Fig. 1. (a) Surface and (b) cross-section SEM micrograph of the PEO coating in Mg3Zn0.4Ca alloy. (c) XRD pattern of PEO coating.






Fig. 2. (a–d) Evaluation of the withdrawal speed of dip coating of 3D PLA printed pieces in PLA polymer solution. (e) Evolution of average of pore size.


Fig. 3. Scheme of the formation of PLA layer at several withdrawal speeds.



Fig. 4. (a–d) Secondary electron top view image and (e–h) backscattered electron secondary electron cross-section images of PLA and PCL on PEO-coated samples at 25, 50, 75 and 100 mg/mL.



Fig. 5. Variation of (a) pores size and (b) thickness at different conditions of studied as polymer concentration, number of dipping cycles and withdrawal speed.



Fig. 6. (a–c) Secondary electron top view and (d–f) backscattered electron cross-section images of PLA and PCL on PEO-coated samples at 1, 2 and 3 cycles at 75 mg/mL of polymer concentration and 2 mm/s.



Fig. 7. (a–c) Secondary electron top view and (d–f) backscattered electron cross-section images of PLA and PCL on PEO-coated samples at withdrawal speed of 0.5, 1 and 2 mm/s at 75 mg/mL of polymer concentration and 2 cycles.



Fig. 8. (a, c) SE plan view micrographs and (b, d) BSE cross-section of SEM images for (a, b) PLA/-coated Mg3Zn0.4Ca and (c, d) PCL/PEO-coated Mg3Zn0.4Ca at 75 mg/mL, 2 cycles and 2 mm/s of withdrawal speed.



Fig. 9. Hydrogen evolution of Mg3Zn0.4Ca, PEO and PCL-coated specimens after 13 days of immersion in inorganic part of α-MEM at 37 °C.







Fig. 10. Backscattered cross-section images of (a–d) PEO treated surface and (e–h) PCL-coated samples after (a, c, e, g) 4 h, and (b, d, f, h) 8 h of immersion in inorganic α-MEM at 37 °C.



Fig. 11. SEM images of (a, c) secondary electron top view and (b, d) backscattered cross-section images of (a–c) HHC-PLA and (d–f) HHC-PCL-coated samples.



Fig. 12. Hydrogen evolution of bulk material, PEO, PLA and PCL-coated samples after 17 days of immersion at 37 °C.





Fig. 13. Secondary-electron cross-section image of PLA- (a–c) and PCL- (d–f) based HHC on Mg3Zn0.4Ca alloy after 17 days of immersion in inorganic α-MEM solution. (c, e) EDS analysis of the corrosion products from PLA and PCL-coated specimens.


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