Synergetic effects of H2O2 concentration and pH value on corrosion behavior of biomolecular coatings on 3D-printed porous low elastic modulus titanium alloy scaffolds under equilibrium conditions

We investigated the synergistic effects of H 2 O 2 concentration and pH on corrosion behavior of biomolecular, type I collagen, coatings on 3D-printed porous low elastic modulus Ti–24Nb–4Zr–8Sn (Ti2448) alloy scaffolds under equilibrium conditions in simulated inflammatory environment ( i.e. , acidic environment containing H 2 O 2 ). Corrosion behavior in pH 7.4 or 5.2 simulated body fluid (SBF) containing 0, 30, or 150 mM H 2 O 2 was assessed using potentiodynamic polarization curve near corrosion potential, electrochemical impedance spectroscopy at open-circuit potential (OCP), and ion release at OCP. For biomolecular-coated scaffolds, decreasing pH concurrent with the presence of H 2 O 2 led to increase corrosion potential. In SBF with 30 mM H 2 O 2 , decreasing pH had no effect on corrosion rate or polarization resistance of biomolecular-coated scaffolds. However, in SBF with 150 mM H 2 O 2 , decreasing pH led to decrease corrosion rate and increase polarization resistance. The impedance of biomolecular-coated scaffolds decreased with increasing H 2 O 2 concentration and decreasing pH. Regardless of H 2 O 2 concentration and pH, the electrochemical equivalent circuit corresponding to the surface-untreated scaffolds under equilibrium conditions was a resistor-capacitor (RC) circuit, whereas the biomolecular-coated scaffolds presented two RC circuits corresponding to a dense inner protective film and a non-dense outer film. In acidic SBF containing 150 mM H 2 O 2 , the metal ions release from the biomolecular-coated scaffolds under equilibrium conditions was roughly half that from the untreated scaffolds. These findings confirmed under equilibrium conditions in simulated inflammatory environment, the type I collagen coatings on Ti2448 alloy scaffolds improved corrosion resistance by minimizing susceptibility to H 2 O 2 concentration and acidic environment.