An assembly, especially an assembly for an electrochemical sensor, includes a functional body of a first material, wherein the surface of the functional body is covered, at least sectionally, with a plastic, protective body. At least one free section of the surface of the functional body is not covered with a plastic, protective body, and wherein the free section is bordered by at least one surrounding, self-closing, boundary line, at which the plastic, protective body lies against the functional body. In the plastic, protective body, spaced from the boundary line, an elastic sealing ring lies sealingly against the surface of the functional body, in order to seal the functional body against a gap arising, in given cases, from the boundary line between the plastic, protective body and the functional body.