Alginate/Bioglass® composite coatings on stainless steel deposited by direct current and alternating current electrophoretic deposition

Direct current (DC) and alternating current (AC) electrophoretic deposition (EPD) approaches involving different number of EPD cycles were developed for the fabrication of alginate/Bioglass® composite coatings from water-based suspensions. The high stability of the colloidal suspension was confirmed by zeta-potential assessment and the properties of coatings deposited from both DC-EPD and AC-EPD were quantitatively compared by using a range of characterization methods. The deposition yield and coating composition were determined by mass and thermogravimetric analysis. Coatings with different microstructure and thickness were observed by scanning electron microscopy. Significant differences in surface roughness and hydrophilicity (determined by water contact angle measurement) of coatings obtained by DC-EPD and AC-EPD were identified and discussed. The coating adhesion strength and corrosion resistance were evaluated by standard tape test and electrochemical method, respectively, and the experimental data showed the superior adhesion and corrosion resistance of AC-EPD coatings compared to DC-EPD coatings. In order to investigate the in vitro bioactivity, all coatings were immersed in simulated body fluid for 7 days. Results from Fourier transform infrared spectroscopy (FTIR) analysis showed the typical characteristic peaks of hydroxyapatite formed on both DC- and AC-EPD coatings. Based on the results of this study, bioactive alginate/Bioglass® coatings are proposed as suitable candidates for applications in dental and orthopedic metallic implants and for bone tissue scaffolds.