NDT Methods – Liquid Penetrant Testing

What is liquid penetrant testing?


Manufactured Part being Tested

Another form of non-destructive testing used to identify surface flaws is liquid penetrant testing (PT). This method can be used on either ferrous or nonferrous materials, however when dealing with ferrous materials magnetic particle testing is commonly used instead. To perform liquid penetrant testing the surface of the piece must be cleaned thoroughly beforehand. The object is then submerged in, or brushed with the penetrant, and is allowed to have it sit for anywhere from around five minutes to one hour. This gives the penetrant time to sink into the cracks and defects. After this step the excess penetrant must be removed, however it must be done carefully so as to make sure that the liquid in the flaws stays in place. A developer is applied afterwards to bring up the penetrant from the defects, so they are visible. This process usually takes at least ten minutes. Once all defects have been identified the left over penetrant and developer must be cleaned off.

Liquid penetrant testing is usually used on materials like glass and rubber, and metals such as aluminum, copper, or titanium. This method is quick, simple, and portable; however it is limited in that it is only able to detect flaws on the surfaces of materials. Liquid penetrant testing is commonly used on welds, as well as parts in the automotive and aerospace industries made of materials such as aluminum and titanium.

Here at AXIS we primarily doing PT on aluminum components in shop fabrication.   Please contact us if we can help you and your third party quality control system.

For Links to previous Non-Destructive Testing Blogs

Ultrasonic Testing

Penetrant Testing

X-Ray Fluorescence

Ferrite Testing

Magnetic Particle Testing


Until Next week,

Bonnie Pankratz