Something like this?

If you have Adobe Photoshop (30 day trial available) there are quite a few 'rusty' old text styles and actions available for free at
The Adobe Studio Exchange. You have to sign up to get access but that's free, too.
Or, if you don't have or don't want Adobe PS, you could maybe try Flaming Pear's free 30 day demo of 'Superblade Pro' which works in Paintshop Pro if you have that? There are loads of rusty presets available for it all over the net. Try a Google search for +Blade Pro+presets+rusty and it should turn up something like this
http://www.dragonmyth.com/ariel/blade/blade12.htmOr, if you wanted to do it from scratch you could try here
http://arc.ireed.net/misc/prevd/arc6/tutorials/psp/Make your text, select it with the magic wand and then fill with the rust texture?
Hope this helps

Gilly