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Post by railtwister on Feb 2, 2015 11:06:59 GMT -8
The other day, after setting up some of my T-Trak N scale modules, I wanted to run a couple of my Atlas N SD35's, one in ACL black and yellow, and a second one in a similar scheme but lettered for SCL. Before even opening the original clear plastic box, I could see there was something terribly wrong with my ACL loco, since the handrails were very distorted. Closer inspection revealed that the shell had ruptured due to pressure from the frame expanding as a result of "Zinc Pest" metal deterioration. There was an almost 1/8" gap in the walkway on the loco's left side, the rear end of the long hood was split wide open vertically from the light to the bottom of the shell, and the whole nose section of the short hood was broken clean off. As I tried to take the loco out of the OEM foam lining, the nose and both trucks fell off. The only thing salvageable on the ACL body were the number boards and the fuel tank. I then checked my SCL unit and found that while there were no breaks in the body shell, it was almost impossible to remove the frame because it had started expanding too, but thankfully wasn't as advanced as the ACL version. I compared the two frames and measured them, the ACL frame was 1/8" longer than the SCL frame. The SCL loco can be saved by replacing the two frame halves, since it's shell is still intact, but the ACL loco is U salvageable, unless I can get a new shell. Both of these locos were essentially brand new in the box, when I last took down the T-Trak layout perhaps 10-12 months ago, and that was shortly after I purchased them from a local hobby shop that was clearing out their train department.
I haven't seen or heard of problems caused by Zinc Pest in our hobby for over 30 years, so I thought it was a thing of the past (but, apparently it's not). Has anyone else on this list had similar problems with their Atlas locos (especially the N scale SD35, but maybe others as well)? Even though I realize these locos are long out of warranty time-wise, I feel like the metal they are made of shouldn't self-destruct after any length of time...
I posted similar comments as well as photos over on the Trainboard Forum but so far no one has spoken up with similar problems.
Bill in FtL
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Post by dkalkman on Feb 2, 2015 18:29:47 GMT -8
I purchased new on 6/10/2000 from my LHS 3 Atlas N SD35s - 2 PRR, 1 WM. I just completed an inspection of each of the 3 which included removing the body shells. No problem of any type was found on any of the 3 SD35s. For 14 years, mine are stored in a room with little temperature or humidity variation. Could storage conditions have contributed to the problem you're experiencing?
Don Kalkman Towson, MD
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Post by railtwister on Feb 3, 2015 5:28:58 GMT -8
I purchased new on 6/10/2000 from my LHS 3 Atlas N SD35s - 2 PRR, 1 WM. I just completed an inspection of each of the 3 which included removing the body shells. No problem of any type was found on any of the 3 SD35s. For 14 years, mine are stored in a room with little temperature or humidity variation. Could storage conditions have contributed to the problem you're experiencing? Don Kalkman Towson, MD Hi Don, I seriously doubt it, since other locos (including 2 WM "Circus" SD35's from an earlier run) stored in the same area didn't have the problem. Besides, why do they call the metal "pot metal"? You would think metal used in pots would see far greater changes in temperature and humidity than could be possible in a layout room. Years ago, I read that the problem was caused by impurities in the Zinc alloy, especially traces of lead, which makes sense if you consider the materials contained in a car battery. In any event, thanks for checking your roster and reporting your findings. Hopefully, the problem will be limited to just a few pieces from a specific run, rather than being widespread. I think these paint schemes were originally announced in 2009. In addition to the swelling, my frame pieces had many tiny cracks in the surface of the metal, and that surface also had a rather porous, dull gray look to it. Other locos frames looked smoother and had a brighter, more silvery color. Bill in FtL |
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hhr
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Post by hhr on Feb 3, 2015 8:44:47 GMT -8
Hmmm..interesting and disconcerting at the same time. After reading this, I did a quick roster check, and only the usual suspects were affected. About 25% of my early Kato manufactured Con-Cor units are affected with Zinc Pest to varying degrees, all of them are "shelf queens" anyway. Then there are the Rivarossi made Atlas units of the same era, crumbly frames have meant that nearly all of them are out of service.
No problems found with anything made after around 1976, but it sounds like the folks in China have not monitored the quality of metal being cast. Or it's a case of "throw whatever scraps and cr*p back into the pot for another pour".
I seem to recall that certain storage conditions can cause or accelerate the problem, one article on the issue affecting Marklin trains suggested that storage away from light was a contributing factor. But after extensive Google searches, I can't find that article again to post a translation.
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Post by douggosha on Feb 3, 2015 9:37:37 GMT -8
Although it makes sense that storage in a more humid environment would accelerate any corrosion of impurities and resulting deterioration of the zinc/aluminum casting, I don't think any definitive answer has ever been produced.
I don't see how storage in a dark place would result in quicker deterioration unless there was increased humidity present.
Bill, after looking at the pictures of your frame, I conclude that it is indeed exactly the same thing that happened to the old Rivarossi and other manufacturers' castings.
Doug
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hhr
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Post by hhr on Feb 3, 2015 19:53:21 GMT -8
From a post by "Loose Nut 45" over on the Mamod Steam Forum in 2006...
"Zinc Pest:
From what I can gather, when Mazac is produced, its crystalline structure contains boundaries between the harder zinc crystals and those crystals formed by the melting and fusion of zinc and aluminium. Impurities such as cadmium, tin and lead, are activated by moisture, which starts an electrochemical process, by which lead (insoluble in Zinc) is drawn out from between the alloy crystals and cadmium is leached from the actual crystals themselves. The impurities are then deposited at the boundaries between the two types of crystal.
