• Please review our updated Terms and Rules here

Cleaning up green trace corrosion

Uniballer

Experienced Member
Joined
Apr 3, 2014
Messages
433
Location
USA
I pulled a '94 era 486 board ("ExpertBoard" with Opti chipset) out of the mothballs the other day just for the hell of it. I stuck a CPU, 32MB RAM, and an ISA video card on it and the BIOS came up, but said there was a keyboard error. Uh-oh. Of course the 3.6V barrel-type Ni-Cd battery had leaked, and took some traces out. Not bad on the top of the board, but on the back under a "No CFC Cleaning - Semi-Aqueous" label the traces had all turned to green goo, right through the solder mask (it's the brown crap, not the better green mask, so it's really visible). This included two of the traces for the keyboard connector, so I had to repair them. I flushed and brushed with isopropyl alcohoI, then I had to use lots of flux to get the slightly corroded solder connections to melt. After bridging the ruined traces with wire it managed to boot FreeBSD 4.3 all the way up from an IDE hard disk.

I removed the battery that I believe was the source of the corrosion. How do I stop the corrosion from creeping further? Will the isopropyl alcohol do it? Or do I need to flush the board with something else? Or is it a lost cause?

Since the board is already hacked up I'm hoping to put a CR2032 battery and a 1N5817 Schottky diode in place of the original battery. That would only give me about 3 volts, though. Is there a better option?

Ideas and criticism welcome.

Please excuse thread placement (or move this) if you feel it belongs in the "Later PCs" category rather than as a general question.
 
Last edited:

EverythingIBM

Experienced Member
Joined
Aug 23, 2010
Messages
367
Location
Canada
Baking soda neutralizes battery acid.
Also supposedly cocacola can be decent for removing corrosion, I never tried it yet though (was going to later).
 

Stone

10k Member
Joined
Nov 3, 2009
Messages
12,814
Location
South Jersey, USA
Baking soda neutralizes battery acid.
While this statement is in itself correct it's application is out of place here. Baking soda does neutralize battery acid but NiCads leak an alkaline goo, not acid, so you need a weak acid like vinegar to clean up the basic, not acidic mess.
 

Chuck(G)

25k Member
Joined
Jan 11, 2007
Messages
40,246
Location
Pacific Northwest, USA
Stone's correct, but I'd just use water and perhaps a a couple of drops of very mild dishwashing (not dishwasher) detergent. Rinse with clean water and dry.
 

barythrin

Veteran Member
Joined
Oct 5, 2005
Messages
6,256
Location
Texas
Baking soda neutralizes battery acid.
Also supposedly cocacola can be decent for removing corrosion, I never tried it yet though (was going to later).

The coke solution technically works but is usually a bad idea since you'll then have to clean up all the syrup off your sticky items. For a clever but similar idea I used club soda (no sugar, just carbonated water) which also cleaned up lead-acid buildup. But as Stone hinted at, that may not be the right solution if it's an alkaline based corrosion.
 

Stone

10k Member
Joined
Nov 3, 2009
Messages
12,814
Location
South Jersey, USA
The coke solution technically works but is usually a bad idea since you'll then have to clean up all the syrup off your sticky items. For a clever but similar idea I used club soda (no sugar, just carbonated water) which also cleaned up lead-acid buildup. But as Stone hinted at, that may not be the right solution if it's an alkaline based corrosion.
Coke *is* acidic and therfore quite unlike the baking soda which is basic. :) That's why coke does work. Coke contains citric acid, carbonic acid and phosphoric acid as do most sodas. I don't think that club soda contains the phosphoric acid and maybe not the citric acid either.
 

modem7

Veteran Member
Joined
May 29, 2006
Messages
8,269
Location
Melbourne, Australia
Since the board is already hacked up I'm hoping to put a CR2032 battery and a 1N5817 Schottky diode in place of the original battery. That would only give me about 3 volts, though. Is there a better option?
Your motherboard may have a connector/header for an 'external' battery. See [here].
 

Chuck(G)

25k Member
Joined
Jan 11, 2007
Messages
40,246
Location
Pacific Northwest, USA
Most CMOS MC146818-type RTCs are good down to about 2.2V. If the schottky diode has you worried about the voltage drop, use a MOSFET. An N-channel MOSFET can be inserted into the negative rall (drain to battery negative, source to load negative, gate to common + rail. Or use a P-channel MOSFET the same way in the + supply line). The voltage drop will be extremely small, as the FET is pretty much a purely resistive device, so you're looking at an insertion loss of 20 or 30 milliohms.

