[Premium-Rx] NiCad Battery Corrosion

[GandalfG8 at aol.com]

Hi Chuck
You're certainly not the only one to suffer.
Virtually every piece of kit from the late 70s to 80s, radio or test gear, 
that I've bought n the past year or so has either suffered damage or is close 
to it.
The main problem seems to be that Ni-Cads were regularly fitted when 
microprocessor control started to become common and so often they were 
treated as fit and forget items by the users.
As far as I can tell most charging circuits are already ok. It's just that 
the batteries have been left for far too long and sometimes not changed in 
over 20 years.
In this case prevention, changing batteries regularly, is certainly much 
better than cure.
The effects vary too depending on materials.
Tinned, or bare, copper tracks are very vulnerable and just get eaten away in 
time. I've had to resort to stripping boards at times, washing in soapy water 
is a reasonable treatment then, and sometimes have had to polish with wire 
wool and repair and re tin damaged tracks.
I've got an HP 3586 PSU board waiting for attention at the moment. All tracks 
on this are gold plated, and seem to have resisted corrosion, but in this 
case there's a heavy build up of hard green deposits that are quite difficult 
to remove without scraping. This has spread to the edge connector and 
motherboard below.
Whether the plating is porous and the deposits indicate an attack on the 
copper below I just don't know.
On this particular board the body of one carbon composition resistor has been 
eaten away, leaving a much reduced diameter, but the painted colour code 
bands haven't been affected and now sit as movable rings around the 
component:-)
regards
Nigel Clarke
G8PZR



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