Self-healing performance and corrosion resistance of graphene oxide-mesoporous silicon layer-nanosphere structure coating under marine alternating hydrostatic pressure

Alternating hydrostatic pressure (AHP) is the main cause of the marine coating failure of deep-sea tools and equipment. Herein, we synthesized a novel nanostructure, namely, graphene oxide-mesoporous silicon dioxide layer-nanosphere structure loaded with tannic acid (GSLNTA), as a self-healing coating additive. The anticorrosion and anti-AHP performance and the self-healing capability of GSLNTA coating were evaluated through electrochemical impedance spectroscopy, field emission scanning electron microscopy, Fourier-transform infrared spectroscopy, and alternating current scanning electrochemical microscopy (AC-SECM). Results showed that the nanolayer structure of GSLNTA effectively inhibited corrosion mass transmission under simulated deepsea AHP. The nanospheres of GSLNTA released inhibitors to form a ferric tannate film on the exposed metal surface under AHP. The nanolayer and nanosphere of GSLNTA self-healing coating exerted a synergistic effect on anti-corrosion and anti-AHP performance and blocked corrosion factor transmission and coating failure in deepsea applications. AC-SECM revealed the advantages of local impedance complementation of different electrochemical parameters (vertical bar Z vertical bar and -phase) to monitor the self-healing of coatings with GSLNTA. This work also investigated the self-healing performance of alkyd varnish coating embedded with synthetic GSLNTA in protecting steel surfaces. Self-healing materials have an active healing capability to prolong the life of organic coatings after unwanted external damage in deep-sea environments.