Liquid penetrant inspection is a universally used method for detecting and visualizing surface defects in non-porous materials. The basic principle of the method is very simple. First, the surface of the part to be inspected must be cleaned of any dirt, grease, or general contamination.
Next, a colored product, known as penetrant, is applied, and if there is any crack or defect, the penetrant is drawn into it by capillary action, regardless of the size of the crack. Excess penetrant is then removed from the piece.
To leave the surface clean again except for the penetrant already introduced into the defect. Next, a coating of a highly absorbent product, known as a developer, is applied. This acts like blotting paper and causes the penetrant to be drawn out of the crack, making it visible and thus allowing its location and approximate size to be determined.
The main advantages of liquid aerosol inspection, over other crack detection methods, are that it can be performed on ferrous and non-ferrous materials regardless of the shape and size of the part to be inspected, the cost-effectiveness ratio is very good, and the procedure is extremely simple.
