What is the difference between magnetic particle testing (MT) and liquid penetrant testing (PT) in weld inspection?

What is the difference between magnetic particle testing (MT) and liquid penetrant testing (PT) in weld inspection?

• A. MT detects internal defects only; PT detects external.
• B. MT detects surface defects via eddy currents; PT detects color changes.
• C. MT detects surface and near-surface defects in ferromagnetic materials using magnetic fields; PT detects surface-breaking defects via penetrant liquids.
• D. MT detects defects in nonferromagnetic materials; PT detects defects in ferromagnetic materials.

Answer: (C)

Magnetic particle testing relies on magnetizing a ferromagnetic part and using magnetic particles to form visible indications where flux leaks at flaws. This makes it effective for surface and near-surface defects in materials like iron and steel. Liquid penetrant testing, on the other hand, looks for openings in the surface by letting a liquid seep into cracks and then drawing it out with a developer to reveal surface-breaking defects under proper lighting. It isn’t limited to ferromagnetic materials and focuses on flaws that break the surface. So the best answer correctly states that MT detects surface and near-surface defects in ferromagnetic materials using magnetic fields, while PT detects surface-breaking defects via penetrant liquids.

Magnetic particle testing relies on magnetizing a ferromagnetic part and using magnetic particles to form visible indications where flux leaks at flaws. This makes it effective for surface and near-surface defects in materials like iron and steel. Liquid penetrant testing, on the other hand, looks for openings in the surface by letting a liquid seep into cracks and then drawing it out with a developer to reveal surface-breaking defects under proper lighting. It isn’t limited to ferromagnetic materials and focuses on flaws that break the surface. So the best answer correctly states that MT detects surface and near-surface defects in ferromagnetic materials using magnetic fields, while PT detects surface-breaking defects via penetrant liquids.