Corrosion Studies on the Hydroxyapatite-Gelatin-Mono Layered Graphene Oxide Nanocomposite Coating on SS316L

Stainless steel 316L (SS316L) is a good candidate for metal implants due to its excellent tensile strength and high corrosion resistance. However, its surface needs to be improved to enhance biocompatibility, bioactivity, and antimicrobial functions. Among bioceramics, hydroxyapatite (Ca10(PO4)6(OH)2) is widely used in medical applications due to its mineral composition, which is similar to the natural hard tissues of the body, and its biomimetic morphology. Chitosan possesses attractive biological properties such as good biodegradability, non-toxicity, biocompatibility, and cellular bioavailability. Graphene oxide demonstrates antibacterial activity against bacteria, fungi, and viruses, which can help limit cancer-causing infections in surgeries. Accordingly, an HA-based nanocomposite (HA-CS-GO) was deposited on SS316L sheets by electrophoretic deposition. Nanoparticle HA was synthesized via the sol-gel method. The coating was applied at 80V for 1 minute. To study the products and coating, various analyses were employed, including XRD, SEM, FTIR, electrochemical impedance spectroscopy (EIS), and polarization analysis. The results confirmed the successful synthesis of HA. The nanocomposite coating (thickness ~12.7 µm) was properly deposited on SS316L. The corrosion resistance improved with the coating; the current density decreased from 7.6 to 1.4 µA·cm⁻². The mechanism of corrosion was evaluated by EIS data. The corresponding equivalent circuit was proposed, and the dielectric capacitor and resistance values were estimated.