Corrosion Behavior of Electroplated Nd2Fe14B Magnets Under Simulated Oral Conditions

Magnets have shown remarkable clinical results in orthodontics; however, the corrosion of magnetic alloys in the oral environment is a major concern. This study aimed to compare the corrosive behavior of Nd2Fe14B magnets coated with silver (Ag) and gold (Au) via electroplating in a simulated oral environment. Magnets were immersed in 20 ml of 1% lactic acid and maintained at a constant temperature of 37 °C for 70 days. The magnetic field was measured weekly using a Hall probe. The structural and compositional evolution of the materials was monitored via XRD, EDS, WDS and DTA/TG. The morphological characteristics were monitored via SEM, while Fe leaching was monitored via atomic absorption spectrometry. Additionally, Student’s t-test and ANOVA were used for statistical analysis. The average iron concentration in the Ag-coated magnets was higher than that in the Au-coated magnets; however, the difference was not statistically significant. The Ag-coated magnets exhibited a significant iron concentration reduction over time (F = 4.29; p = 0.01). The magnetic-field strength of the Au-coated samples decreased less than that of the Ag-coated samples, but not significantly. The magnetic field decreased as a function of time and both groups were immersed in the lactic acid solution (F = 46.91; p < 0.001). The magnets exhibited high chemical reactivity in acidic environments, significantly compromising their microstructure and magnetic flux, which are essential for orthodontic forces.