The present invention relates generally to a bio-degradable implant based on magnesium having a reduced corrosion rate and to a method for the production of such an implant. It is a a method for treating a surface of a bio-degradable metallic implant comprising the following steps: providing a dispersed system comprising a colloid-dispersed apatite and adding an apatite powder to the dispersed system, subjecting an implant to the dispersed system such that a surface of the implant which is to be treated is immersed in the dispersed system wherein the implant comprises a magnesium based alloy, applying an AC voltage difference between the implant as a first electrode and a second electrode positioned in the dispersed system for generating a plasma electrolytic oxidation on the immersed surface of the implant so that the immersed surface is converted to an oxide film which is at least partially covered by apatites formed by the colloid-dispersed apatite and the apatite powder. The evolution of corrosion induced hydrogen gas evolution is decreased and osseointegration is improved.