Yes, Zinc pest has been a problem since the first diecast zinc alloys were used. It is the result of lead (Pb) or other impurities in the melt. So if you think about it, it means if I am making a run of boilers on a machine and my melt is poisoned, all of them will be bad. If I make ten separate runs, and only one run was poisoned, then 1/10th of my production is bad. This is also why you will find locos with bad wheels but other parts good for example. These attachments are not mine, but are representative of what is going on. I've seen zinc pest In everything that you can think of that might have used a zinc alloy casting, and you probably have as well. Slotcar frames, automobile outer mirror castings (Triumph in my case), kitchen appliances (blender etc) heater duct blower motor frame on my 72 Porsche, etc, etc, etc. That shell is a an MTH railking tender I saw on ebay. So considering it is the result of poor quality control in effect, and most of your train suppliers get stuff from China, and do not have control over the factory, AND the failure does NOT usually manifest itself immediately, it should be easy to see how this can happen repeatedly and really, there is not much Lionel or MTH or XXX can do about it after the fact. We all know most of these mfr's do not really stock spare parts any more. They make xx number of extra items and those are robbed for spares as needed. When Lionel lived in Michigan, they did have spare parts, shells etc. They also did their own casting...
