Dear Ruhl,
Rust, the stuff you find on your barbell plate, is iron (III) oxide. The iron in rust is Fe3+. Your body can only utilize Fe2+, not Fe3+. Rust is toxic, and scraping off little specks does not mean you won't risk poisoning as the others have highlighted.
Furthermore, do you really need iron supplements? If you eat meat (especially red meat) on a frequent basis, you probably do not need iron supplementation.
Please do not scrape the specks of iron off your barbell plate.
Godspeed, and happy HSTing.