How is demagnetization achieved after performing MPT?

Demagnetization is an essential step after performing Magnetic Particle Testing (MPT) to ensure that any residual magnetism does not interfere with the subsequent use of the material. The correct method for achieving demagnetization in this context is through the use of alternating current (AC) or a demagnetizing coil.

When AC is applied, it creates a magnetic field that alternates direction, gradually reducing the magnitude of the residual magnetism within the material. This process effectively disrupts the aligned magnetic domains that were oriented during the magnetization phase of MPT, leading to a randomization and a net reduction in the overall magnetic field within the component.

Demagnetizing coils specifically designed for this purpose are often used in industrial settings to ensure an effective removal of magnetism. As the component is passed through or around the coil, the alternating current creates fluctuating magnetic fields that facilitate this demagnetization process efficiently.

Heating the material can change its properties, but it is not a standard method for demagnetization in magnetic particle testing circumstances. Direct current (DC) could potentially magnetize or maintain magnetism rather than demagnetize. Mechanical vibration might have some effect on very strong magnetism in certain conditions but is not a reliable or widely used method