The rack in the dishwasher is metal grid-work w/a rubber-like coating. The bottom area is a grid with many upright 'tangs' that hold plates on their edge. A plate's edge sits on 2 bars of the grid and is supported by 2 uprights that come up from the grid. It is an older dishwasher and some of the areas where the plate sits on the grid and the ends of some of the upright tangs have lost their rubber coating and rusty metal is exposed. Several plates that were washed while in contact w/the rust now have orange rust marks where there was contact w/bare metal and the marks do not rub or wash off. It makes it look like they weren't cleaned but they were. Is there a chemical that won't harm the plate but will remove the rust marks? Is there a special abrasive needed? (The plates are an unremarkable whitish glazed ceramic.) BTW, I've just covered the rust areas with white kitchen/bath silicone sealer... waiting to see how that works out.