I have oiled my plates. I dont always train in my garage, so sometimes my plates go unused for quite a long while. I also "sourced" some 45s that were very heavily rusted. On those, I knocked down the rust with a steel brush, then sprayed the plates with a light oil, then wiped them down with an oily rag. Leaves a very thin protective layer on that impedes rust. I dont keep them slick or wet with oil, but every so often I will use the oily rag to wipe off some of the orange light rust that builds up. Again, I dont use them all the time, so its preventititve. I did have some one inch "training plates" that I use on a 1 inch exercise bar for my kids to play with. These, too, simply live on the bottom of my plate tree, so I just sprayed those with the oil and ignore them. Two years later, despite a damp, humid garage environment, they are still black and unrusted.