Liquid penetrant

Dye Penetrant Inspection is used generally in the detection of flaws in Non-ferrous alloys, but is not limited to these and can be used for the inspection of Ferrous material where Magnetic Flaw Detection techniques are difficult to apply. In some cases Dye Penetrant Inspection can also be used on non-metallic materials.

There are two processes available: one is the use where the Penetrant contains an Emulsifying Agent, i.e. Water-Emulsifier or Water-washable, and in the other a dye solvent has to be applied separately after the penetration time has elapsed. These processes can be sub-divided even further where the use of dry developer may produce a better result or by the use of a wet developer.

All the processes consist of applying a penetrant dye (generally red) to the surface of the item being tested, waiting a certain time to allow the dye to soak into any flaws, then removing any extra dye remaining on the surface. A white Developer is then applied, the purpose of which is to draw to the surface any dye which has penetrated into defects in the surface, a process similar to the action of blotting paper. Any red stains indicate the position and type of defects in the surface under inspection.