Electrophoretic deposition of chitosan/gelatin/bioactive glass composite coatings on 316L stainless steel: A design of experiment study

Electrophoretic deposition (EPD) of composite coatings based on chitosan, gelatin and copper doped bioactive glass (Cu-BG) particles on 316L stainless substrates (SS) was investigated. Despite the fact that EPD offers easy control over the thickness and morphology of the produced coatings, the optimization of the EPD process is a tedious task due to the fact that a high number of variables (applied voltage, deposition time, distance between the electrodes, concentration of the suspension and pH of the suspension) is involved. Therefore, we used the Taguchi Design of Experiments (DoE) approach for accurate and economical process (reduced number of experiments) optimization. The suspension composition (chitosan, gelatin and Cu-BG ratio) and electric field related parameters (voltage and time) were optimized by L-25 type Taguchi array. The best coatings were obtained at the applied voltage of 30 V, deposition time of 5 min and the concentration ratio between chitosan/gelatin was 50:50 (vol%). Scanning electron microscopy (SEM) images revealed that Cu-BG particles were fairly homogenously dispersed in the chitosan/gelatin matrix. Fourier transform infrared spectroscopy (FTIR) and energy dispersive spectroscopy confirmed the presence of chitosan, gelatin and Cu-BG particles (qualitatively). The tape test (ASTM D3359-97 and B571-97) elucidated the appropriate adhesion strength of coatings (obtained by EPD using optimized parameters) for orthopedic applications. Moreover, chitosan/gelatin/Cu-BG coatings exhibited suitable hydrophilicity.