The greater the moisture and the finer the crystals, the faster the corrosion.
Crystals are smaller when the cooling of the casting is rapid.
The practical upshot is that moisture starts a process on the surface of the metal, which induces the impurities to collect and push the crystals apart. This results in cracks and the growth or ‘blooming’ of the casting.
The Cure:
Sorry, there isn’t one. However, bearing in mind that moisture is the activator, reducing it is going to help slow down, or even prevent the curse. So here are some suggestions:
. Don’t store models in cardboard boxes.
. Don’t store models in the attic, garage or anywhere where rapid temperature changes are likely.
. Don’t wrap models in paper or cotton wool-both trap moisture. Bubble wrap is OK as a lining to a box, or as a cover, but never wrap it tightly round a model or box.
. Do invest in good quality plastic storage boxes. If you have ultra valuable or precious items, you may consider the complex process of boxing the items, then placing the box in one of those giant vacuum bags used for storing duvets and sucking the air out. Do a trial run first and if the empty plastic storage box is up to the job, repeat the process with the models in the box. I must stress, NEVER vacuum seal cardboard boxes of any sort-they WILL distort!
. Do invest in silica gel as it’s great at absorbing moisture.
There are two ways of obtaining silica gel (actually crystals): vendors on eBay will happily sell you sachets in a variety of sizes and in varying quantities. You can also DIY it, by buying large bags of crystals. The next step is to buy some Elmers paper glue, or similar and pop along to your local convenience store or supermarket. Buy the cheapest square tea bags. Cut along one edge, empty the tea out and fill with silica crystals. Seal with glue and allow seam to dry. If you don’t have access to the internet, pop along to your local pharmacy (which is what I did) and they can order tubs of silica for you. For the super-mean; get friendly with someone who works in a shoe or handbag shop.
The final thought is; always check your collection on a regular basis. Any signs of damp -dulling, pitting or bubbling of paint- means you have to act fast!"
Basically, Loose Nut provided the same info found on the Marklin Forum long ago. It's just a shame to think that a problem supposedly eradicated decades ago, might be showing uo again.
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Post by Deleted on Feb 3, 2015 20:02:03 GMT -8
...Do invest in silica gel as it’s great at absorbing moisture. There are two ways of obtaining silica gel (actually crystals): vendors on eBay will happily sell you sachets in a variety of sizes and in varying quantities. You can also DIY it, by buying large bags of crystals. The next step is to buy some Elmers paper glue, or similar and pop along to your local convenience store or supermarket. Buy the cheapest square tea bags. Cut along one edge, empty the tea out and fill with silica crystals. Seal with glue and allow seam to dry. If you don’t have access to the internet, pop along to your local pharmacy (which is what I did) and they can order tubs of silica for you. For the super-mean; get friendly with someone who works in a shoe or handbag shop... You can often find tubs of silica gel at WalMart or camping stores sold under the DampRid name. Intended for drying out closets or RVs. Cheap. Amazon Prime has it 4 lbs for $10 (inc. shipping). Amazon also has silica gel in sachets, 50 for $12 example. |
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hhr
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Post by hhr on Feb 6, 2015 1:32:28 GMT -8
Good tip on where to find Silica Gel omaharoad, muchly appreciated!  |
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Post by mvlandsw on Jan 23, 2016 18:09:29 GMT -8
Just yesterday I had a pair of Central Valley HO passenger trucks from the 1970's break apart when I took them out of their box. I don't recall ever having this trouble with their products.
How long is the silica silica gel effective? Can it be reactivated if it becomes ineffective? I use it in a jar with a tube of CA glue which seems to extend the usable life of the glue.
Mark |
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Post by atsfgp7u on Jan 31, 2016 20:16:22 GMT -8
Hi Bill, It doesn't help your situation but here is an explation of why these metals are called pot metal (from Wikipedia) "Pot metal—also known as monkey metal, white metal, or die-cast zinc—is a colloquial term that refers to alloys of low-melting point metals that manufacturers use to make fast, inexpensive castings. The term "pot metal" came about due to the practice at automobile factories in the early 20th century of gathering up non-ferrous metal scraps from the manufacturing processes and melting them in one pot to form into cast products. A small amount of iron usually made it into the castings, but too much iron raised the melting point, so it was minimized". Here is a link to the full article- en.wikipedia.org/wiki/Pot_metalSadly, it explains exactly why we have these problems on some locos, not others. Dave |
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kirk
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Post by kirk on Jun 8, 2016 11:38:51 GMT -8
Hi Bill, It doesn't help your situation but here is an explation of why these metals are called pot metal (from Wikipedia) "Pot metal—also known as monkey metal, white metal, or die-cast zinc—is a colloquial term that refers to alloys of low-melting point metals that manufacturers use to make fast, inexpensive castings. The term "pot metal" came about due to the practice at automobile factories in the early 20th century of gathering up non-ferrous metal scraps from the manufacturing processes and melting them in one pot to form into cast products. A small amount of iron usually made it into the castings, but too much iron raised the melting point, so it was minimized". Here is a link to the full article- en.wikipedia.org/wiki/Pot_metalSadly, it explains exactly why we have these problems on some locos, not others. Dave I had the same problem happen to some Lionel drivers from the 1930s back when I was collecting the stuff in the 70's the wheels fell apart, I had to get get restoration wheels and lost about 25% of my investment. I used the silica jell and it helped, if you get the type that changes color you can reheat it in the oven and have it go back to the original color and reuse it. I found complaining to the makers will often get you replacement parts as a manufacturing defect. |
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