Abstract: A device for protecting, before use, threadings and butt-type joint bearing surfaces (66) which contribute to the hermetic character and to the threadings (55) of male or female joining regions of metallic tubes.It comprises a ring (56) of plastics material which is screwed onto the threading (55) of the metallic tube (54). A first lip (63) rests in a resilient tight manner on the joint bearing surface (66) in the vicinity of the inner edge (65) thereof. A closed annular volume (67) protects the bearing surface of the joint. A second lip (59) protects the threaded region.This device is used in particular for the frustoconical joint bearing surfaces of tubes with a frustoconical threading. The ring can be clothed by a metallic reinforcing sleeve (68).