I checked it in the CS and there's no script attached to the sword, also there's nothing in it's enchantment about corroding armor, so looks like it may just be your imagination. Also you may have another piece of equipment on that has a corrode armor enchantment (though I'm not sure if that's even possible to put on armor).
Yeah, I did some testing, and it was just my imagination. I haven't played in a while, and I didn't remember the condition that the guards armor was at when they died before. During testing it was at about the same no matter what weapon I used, as long as it wasn't enchanted to do more damage.
I was trying do decide on whether to use blade or blunt on my new battlemage, and I guess I was just jumping at shadows trying to find a signature weapon for him. <_<