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How do I get the battery corrosion completely neutralized?

seaken

Veteran Member
Joined
Jun 20, 2016
Messages
563
Location
Shokan, New York
I have been working a couple old 80286 motherboards where the Varta battery has leaked and caused some corrosion on the motherboard. I am using some white vinegar to neutralize the battery corrosion and then cleaning with water and isopropyl alchohol. I have done this a few times and it has worked for me in the past. But this time I think the level of corrosion is more than I have seen before. After a couple of cleanings I still see some aquamarine color on the traces on the motherboard. I clean it again and after it dries I still see some aquamarine color on the board. What should I be looking for? Should it be black? Is the aquamarine color evidence of more corrosion that needs to be removed? I think so, but I am not very experienced yet in doing this type of cleaning? How far should I go? Keep cleaning until the aquamarine color is gone?

Thanks for your opinion and help.

Seaken
 
What you may be seeing is delamination of the board layers (a very bad thing). Any way you can post some photos?
 
When I rebuilt my Lisa's I/O board I pulled the socketed chips and let the whole board soak in a pan of 50/50 vinegar and water and stirring a few times over the course of the day. By the end of the day the water had turned a blue tint from the reaction process and then ti was good for a toothbrush scrub and hot rinse before being left to dry overnight. I found that in some areas where the masking over the traces had been compromised you had to soak the battery leakage out or it just came back.
 
I use naval jelly thinned out with like 1/6th water. Brush it on and let it sit overnight or so then rinse off really good. Reseat any chips that are socketed after dry. I used to use vinegar, but it left the solder joints really dull colored, don't have that problem with naval jelly.
 
I'll try to post some pics. Haven't tried that before. Here goes ...

This what it looked like before I started cleaning

IMG_20220620_143532323.jpg
 
Okay, that worked. (I wasn't sure if there was a size limit, etc.)

After about three sessions of cleaning with vinegar followed by distilled water and IPA there is still some greenish colored residue. I guess I will keep going until the green is gone. It was the worst I've seen before. This board may be damaged beyond my abilities to repair. But I want to get rid of the corrosion before I try to power it up.

Thanks for looking,

Seaken
 
I've used tissue paper before to keep the area moist with vinegar. If you layer it up a bit the paper soakes up the green. One motherboard was like 10 goes at it.
 
It's under the lamination on the board. A lot of this kind of problem happens in Amiga restoration.

You'll need to lightly sand off the laminate and get all the corrosion gone down to the bare copper, then re-coat it. This means removing all the components around it. Some just use nail polish to re-coat, but you can also get the real UV-curable stuff also.
 
Just use naval jelly... it doesnt dry out, it doesnt discolor the solder to a nasty grey, and will clean up way faster and make the copper shiny....
 
Yes, I like that idea. I've used Naval Jelly many times in my wood stove trade. But I also know it is way stronger than white vinegar. What do you think is a good percentage for the acid when using Naval Jelly? The white vinegar is 5% I think. Do you think I should shoot for about 10%, or 15%? You mentioned 1/6 earlier. Did you mean you mix 1 part jelly to 6 parts water?

I'll pick some Naval Jelly tomorrow and get ready to try it out.

Seaken
 
I also think that the light sanding idea is good. I have another board where the green seems to be stuck. I'll try the light sanding idea on that one.

Thanks for the ideas,

Seaken
 
Ya water it down to bout 1/6th strength. It will start out slow that way till the water evaporates. Make sure to use distilled water.
 
I was not able to out to get the Naval Jelly today. But I did make some good progress just using the Vinegar. I layed the cotton swabs soaked with the vinegar on the green stuff. I also used a pen eraser to lightly lift some of the debris. I kept doing this until the green did not come back. It worked good to finally get rid of the green.

Thanks to the ideas you all shared I now have a better idea of how to clean the corosion from the motherboard.

Seaken
 
So the good news is that I was finally able to get rid of the green corosion. The bad news is that this motherboard is not working after I power it on. At first I got nothing. And then I realized that there was no speaker attached. After I attached the speaker I did hear some beeps. But no video. I will start another thread on how to troubleshhot the motherboard.

Seaken
 
Ya some those traces look toast, alot of probing with a multimeter is in your future! ;)

You got this! 👍
 
You will need to remove every component around the area as well, nasty things will appear under chips and sockets. There is extended damage and a repair is not guaranteed.
 
Personally I've given up on them with less battery damage! That looks a real mess and I think I'd only spend the time on it (incl removing at least 4 of those small 74 logic chips, the k/b controller chip, k/b socket, power prongs and at least one of the ISA slots) if it were a special computer in some way. And where pads and things are that corroded de-soldering is very difficult. It will be immensely time consuming and likely very frustrating attempting to fix that one.
 
Those fat traces near the ISA slots are for power, could be your card isn't getting any. That's where I'd start checking.
 
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