Metal coating method for plastic outer shape requiring robustness

A metal coating method for a plastic outer part of a prosthesis requiring robustness, the metal coating method comprising:

• providing the plastic outer part of the prosthesis, the prosthesis having a joint part;
• performing a cold plasma treatment by treating the plastic outer part with cold plasma to introduce a polar functional group to a surface of the plastic outer part;
• forming a metal coating layer, by an electroless plating method, on the surface of the plastic outer part which has been treated with the cold plasma, the electroless plating including depositing the metal coating layer with a reducing agent without flowing electricity;
• and
• heat-treating the plastic outer part and the metal coating layer thereon to increase an adhesive strength between the metal coating layer and the plastic outer part to 1,000 g/cm2 or more,
• wherein in the forming of the metal coating layer, the metal coating layer comprises an alloy containing chromium, such that a tensile strength to hardness (N/mm2/Hv), defined as the tensile strength (N/mm2) of the plastic outer part with the metal coating layer thereon with respect to a hardness (Hv) of the metal coating layer, is 3.00 N/mm2/Hv or more, and
• wherein the metal coating layer includes a portion formed on the joint part of the prosthesis, and the portion of the metal coating layer formed on the joint part contains organic and inorganic particles of polytetrafluoroethylene (PTFE) or a boron (B) compound to reduce friction of the joint part,
• wherein, in providing the plastic outer part of the prosthesis, a plastic containing plant powder or poly ethic acid (PLA) is used as the plastic outer part of the prosthesis.