FWIW
 

Uniballer

Experienced Member
Joined
Apr 3, 2014
Messages
433
Location
USA
Your motherboard may have a connector/header for an 'external' battery. See [here].

You are right. At first, I didn't think so. But on careful examination of the board I found a four-pin header called simply "J4" jumpered between pins 2 and 3. Checking the manual it says to pull the jumper and connect the external battery between pins 1 and 4. The connections aren't labeled, though, so I'll have to ring it out to see what side is positive and negative. Thanks.
 

Uniballer

Experienced Member
Joined
Apr 3, 2014
Messages
433
Location
USA
I did some testing. I found another 486 board from the same era with even worse corrosion. I'm not sure if there was only one kind (encrustation near the barrel-type NiCd), or if the smooth green corrosion on pin and socket pins, and in a couple of the ISA slots, was a different kind.

I tried water from a reverse-osmosis system. This is not distilled water, but still should have no dissolved minerals. Some people say that a high level of dissolved oxygen makes it more chemically active than distilled water. I applied the water and brushed it with an old toothbrush. This certainly had a good effect on the encrustations near the battery, but I did not see any effect on the smooth green corrosion.

I tried white distilled vinegar in a similar manner, and saw no additional effect. I removed a chip that had the smooth green corrosion on some of the pins and put it in a small container of room-temperature vinegar. I checked it at 1 minutes, 5 minutes, 10 minutes, and 24 minutes of contact time. At the earlier checks there was no visible change, nor did the toothbrush do anything to the corrosion. At the last check there was a noticeable visual change, and the toothbrush appeared to remove any remaining green corrosion, although there did appear to be some blackish discoloration. I rinsed everything off with the R/O water. If I intended to try to use this board I would probably flush with isopropyl alcohol before final drying.

Any comments or suggestions?
 

Uniballer

Experienced Member
Joined
Apr 3, 2014
Messages
433
Location
USA
I poured white distilled vinegar onto the socket that held the chips with the corroded pins. I hit it with a toothbrush after about 20 minutes. It had little effect. I am assuming that it simply didn't manage to stay there in sufficient concentration for the whole time. I don't know how to improve that without dipping the board in a vat of weak acetic acid, unless there is an organic acid gel (toilet bowl cleaner? What do I have to lose?).

Hmmm... I also have a citric acid-based product that is intended to clean up thermal compound...
 

Agent Orange

Veteran Member
Joined
Sep 24, 2008
Messages
6,202
Location
SE MI
I poured white distilled vinegar onto the socket that held the chips with the corroded pins. I hit it with a toothbrush after about 20 minutes. It had little effect. I am assuming that it simply didn't manage to stay there in sufficient concentration for the whole time. I don't know how to improve that without dipping the board in a vat of weak acetic acid, unless there is an organic acid gel (toilet bowl cleaner? What do I have to lose?).

Hmmm... I also have a citric acid-based product that is intended to clean up thermal compound...

Uni:

This subject has been covered a zillion times on the forum. Try doing a forum search. I've always had fair success with baking soda, distilled water, and a tooth brush when dealing with light surface corrosion. Good luck.
 

Caluser2000

Veteran Member
Joined
Jan 3, 2010
Messages
4,672
Location
New Zealand
I've used a diluted white viniger and cotton buds in the past and it's worked a treat. Guess I didn't try to over think it.
 

Uniballer

Experienced Member
Joined
Apr 3, 2014
Messages
433
Location
USA
Uni:

This subject has been covered a zillion times on the forum.
Please provide links to good posts on this topic.
Try doing a forum search.
I did so before posting. The search is not very effective because it apparently finds threads, not posts. After reading the first twenty or so threads that the search returned I gave up.
 

Stone

10k Member
Joined
Nov 3, 2009
Messages
12,814
Location
South Jersey, USA
Please provide links to good posts on this topic.
I did so before posting. The search is not very effective because it apparently finds threads, not posts. After reading the first twenty or so threads that the search returned I gave up.
Google's search results from THIS site are about 1000 times more rewarding than vBulletin's built-in search feature! :) Give it a try.
 
Top