Molecular Understanding of the Interfacial Interaction and Corrosion Resistance between Epoxy Adhesive and Metallic...

The epoxy adhesive-galvanized steel adhesive structure has been widely used in various industrial fields, but achieving high bonding strength and corrosion resistance is a challenge. This study examined the impact of surface oxides on the interfacial bonding performance of two types of galvanized steel with Zn-Al or Zn-Al-Mg coatings. Scanning electron microscopy and X-ray photoelectron spectroscopy analysis showed that the Zn-Al coating was covered by ZnO and Al₂O₃, while MgO was additionally found on the Zn-Al-Mg coating. Both coatings exhibited excellent adhesion in dry environments, but after 21 days of water soaking, the Zn-Al-Mg joint demonstrated better corrosion resistance than the Zn-Al joint. Numerical simulations revealed that metallic oxides of ZnO, Al₂O₃, and MgO had different adsorption preferences for the main components of the adhesive. The adhesion stress at the coating-adhesive interface was mainly due to hydrogen bonds and ionic interactions, and the theoretical adhesion stress of MgO adhesive system was higher than that of ZnO and Al₂O₃. The corrosion resistance of the Zn-Al-Mg adhesive interface was mainly due to the stronger corrosion resistance of the coating itself, and the lower water-related hydrogen bond content at the MgO adhesive interface. Understanding these bonding mechanisms can lead to the development of improved adhesive-galvanized steel structures with enhanced corrosion resistance.