Pump unit for a centrifugal pump and centrifugal pump

A pump unit for a centrifugal pump for conveying a fluid, comprising:

• a pump housing including an inlet and an outlet for the fluid;
• a rotor arranged in the pump housing to convey the fluid, the rotor configured to be rotated about an axial direction, the pump unit being configured to contactless magnetic levitate the rotor and contactless magnetic drive the rotor, the pump housing having a bottom part and a cover to close the bottom part, the bottom part having a cylindrical cup to receive the rotor and a substantially ring-shaped first sealing surface to configured to cause sealing interaction with the cover, and the cover having a substantially ring-shaped second sealing surface configured to cause sealing interaction with the first sealing surface, one of the first and second sealing surfaces being a ribbed surface with at least one radial sealing rib extending in a circumferential direction along the entirety of the one of the first and second sealing surfaces, and an other of the first and second sealing surfaces is a smooth surface;
• and
• a radial reinforcing element configured in a ring-shaped manner and extending radially outwards around the first and second sealing surface, and the radial reinforcing element being a metallic ring encapsulated with a coating of a plastic material.