## 5 Conclusions  
The scope of the present paper was initially addressed to understand the corrosion mechanism and to evaluate by biocompatibility tests the possibility using such system as a targetable viable system for bioresorbable implants. The major drawback of using magnesium and its alloys in many engineering applications is its low corrosion resistance, especially when exposed to aqueous electrolytic environments. However, this characteristic may become an intriguing property for biomedical applications, where the in vivo corrosion of the magnesium-based implant, if adequately controlled, involves the formation of a soluble, nontoxic oxide and Mg ions that are harmlessly and easily excreted in urine. In addition, due to its functional roles and presence in bone tissue, magnesium may have stimulatory effects on the growth of new bone tissue [27; 28; 29; 30]. Thus, it is predictable that magnesium and its alloys could be applied as lightweight, degradable, load-bearing orthopedic implants, which would remain present in the body and maintain mechanical integrity over a planned, controlled time scale while the bone tissue heals, eventually being replaced by natural tissue using biomechanical approaches [31; 32; 71; 72]. The unfortunate complication is that pure magnesium can corrode too quickly in the physiological pH (7.4-7.6) and the high-chloride environment of the physiological system; polymer PHB was therefore investigated in our study as a potential magnesium alloy corrosion-controlling coating. SEM analysis showed that the morphology of the AZ31 magnesium alloy was changed, depicting smooth and flat features formed after PHB coating treatment. FTIR spectra confirmed the molecular and chemical composition for AZ31 and AZ31 coated with PHB. It indicated that AZ31 indeed formed a magnesium hydroxide layer on its exposed surface after hot water treatment. Wettability studies confirmed that PHB coating made the surfaces less hydrophilic. Static degradation and electrochemical experiments demonstrated that the corrosion rate decreased for PHB-coated AZ31 as compared to untreated surfaces. The corrosion controlling ability can be related to resistance to corroding molecules' diffusion to the metal surface, and to Mg ions' counter-diffusion to the solution, exerted by the polymeric film. The degradation rate can be then further reduced by increasing the polymeric film thickness and, hence, the diffusive hindering. This feature can allow specifically tailoring the coating thicknesses for different specific resorbable prosthetic applications. In vitro analysis by indirect MTS assay showed that the experimental group may promote the proliferation of cells due to the presence and control of the PHB polymer coating. The hemolysis rate of the material indicated that PHB coating was indeed effective to slow down the degradation rate of magnesium alloy. Finally, NO and T-AOC analysis displayed PHB coating showed good biocompatibility. This demonstrates that the PHB polymer coating can effectively avoid, in a potential clinical application of this Mg alloy, the detrimental effect of an intense and uncontrolled release in the body of Mg ions by reducing the metal degradation rate (which was evaluated. from the corrosion tests reported in Figure 4a. to be four times slower than that of the bare uncoated Mg alloy at 1.25 vs. 5.5 mg/cm\({}^{2}\)day) and hence reducing the concentration of magnesium ions around this potential resorbable implant. Moreover, due to the diffusive nature of the control exerted by the polymer coating, corrosion rates may be programmed to specific times and levels of Mg ion concentration by properly modifying the coating thickness. Conceptualization, G.W. and A.A.; methodology, D.A., S.L., L.W., R.A., and V.P. ; validation, Z.H., J.T., L.C., and S.G.; formal analysis, A.A. and Y.C. ; writing--original draft preparation, G.W. and A.A.; writing--review and editing, A.A.; visualization, R.A. and A.A.; supervision, G.W. and A.A.; funding acquisition, A.A., G.W.