electrophoretic deposition of organic/inorganic based nanocomposite coating on biodegradable mg alloy: characterization and corrosion behavior

The high degradation rate of magnesium implants in the body fluid is one of the challenges of their use in orthopedic applications, for which solutions must be provided. for this purpose, in this research, a carboxymethyl cellulose (cmc)- akermanite (ak) nanocomposite coating was applied on an az31 magnesium substrate through the electrophoretic deposition (epd) process. cmc, which is an organic part of the nanocomposite coating, was chosen for the purpose of the coating matrix, while akermanite, which is an inorganic component, was used as the filler particles of the coating. investigating the morphology and chemical bonding of the coating, as well as phase characterization, were done using scanning electron microscopy (fe-sem), fourier transform infrared spectroscopy (ftir), and x-ray diffraction (xrd). eds analysis (energy-dispersive x-ray spectroscopy) was used to show the presence of elements in the applied coating, which confirmed the presence of ca, si, o, and mg. the presence of these elements was due to the presence of akermanite in the coating, and xrd results confirmed the presence of this phase. c-o-c, -ch2 and hydroxyl bonds caused by the presence of cmc in the ftir spectrum of the nanocomposite coating, along with the functional groups related to akermanite such as o-mg-o, o-si-o, and si- o, the successful application of the cmc/ak nanocomposite coating produced. to assess the wettability properties, the contact angle test was conducted, which showed that the application of cmc/ak nanocomposite coating decreased the contact angle from 69.62±3.72 o to 46.12±2.31 o . increasing the wettability of the implant surface is desirable in bio-orthopedic applications. in addition, the corrosion behavior of uncoated and coated magnesium az31 samples in simulated body fluid was compared using electrochemical impedance spectroscopy and tafel polarization. also, the effect of voltage on the coating morphology was investigated. the obtained results showed that the cmc/ak nanocomposite coating, which was applied at 40 v voltage, significantly improved the corrosion resistance of the magnesium substrate due to its uniform structure without pores and cracks. so that the resistance of the charge transfer and the film (or coating) of the substrate increased from 39.23 and 162.2 (ohm.cm 2 ) to 132.6 and 905.8 (ohm.cm 2 ) for the cmc/ak nanocomposite coating sample, respectively. by comparing the impedance modulus of the bare and cmc/ak samples, it was concluded that the corrosion resistance is improved in all frequency ranges by applying the nanocomposite coating. importantly, the corrosion current density (i corr ) of the coated sample was 5.85×10 -6 (a/cm 2 ) and that of the uncoated mg alloy was 5.1×10 -5 (a/cm 2 ), indicating a substantial decrease in i corr . also, according to the polarization results, the corrosion potential (ecorr) decreased with the application of the coating, which indicates a decrease in the tendency of the substrate to participate in electrochemical corrosion reactions. therefore, the cmc/ak nanocomposite coating was introduced as a biocompatible coating in order to improve the corrosion resistance of magnesium implants.