PLC board corrosion
 

I got me Pro-Face PLC back from the manufacturer today. I had posted
about the failure a few weeks ago. It turns out that there was some
sort of corrosion on the main board and the video board. The PLC is in
a gasketed enclosure with three Greenfield cables coming in. The
machine or the control box never got wet and there is nothing in the
air. The heat goes from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it
from happening again? A light bulb running all the time? A vent fan?
Maybe the thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg

PLC board corrosion
 

"Tom Gardner" wrote in message
...

I got me Pro-Face PLC back from the manufacturer today. I had posted about
the failure a few weeks ago. It turns out that there was some sort of
corrosion on the main board and the video board. The PLC is in a gasketed
enclosure with three Greenfield cables coming in. The machine or the
control box never got wet and there is nothing in the air. The heat goes
from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it from
happening again? A light bulb running all the time? A vent fan? Maybe the
thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg

Where I work, we had a problem with corrosion on the Siemens Microbox PLC's.
Siemens sent one of their engineers in from Germany, he went around doing
air samples trying to figure out what was going on. Air samples showed no
problem. We also had the same problem with hard drives, not sure why the
problem was with MicroBox PLC's and Hard drives, other electronics didn't
seem to have the problem.

What we ended up doing is spraying the circuit boards with a coating we got
from the local electronics supplier, IIRC they called it conformal coating.
I don't know if it was a certain flux or solder, but some boards had this
problem, others didn't. McMaster Carr used to sell an insulating varnish
for electric motor coils, I would think it would work good too. Coating the
boards changed the life of the boards from months to years.

Good Luck

RogerN

PLC board corrosion
 

"Tom Gardner" Mars@Tacks wrote in message
...
I got me Pro-Face PLC back from the manufacturer today. I had posted about
the failure a few weeks ago. It turns out that there was some sort of
corrosion on the main board and the video board. The PLC is in a gasketed
enclosure with three Greenfield cables coming in. The machine or the
control box never got wet and there is nothing in the air. The heat goes
from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it
from happening again? A light bulb running all the time? A vent fan?
Maybe the thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg




Something corrosive is outgasing and being trapped in your tightly closed
box. When PVC breaks down it can outgas HCl. Some silicones outgas acetic
acid. Other plastics can outgas formic acid or formaldehyde.

PLC board corrosion
 

Tom Gardner Mars@Tacks fired this volley in news:EI-
:

The
machine or the control box never got wet and there is nothing in the
air. The heat goes from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it
from happening again? A light bulb running all the time? A vent fan?
Maybe the thing shouldn't be that well sealed?


Tom, I don't know what the insulation system is on those cables. More
likely than letting in (excessive) moisture, the cable is gassing off HCl
as PVC in it decomposes. It takes only trace amounts of HCl and moisture
in the air - especially trapped - to cause serious bare-metal corrosion.

Also, if there's any H2S in the atmosphere from the gas furnaces, that
can contribute a lot to corrosion, assuming any of that air can get into
the enclosure. You'll notice the edges of mirrors turning black if H2S
is the culprit, and the corrosion of tin/lead or RoHS lead-free solders
due to H2S will be almost jet black, and 'velvety' looking.

LLoyd

PLC board corrosion
 

On 1/24/2013 1:12 AM, RogerN wrote:
"Tom Gardner" wrote in message
...

I got me Pro-Face PLC back from the manufacturer today. I had posted about
the failure a few weeks ago. It turns out that there was some sort of
corrosion on the main board and the video board. The PLC is in a gasketed
enclosure with three Greenfield cables coming in. The machine or the
control box never got wet and there is nothing in the air. The heat goes
from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it from
happening again? A light bulb running all the time? A vent fan? Maybe the
thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg

Where I work, we had a problem with corrosion on the Siemens Microbox PLC's.
Siemens sent one of their engineers in from Germany, he went around doing
air samples trying to figure out what was going on. Air samples showed no
problem. We also had the same problem with hard drives, not sure why the
problem was with MicroBox PLC's and Hard drives, other electronics didn't
seem to have the problem.

What we ended up doing is spraying the circuit boards with a coating we got
from the local electronics supplier, IIRC they called it conformal coating.
I don't know if it was a certain flux or solder, but some boards had this
problem, others didn't. McMaster Carr used to sell an insulating varnish
for electric motor coils, I would think it would work good too. Coating the
boards changed the life of the boards from months to years.

