Both double cut and satin are finishes, NOT a coating. Both leave the blade metal exposed and the knives should be dried and have some sort of anti-corrosive treatment (oil, wax, WD-40, Tuff cloth) before putting them away.

Several folks have reported that the double cut tends to rust more easily than satin due to the microscopic pits. With either satin or double-cut I would recommend keeping the blades clean, dry, and treated for storage.