#0002: Cleaning up after an alkaline battery leak

This will be a rather basic guide on how to clean out a device after an alkaline battery leak.

Whenever I come across an old device, that for some initially unknown reason refuses to power on. Chances are, that someone left disposable alkaline batteries inside it, and that they have leaked. There are a number of reasons as to why people leave batteries inside devices. Predominantly: laziness, ignorance, or forgetfulness. There are also a number of reasons as to why these same forgotten batteries leak. Batteries with mixed charges, reverse charging each other, or a constant low current draw causing leaking; are but two examples.

Unfortunately, a more in depth look into what causes disposable batteries to leak is outside of the scope of this article. However it is something that I am interested in exploring at a later date. Check the further reading section of this article for the hotlink to that, when I eventually get round to penning it.

I cannot count the number of times I have opened the battery compartment of a device, that has been left in storage for a while; only to be greeted with a vented battery, rust, and the the blue-white fuzzy carpet of alkaline crystals growing out of it. Meshing into, fusing with, and corroding the negative terminal’s spring contacts. This infection then proceeded down the circuit and further into the device and onto more complicated/valuable components. In this regard, an unstemmed battery leak has the potential to brick a device.

So, how do you deal with it? Well, if caught early and the leak hasn’t progressed far beyond the battery itself, and a bit of surface level corrosion on the spring contacts; then it is really not much of an issue. A quick wipe down with a damp cloth after disposing of the batteries, should suffice. I recommend using isopropyl alcohol to dampen the cleaning cloth, mainly because it becomes non-conductive very quickly by evaporating readily. It also doesn’t leave any contaminants like water might. However water is fine to use in a pinch; just make sure it is fully evaporated and that there is no substance residue left after cleaning; before you power up the device.

If the leak has had the time necessary to progress further into the circuit and deeper into the metals. That’s when you have to take more invasive steps in order to remove it. There are two main ways to deal with an advanced battery leak. Which one to use, largely depends on circumstance. The most important factor being whether or not the affect parts can be removed from the device.

Method #1: Acid Bath

The first method of remedy, requires the removal of the affected parts and the use of an acid bath. Removing the affected parts, will likely require de-soldering. Next, create a bath, of vinegar and water at a ratio of approximately 1:3. So 25% vinegar and 75% water, or thereabouts. This leaves you with a mildly acidic solution for you to submerge any affected parts within. Mix the solution well, then drop the parts in. Leave it for some time. How long for based on your own judgment. I recommend 30 minutes to a couple of hours depending on the invasiveness of the alkaline crystals into the metals.

Remove the parts from the solution when you think that they have been in there long enough. At this point, they will require brushing down, to remove any stuck on materials. Use a strong bristly brush for this, something like a firm toothbrush will do. For those wondering, a wire brush would probably be overkill for this application, especially since the subjected parts would likely be rather small, and wire brushes are traditionally made for uses with larger items. Wire brushes will also likely remove the finish on the metal parts, that is if the acid bath hasn’t done so already.

The main reasons why I recommend using a mildly acidic solution to counteract the alkaline crystals is: one, in order to minimise the severity of the reaction between acid and alkaline; and thus minimise the chances of additional corrosion or damage done to the metals in the process; and two, to minimise the chances of the acid removing or damaging the metal’s finish by reacting with it. It should be noted that plenty of parts in modern mass produced devices are made up of mixed metals, then given a chrome finish for uniformity.

I should note that when I say ‘part’, I am referring to simple primarily metal constructs within devices; such as spring terminals or basic switches. I am not referring to more complicated components such as resistors, capacitors, transistors, or anything more sophisticated than those examples. This is because the acidic solution is very likely to compromise the internal structure or chemistry of any components submerged within it, if the leak’s corrosion hasn’t done so already. Bricking the component in the process. More on what to do with leak affected components mentioned later.

After brushing all foreign materials off of the parts, dry them off, then wipe them down with a cloth laced with isopropyl alcohol. Continue until you are confident that you have removed all contaminants including traces of alkaline crystals and the acidic solution. Once this is done leave the parts to dry fully, before then placing them back into the device and likely soldering them back into the circuit they come from. That’s it, done.

Method #2: Acid Wrap

The second method of removing alkaline crystals is used when the affected part cannot be removed either from the device or it’s circuit for whatever reason. A good example of this is when a part is either welded, crimped, or glued into place; making it’s removal potentially too destructive to consider lightly.

This method requires either tissue paper or cloth. Id est, something that can soak up liquid and cling to a particular structure without external pressure/force. I use tissue paper for this example. Soak the tissue paper in a diluted acidic solution; enough so that it has plenty of solution available but not enough that it drips excess. Then wrap it around the affected parts and wait for time, before removing it and brushing off any loose materials. Rinse and repeat until it looks done. Then clean and wipe down the part with an isopropyl laced cloth. Done.

You can adjust the ratio of vinegar to water to your liking. I still recommend a mildly acidic solution to minimise the severity of the reaction (and any damage caused from it), but the more acidic the solution is, the quicker it’ll dissolve the alkaline crystals off of the affected parts. From my experience a ratio of 1:1 seems to work out well.

Another tip for this method is to properly isolate the rest of the device from the part you are currently working on. This is done to avoid any accidental drips from the tissue paper or off-spray caused by brushing. Vinegar-water and electronic components are best left separated. With that in mind, I recommend using a plastic bag and tape. The plastic bag functions as a waterproof membrane and the tape holds it in place. Simple.

Dealing with components

Now that the basic method of cleaning metal parts has been explored, you may be wondering as what to do when the leak has reached more complex components. Well, the answer is simple. Try to remove whatever battery residue you can mechanically; i.e. just using a brush or a small chisel of some sort. Then de-solder/remove the component from the circuit. Test it appropriately. I recommend having both a multimeter as well as a multi-function tester on hand for this. If it is still within specification, solder it back into circuit; if not, replace it. There is not much one can do for any affected components beyond this. Once a capacitor or resistor is broken, it needs to be replaced.

Conclusion

As a final note, I should also mention that in a lot of situations: replacement of the affected metal parts is probably the more appropriate recourse to severe leak damage then repair might be. This means replacing spring terminals, and creating jumper wires as replacements for corroded PCB traces. This is because the repair can weaken the metal, leaving one with brittle spring terminals or a trace with more resistance in it than initially intentioned. However having said that, if you either can not remove the part, or don’t have the prerequisite replacements: then an ugly repair is better than no repair at all.

Sources/References/Further reading:

https://en.wikipedia.org/wiki/Alkaline_battery#Leaks

https://upload.wikimedia.org/wikipedia/commons/7/76/Alkaline_Battery_Leakage_Inside_a_Product.png

https://en.wikipedia.org/wiki/Isopropyl_alcohol