Long-term high-temperature resistant biotemplated composite coating for AZ91D magnesium alloy protection

Integrating different active substances through carriers and fully exerting their synergistic corrosion inhibition ability is an efficient anticorrosion strategy. Biotemplate (diatomite) was used to integrate polyaniline and sodium phosphate, an active antiseptic filler (PANI/DM/SP) was prepared in this work. Moreover, active fillers were combined with epoxy resins to prepare high-efficiency anti-corrosion coatings for magnesium alloy protection. The stability of the corrosion inhibitor (sodium phosphate) released by the active filler was analyzed by establishing a mathematical model. Simultaneously, electrochemical impedance spectroscopy tests demonstrate excellent corrosion inhibition properties of active fillers and the impedance modulus of composite coatings was three orders of magnitude higher than that of the EP coating, due to the synergistic effect of each component of the active filler. In addition, the mechanical properties of the composite coating were significantly improved, with tests showing a 51.31% increase in rub resistance and two grades of adhesion improvement (ASTM standard). The key of this work was to give full play to the slow-release characteristics of diatomite through scientific methods and promote the synergistic anticorrosion effect of sodium phosphate and polyaniline.