You put a lot of effort into prepping a chassis covered with grease, oil and other nasty stuff. Then there's the repairs to be done. So, after all this time, money and effort, why cheap out on hardware store paint?
Try a good industrial coating like this stuff:
EnduraA criticism of this paint is that it may fade due to UV exposure. That shouldn't be a problem for the chassis.
i see that the OP is in NY. I sure road salt is an issue as it is here. You want something tough!
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Frame Paint