A rotor (1-3) moulded of plastic material, intended for rotary installation in a cavity of a pump body and for reception of one or more vanes forming the pumping members, characterized in that at least a part of the surfaces thereof, intended to undergo sliding displacements against other pump members, is covered by at least one metallic foil (4) caused to adhere to the subjacent surface of plastic material. The metallic foil can consist of a steel sheet or an aluminum alloy sheet, intended for reducing the resistances to the sliding as well as for mechanically reinforcing the rotor. The metallic foil can be fastened to the plastic material body (1) of the rotor by a co-moulding operation, or it can be mechanically fixed to the body (1) of the rotor moulded of plastic material.