Modified Ni-Al layer double hydroxides as nanoparticles for self-healing anti-corrosion composite coating

Corrosion is a major concern for metallic structures, leading to significant economic losses and safety risks. Self-healing coatings have recently emerged as a promising solution to mitigate corrosion issues. This research develops a novel self-healing anti-corrosion composite coating using Ni-Al double layer hydroxide (LDHs) modified with phosphate ions as inhibitor. 1 wt% of modified particles were incorporated into the polyurethane (PU) matrix to form a coating (PU-LDH-PO4) and was applied on the carbon steel substrate. Reference coating (PU-LDH-NO3) was also formed for comparison purposes. The LDH serves as a reservoir for the inhibitor, which gradually released in response to corrosion-induced damage. The inhibitor release inhibits the corrosion process and promotes the formation of a protective passive film on the metallic surface. FTIR and FE-SEM coupled with EDS confirmed the successful loading of phosphate ions in the layered structure of Ni-Al LDH. The corrosion resistance of the self-healing composite coating was evaluated by electrochemical impedance spectroscopy (EIS) and salt spray test (SST). These tests demonstrate a higher and more robust inhibition efficiency (98 %) and self-healing effect compared to the reference coating. The enhanced corrosion ability of developed modified coating can be attributed to the effective and controlled release of inhibitor ions as well as the entrapment of aggressive chloride ions (Cl−) through the ion exchange mechanism. This composite coating demonstrated enhanced corrosion resistance and self-healing properties, making it a promising candidate for applications in protecting metallic structures against corrosive environments.