On Thursday, December 6, 2012 10:58:47 AM UTC-7, jeff_wisnia wrote:

We have a well functioning microwave oven with a rusty circular
track on the bottom of the oven where the plastic wheels
supporting the rotating glass dish have rolled for several years.

The track looks awful and it's spread to about 3/4" in width now,
much wider than the wheel treads and I'm thinking it may soon rust
right through the oven floor.

I tried painting it with white automotive touchup paint a while
back, but that only lasted about a week before flaking off.

Can someone name a really tough white paint, maybe an epoxy based
one, that I can use to put a heavy durable coating over that rusty
"track"?

Failing that, I guess I can take the time to cut a circular band
out of aluminum or stainless sheet metal and epoxy it over the
rusted area with conductive epoxy to avoid the possibility of
it arcing to the oven floor.

How did you prepare the metal surface before painting it? Because
even car touch-up paint should have lasted a lot longer than a week,
but in general you don't want to use it in a steamy environment
because it's lacquer and is much more porous than enamel. You
should have sanded down to the original primer or to bare metal
and prepared the bare metal with phosphoric acid to make the paint
stick better. Naval Jelly is phosphoric acid and removes rust.
You don't need epoxy paint, just any non-toxic enamel that doesn't
contain pure metal (almost any white enamel will do). Appliance
parts supplies and MCM Electronics sell spray-on microwave oven
cavity paint that's suitable.