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Corrosion Damage ¨C TM500 Plugins
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I have some TM-500 plugins that have been stored for a number of years in the garage in what I thought was a safe plastic storage container that is almost fully sealed from the atmosphere. To my horror when opening the box on the weekend all plugins have suffered some amount of corrosion damage. Examples of the damage include hardware items such as screws rusting, aluminium oxidisation and plastic (typically inner cables) showing chemical deposits on the outer surfaces. A couple of the plugins were fully wrapped in bubble wrap and have also suffered damage.
I had wondered if moisture had got inside the container which is possible given that a small amount of air would be able to get insider the container around the opening however given the nature of the damage this does not seem to add up. My suspicion is that the foam inside the container has emitted some sort of chemical that has caused the corrosion possibly Methylene Chloride which is apparently used in the production of polyurethane foams. Would this make sense or is something else the likely cause of the issue? |
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The old black anti-static foam was notorious for breaking down and
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emitting some kind of gas that would attack ANY nearby metal, even gold or nickel plating. It's common to find test equipment accessories, from HP and others, in the original boxes and the outside of all of the metal items is badly corroded. On Mon, Mar 15, 2021 at 10:25 PM <christopherbath@...> wrote:
I have some TM-500 plugins that have been stored for a number of years in |
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I am surprised that gold was affected. I thought gold did not react chemically so I looked it up. It is pretty inert except for reacting with cyanide.
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Perhaps one of the chemists on this list could weigh in. DaveD On Mar 15, 2021, at 23:07, - <rrrr6789@...> wrote: |
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Two things I can think of. One is something deposited on the gold, not an
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actual reaction. The second is something I have seen with gold plating. I have seen this with gold over nickel. If conditions result in any condensation on the plated item, micro (or macro) pores could allow for some electrolytic degradation of the metal under the gold. This causes the gold plating to "bubble" up and split. The gold itself does not react since it is usually less active on the electrolytic scale but it does damage the plating mechanically. On Tue, Mar 16, 2021, 07:33 Dave Daniel <kc0wjn@...> wrote:
I am surprised that gold was affected. I thought gold did not react |
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I was told that the foam would break down and release flourine and that
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that was what attacked the gold and even stainless steel. I've opened up dozens of HP TE accessory boxs that have been closed for many years and found everything in the box in this conditon. But whatever it was that attacked the metal was a gas and not a liquid and it attacked all of the metal surfaces, even those not in contact with the foam. OTOH as stevenhorii pointed out gold itself is pretty porous and the agent might not have attacked the gold directly but simply penetrated the gold and attacked the metal underneath and caused the gold to crumble off. I used to see that a lot in battery powered devices like the HP calculators that had gold plated steel battery contacts when the batteries had been left in them too long and had leaked electrolyte. I will bet that you can go on Ebay and search for "HP calculator" and find pictures of some in that condition. The electrolyte would also attack the gold plated copper that was used in what was called the "port block" in the HP 41s. It was common to open up HP41s and find the gold plating in little tiny loose flakes and no copper left on the Kaptan strip that formed the battery contacts and the four port connectors. On Tue, Mar 16, 2021 at 7:33 AM Dave Daniel <kc0wjn@...> wrote:
I am surprised that gold was affected. I thought gold did not react |
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A couple of questions and comments.
I see you have indicated that there is a foam product present in the container. Can you better describe the appearance of it to help define what it is? Yes, there are foam products releasing agents that can cause deleterious effects on metals and such. What type of container are the plug-ins housed in? You mention that the container is ¡°¡almost fully sealed¡¡±. One must remember that through ambient temperature changes air tends to expand and contract. This allows any container that is not totally sealed to ¡°breathe¡± and allow any external humidity inside. Is the foam being held in place by any adhesives? I once encountered a waterproof transit case that had standard low density foam fastened inside with an adhesive. Over time the contents of the case showed signs of deterioration similar to what you are experiencing. It turned out that the adhesive was releasing a product that caused the problem. And since the container was totally sealed from any environmental effects the inside of the case was a perfect chamber to contain the corrosive atmosphere. Do you live in an area that has a relatively humid environment? While working in the tropics I came upon an older piece of HP equipment that was supposedly in ¡°safe¡± storage but the room was not dehumidified. When I picked it up there was heard rattling inside. Opening it up I found that all of the discrete transistors had lost their gold plating (gold was frequently used I those days to plate leads) and the moisture had attacked the steel wire thereby corroding it to the point where there was no metal left and the transistors simply fell off the printed circuit boards. Obviously there were also signs of corrosion on other parts as well including ¡°worm tracks¡± on the anodized front panel where the moisture went under the sealed anodic oxide surface and made very fine random tracks on the raw aluminum as it made its way along. Greg |
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That porosity is why gold flash is so useless; basically decorative.? For professional equipment, we always specified 30u" of Au, 15u" was the absolute minimum.? Flash was considered worse than no gold, and verboten.
