Dopamine-Functionalized Graphene Oxide with Coordinated Calcium Ions for Self-Healing and Corrosion-Resistant Epoxy Coatings

In this study, dopamine (DA) was covalently grafted onto graphene oxide (GO) to form a functionalized nanofiller, onto which calcium ions were subsequently coordinated, yielding GO–PDA–Ca nanocomposites for epoxy coating applications. This work was motivated by the need to mitigate corrosion and performance loss of conventional epoxy coatings after microdamage in aggressive environments. The experimental results demonstrated that the impedance value of the GO-PDA-Ca/EP composite coating reached its peak at 4.92 × 10 7 Ω cm 2 after 2 hours of immersion. Even after 42 days of immersion, it still retained a relatively high impedance value of 3.54 × 10 7 Ω cm 2 , which was three orders of magnitude higher in comparison to that of the pure EP coating. The self-healing properties of the coating were examined. Upon damage, the structure was effectively repaired via dynamic coordination between catechol groups in PDA and Ca 2+ . SEM images confirmed that the artificial defect was successfully repaired. This coating was promising for extending service life and improving the safety of metal components in corrosive environments, such as in the oil and gas industry.