Page 71 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

IMPROVEMENT OF CORROSION RESISTANCE OF COMMERCIAL PURE MAGNESIUM AFTER ITS MODIFICATION BY SINGLE AND TWO-STEP ANODIZATION
The chemical composition of the coatings was determined by XRD (Fig 5) and EDS (Table 3). The grazing incidence XRD analysis was carried out on anodized samples due to the high intensity of the substrate peaks that hid coating peaks, therefore, a grazing angle of 2° was used to characterize the crystalline composition. All the samples showed magnesium oxide as the main crystalline phase, neither Si nor F were detected forming other compounds. EDS values included in Table.3, still include a lot of substrate material as observed by the high amounts of Mg detected. How- ever, these values are useful to analyze the effect of the additives. This analysis evidenced a similar incorporation of silicon from the base anodizing solution for all samples, except for the sample treated in NAF, in which Si is much lower and only in this case fluoride was detected.
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Fig. 5. XRD patterns of samples of Mg samples anodized. The main component of the all anodic films was Magnesium oxide. NAF(A), HMT (B), MAN(C), NAF-HMT (D) and NAF-MAN (E).
Table.3. Composition of the coatings by EDS (% weight-mapping)
The mean roughness (Ra) of the coatings with different anodic coatings as measured by AFM ranged from 160 to 198 nm (Table 4). This was similar to untreated c.p Mg which had and Ra of 172 nm (Fig. 6). Additionally, Rq values were pretty similar for all the treatments and ranged from 205 to 256 nm (Table 4). From the AFM images is observed how in all cases the polishing lines remain being observed after anodization. This feature is less evident for the thicker coatings MAN and NAF MAN. However, both SEM and AFM show that surface morphology varies with anodization, this features will probably affect more other characteristics of the surface, such as wettability and cell-material interactions
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