Corrosion behavior of AZ۹۱ alloy with plasma electrolyticoxidation coating in simulated body fluid solution

Recent research in orthopedic implant materials has focused on the use of magnesium alloysas a base material due to its mechanical properties similar to that of human bone. Rapid corrosionof magnesium materials in aqueous environments poses a significant hurdle to their applicationas a biomedical implant. Plasma electrolytic oxidation (PEO) is one potential coating technologyfor the improvement of the corrosion resistance of magnesium and its alloys. The processingparameters of PEO, such as the applied voltages, current density, duty cycle, oxidation time, andthe electrolyte concentrations, are some of the major factors which determine the quality of thecoatings in terms of corrosion behaviors in simulated body fluid (SBF). In this study, the sampleswere treated for ۲۰ min at ۵۰, ۱۰۰, ۱۵۰ mA.cm-۲ current densities. The phase composition,morphology, chemical composition, thickness, roughness and corrosion resistance were studiedby X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energydispersivespectroscopy (EDS), thickness measurer, surface roughness tester andpotentiodynamic polarization in SBF solution. It was found the thickness of the PEO coatingincreases with increasing current density. It is generally expected that a thicker coating gives riseto better corrosion resistance. But the variation of corrosion resistance with thickness is notlinear. This indicates that the defect density is the dominating influence rather than the coatingthickness. Increasing the coating thickness did not reduce the amount of open defects thatprovided access for the SBF to the AZ۹۱ alloy substrate.

کلیدواژه ها:

Orthopedic magnesium implant ، PEO method ، Thickness ، Corrosion resistance ، SBF solution