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

Abstract

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.