What is a good and lasting way to prevent cast iron tops from rusting. I live in Minnesota and am having trouble keeping up with the rust. I’ve used car wax and some other oils advertised to control rust but especially this summer I have to re coat everything every couple of weeks at the longest! I was gone for 10 days and just spent 2 hours sanding the tops with 400 grit paper and then put on a heavy coating of car wax. Any other suggestions?