Surface coil
A flat eddy current coil placed directly on the workpiece. It detects microcracks on flat or slightly curved surfaces.
Physicochemical mechanism of action
The surface coil generates a homogeneous magnetic field that penetrates the workpiece surface. Microcracks affect this field, causing a change in magnetic induction.
Metallurgical relevance & risks in welding
Incorrect settings or incomplete inspections can lead to overlooked microcracks, which can later become cracks or corrosion. Failure to detect microcracks can endanger the service life and safety of the workpiece.
Workshop practice & instructions
• Make sure the surface coil is clean and free of contaminants, as these can affect the inspection.
• Adjust the coil currents and frequencies precisely to the material type and geometry of the workpiece.
• Carefully review the results from the surface coil and watch for anomalies that could indicate a faulty inspection.