Pulse electrodeposition of hydroxyapatite/chitosan coatings on titanium substrate for dental implant

In this work, calcium phosphate/chitosan coatings were produced by the pulse electrodeposition method with variation of the deposition cycle and contents of chitosan solution. To investigate the morphology of the crystals and the electrochemical properties of hydroxyapatite/chitosan coating, a uniform hydroxyapatite coating was applied on the Ti-6Al-4 V substrate using the pulse voltage electrodeposition method. The coating formed in the as-deposited condition was identified as dicalcium phosphate dihydrate (DCPD) (brushite), which was converted to hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂) after immersion in 1 M NaOH at 80 °C for 2 h. The XRD patterns confirmed the formation of DCPD and HA. During electrodeposition, the H₂PO₄ ⁻ ion was reduced and the reaction between Ca²⁺ ions and the reduced phosphate ions induced the formation of DCPD, which was converted to HA following treatment in NaOH. The coatings were composed of 5 to 20% chitosan by volume. Homogeneous nano-size deposits were formed under the controlled deposition period of 15 cycles and chitosan content of 15 v%. The composite coatings showed significant improvement in corrosion resistance compared to the bare Ti-6Al-4 V substrate.