At first I thought that your habit was to heat your weights in the oven before lifting them and I thought, ‘Damn, that’s hardcore. A little overkill, don’t you think?’
No I'm not that crazy yet. Lol. I de-rust and then cost them in some spray rubber or truck bed liner paint or something similar. Set a piece of 2 inch PVC in the center then fill the drum with concrete. Concrete hold the PVC in and adds weight. 2 inch PVC fits perfectly around a standard Olympic style barbell. I then even the weights out using epoxy and bbs and stuff. I usually get them to be withing .02 or so of the target weight which is way better accuracy than most manufactured weight plates and, IMHO,look way cooler. I got sets ranging from 15, 20, 25, 30, and 35 lbs. I also made some 5 and 10lb weights from just concrete and used a bucket for the mold. All in all I've probably saved myself several hundreds of dollars on weight plates