Good Luck

RogerN




Thanks Roger, I'll take your advise. The flux thing is the only thing
that makes sense.

PLC board corrosion
 

On 1/24/2013 2:23 AM, anorton wrote:

"Tom Gardner" Mars@Tacks wrote in message
...
I got me Pro-Face PLC back from the manufacturer today. I had posted
about the failure a few weeks ago. It turns out that there was some
sort of corrosion on the main board and the video board. The PLC is
in a gasketed enclosure with three Greenfield cables coming in. The
machine or the control box never got wet and there is nothing in the
air. The heat goes from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it
from happening again? A light bulb running all the time? A vent fan?
Maybe the thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg


http://i954.photobucket.com/albums/a...psb1238b22.jpg


http://i954.photobucket.com/albums/a...pscbe73616.jpg




Something corrosive is outgasing and being trapped in your tightly
closed box. When PVC breaks down it can outgas HCl. Some silicones
outgas acetic acid. Other plastics can outgas formic acid or formaldehyde.



So, maybe being so sealed up can cause problems. I don't have any other
electronics having problems for many years and this one is only one year
old and the only one in a sealed box.

PLC board corrosion
 

On 1/24/2013 7:25 AM, Lloyd E. Sponenburgh wrote:
Tom Gardner Mars@Tacks fired this volley in news:EI-
:

The
machine or the control box never got wet and there is nothing in the
air. The heat goes from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it
from happening again? A light bulb running all the time? A vent fan?
Maybe the thing shouldn't be that well sealed?


Tom, I don't know what the insulation system is on those cables. More
likely than letting in (excessive) moisture, the cable is gassing off HCl
as PVC in it decomposes. It takes only trace amounts of HCl and moisture
in the air - especially trapped - to cause serious bare-metal corrosion.

Also, if there's any H2S in the atmosphere from the gas furnaces, that
can contribute a lot to corrosion, assuming any of that air can get into
the enclosure. You'll notice the edges of mirrors turning black if H2S
is the culprit, and the corrosion of tin/lead or RoHS lead-free solders
due to H2S will be almost jet black, and 'velvety' looking.

LLoyd


No problems with the mirrors in the bathrooms. The only air exchange in
the box is through the Greenfield. The only other electronics that has
failed has been the PS on a Chinese DRO on a BP. I looked at the boards
with a loupe and didn't see ANY issues.

PLC board corrosion
 

On Thu, 24 Jan 2013 09:38:34 -0500, Tom Gardner Mars@Tacks wrote:

On 1/24/2013 1:12 AM, RogerN wrote:
"Tom Gardner" wrote in message
...

I got me Pro-Face PLC back from the manufacturer today. I had posted about
the failure a few weeks ago. It turns out that there was some sort of
corrosion on the main board and the video board. The PLC is in a gasketed
enclosure with three Greenfield cables coming in. The machine or the
control box never got wet and there is nothing in the air. The heat goes
from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it from
happening again? A light bulb running all the time? A vent fan? Maybe the
thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg

Where I work, we had a problem with corrosion on the Siemens Microbox PLC's.
Siemens sent one of their engineers in from Germany, he went around doing
air samples trying to figure out what was going on. Air samples showed no
problem. We also had the same problem with hard drives, not sure why the
problem was with MicroBox PLC's and Hard drives, other electronics didn't
seem to have the problem.

What we ended up doing is spraying the circuit boards with a coating we got
from the local electronics supplier, IIRC they called it conformal coating.
I don't know if it was a certain flux or solder, but some boards had this
problem, others didn't. McMaster Carr used to sell an insulating varnish
for electric motor coils, I would think it would work good too. Coating the
boards changed the life of the boards from months to years.

Good Luck

RogerN




Thanks Roger, I'll take your advise. The flux thing is the only thing
that makes sense.
Many years ago I worked on flight hardware for NASA. I recommend using
190 proof Everclear to remove any visible dried flux on circuit boards
before applying conformal coating to a board. Don't conformal coat any
contacts or socket interiors.

