What really get the job done is a big, powerful 7" angle grinder/sander with a welder's cup wire brush on it. The wires are almost as big as a cheap coat-hanger and they are braided or grouped in 1/4" bundles around the circumference of the wheel. There is a non cup radial version as well. These two will throw the old sealer completely across the garage. You can do the whole floor in less than an hour. Go rent the grinder and buy one or both of these for about $15 ea.
AFA replacement goes, pitting is nothing unless you are building a show/race car and all the interior metal will be exposed and painted. If it feels strong and you can't poke through it with a screw driver, clean off the rust scale and treat it with phosphoric acid and then rust encapsulating paint.
Search for all the rust info you'll ever want to know using the words "POR 15." Or, just use the word rust and my user name. That alone will bring up enough posts to keep you busy for a couple days.
