The present article addressed the effects of Al2O3 and CuO additives on bioactivity and protective behavior of SiO2-Na2O-CaO-P2O5 double-layer glassy coating on 316 L stainless steel. For this purpose, several coatings with different Al2O3 (0, 3, 6, and 12 wt.%) and CuO (0, 1, 2, and 3 wt.%) contents were deposited by sol-gel dip coating. Scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), in vitro bioactivity assay, potentiodynamic polarization (PDP), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the samples. The incorporation of Al2O3 up to 6 wt.% decreased the formation of cracks and improved the anti-corrosion behavior where, the corrosion current density was 0.048 μA.cm−2. Addition of Al2O3 up to 3 wt.% could effectively improve the bioactivity as it facilitated the hydroxyapatite (HA) formation (21.98 wt.% after immersion in SBF for 7 days). Thus Al2O3 content of 3–6 wt.% was determined as the optimal value, providing the coating with thickness of 3 µm, mean roughness of 98 nm, and adhesion strength of 4.3 MPa. Results also revealed that incorporation of CuO up to 3 wt.% modified the coating structure such that the mean particles size of the coating declined to 416 nm from 1368 nm.
Tohidifar et al. (Fri,) studied this question.