Unraveling the critical role of adhesion layer design in superhydrophobic coatings for superior corrosion protection of sintered Nd-Fe-B magnets

Although superhydrophobic coatings have been widely employed for corrosion protection due to their low surface energy, their low surface energy characteristic also results in weak interfacial adhesion and the influence of interfacial adhesion on the overall anti-corrosion performance remains poorly understood. Herein, we explored the corrosion resistance of superhydrophobic coatings on sintered Nd-Fe-B magnets from the perspective of work of adhesion (Wₐ), which represented the interfacial stability and bonding strength. By precisely controlling the PDA shell thickness and the degree of hydrophobization, the work of adhesion can be regulated correspondingly. The results revealed that the overall anti-corrosion performance of superhydrophobic coatings was directly proportional to the work of adhesion. At an optimized Wₐ of 49.44 mN·m -1 , the coated magnet exhibited a low corrosion current density of 1.09 × 10 −8 A/cm 2 , which was three orders of magnitude lower than that of 3.27 × 10 −5 A/cm 2 for bare Nd-Fe-B magnet. Moreover, outstanding protection durability was also demonstrated in both acidic and alkaline environments with robust interfacial contact. In contrast, weak adhesion induced the formation of interfacial gaps, which served as preferred penetration pathways for the corrosive medium. This study evidenced the importance of interfacial structural integrity, revealing the critical role of adhesion layer design in enabling robust and durable anti-corrosion performance of superhydrophobic coatings.