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-Dave On Tuesday, March 16, 2021, 05:06:56 AM PDT, stevenhorii <sonodocsch@...> wrote:
Two things I can think of. One is something deposited on the gold, not an actual reaction. The second is something I have seen with gold plating. I have seen this with gold over nickel. If conditions result in any condensation on the plated item, micro (or macro) pores could allow for some electrolytic degradation of the metal under the gold. This causes the gold plating to "bubble" up and split. The gold itself does not react since it is usually less active on the electrolytic scale but it does damage the plating mechanically. On Tue, Mar 16, 2021, 07:33 Dave Daniel <kc0wjn@...> wrote: I am surprised that gold was affected. I thought gold did not react |
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Greg,
I don't remember if the foam in the HP boxes was glued in or if it was cast in place but I thinnk it was glued in. But it was a very dark gray and almost black color and it was an open cell foam with very tiny (~ 1/32") cells. In the open areas where nothing had touched it the foam would look fine until you touched and when you did, it just collapsed with no resistance. It usually crumbled to a dark powder and you could wash most of it out with soap and water but it always left a certain amount behind that was nearly impossible to remove. Besides that used by HP, i've also seen sheets of anti-static foam that ICs were stored in and it did pretty much the same. It would just crumble without being touched and it would attack the legs of the ICs and occasionally completely eat them away from the IC body. I will look around on the internet and see if i can find any pictures. On Tue, Mar 16, 2021 at 12:11 PM Greg Muir via groups.io <big_sky_explorer= [email protected]> wrote: A couple of questions and comments. |
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PS, the HP Accessory boxes were one piece boxes and had a snap on the
front. All of it was in one piece,; both halves of the box, the hinge and the snap. they fit together pretty well but they certainly weren't airtight. It is humid here but the place that nearly all of our equipment came from was a large US government facility and it was well air conditioned so I think the items were kept inside in AC storage but I can't say that for certain. On Tue, Mar 16, 2021 at 12:11 PM Greg Muir via groups.io <big_sky_explorer= [email protected]> wrote: A couple of questions and comments. |
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Greg,
This is what the HP Accessory boxes looked like and this appears to be the same kind of foam although it doesn't appear to be deteriorated. But sometimes the foam that we encountered didn't appear to be deteriorated either until we touched it. < Here is another HP Accessory box but the hinge on this one wore out and the top of the box is missing. That is a very common problem with this type boxes. Also the flex part of the front latch would wear out and the latch would fall off. < > But this box has closed cell foam in it and I don't recall ever having problems with that. On Tue, Mar 16, 2021 at 12:11 PM Greg Muir via groups.io <big_sky_explorer= [email protected]> wrote: A couple of questions and comments. |
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There were some "miracle material" foams and tough flexible plastics used in the 1960s and 70s. Many of them decompose to very vile residues that are often corrosive. One that had? devastating consequences to an industry and cost tens of millions to? remedy was the adaptation of polyurethane sheet that was not made correctly. In many cases, someone eager to embrace a new material would take shortcuts or not do adequate research regarding critical details in the formulation. If this stuff decomposes in a closed environment?? and was blown with hydrochloroflorocarbons, that would add some very corrosive? elements that might become part of the brew. I have cleaned up many items damaged by these residues.
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??? Bruce Gentry, KA2IVY On 3/16/21 14:04, - wrote:
A couple of questions and comments. |
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I guess I am getting a little confused at this time but better understand the situation. Somewhere in there the Tektronix subject changed to HP and storage turned into accessory cases.
Earlier model HP accessory cases were notorious for breakdown of the foam liners. I have witnessed anything from the foam crumbling to dust (as you mentioned) all the way to it turning into a sticky goo that captured the contents and took considerable cleaning to remove with some corrosive effects along the way. The dust aspect seemed to be simply from age and the goo from high humidity conditions. Older Tek portable scopes that had the front accessory covers (453, etc.) were known for either disintegrating dusty foam and/or the fastening material drying out releasing the foam from the cover. The darker open cell foam you indicated in the one web link appears to be a later version product. I have seen it in newer cases and always recognize it from its more darker color and coarser cell size. I order closed cell foam to build up transit cases and have never had any problems using it. But I also order the foam from those sources who also build up custom cases so always feel relatively assured that their products are safe. The downside to it is that they tend to extract high prices for the foam. I¡¯m not certain if you brought the subject into your discussion regarding the TM500 plug-in accessory modules or not but they contain a hard plastic liner and fortunately no foam products (at least to my knowledge given the several I have here in the lab). Either way I am sorry for your discovery. It¡¯s always disheartening to pull out an older piece of hardware and find irreparable damage. I think foam manufacturers are now a little more sensitive to the ingredients in their products and the subsequent damage that can be caused. And if there is any uncertainty about foam in older equipment that still is in relatively good condition it is better to err on the cautious side and replace it if possible. Calls to the foam manufacturers to verify their products is a wise step in assuring that there will be minimal surprises in the future. Greg |
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It could just be galvanic corrosion. The graphite in the conductive foam is at the very top of the galvanic series () and can corrode even noble metals like gold and platinum in the presence of sufficient moisture to enable the reaction.
