There are plenty of rusty metals at Mayang's Free Textures. Theire licence is reproduced below:

These textures are Copyright ? Mayang Murni Adnin, 2001-2004. They have all been taken by our own cameras or created by ourselves. They are free to use for all uses, whether commercial or non-commercial (you may incorporate them into your work with no requirement to pay us any licensing fee etc). However, you may not sell any or all of these textures. Any redistribution of any of the textures should credit the authors and this web site, and a maximum of 50 of these textures may be redistributed together.