Polydopamine modified ultrathin hydroxyapatite nanosheets for anti-corrosion reinforcement in polymeric coatings

It is known that two-dimensional nanosheets such as graphene, hexagonal boron nitride and layered double hydroxide can provide organic coatings with enhanced anticorrosion performance due to the high aspect ratio and excellent barrier property. As a kind of biocompatible material, the corrosion resistance of hydroxyapatite (HAp) in the biological body leads to its wide application. In this work, ultrathin HAp nanosheets were noncovalently functionalized by situ self-polymerization of dopamine chemistry with an aim to improve their compatibility and dispersibility in epoxy matrix. Electrochemical impedance spectroscopy (EIS) illustrated composited coating exhibited a higher value of impedance at low frequency compared to pure epoxy coating after 50 days of immersion in 3.5 wt% NaCl solution. Local electrochemical impedance spectroscopy (LEIS), spray tests and corrosion products characterization were also carried out to evidence that the modified HAp nanosheets could significantly improve the anti-corrosion performance of epoxy coatings via the enhanced barrier property and corrosion inhibiting effect of polydopamine, which is expected to be widely applied as nano reinforcing fillers in the anticorrosion field.