The bike co-ops don't want steel rims from the 1970s either, you can do them a favour and save them the time and take that kind of stuff to your local transfer station if they have metal sorting. You could look up metal recyclers in your area too. When I did my big purge years ago I put all the alloy stems, cranks, hub shells, rims, kickstands etc.. in a pile I made sure there was very little or no steel in it (save some rim eyelets)... I got $45 for it as scrape metal. I know the bike co-op has more alloy threadless stems than they know what to do with, same kickstands, and no one needs to save a cracked or otherwise crappy crank. So it got recycled and will be more useful. I know sometimes it can be hard to recycle something that was manufactured and useful but the more metal recycle the less has to come out of the ground destroying our environment so... there is karma in the scarping of metal too...