Electrochemical Characteristics of Octacalcium Coatings on Plasma Electrolytic Oxidized CW-titanium Surface

摘要

Pure titanium and its alloys are primarily used in dental implants. However, surface inactivation can delay the healing process after clinical surgery. As a result, various studies are exploring the coating of bioactive mate rials. OCP (Octacalcium Phosphate) is one of the naturally occurring calcium phosphates in living organisms. It degrades safely in biological conditions and is known as a precursor to biological apatite crystals found in bones and teeth due to its crystall ographic similarity. The corrosion impact of mechanically and electrochemically coating OCP onto cold-worked pure titanium(CW -Ti) surfaces treated by plasma electrolytic oxidation (PEO) was comparatively investigated. The mechanical coating process was car ried out using 30g of OCP powder and zirconia balls at 35rpm for 6 hours, while the electrochemical coating process involved electrodeposition using a solution of 0.042M Ca(NO 3)2 and 0.025M NH 4H2PO4. The corrosion resistance of the coatings was measured in 0.9% NaCl solution using AC impedance and potentiodynamic polarization. Additionally, FESEM was used to analyze the microstructural characteristics before and after PEO treatment and corrosion testing. The experiments were repeated under consistent condit ions to ensure statistical significance. The results of this study showed differences depending on the coating method. The mechanical method resulted in OCP filling the PEO pores, while the electrochemical method caused OCP to form around the pores, leading to different outcomes. However, both methods exhibited higher impedance compared to samples without OCP, indicating that OCP delayed the diffusion or mass transport of ions or reactants at the electrode-electrolyte interface. This led to the formation of a protective layer on the electrode surface, reducing the overall corrosion rate. These findings confirm the potential of OCP coatings to protect against corrosion in implants. (Supported by National Research Foundation of Korea: 2023-GJ-RD-0008; hcchoe@chosun.ac.kr).