I have seen very severe corrosion on the pins of ICs placed in this conductive foam when stored in a humid conditions but in an otherwise open enclosure. The corrosion only occurred on the area of the pins in direct contact with the conductive foam. Areas not in direct contact with the foam were completely unaffected so it seems unlikely that there was any gaseous agent causing the corrosion. |
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Hi,
Sorry for the very long delay in replying. Inside the container is a black open cell foam with comparatively large cells. The foam had not broken down. It does appear the foam was glued in place and it is possible that the glue may have caused the issue. The outside of the box is made from plastic (possibly polyethylene). The case is almost airtight however would still allow any external humidity into the storage container. On top of the box was some other plugins with only a sheet of bubble wrap left on top of them which are totally unaffected, so it is very likely that something inside the box had caused the issue. The box from what I can tell is not that old and the plug-ins had probably been in the box for about 5 years. The damage is strange. I am not a chemist, and my knowledge of chemistry is limited however the damage represents to me what I suspect is from a gaseous corrosive chemical presumably that may have formed from either the foam or glue possibly under summer conditions when the ambient temperature may have exceeded 40 degrees Celsius (104 degrees Fahrenheit). The damage included the following: ? Corrosion to steel components such as screws and the coating (possibly zinc or similar) ? Oxidisation to aluminium including some small pitting in some areas. ? Damage (reaction) to copper and brass from penetration through plating such as nickel plated brass. Some tracks with silk screened coatings on top showed some very minor damage. Gold plated components feared much better with almost no damage. ? Penetration inside some magnetically latching relays where the chemical appears to have penetrated the epoxy potting causing corrosion to some of the mechanical parts. ? Accelerated damage where dissimilar metals had been in contact such as the screws with the aluminium frame. ? Inside the one of the plugins there is a plated steel or iron component that has had some of the plating come off. Obviously the chemical had penetrated the plating (which would be to some extent porous anyway. ? Some ¡°worming¡± to one aluminium front panel underneath the anodized finish. The modules were no better off being fully wrapped in bubble wrap inside the container. The chemical also seems to have formed on the outside to the plastic components however after cleaning with ethanol the plastic does not appear to have been affected. Any idea on what the chemical is that may have formed? Thanks, Chris |
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On Sat, Apr 24, 2021 at 02:58 AM, <christopherbath@...> wrote:
I am not a chemist, and my knowledge of chemistry is limited however theI'm not a chemist either, but the answer may be simpler that you suspect. Your box is not hermetically sealed, so air will leak in and out of it with changes in barometric pressure. Thus, over time, this box "breathes". There's also a daily rise and fall in ambient temperature. As a result, there will be times when humid air is carried into the box just before the temperature drops below the dew point. This results in dew forming on anything in the box. It's just water, but it has condensed out of the air and has condensed on anything that is exposed to the air in the box, which means anything that isn't hermetically sealed. This happens in cars, where rust appears to come out of places that have not been exposed to weather. These are sometimes referred to as "trapped volumes." It is common for trapped volumes in cars to have to paint or any other rust prevention coating, so they rust silently until the rust bubbles appear. This same problem happens in the gas tanks of stored cars: Dew typically forms inside the top of the tank, drips into any gas that's still in there, and eventually falls to the bottom, where it rusts the bottom of the tank. So it's certainly possible that there's something special going on in your box, but it's also possible that this simpler explanation is all you need. |
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I've been told that that foam breaks down and releases some kind of
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Fluorine gas or compound. Whatever it is, it seems to attack just about every kind of metal including stainless steel. Also gold, or possibly it penetrates the gold layer and attacks the underlying metal. There was a long discussion about this on the list a couple of months ago. On Sat, Apr 24, 2021 at 3:58 AM <christopherbath@...> wrote:
Hi, |
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Not to rub salt in the wound, but by coincidence just yesterday I was inventorying some electronic parts I have. They are stored in OEM packaging dated 1965. They were stored the old fashioned way, taped up in crinkle paper wrap. They have never been opened since 1965, so I opened one up just to check it.
The part was perfect. Bright shiny contacts, no corrosion, no funk, no issues. That¡¯s 56 years, and no issues. Like you guys and gals, I remember when the various kinds of foams became available. They looked cool, seemed to provide better protection against physical shock, etc., so I used them for a while, until I opened up an anvil case that had been stored for several years, and found a mass of goo-coated equipment...ruined by the degrading foam. I went back to paper to wrap parts, and keep them in snap lid plastic containers. Sometimes I toss in a bag of silica gel, because the containers do breathe a bit. Yes, I take the risk of the static danger from the paper. If I am really worried about it I spray the paper with fabric softener and let it dry in the sun. The fabric softener eliminates the static threat. Sometimes the old way is the right way. Try paper. It works pretty good. |
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