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 (R_cν) of plasma-sprayed coatings of aluminium and AlCr₆Fe₂ alloy, compared with uncoated AZ91 in borate buffer with pH 9.1.