I moved to a high humidity area a few years back. We are on a slope overlooking the ocean so we get a constant sea breeze which is death for cast iron. In my workshop I run a dehumidifier 24/7 and I have no rust on my metalworking machines. The woodworking stuff on the other hand are in the garage and did start to suffer from surface rust. I found that covering the table saw with an old dogs blanket has helped a lot. But, and this is a big but, the blanket must not rest on the cast iron. The cross slide table and fence are arranged in such a way that the blanket does not lie on the table surface.