached. Use enough water to make it drippy, then wait 3 or 5 seconds.

9) RINSE thoroughly - get that baking soda dissolved and out of the device. Baking soda is only *mildly* alkaline so is not very corrosive, but it can neutralize leftover vinegar easily. It's also *very* water soluble so it can rinse completely away. I do this outside as well, but a big sink works.

10) Shake, blow, drip, whatever, to get most of the water out. The idea is not to dry the device yet, just get rid of the baking-soda water

11) Repeat the rinse/shake cycle (steps 9, 10) to "purify" the remaining water (gets the baking soda contamination out while leaving only pure water behind). You can repeat as many times you feel necessary for your device... for easy stuff a 2nd rinse is all that is usually needed.


12a) At this point you should've used canned air or whatever shaking and tipping to get all but a bit of moisture out of your device... time for the IPA. The alcohol acts as a "dryer" by taking the water with it when it rinses out and evaporates quickly. It is flammable and will make a lot of alcohol fumes so have plenty of ventilation and no pilot lights or other sources of ignition nearby! (Don't do this near your natural gas water heater in the garage, for example). I use 99.98%, but you can get away with 99% or even 98%, just be aware that other % is water, so you will be leaving more moisture in your device than you really should...

12b) Pour and/or spray the IPA over the device, tilted so it can run away from switches or other parts you don't want to have it run into... be generous- you want the IPA to take the moisture and any other contaminates with it and out. I will sometimes use canned air to help blow the IPA out and dry the device.

12c) Device should be dry now, but if it's not, let it sit awhile to air dry. Don't skip the air-dry step! Give it at least 10 or 15 minutes for the IPA to be gone. You can gently bake out any remaining moisture with a hot air gun (or hair dryer gun) set on LOW LOW... some electronic parts can't take a lot of heat. Follow whatever other steps you need to finish repairing your device- this instructable has some very good ideas.

Sorry for the length of this, but I see too much misunderstanding and disinformation about how to do this properly that I should probably just put up a full instructable once and for all. I use this exact technique on industrial, commercial, and consumer devices... most of which can be salvaged this way. Sometimes circuit board traces are destroyed and you have to solder bits of wire to fix it, but only for high-value devices where the extra labor is worth it.

2 replies

Reply 2 months ago

I agree with the author this needs to be its own instructible so that it can be referenced by other people doing their cleaning.


Reply 2 months ago

Wow - thanks for the great response! you need to create a 'ible and get this info out into the world.


2 months ago on Step 2

That's what happens when you use Duracell batteries. Great way to clean up the mess that they leave though.

Thanks for the helpful tip.


3 months ago

Great instructable. Electronics stores sell a variety of battery terminals and good quality wire.

1 reply

3 months ago on Step 12

Or use due electric grease on terminals