Fill a 5-gallon bucket about 3/4 full of water. Add 1 to 2 cups of powder detergent. Pour some of the water over a section of the concrete floor. Scrub the moistened concrete with a broom to remove surface dirt. Repeat until the entire concrete surface is clean. Rinse the surface with clean water from a garden hose.
Fill a 5-gallon bucket about half full of water. Add 1 cup of rust stain remover into the water. Put on a pair of rubber gloves and dip a rag into the water. Wring the rag out over the rust stains on the concrete surface. Scrub the rust stain to clean it off the concrete.
Wait about 24 hours for the concrete surface to completely dry. Attach a paint roller to an extension pole. Dip the paint roller into concrete sealer. Roll the sealer onto the concrete surface in a back and forth motion, the same way you would if you were painting a wall. Cover the entire concrete surface with sealer.