Improving the inflammatory-associated corrosion behavior of magnesium alloys by Mn3O4 incorporated plasma electrolytic oxidation coatings

Biodegradable magnesium alloys for orthopedic bone fixation have been introduced for various fields of application. The corrosion resistance of magnesium implants weakens in physicochemical environments and is further compromised during post-implantation inflammation. In this study, Mn3O4-incorporated plasma electrolyte oxidation (PEO) coatings were developed on Mg-Zn-Ca substrate through two approaches: the addition of KMnO4 salt and the inclusion of Mn3O4 nanoparticles into the electrolyte composition. Incorporating additives into electrolytes led to a reduction in surface porosity and an increase in coating thickness in both synthesis approaches. The electrochemical and immersion corrosion tests were conducted under simulated normal conditions and inflammatory conditions, where inflammatory solutions were prepared with the addition of hydrogen peroxide (H2O2) and hydrochloric (HCl) acid. Both corrosion studies revealed that inflammation significantly increased the corrosion rate of the uncoated Mg-Zn-Ca biomaterial, escalating from approximately 2 mm·y-1 to 16 mm·y-1. Moreover, corrosion studies showed that the composite PEO coatings, incorporating Mn3O4 nanoparticles (MnPR-PEO), demonstrated superior corrosion performance among all coated samples. Potentiodynamic polarization results indicated a substantial reduction in corrosion current density, decreasing from 73.9 μA·cm−2 for basic PEO coatings to 5.5 μA·cm−2 for MnPR-PEO coatings. The improved performance of Mn3O4-incorporated PEO coatings, attributed to their catalytic H2O2 scavenging, suggests promise for magnesium implants, offering enhanced corrosion resistance and potential biomedical application benefits.