Corrosion-resistant magnetic pumps are widely used in chemical, pharmaceutical, environmental protection and other industries due to their advantages of no shaft seal, zero leakage and resistance to acid & alkali corrosion. Power transmission relies on magnetic coupling between inner and outer magnets without mechanical contact. However, demagnetization may occur during long-term operation, directly reducing pump flow and head, or even causing complete failure. Demagnetization of magnetic pumps is not simple natural aging. It is mostly triggered by abnormal working conditions, improper operation and equipment faults. High-temperature damage is the primary cause, together with medium corrosion and mechanical failures.
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1 High Temperature — The Leading Cause of Irreversible Demagnetization
Excessive high temperature is the leading cause of irreversible demagnetization. Permanent magnet materials such as neodymium iron boron and samarium cobalt used in magnetic pumps have fixed temperature resistance limits. Conventional NdFeB magnets cannot withstand temperatures above 120°C. Once exceeding the critical temperature, the magnetic domain structure inside the magnet will be destroyed, resulting in permanent loss of magnetism.
Dry running is a common trigger. When the pump cavity is not filled with medium, the bearings lose lubrication and cooling. High-speed friction generates rapid heat buildup, which conducts directly to the inner magnetic rotor. Meanwhile, eddy current loss on the containment shell, blocked cooling channels and insufficient medium flow trap heat inside the pump, which can demagnetize the magnets in a short time.
2 Corrosion and Impurity Interference Accelerate Demagnetization
Although corrosion-resistant pumps are designed for acid and alkali media, long-term transportation of highly corrosive liquids gradually erodes the protective coating on the magnet surface, damages the magnet substrate and weakens magnetic performance. Besides, ferromagnetic impurities mixed in the medium will adhere to the magnetic rotor surface, disturb magnetic field distribution, increase transmission load, worsen heat and wear, and indirectly induce demagnetization.
3 Improper Operation and Mechanical Faults — Secondary Triggers
Frequent start-stop creates instantaneous impact heat that repeatedly damages magnets. Worn bearings, rotor axial movement and deformed containment shells widen the magnetic transmission air gap, reduce magnetic transfer efficiency and cause local frictional heating. In addition, reverse magnetic fields generated by electrical faults can offset part of the original magnetism and lead to magnetic attenuation.