Self-healing coating lets Nd-Fe-B magnets resist saltwater, ice and mechanical damage

Since their discovery thousands of years ago, magnets have fascinated humankind with their unique properties. Even today, scientists are studying and finding new applications for these materials.

In 1984, the development of neodymium-iron-boron (Nd-Fe-B) magnets revolutionized this field. Known for their unparalleled magnetic strength, these magnets have now become ubiquitous, serving as critical components in renewable energy systems and advanced electronics.

However, their susceptibility to degradation under moisture, salt spray, and temperature fluctuations has, thus far, strongly limited their deployment in harsh environments. Traditional protective coatings such as Ni-Cu-Ni, Zn, and epoxy resin often fail under prolonged exposure, leading to catastrophic magnet failure.

To overcome these challenges, a team of researchers from the Institute of Advanced Magnetic Materials at Hangzhou Dianzi University, led by Dr. Zhen Shi (first author) and Prof. Xuefeng Zhang (corresponding author), has developed a “slippery liquid-infused porous surface” (SLIPS) coating for Nd-Fe-B magnets through a multi-dimensional design strategy.

The team’s work is published in the journal Small.

Elaborating on their findings, Prof. Zhang says, “This technology could revolutionize motor applications, ranging from aerospace systems to deep-sea robotics and polar infrastructure, by preventing saltwater, humidity, and temperature fluctuation-induced magnet degradation. Moreover, we can significantly extend motor lifespans while reducing maintenance costs.”

In this study, the team chemically engineered silica nanoparticles to form a dense polymer network with enhanced interfacial adhesion and locked lubricant film. Consequently, the resultant coating enables Nd-Fe-B magnets to resist corrosion, humidity, mechanical stress, and extreme temperatures with unprecedented durability.

Through extensive experimentation, the researchers found that there was no corrosion detected even after 136-day immersion in 3.5 wt.% saltwater. Furthermore, the novel SLIPS coating delays ice formation with a 10-fold longer freezing time and reduces ice adhesion strength by 75% at -20°C, as well as repairs mechanical scratches autonomously and restores surface functionality.

Compared to commercial Ni-Cu-Ni, Zn, and epoxy resin coatings, SLIPS coating demonstrates super-stable corrosion protection for Nd-Fe-B magnets. In electrochemical experiments, the impedance modulus of SLIPS coating at 0.1 Hz can be maintained at 3.31×10⁸ Ω·cm² even after 132-day immersion, far surpassing that of commercial coatings. Notably, the impedance modulus of all commercial coatings deteriorated within 14 days.

Dr. Shi briefly highlights the technological impact of this new coating, explaining, “Our multidimensional design bridges the gap between laboratory innovation and real-world applications. By addressing corrosion and icing simultaneously, we have transformed Nd-Fe-B magnets into reliable components even for the most demanding environments.”

Lastly, the research team further noted that the self-healing capability of the SLIPS coating ensures longevity even after physical damage, a critical feature for mission-critical systems in remote or inaccessible locations.

While initially tested for offshore wind turbines, the robustness of the proposed technology suggests transformative potential across various industries. Aerospace engineers could leverage these magnets for lightweight, high-efficiency motors in satellites, while polar research equipment and deep-sea exploration tools utilizing this innovation could achieve unprecedented reliability.

Provided by
Hangzhou Dianzi University