An apparatus for applying a liquid coating to a deicer composition, methods of applying a liquid coating to a deicer composition, and solid deicer compositions that have been coated using the apparatus or method of the invention are disclosed. The apparatus includes a screw conveyor that has a housing, at least one screw with a plurality of flights, an inlet for uncoated deicer, an inlet for a liquid coating composition, and an outlet for deicer coated with the liquid coating composition. The screws contain protrusions or tabs that extend from the surrounding surface of the screw. These protrusions or tabs aid in the mixing of the solid deicer and the liquid coating composition in order to provide a well-mixed deicer that resists caking while avoiding losing the coating composition to leaching.