Conductive foam problem
 

Seeing someone else's post on foam problems reminded me.
Years ago I had 3 A4 size sheets of black conductive foam covered with ICs
and for storage placed one each in a new manilla envelope with
details written-up on them. Stored with open flaps, vertically
in a drawer of a filing cabinet indoors, not in a shed. A few years later
came to
use one and all the pins on all the ICs were affected by rust
to the point that some were rusted away totally.
Gummed flaps on envelopes were fine unstuck and no other traces of damp.
Anyone else experience of this?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:
Seeing someone else's post on foam problems reminded me.
Years ago I had 3 A4 size sheets of black conductive foam covered with ICs
and for storage placed one each in a new manilla envelope with
details written-up on them. Stored with open flaps, vertically
in a drawer of a filing cabinet indoors, not in a shed. A few years later
came to
use one and all the pins on all the ICs were affected by rust
to the point that some were rusted away totally.
Gummed flaps on envelopes were fine unstuck and no other traces of damp.
Anyone else experience of this?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




yes

but I have no idea of the cause

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

"CJT" wrote in message
...
N Cook wrote:
Seeing someone else's post on foam problems reminded me.
Years ago I had 3 A4 size sheets of black conductive foam covered with
ICs
and for storage placed one each in a new manilla envelope with
details written-up on them. Stored with open flaps, vertically
in a drawer of a filing cabinet indoors, not in a shed. A few years
later
came to
use one and all the pins on all the ICs were affected by rust
to the point that some were rusted away totally.
Gummed flaps on envelopes were fine unstuck and no other traces of damp.
Anyone else experience of this?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




yes

but I have no idea of the cause

--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form .

I should have added it was the soft rather than more rigid foam type.
Anyone know what chemicals, initially anyway, are in conductive foam ?

"N Cook" wrote in message
...
Seeing someone else's post on foam problems reminded me.
Years ago I had 3 A4 size sheets of black conductive foam covered with ICs
and for storage placed one each in a new manilla envelope with
details written-up on them. Stored with open flaps, vertically
in a drawer of a filing cabinet indoors, not in a shed. A few years later
came to
use one and all the pins on all the ICs were affected by rust
to the point that some were rusted away totally.
Gummed flaps on envelopes were fine unstuck and no other traces of damp.
Anyone else experience of this?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Sounds like the dreaded black wire corrosion of the past

Possibably caused by the carbon black in the insulation / foam.

Hugh

"Hugh Prescott" wrote in message
...

"N Cook" wrote in message
...
Seeing someone else's post on foam problems reminded me.
Years ago I had 3 A4 size sheets of black conductive foam covered with
ICs
and for storage placed one each in a new manilla envelope with
details written-up on them. Stored with open flaps, vertically
in a drawer of a filing cabinet indoors, not in a shed. A few years
later
came to
use one and all the pins on all the ICs were affected by rust
to the point that some were rusted away totally.
Gummed flaps on envelopes were fine unstuck and no other traces of damp.
Anyone else experience of this?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Sounds like the dreaded black wire corrosion of the past

Possibably caused by the carbon black in the insulation / foam.

Hugh




Interesting but the 'rust' I observed was standard iron oxide brown in
colour - not necessarily rust as such but certainly that colour.

On Sat, 6 Aug 2005 08:02:57 +0100, "N Cook" wrote:

Seeing someone else's post on foam problems reminded me.
Years ago I had 3 A4 size sheets of black conductive foam covered with ICs
and for storage placed one each in a new manilla envelope with
details written-up on them. Stored with open flaps, vertically
in a drawer of a filing cabinet indoors, not in a shed. A few years later
came to
use one and all the pins on all the ICs were affected by rust
to the point that some were rusted away totally.
Gummed flaps on envelopes were fine unstuck and no other traces of damp.
Anyone else experience of this?


My guess would be that something in the foam is corrosive, or that the
foam attracts moisture. Rust isn't surprising since ICs often have
tinned steel pins. Are all the ICs made by the same company?
Andy Cuffe

-- Use this address until 12/31/2005

-- Use this address after 12/31/2005

"N Cook" ) writes:
Seeing someone else's post on foam problems reminded me.
Years ago I had 3 A4 size sheets of black conductive foam covered with ICs
and for storage placed one each in a new manilla envelope with
details written-up on them. Stored with open flaps, vertically
in a drawer of a filing cabinet indoors, not in a shed. A few years later
came to
use one and all the pins on all the ICs were affected by rust
to the point that some were rusted away totally.
Gummed flaps on envelopes were fine unstuck and no other traces of damp.
Anyone else experience of this?

I don't know the answer, but I'm surprised you didn't have a bigger
problem.

I find that black foam deteriorates with time. I was going through
a box of old ICs recently, and some of the ICs once well protected
were loose because the foam had crumbled.

The mroe recent pink and more solid foam has stood up better.

Which may be why there was a switch to the pink foam.

Michael

"Hugh Prescott" wrote in message
...

