Remove the board entirely. Remove all the batteries and throw them away.

Now comes the cleaning part: use vinegar and a toothbrush, and remove all electrolyte residue.
Check all the contacts and make sure they look ok.
Then you have to clean it: Use soap/detergent and water and repeat the same procedure. Let it dry for one day or so.

There may be some components you'll have to replace because it looks compromised.
But you could still give it a try and hopefully it will work.

Good luck!

tauro wrote on 2024-02-10, 20:30:

Remove the board entirely. Remove all the batteries and throw them away. […]
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Remove the board entirely. Remove all the batteries and throw them away.

Now comes the cleaning part: use vinegar and a toothbrush, and remove all electrolyte residue.
Check all the contacts and make sure they look ok.
Then you have to clean it: Use soap/detergent and water and repeat the same procedure. Let it dry for one day or so.

There may be some components you'll have to replace because it looks compromised.
But you could still give it a try and hopefully it will work.

Good luck!

I did clean it with vinegar however I don't have any detergent to hand and I've simply dabbed up the vinegar with a paper towel,

Would IPA work?

I don't think using IPA is the right thing to do. You need to use some sort of detergent or soap and lots of water and a brush. Some people use a dishwasher. Make sure contacts look shiny. You really need to clean off the vinegar. Remember to wait a couple of days until it dries before plugging it in again.

tauro wrote on 2024-02-12, 13:13:

I don't think using IPA is the right thing to do. You need to use some sort of detergent or soap and lots of water and a brush. Some people use a dishwasher. Make sure contacts look shiny. You really need to clean off the vinegar. Remember to wait a couple of days until it dries before plugging it in again.

Any specific type of soup you would recommend? I'm not sure how this would make the dull contacts shiny again but it's worth a shot.

I use regular dish detergent. You could use any detergent I guess. Get creative. Give it a try and see how it goes, don't worry, nothing bad will happen. Remember to let it dry.

To clean that type of battery corrosion, personally I clean it dry by brushing and scraping off the green crust just lightly to start, then clean it using IPA soaked cotton buds. At this point it should be possible to see which areas of soldermask are damaged, because some traces will have dark patches and I usually gently scrape those off to see how the copper is underneath.
This type of battery corrosion weakens solder significantly so you should be able to remove those batteries and their connectors with some pliers by twisting them in place from the top. You'll need to clean under the battery connectors where there can be vias and traces that have got the worst of the battery damage. The connectors can be replaced later or what I do is solder replacement wires directly later to GND and an RTC battery + test pad, the pads that connect the battery originally are usually un-usable.
Make sure to clean the back side of the board in that area too, there are a bunch of SMD resistors & capacitors in that area on the back.

Once the worst of the corrosion and electrolyte is removed that way, put small amounts of white vinegar or lemon juice onto the PCB where the green corrosion covered and it should start to fizz where it's neutralizing the alkali of the battery's electrolyte. Don't leave it long because that is acidic and if left too long the remnants of some vias and traces in the board can get cleaned away too.
Mop that up with cotton buds and paper kitchen towel, then carefully rinse the area that had the acidic cleaner applied. Then dry it, spray some IPA onto the area and dry it with a hair dryer to blow water residue & IPA out from underneath any chips.

Here's how one of mine looked after repairing some traces and vias that were destroyed by the corrosion:

That board is probably the worst corrosion I've seen on that motherboard type, some traces might need to be patched after cleaning.
edit: that motherboard type and screen type is shared with all these models so you should be able to source a replacement: 300cds, 305cds, 310cds, 315cds, 320cds, 325cds. The Pentium II version should be a drop in replacement assuming it's still got the CPU card and heatsink fitted so that includes 4000CDS, 4005CDS, 4010CDS, 4015CDS. The screen and screen cable you have will only work with the STN type screen so TFT versions are no good.
If the mainboard is unfixable, it may be better to use its plastic parts & keyboard to fix up a TFT version (CDT) instead.

I happen to own a 4000 CDS oddly enough!