Electrophoretic deposition of Baghdadite/Halloysite nanotube coatings for infiltration-driven corrosion protection of additively manufactured porous Mg–Zn–Zr alloy

Abstract

Electrophoretic deposition (EPD) of Baghdadite/halloysite nanotube coatings on additively manufactured porous ZK60 (a magnesium‑zinc‑zirconium alloy) scaffolds is demonstrated. Unlike conventional EPD on dense substrates, deposition follows a Darcy-coupled infiltration mechanism, coupling particle migration with solvent flow through interconnected pores. Increasing voltage from 20 to 60 V enhances coating density, uniformity, and pore sealing. Electrochemical impedance spectroscopy shows a ∼ 25× increase in charge transfer resistance at 60 V, corresponding to ∼96% protection efficiency. Potentiodynamic polarization confirms a corrosion rate of 0.044 mm/year — over 500 times lower than uncoated ZK60. The coating transitions corrosion from defect-driven attack to diffusion-limited behavior. Voltage is the key parameter controlling structure–transport–corrosion coupling in porous magnesium.