Cerium-based sealing of PEO coated AM50 magnesium alloy

Abstract

Environmentally friendly Ce-based sealing post-treatments were developed for PEO coatings on AM50 magnesium alloy. The influence of the Ce(NO3)3 concentration in the Ce bath and the time of the sealing process were evaluated in terms of morphological and structural properties using SEM, EDS and XRD. Ce content in the layer increased with both the amount of salt in the solution and the time of the sealing post-treatment process due to a higher Ce product accumulation into the pores and cracks of the coatings. Sealed PEO coatings revealed an improvement in the corrosion protection properties as measured by electrochemical impedance spectroscopy. Differences in the corrosion resistance values for the sealed coatings indicate a strong relation between the parameters of the sealing process and its effectiveness, showing higher resistance for the sealed PEO coating developed after 3 h of immersion in 10 g/l Ce(NO3)3 sealing bath.