PLC board corrosion
 

On Thu, 24 Jan 2013 00:14:14 -0500, Tom Gardner Mars@Tacks wrote:

I got me Pro-Face PLC back from the manufacturer today. I had posted
about the failure a few weeks ago. It turns out that there was some
sort of corrosion on the main board and the video board. The PLC is in
a gasketed enclosure with three Greenfield cables coming in. The
machine or the control box never got wet and there is nothing in the
air. The heat goes from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it
from happening again? A light bulb running all the time? A vent fan?
Maybe the thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg


============================
Hey Tom,

We had a multi-lane bi-directional stepper switch ( 18P25T ) in a salt
plant, that would corrode to un-usability every six months, and the
switch and our labour to replace it was considerable. It sat in a
closed but not sealed cabinet, and there was no direct heat in the
machine room, so the temperature varied quite a bit by season. I put
a Plexiglas window in the swing lid of 12" X 12" X9" deep gasketed
cabinet and a 60 watt "Rough Service" light bulb with a simple light
dimmer to make the bulb just glow at about 25 watts. Took twice as
long to do this the one time, including installing, moving, re-wiring,
and caulking the wire-cable so the box was essentially air-tight. In
the 9 more years that I was still in the trade, the switch stepped
without failure, and used the same light bulb.

Worked for me.

Brian Lawson

PLC board corrosion
 

On Thu, 24 Jan 2013 09:38:34 -0500, Tom Gardner Mars@Tacks wrote:

On 1/24/2013 1:12 AM, RogerN wrote:
"Tom Gardner" wrote in message
...

I got me Pro-Face PLC back from the manufacturer today. I had posted about
the failure a few weeks ago. It turns out that there was some sort of
corrosion on the main board and the video board. The PLC is in a gasketed
enclosure with three Greenfield cables coming in. The machine or the
control box never got wet and there is nothing in the air. The heat goes
from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it from
happening again? A light bulb running all the time? A vent fan? Maybe the
thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg

Where I work, we had a problem with corrosion on the Siemens Microbox PLC's.
Siemens sent one of their engineers in from Germany, he went around doing
air samples trying to figure out what was going on. Air samples showed no
problem. We also had the same problem with hard drives, not sure why the
problem was with MicroBox PLC's and Hard drives, other electronics didn't
seem to have the problem.

What we ended up doing is spraying the circuit boards with a coating we got
from the local electronics supplier, IIRC they called it conformal coating.
I don't know if it was a certain flux or solder, but some boards had this
problem, others didn't. McMaster Carr used to sell an insulating varnish
for electric motor coils, I would think it would work good too. Coating the
boards changed the life of the boards from months to years.

Good Luck

RogerN




Thanks Roger, I'll take your advise. The flux thing is the only thing
that makes sense.

Ive had pretty good luck with Krylon transparent spray for
distributors or similar. Its a very thin spray "paint"

Some guys swear by this. Ive not used it..but have had pretty good
reports on it.

http://www.corrosionx.com/corrosionx.html

it has the benifit of killing existing corrosion on circuit boards

"conformal" coatings are good..but make future service problematic.
They basically varnish the boards and glue everything together.

If there is something ON the boards that is creating a problem..you
have just sealed it under the coating..and it will spread under it.

Gunner

Gunner

The methodology of the left has always been:

1. Lie
2. Repeat the lie as many times as possible
3. Have as many people repeat the lie as often as possible
4. Eventually, the uninformed believe the lie
5. The lie will then be made into some form oflaw
6. Then everyone must conform to the lie

PLC board corrosion
 

On 1/24/2013 12:15 PM, wrote:
On Thu, 24 Jan 2013 09:38:34 -0500, Tom Gardner Mars@Tacks wrote:

On 1/24/2013 1:12 AM, RogerN wrote:
"Tom Gardner" wrote in message
...

I got me Pro-Face PLC back from the manufacturer today. I had posted about
the failure a few weeks ago. It turns out that there was some sort of
corrosion on the main board and the video board. The PLC is in a gasketed
enclosure with three Greenfield cables coming in. The machine or the
control box never got wet and there is nothing in the air. The heat goes
from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it from
happening again? A light bulb running all the time? A vent fan? Maybe the
thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg

Where I work, we had a problem with corrosion on the Siemens Microbox PLC's.
Siemens sent one of their engineers in from Germany, he went around doing
air samples trying to figure out what was going on. Air samples showed no
problem. We also had the same problem with hard drives, not sure why the
problem was with MicroBox PLC's and Hard drives, other electronics didn't
seem to have the problem.

What we ended up doing is spraying the circuit boards with a coating we got
from the local electronics supplier, IIRC they called it conformal coating.
I don't know if it was a certain flux or solder, but some boards had this
problem, others didn't. McMaster Carr used to sell an insulating varnish
for electric motor coils, I would think it would work good too. Coating the
boards changed the life of the boards from months to years.

