A ROTARY ROOT''S TYPE PUMP FOR CONVEYING VISCOUS FLUIDS WITH CORROSIVE PROPERTIES IN WHICH EACH OF TWO ROTORS HAS A BODY OF METAL TO WHICH STRIPS OF A NON-CORROSIVE AND WEAR-RESISTANT PLASTIC ARE REMOVABLY SECURED WHICH FORM AT LEAST THE OUTWARDLY PROJECTING ROTOR HEADS WHICH ARE SLIDABLE ALONG THE INNER WALL OF THE PUMP HOUSING WHICH IS PROVIDED WITH A COATING OF ENAMEL AND ALONG THE CORE OR THE REDUCED PARTS BETWEEN THE HEADS OF THE OTHER ROTOR.