Development of a plasma surface treatment for magnesium alloys to ensure sufficient wear and corrosion resistance

Extensive investigations of the authors showed the possibility of producing reliable plasma vapour deposition (PVD) hard coatings on magnesium alloys with good wear properties comparable to PVD coated steel or titanium based alloys. In presence of corrosive mediums crucial contact and pitting corrosion, induced by process related coating pinholes are the main failure mechanisms of coated magnesium alloys, even without any tribological load applied. The authors developed the new method of plasma anodisation to ensure acceptable corrosion resistance. In contrast to conventional anodisation processes the aqueous electrolyte is substituted by an oxygen plasma. The main advantages are that the process uses no toxic electrolytes, there is no waste and anodising and PVD-coating can be done in one process. The article gives a brief view of our extensive work starting from the first approach in PVD deposition of magnesium alloys up to the present work in establishing the plasma anodisation.