I used to work in a factory that made wire racks for Magic Chef ovens.
There was a considerable reject rate on the racks. A lot of the chrome
was flaky and/or rough textured, discolored, and some of the wire spot
welds came loose in the chroming baths. And this was with brand new wire.
So don't expect perfect results having old pitted, rusty racks rechromed.
The old chrome will have to be completely removed, the racks acid dipped
to eat all the rust out of the pits, and then treated and plated.
A 30 year old fridge isn't long for this world anyway, so I don't think
I'd go to such trouble and expense. I do have a 1958 GE (house)
refrigerator that is still going strong after 45 years. It has anodized
aluminum shelves, so no chrome pitting and flaking.
Al Grayson