After I read this and previous topics on the subject, I am so glad that I sold most of my IMs. All that I have left are a NYO&W FT pair and one F-3A plus two B&O F-7 A-B pairs. I check them constantly for frame rot. None has shown Y-E-T.
I do not understand the Zamac frame rot. This Zamac stuff had problems way back in the 1930’s. Surely the metal experts know how to make this stuff with out it becoming a pile of crumbling crap. Or is it a cost of production issue? Like let’s cut back on the expensive material and sub something else?
You got it with that last answer. The supplier to the factory says let's go cheap and no one will notice and they are right until years later when things start crumbling. It may be awhile but unfortunately, this won't be the last time we see this problem
The solution was found in the early sixties and it has been well-known how to avoid the problem. It's a matter of incompetence/carelessness and maybe cost but I can't imagine it being that more expensive to make it correctly. Skullduggery probably plays a part, too. Doug
Scrap is likely the actual issue. The wiki article on Zamac rot says it is mostly caused by lead impurities, so I suppose the QC test would be a lead test. And the factory would need to do things like source high purity zinc alloys, and not do something foolish like throw scrap lead solder into the metal pot. This is rather silly of an issue to have to deal with. Micro-Trains makes die-cast car chassis all the time, and you never hear about their products having issues. Hot wheels, because they are children's toys, have to meet standards for lead, and so you never hear of zinc rot in these die cast items. Although I bet Hot-Wheels tests the metal before and after.
Sorry to burst your bubble, but MT DID have an issue with a batch of boxcar frames......ended up breaking the shells in the thin area at the bottom of the doors........I've only hear of that one instance though.
Well, you didn't burst MY bubble. It was burst in the early seventies when my Atlas/Rivarossi 0-8-0 frame started falling apart in the drivers area and my Atlas/Rivarossi E8 frame broke in the very thin areas where the motor is mounted, cracked, and swelled up. I fixed both frames and they are still in the two locomotives to this day.The work on both frames was pretty extensive, reattaching many small pieces to the 0-8-0 frame and filing the driver slots back to usable dimensions, and using a milling machine to get the E8 frame back to its original dimensions. Doug
I guess, considering the number of cars Micro-Trains has manufactured, over the years, their Zamac problem is pretty insignificant. Doug
Also from Wiki: Zinc pest (from German Zinkpest), also known as zinc rot and zamak rot, is a destructive, intercrystalline corrosion process of zinc alloys containing lead impurities. While impurities of the alloy are the primary cause of the problem, environmental conditions such as high humidity (greater than 65%) may accelerate the process.
Thats what I don't understand ........ high humidity here is the status quo. It's sub tropical and some days I can cut the air with a knife and yet no sign of zinc rot for my locos or anyone I know in the local area ( by local I mean 6 times the size of Texas ). Yet I see IM has a bad reputation in New Zealand ....... I'm not really familiar with the weather there but I had the impression it was cooler and low-is humidity Then ......... I somehow ended up having Youtube recommend a video on gallium .......... WOW ......... what that stuff does to some metals is incredible. I was tempted to do an experiment with some gallium and maybe an expendable matchbox car. I was just thinking of storing it in a box without either touching to see if could affect the metal. Gallium can be found in high temperature thermometers among other things.
Although moisture and temperature are factors in all chemical reactions, in the Zamac case, the overriding factor is the formulation, not the environment. So, if the formulation is correct, humidity isn't going to do much, if anything. Doug
I believe that they mean high humidity when the forming process is taking place, allowing water to contaminate the zamac whiile it is in a liquid state, not after it has solidified.
Not locomotive frames, but in casting lead bullets we often use wheel weights. You have to be careful not to allow zinc weights into your alloy or the bullets' weight and center of gravity can be compromised even in something this simple.
That's not the case when modelers talk about different environments in forums. They are talking about where their locomotives are stored. Also, it's not likely there will be much moisture while the mixture is formed with all that heat. Moisture will have evaporated. Doug
Just out of curiosity is the new F7'S that were released a couple of months ago know to have these issues. I purchased 2 and now having second thoughts about it. Also I wonder if a person could use a kato F7 chassis to replace the IM one?
The newer releases haven't had an issue to the best of my knowledge.........IM ran out of frames to replace the rotting ones, so the new releases should be from a whole new batch. Doesn't mean the new ones won't have the issue, but I seriously doubt IM would knowingly send out another bad batch. I'm not sure they could survive another major PR issue. I have a dozen of the old F7s and haven't had any issues. And Kato will not work.......There's a width issue, and Kato uses truck mounted rear couples vs body mount on the IMs
