Surface rust prep before sound deadning

Hi All, I will be redoing the interior on my 67 notch back barracuda and am interested in how you guys prep before laying down a sound deadning material. The floors front and back are original and solid with light surface rust. I want to put something on the surface rust to stop it from getting worse before the deadning material to make sure no issues happen later down the road. how have you guys gone about doing this?

Any thoughts? Recommendations on deadning material you have had good experiences with would be appreciated also.

Thanks FABO!