In-situ construction of functional carbon layer on the plasma electrolytic oxidation-pretreated Ti-6Al-4V alloy to enhance anti-static properties

Abstract

Thermal control coatings prepared by plasma electrolytic oxidation (PEO) have shown broad application potential, especially in the aerospace field. However, the high insulation nature results in charge accumulation during the real application in spacecraft, aggravating the risk of electrostatic discharges and endangering equipment's safety. Herein, a functional anti-static thermal control composite coating on the surface of Ti-6Al-4V alloys was constructed by preparation route involving in-situ polymerization and carbonization of polydopamine (PDA) on the PEO layer. After the introduction of carbonized PDA, the composite coating retained the pristine porous structure of the PEO coating with improved crystallinity. Notably, the consecutive functional carbon layer ingrates the graphite nanocrystals and N-doped graphite to achieve high conductivity and then renders the composite coating with the lowest volume resistivity (6.04 × 104 Ω m) and surface resistance (9.0 × 107 Ω/□). Moreover, the two-step prepared coating showed high absorption (200–2500 nm, 0.929) and emission (2–16.6 μm, 0.921) along with excellent stability at high temperature (∼200 ℃) and low temperature (∼−200 ℃) even over 48 h. This contribution reveals a promising direction to widen the practical application of the PEO thermal control coating.