Degradation of the mechanical properties of copper and copper based alloys after the treatment with telluride bismuth (Bi2Te3) at 570oC has been studied in the present work. The experiments were performed in a H2 deoxidizing atmosphere. The kinetics of embrittlement of pure copper has been shown to be parabolic. Bi2Te3 was in the solid state and was not in direct contact with the copper specimens during the experiments, i.e. the plating was performed through the gas phase. The brittle fracture along the GB was observed after 3 point bending test. The surface of fracture was investigated with the use AES. It was shown that intergranular penetrations of liquid bismuth and bismuth from Bi2Te3 have different mechanisms.