Cathodic bias control of current density and its impact on MAO coating formation and corrosion resistance of AZ31B magnesium alloy
Journal
Surface and Coatings Technology
Journal Volume
515
Start Page
132612
ISSN
02578972
Date Issued
2025-11-01
Author(s)
Abstract
This study investigates how varying cathodic current density, under a fixed total cathodic charge, influences the micro-arc oxidation (MAO) behavior of AZ31B magnesium alloy. By systematically adjusting the cathodic current density and duration, while maintaining a constant total cathodic charge, MAO coatings were fabricated and characterized. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were employed to evaluate the electrochemical performance and microstructural features of the coatings. The results reveal that coatings produced with cathodic current densities exceeding the anodic current density exhibited markedly lower impedance values (∼105 Ω·cm2), whereas coatings formed with cathodic current densities equal to or lower than the anodic current density showed significantly higher impedance (∼106 Ω·cm2). Cross-sectional SEM analysis further identified the presence of inward-growing atypical regions in the 4N sample, which lacked MgF2 enrichment at the substrate interface. This microstructural deficiency is proposed to contribute to the observed decrease in corrosion resistance. Overall, the findings demonstrate that cathodic current density critically influences the coating formation mechanism, microstructure, and corrosion performance of MAO-treated magnesium alloys.
Subjects
Cathodic current density
Corrosion resistance
Electrochemical impedance spectroscopy
Magnesium alloy
Micro-arc oxidation
Publisher
Elsevier B.V.
Type
journal article