Corrosion Protection of Magnesium Alloys via Diffusion Coatings by the Slurry Coating Methode

Abstract

This thesis investigates the creation of diffusion layers by the slurry coating method using Al and Zn powders on AZ31 and AZ91. The method was applied at 450°C, 420°C and 380°C in an $Ar/H_{2}$. Secondary electron microscopy, backscattered electron microscopy, energy dispersive x-ray spectroscopy (EDX) and potentio dynamic measurements were used to classify the diffusion layers. Diffusion coatings were successfully produced at a temperature of 450°C for a Zn slurry and a mixed Al-Zn slurry. These diffusion layers were in general rich on zinc and several hundred $\mu m$ thick. Electrochemical measurements showed that $E_{corr}$ became more anodic by a zinc rich diffusion layer, but $i_{corr}$ did not change. All in all, it could be shown that diffusion layers could be produced by the slurry coatings method for Zn and Al-Zn slurries and opportunities for further process optimisations addressed.