I’ve worn many pairs of blue jeans in my life but never had the zippers or buttons rust out. Is there some kind of protective coating that prevents this from happening? You would think that with all the washing, drying and everyday abuse these things take they might fall apart sooner, but that doesn’t seem to be the case.
Zippers aren’t ferritic (not made form iron). Without iron, you cannot make iron oxide (rust). This cite lists some typical zipper materials including brass, nylon, and aluminum.