A highly responsive healing agent for the autonomous repair of anti-corrosion coatings on wet surfaces. In operando assessment of the self-healing process

Abstract

A methodology to enrich epoxy coatings of an effective self-healing feature on wet surfaces was developed as a further step on for practical corrosion protection issues. To this aim, a polyetheramine was chemically engineered by grafting catechol units and then successfully encapsulated in microcapsules (MCs) to be finally embedded into an epoxy resin deposited on steel panels. Fourier transform infrared spectroscopy (FTIR), thin-layer chromatography, and 1D and 2D nuclear magnetic resonance spectroscopy confirmed the successful polyetheramine modification by dopamine units. Different dosages of catechol-modified polyetheramine were encapsulated within poly(styrene-co-acrylonitrile) shell via electrospray method to study the influence of dopamine grafting on the healing performance. Scanning electron microscopy (SEM) analysis revealed the formation of the spherical MCs, while FTIR and TGA analyses confirmed the successful encapsulation. The highly responsive self-healing coatings were then prepared by embedding amine- and isocyanate-containing MCs (1:1 weight ratio; 3 wt% overall) as a dual-capsule system exploiting the polyurea formation as a fast healing reaction. In operando electrochemical impedance spectroscopy (EIS) tests were employed to study the underwater self-healing performance. According to the EIS results, monotonically increasing variation with time of the charge transfer resistance was correlated with a fast and effective underwater self-healing performance for the sample using 40 wt% of a catechol-modified healing agent. Such results, combined with others including SEM investigation on the underwater healed samples, point to an improved adhesion of the growing dopamine-bearing polymer to both underlying metal and epoxy edges of the scratch. Graphic abstract

Synthesis of TiO2 nanogel composite for highly efficient self-healing epoxy coating

“…Measurements were conducted on the scratched coatings with an electrolyte exposed area of 0.785 cm 2 after immersion in 3.5 wt% NaCl for 18 days. The scratch dimensions and the electrochemical cell assembly have been reported in detail in our previous work [40] . The EIS tests were carried out at open circuit potential (OCP) within the frequency sweep range of 10 5 to 10 −2 Hz using a 10 mV amplitude sinusoidal voltage.…”

Corrosion Resistance Evaluation of Self-Healing Epoxy Coating Based on Dual-Component Capsules Containing Resin and Curing Agent

“…The EIS measurements were also carried out on the scratched and immersed coatings to investigate their corrosion properties and healing efficiency [45]. Figure 9 represents the EIS results for these coatings after 14 days of immersion in a 3.5% NaCl solution.…”

“…SEM was also used on the scratched and immersed coating containing 1 wt% of MCs to visually investigate the healing process [45,51]. Figure 11 shows the micrographs of the scratched coating after healing.…”

Synthesis and characterization of hybrid shell microcapsules for anti-corrosion Ni-Co coating

“…Self-healing coatings can prevent corrosion of the substrate even after being damaged. These have been studied to enhance the lifetime of infrastructure equipment [4][5][6][7][8]. The two common strategies in creating autonomous self-healing coatings are capsule embedment and vascular systems [9,10].…”