This is a real thing although many don't think so .
The same with powder coating ~ yes it's hard as a rock -but- one little chip the water gets in when you're washing or driving in inclement weather, travels to the lowest spot and rusts away .
Honda discovered this when they powder coated the frames on their otherwise excellent Motocycles some years back ~ three year old Motos collapsing the frames whilst underway
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I learned this lesson the hard way in the 1970's with my 1946 Chevy shop truck's rubber floor mats ~ I loved keeping that rig clean so after a year I was gobsmacked when I lifted the one piece floor mat and discovered the floors I'd so carefully de rusted and repainted were all rusty ~ and this in the California Desert .