There's a ton of afflictions, but it seems odd to me that the intuitive but extremely damaging real-world effect due to rust is not one of them.
Tetanus can be lethal and comes due to rust -- so a
natural thing to have in a game where we stick sharp metal objects into
our opponents. To the charge that it's too real-life, we DO use arsenic to induce blindness and we do have epilepsy, etc. I was thinking for the effect temporary paralysis combined with continuous damage,
because as I recall tetanus works by making limbs lock up. So, different from ordinary paralysis. If you have
better ideas for the effect, I am not exactly a combat master.