The eddy current test is based on the principles of electromagnetism. Essentially, an electric current is passed through a coil or probe, generating a magnetic field. When this magnetic field is applied to the material, it is influenced by the material's electrical properties, such as conductivity and magnetic permeability.

If there is a flaw or alteration within or on the surface of the material, circular electric currents called eddy currents are generated. These eddy currents somehow affect the magnetic field, and information is collected from coils or sensors that detect this effect. This information is processed and interpreted by a computer or a specialized device.

The eddy current test has various applications, including:

1. Detection of surface defects: Eddy current testing is used to identify surface flaws such as cracks, corrosion, surface holes, and similar imperfections.

2. Coating quality control: It is employed to assess the quality and thickness of non-conductive coatings.

3. Hardness and conductivity measurements: It can be utilized to determine the material's hardness and conductivity properties.

4. Material identification: Eddy current testing can be used to determine the material's type and composition.

The eddy current test provides fast and precise results and can be applied in many different industries. Specialized equipment and training may be required to conduct this test, so it is important to be performed by experts.