Nitrophenyl layers of varying thicknesses were grafted onto an arc-melted Ti35Zr25Nb25(MoTa)15 high-entropy alloy via electrochemical reduction of 4-nitrobenzenediazonium tetrafluoroborate. A fluorescent peptide derived from bone morphogenetic protein 2 (BMP-2) was then covalently tethered to these films. Electrochemical corrosion behaviour was assessed in 0.1 M NaCl by potentiodynamic polarisation and electrochemical impedance spectroscopy. Grafted nitrophenyl films reduced the corrosion current density (Icorr) by more than 10-fold and diminished anodic current densities by over 1550-fold, while shifting the corrosion potential (Ecorr) to more positive values. Subsequent BMP-2 coupling further increased the resistive impedance of the coating and eliminated diffusion-limited (Warburg) behaviour. These results demonstrate that, for the Ti35Zr25Nb25(MoTa)15 alloy in chloride media, sequential nitrophenyl grafting and peptide immobilisation yield a robust, corrosion-resistant and biofunctional surface.
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