Electrochemical Synthesis of Mesoporous Alumina as an Adsorbent of Corrosion Inhibitors for Active Corrosion Protection in Organic Coatings

This work describes a simple and economical electrochemical route for the generation of mesoporous alumina (MA) particles that can serve as containers for corrosion inhibitors for the active corrosion protection elements of metals when dispersed in organic coatings. The synthesis of precursor slurries was carried out in an electrochemical reactor with aluminum electrodes operating alternately as anodes and cathodes to facilitate metal dissolution and prevent passivation of the electrode surface. The obtained slurries were thermally treated to produce mesoporous alumina particles with adsorbent characteristics suitable for loading corrosion inhibitors. Benzotriazole (BTA) and 8-hydroxyquinoline (8HQ) were chosen as corrosion inhibitors. Dispersed in a commercial polymer matrix and applied to the coating of mild steel samples, the loaded MA improved the corrosion resistance of the coated metal exposed to a simulated marine environment. When physical damage is intentionally caused to expose the underlying metal, the polymer matrix containing BTA-loaded alumina particles retards the corrosion process due to the swelling of the inhibitor from the particles to the exposed bare metal in the scratch. Electrochemical impedance spectroscopy (EIS) measurements showed a marked increase in low-frequency impedance in coatings containing alumina particles, with the BTA-loaded system providing the most durable protection over extended immersion times (with a 50% improvement in corrosion resistance of steel exposed within the scratch). This demonstrates the potential of this approach for long-term corrosion protection applications.