Characterization and Corrosion Studies of Amorphous/Nanocrystalline Conversion Coatings Formed by Applying Static Magnetic Field on AZ91 D Magnesium Alloy

Abstract

The present work explores an environmental friendly method for forming conversion coatings on AZ91D magnesium alloy by applying a static magnetic field. An amorphous / nanocrystalline conversion coating was developed on magnesium alloys in a phosphate-permanganate aqueous solution under a 0.5 Tesla magnetic field. The examinations of the microstructure and phase compositions reveal that the conversion coating is composed of an amorphous structure and nanocrystalline structure with mean size less than 10 nm. In a corrosive chloride solution, the amorphous/nanocrystalline conversion coating with an artificial defect were investigated by scanning vibrating electrode technique (SVET)/ scanning ion-selective electrode technique (SIET) system. The micro-electrochemical results reveal that the amorphous / nanocrystalline conversion coating as a good barrier layer can provide effective corrosion protection for AZ91D magnesium alloy.