EIS and corrosion behaviour of plasma sprayed layers of Al and AlCr6Fe2 on AZ91

This work presents the preparation of coatings of aluminium and AlCr6Fe2 alloy on magnesium alloy AZ91 with metallurgical bonding. Coatings were prepared by plasma spraying system WSP®-H 500. This metallurgical bond (sub-layer) is formed by an eutectic structure consisting of the intermetallic phase Mg17Al12 and the solid solution of magnesium and aluminium. In this work, the layers were studied using electrochemical impedance spectroscopy (EIS). It was shown that there is a several fold increase of the polarization resistance (Rcν) of plasma-sprayed coatings of aluminium and AlCr6Fe2 alloy, compared with uncoated AZ91 in borate buffer with pH 9.1.