Liquid penetrant testing (PT) is one of the most popular Nondestructive Testing (NDT) methods in the industry. It is economical, versatile, and requires minimal training when compared to other NDT methods. Liquid penetrant exams check for material flaws open to the surface by flowing very thin liquid into the flaw and then drawing the liquid out with a chalk-like developer. Welds are the most common item inspected, but plate, bars, pipes, castings, and forgings are also commonly inspected using liquid penetrant examination.
These sensitive methods are used for locating discontinuities such as cracks and pores that are open to the surface. Liquid penetrants are especially useful on materials like aluminum, magnesium, and austenitic stainless steel which cannot be magnetized.