Good Luck

RogerN




Thanks Roger, I'll take your advise. The flux thing is the only thing
that makes sense.
Many years ago I worked on flight hardware for NASA. I recommend using
190 proof Everclear to remove any visible dried flux on circuit boards
before applying conformal coating to a board. Don't conformal coat any
contacts or socket interiors.


Can the Everclear still go in the punch?

PLC board corrosion
 

On 1/24/2013 12:57 PM, Brian Lawson wrote:
On Thu, 24 Jan 2013 00:14:14 -0500, Tom Gardner Mars@Tacks wrote:

I got me Pro-Face PLC back from the manufacturer today. I had posted
about the failure a few weeks ago. It turns out that there was some
sort of corrosion on the main board and the video board. The PLC is in
a gasketed enclosure with three Greenfield cables coming in. The
machine or the control box never got wet and there is nothing in the
air. The heat goes from 65 day to 55 night with overhead gas furnaces.
Could just the Greenfield be letting moisture in? How do I prevent it
from happening again? A light bulb running all the time? A vent fan?
Maybe the thing shouldn't be that well sealed?

Here are some pix of the PLC, and enclosure.

http://i954.photobucket.com/albums/a...pse545a784.jpg

http://i954.photobucket.com/albums/a...psb1238b22.jpg

http://i954.photobucket.com/albums/a...pscbe73616.jpg


============================
Hey Tom,

We had a multi-lane bi-directional stepper switch ( 18P25T ) in a salt
plant, that would corrode to un-usability every six months, and the
switch and our labour to replace it was considerable. It sat in a
closed but not sealed cabinet, and there was no direct heat in the
machine room, so the temperature varied quite a bit by season. I put
a Plexiglas window in the swing lid of 12" X 12" X9" deep gasketed
cabinet and a 60 watt "Rough Service" light bulb with a simple light
dimmer to make the bulb just glow at about 25 watts. Took twice as
long to do this the one time, including installing, moving, re-wiring,
and caulking the wire-cable so the box was essentially air-tight. In
the 9 more years that I was still in the trade, the switch stepped
without failure, and used the same light bulb.

Worked for me.

Brian Lawson


How about a 25w to begin with? How do you judge how much is enough, temp?

PLC board corrosion
 

Tom Gardner wrote:

Hey Tom,

We had a multi-lane bi-directional stepper switch ( 18P25T ) in a salt
plant, that would corrode to un-usability every six months, and the
switch and our labour to replace it was considerable. It sat in a
closed but not sealed cabinet, and there was no direct heat in the
machine room, so the temperature varied quite a bit by season. I put
a Plexiglas window in the swing lid of 12" X 12" X9" deep gasketed
cabinet and a 60 watt "Rough Service" light bulb with a simple light
dimmer to make the bulb just glow at about 25 watts. Took twice as
long to do this the one time, including installing, moving, re-wiring,
and caulking the wire-cable so the box was essentially air-tight. In
the 9 more years that I was still in the trade, the switch stepped
without failure, and used the same light bulb.

Worked for me.

Brian Lawson


How about a 25w to begin with? How do you judge how much is enough, temp?


How big is the case? Ambient temperature of the location? 15 to 30
degrees warmer is usually enough.

PLC board corrosion
 

On Mon, 28 Jan 2013 09:25:38 -0500, Tom Gardner Mars@Tacks wrote:

How about a 25w to begin with? How do you judge how much is enough, temp?


Hey Tom,

A 25 watt bulb at 120 volts will have the life span of a 25 watt bulb,
while a bulb of any higher wattage dialed down will have a
significantly longer life span.

I'm only guessing at what the actual wattage was it was operating at,
but just above a glow.

Brian Lawson

PLC board corrosion
 

On 1/30/2013 1:35 AM, Brian Lawson wrote:
On Mon, 28 Jan 2013 09:25:38 -0500, Tom Gardner Mars@Tacks wrote:

How about a 25w to begin with? How do you judge how much is enough, temp?


Hey Tom,

A 25 watt bulb at 120 volts will have the life span of a 25 watt bulb,
while a bulb of any higher wattage dialed down will have a
significantly longer life span.

I'm only guessing at what the actual wattage was it was operating at,
but just above a glow.

Brian Lawson


I get it!