Wow, everyone is responding as though zinc rot is a certainty?! Is that true?
Not that I've seen. Mind you, I don't own any "modern" Lionel locomotives -- the newest one I have was made about 1991. None of them (fingers crossed) have shown any signs of zinc rot.
The only time I've encountered zinc rot was when I restored my father's 1929 Lionel 252 locomotive. The wheels had crumbled away and had to be replaced with Bowser reproductions.
As an aside, there's really NO excuse for zinc rot still being a problem. All manufacturers have known about the problem for many years, and have had more than ample time to correct it. The fact that they evidently haven't tells me that they don't particularly care.
An interesting facet of this issue is that I have in my collection a Marx 999, 333 and 666. All have die-cast metal boilers, none of which show any zinc rot at all. In fact, the metal they used doesn't even appear to my eye to be zinc. Whatever it is, it has survived intact for many years. Why, then, do today's makers continue to use zinc, when it is known to be a source of problems for at least a minority percentage of their products?
The usual "answer," of course, is that it would be more expensive to use other metals. And yet, I see no signs that modern locomotive manufacturers have any qualms about making their models more expensive.
Even though zinc rot is by no means inevitable, the posts on this (and other) threads tell me that it occurs often enough to be taken far more seriously by Lionel and other hobby manufacturers.