Magnesium (Mg) and its alloys have recently arisen as promising biomaterials fulfilling the requirement of functional bone tissue support and aid to its regeneration. Permanent non-biodegradable implants such as titanium (Ti), cobalt–chrome, and stainless steel can cause inflammation, toxicity (infection), and sometimes improper bone healing. Thus, an additional or alternative surgical procedure is required to remove these implants from the body after the healing process. Mg shows bioresorbable, biodegradable, and biocompatible properties. Furthermore, it degrades without causing any toxicity, and henceforth, additional surgery can be avoided. Apart from its biocompatible properties, it also demonstrates good mechanical properties like low density and elastic modulus in the range compatible with bone structures [3].
Despite all the virtues of Mg, its swift corrosion rate and degradation in an in vivo atmosphere may cause early fracture before complete bone healing, greatly hindering its application as an implant material. Furthermore, gas evaluation due to fast degradation may cause encapsulating processes. To overcome such corrosion behavior, a refinement on Mg-based screw implants by a PEO (plasma electrolytic oxidation) process is
developed, ensuring a dimensional stability of 2 months in a corrosive environment. The current work was accomplished under various PEO regimes to obtain the desired thickness and other essential properties best suited for Mg-based screw implants.
The microstructure, chemical composition, and surface properties of the PEO were investigated and compared via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). SEM/EDS analysis illustrated the morphology of PEO, the elemental/phase distribution, and the formed barrier layer at the substrate/oxide layer interface for different process parameters, drastically altering the corrosion behavior and mechanical properties. The corrosion resistance of various PEO surfaces was studied by using electrochemical analysis techniques such as electrochemical impedance spectroscopy in 0.9-wt% NaCl solution at 36°C. The results showed significant improvement in the corrosion behavior of PEO samples when compared with uncoated Mg surfaces.
