Tetanus is often associated with rust, especially rusty nails, but this concept is somewhat misleading. Objects that accumulate rust are often found outdoors, or in places that harbor bacteria, but the rust itself does not cause tetanus nor does it contain more of the bacteria that causes tetanus.
The rough surface of a rusty nail merely provides a prime habitat for the tetanus bacteria to reside, and the nail affords a means to puncture skin and deliver the bacteria to the wound.
Just thought you'd like to know. Thanks Wikipedia!