"N Cook" wrote in message
...
Seeing someone else's post on foam problems reminded me.
Years ago I had 3 A4 size sheets of black conductive foam covered with
ICs
and for storage placed one each in a new manilla envelope with
details written-up on them. Stored with open flaps, vertically
in a drawer of a filing cabinet indoors, not in a shed. A few years
later
came to
use one and all the pins on all the ICs were affected by rust
to the point that some were rusted away totally.
Gummed flaps on envelopes were fine unstuck and no other traces of damp.
Anyone else experience of this?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Sounds like the dreaded black wire corrosion of the past

Possibably caused by the carbon black in the insulation / foam.

Hugh




I'd never heard that term so I've done a bit of looking into it today.
I've always assumed the black sooty deposit found in conjuction
with copper sometimes, is copper sulphide but putting "black wire corrosion"
and "copper sulphide" in search engines turned up nothing.

Some years I asked a chemist what this black and insulating material
was likely to be that I often find on 20 or 30 year old switches that
because it insulates and unless the wiping type contacts break through it,
stops
the switch action. He said likely Copper Sulphide, in my instances the
suphur from air borne polution and in BWC presumably from battery sulphuric
acid
vapours. Any thoughts ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N Cook" wrote in message
...
"Hugh Prescott" wrote in message
...

"N Cook" wrote in message
...
Seeing someone else's post on foam problems reminded me.
Years ago I had 3 A4 size sheets of black conductive foam covered with
ICs
and for storage placed one each in a new manilla envelope with
details written-up on them. Stored with open flaps, vertically
in a drawer of a filing cabinet indoors, not in a shed. A few years
later
came to
use one and all the pins on all the ICs were affected by rust
to the point that some were rusted away totally.
Gummed flaps on envelopes were fine unstuck and no other traces of
damp.
Anyone else experience of this?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



Sounds like the dreaded black wire corrosion of the past

Possibably caused by the carbon black in the insulation / foam.

Hugh




I'd never heard that term so I've done a bit of looking into it today.
I've always assumed the black sooty deposit found in conjuction
with copper sometimes, is copper sulphide but putting "black wire
corrosion"
and "copper sulphide" in search engines turned up nothing.

Some years I asked a chemist what this black and insulating material
was likely to be that I often find on 20 or 30 year old switches that
because it insulates and unless the wiping type contacts break through it,
stops
the switch action. He said likely Copper Sulphide, in my instances the
suphur from air borne polution and in BWC presumably from battery
sulphuric
acid
vapours. Any thoughts ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




or even spelt Copper Sulfide and BWC no references

I'd never heard that term so I've done a bit of looking into it today.
I've always assumed the black sooty deposit found in conjuction
with copper sometimes, is copper sulphide but putting "black wire
corrosion"
and "copper sulphide" in search engines turned up nothing.

Some years I asked a chemist what this black and insulating material
was likely to be that I often find on 20 or 30 year old switches that
because it insulates and unless the wiping type contacts break through
it,
stops
the switch action. He said likely Copper Sulphide, in my instances the
suphur from air borne polution and in BWC presumably from battery
sulphuric
acid
vapours. Any thoughts ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


or even spelt Copper Sulfide and BWC no references



The black tarnish that you find on old switch contacts is most likely silver
sulfide, since many switches were (and still are) silver plated. It's the
same stuff that gets on your good silverware after having eggs over easy for
breakfast, and then letting the egg residue stay on the silverware for a
while. Eggs are heavy in sulfer content (Remember the rotten egg odor? It's
hydrogen disulfide).
--
Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!

"DaveM" wrote in message
...
I'd never heard that term so I've done a bit of looking into it today.
I've always assumed the black sooty deposit found in conjuction
with copper sometimes, is copper sulphide but putting "black wire
corrosion"
and "copper sulphide" in search engines turned up nothing.

Some years I asked a chemist what this black and insulating material
was likely to be that I often find on 20 or 30 year old switches that
because it insulates and unless the wiping type contacts break through
it,
stops
the switch action. He said likely Copper Sulphide, in my instances the
suphur from air borne polution and in BWC presumably from battery
sulphuric
acid
vapours. Any thoughts ?

or even spelt Copper Sulfide and BWC no references



The black tarnish that you find on old switch contacts is most likely
silver
sulfide, since many switches were (and still are) silver plated. It's the
same stuff that gets on your good silverware after having eggs over easy
for
breakfast, and then letting the egg residue stay on the silverware for a
while. Eggs are heavy in sulfer content (Remember the rotten egg odor?
It's
hydrogen disulfide).
--
Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters
in
the address)

Never take a laxative and a sleeping pill at the same time!!



I've added rec.antiques.radio+phono as their territory probably

I rarely come across silver plating on the switches I replace/recondition.
Usually the black deposit I find is on function and wave change switches.
Usually made by Alps company 1 or 2 lines of brass? contacts set in paxolin,
then sliding phospher-bronze? U channel slider contacts located in black
plastic slider and all housed in tin-plate? cover

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/