This was posted by Michael Apple. If you do get plastic don't buy from Tractor store or any store that carries feeders from china. They can leak toxic chemicals. See his web sites for ordering plastic feeders. If you don't order from these sites at least you have some info as to what to look...
This information is most informative for me. I just read not to use galvanized feeders because of the presence of zinc. Now I'm confused, but I guess if I watch the feeders for any spots, etc. it may be okay.