Abstract: A method is described for protecting piston cylinder devices against corrosion by a pressure resistant thermoset or cured material coating. At least the outer and inner cylindrical surfaces, for example, of a mine prop, that cooperate with a sealing device, are coated with a three-dimensionally cross-linked, cured or thermoset material having a sufficient thickness on the one hand for providing the intended protection against corrosion and on the other hand to avoid excessive radially directed elastic deformations of the coating. An additive is included in the coating to improve the dry lubricating characteristics, and thus the cooperation between the coating and the sealing devices. The three-dimensionally interlinked thermoset material fills all surface irregularities so that gas and water pockets, for example, in a mine prop, are avoided.

Abstract: A hydraulic steel mine prop having a bottom ram including an outer cylindrical tube with a cylinder foot at one end and a collar ring at the other end, and with a top ram coaxially guided in the bottom ram. The top ram is substantially a cylindrical tube with a piston at its one end, whereby the piston is guided in and sealed relative to the inner wall of the outer cylindrical tube, and with a prop head at its other end. The top ram includes an inner prop extension stop and a return spring formed as a screw spring which is secured with one end to the prop head and with the other end to the cylinder foot. The return spring passes through a bore in the piston, whereby a further tube which encloses the spring, is arranged coaxially between the prop head and the piston. The piston includes a safety valve which relieves the pressure from a compression chamber when the piston assumes a predetermined end position.