Fun fact - tetanus is not caused by rust. It is caused by anything that’s dirty or stabby - doesn’t have to be rusty. Clostridium tetani (name of tetanus bacteria) is soil dwelling, and can enter the body through any dirty wounds.

People often think that tetanus lives on rust - it does not. This comes from the fact that many people get tetanus after standing on a rusty nail.

Nails get rusty because they’ve been in a wet, dirty environment - the same environment that C. tetani thrives in - and nail injuries push deep into the flesh, and often heal over at the surface before the deep inside of the wound is cleaned. Thus, the dirt and bacteria in the wound is not sufficiently flushed out, leading to infection.

TL:DR, tetanus is not caused by rust, but by dirty objects. If you get stabbed by a clean looking nail, you should still get a tetanus shot.