Inhibitor-Sandwiched Polyelectrolyte Film for Micro/Nanopore Sealing to Enable Corrosion-Resistant Self-Healing Capability

Layered double hydroxide (LDH) layers have emerged as a promising class of materials in preparing functional coatings due to their specific anion exchangeability. However, most LDH-based films exhibit micro- and nanoscale pores that are not conducive enough to block corrosive media penetration. This report demonstrates a corrosion-resistant LDH-based composite coating with an 8-hydroxyquinoline (8HQ)-sandwiched polyelectrolyte outer film. This polyelectrolyte film is flat and dense, enabling an effective pore-sealing of the LDH layer on the magnesium alloy and preventing the dissolution and diffusion of inhibitor into the bulk solution. This strategy is shown to enhance the corrosion protection performance significantly. Electrochemical measurements, including the scanning vibrating electrode technique (SVET), confirm that the as-prepared composite coating exhibits very high charge transfer resistance (∼90 MΩ·cm2), extremely low corrosion current density (<1.0 nA cm–2), and superior self-healing capability. The high-performance corrosion protection is attributed to a combination of the ion-exchange capability of the LDH phase, corrosion inhibition of the 8HQ inhibitor, intrinsic properties and sealing effect of the polyelectrolyte, and decreased hydrophilicity. These findings provide insight into highly efficient sealing for porous layers on metal surfaces to achieve coating with long-term corrosion protection and self-healing capability.