this is how i did it.
first go to home depot and pick up the swimming pool muriatic acid. its about $10 for 2 gallons.
muriatic acid dissolves rust. when i did mine i had the armor plate off that held the latches so i set the plates up on some boards so that the latches hung down. i then used a small bucket filled with muritic acid under the latches so that they where completely submerged. i let these sit over night then pressure washed them. i think one hour or less would have been fine though.
make sure the small hole in the latch is clear so the acid can flow into it. use a pressure washer to clean it out. once its pressure washed, tap the mounting rod into the latch with a small hammer to get it started working. this worked great for me.
be carful of this muritic acid. it smells really bad and you don't want to get it on you, so be carful how you pressure wash.
also if you use this on cast iron it will start to dissolve the metal if you leave it in there to long.

