Deposition and properties of novel microcrystalline Mg alloy coatings

Abstract

The present work gives and overview of the deposition, microstructure and corrosion properties of magnesium based supersaturated coatings for the corrosion protection of standard magnesium alloy components. Such protective surface layers with high corrosion resistance were produced using physical vapour deposition techniques at different particle energies, such as magnetron sputtering, ion beam sputtering and cathodic arc deposition. For all these films, a homogeneous microcrystalline morphology with a highly oriented basal texture was observed. The solubility limit of all alloying elements studied was largely extended beyond the thermodynamic equilibrium. Thus highly supersaturated single phase coatings free of localised corrosion and/or microgalvanic corrosion effects between different phases were observed, showing low corrosion rates. Furthermore, the less noble corrosion potentials of some alloying systems compared to standard cast or wrought magnesium alloy substrates allow a cathodic protection of the substrate material by the coating.