My 1999-era Sharp Carousel microwave oven is beginning to develop rust
near the bottom of the interior, back wall. I assume that this is
caused by the frequent humidity in the oven, during use. Is there
anything special about the paint that is used in microwave ovens (like
radiation sheilding properties), or can I just sand it down to the
metal and apply some Rust-O-Leum to it?

Thanks,

Franco