Protective Coatings for Magnesium Alloys

Abstract

Magnesium is the lightest construction metal. Its alloys offer facile workability and excellent mechanical properties. This makes magnesium an attractive material especially for transport and electronic industries. However, this highly reactive metal demands outstanding corrosion protection. Because most established coatings are based on organic or organic/inorganic hybrid materials, they lack thermal and mechanical stability. Environmentally compatible and at the same time purely inorganic coatings can not be applied on the thermally precarious magnesium alloys by conventional techniques. Due to their large surface area and short diffusion paths, compacts made of nanoparticles densify at temperatures far below their melting point [1]. Thus originating from SiO2 nanoparticles dense, crack-free protective coatings with a thickness of up to several microns could be applied onto the wrought alloy AZ31 and the cast alloy AZ91 under mild conditions via dip coating, brushing or electrophoretic deposition techniques. Texture and composition of these coatings are studied e.g. by IR, AFM, REM. Their corrosion protection properties and resistance are investigated using standard tests as well as electrochemical methods