Enhanced adhesion and corrosion resistance of steel under hygrothermal conditions through an interfacial catechol-epoxy primer containing aniline trimer

As the non-covalent interfacial interactions of adhesive-metal bonds are inherently susceptible to disruption by water molecules, bonding structures often culminate in failure under hydrothermal conditions. Herein, we designed a novel primer composed of catechol-based epoxy adhesive containing the aniline trimer, which enhances both the adhesion properties and anti-corrosive performance for ordinary epoxy adhesive. The lap shear strength of Q235 steel coated with EP-AT-CMB increased from 8.36 MPa to 22.07 MPa compared to untreated substrates. Notably, the adhesion strength of Q235 steel coated with EP-AT-CMB remained robust at 14.16 MPa after being immersed in water for 4 days, whereas the untreated samples experienced a near-total loss of adhesion strength. The superior anti-corrosion capability of EP-AT-CMB specimens is attributed to two factors: (1) the high density of hydrogen bonds of the primer/metal interface exhibit a barrier property for water molecules; (2) the electroactivity aniline trimer, which facilitates the formation of a passive film composed of Fe2O3 and Fe3O4. The synergism between the catechol structure of the primer and the electrochemical behavior of the aniline trimer enhances the durability of the adhesive structure, offering a practical and durable primer material for a wide range of applications.