Page 55 - Magnesium-based supports for stem cell therapy of vascular disease - Mónica Echeverry Rendón

NOVEL COATINGS FOR COMMERCIAL PURE MAGNESIUM OBTAINED BY PLASMA ELECTROLYTIC OXIDATION THROUGH THE ADDITION OF ORGANIC ADDITIVES
With respect of the thickness, it was expecting a progressive increase with the increment of the applied voltage, however this effect was not that strong as it was with the others additives; all the coatings were in the range of 4.- 4.9μm. internal morphology of the coatings consisted of interconnected pores in the outer layer with a barrier layer of a about 0.7μm which was similar to the obtained in HMT.
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Fig. 8 Top-view SEM image of the surface (1000X and 5000X) and cross-section of c.p Mg treated with MAN at potentiostatic mode.
In Fig. 9, it has been plotted either the anodizing current density (galvanostatic tests) or the anodizing voltage (potentiostatic tests) against the thickness of the coating obtained in the different conditions studied here. As observed there is a direct relationship between both parameters (current density and voltage) and the thickness for all electrolytes. It is also seen how the additive employed and the anodizing method have a great effect on the rate of coating growth. For galvanostatic control, MAN induces the higher growth rates (see Fig. 9 Left), whereas for potentiostatic anodization, NAF leads to thicker coatings, despite of employing lower anodizing voltages (see Fig. 9 Right). This could be explained as NAF has the higher electrical conductivity of all the solutions employed.
Fig. 9 Coating thickness vs either applied voltage (potentiostatic mode) (Right) or current density (gal- vanostatic) (Left) for anodizing of c.p Mg in various electrolytes.
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