Classifications of Penetrant Materials

From 1955, classification or designation of penetrant materials has followed the military specification, MIL-I-25135. At that time, penetrant materials were listed as six family groups. In 1964, a seventh group, Group VII, consisting of aerosol packaged group VI penetrants was added. In 1982, another change in designation occurre when Group VI was subdivided into Group VIA, High sensivity, and Group VIB, Ultra high sensivity penetrant.

Table 1.1 is a listing of the original groups. This table is provided because there are a number of outdated process specifications still in use with these designations.

By 1980, it became apparent that additional designations were necessary to include:

1. Types of penetrants dye
2. Methods of removal
3. Penetrant sensitivities
4. Form of developers
5. Classes of solvent removers

The MIL-I-25135D revision, released in June 1985, incorporated these designations. A subsequent revision, MIL-I-25135E, was released in June 1989. A consensus document (SAE/AMS( superseded MIL-I-25135E in August  1996, however, the designations are identical.

The revisions also eliminate the family group (Penetrant, emulsifier and developer) and substitute the system concept or postemulsifiable penetrants.

The system concept is based on the fact that manufacturers formulate their penetrants and emulsifier/removers to be used together. THe use of the manufacturer´s penetrant with another manufacturer´s lipophilic elulsifier or hydrophilic remover may not produce optimal results.

Therefore, a manufacturer´s penetrant and emulsifier/remover ate considered to be a system and the components are not interchangeable from manufacturer to manufacturer.

Developers and solvent removers are not part of the system and,  therefore, any qualified material may be used.

However, because each manufacturer has it own propietary formula, the specification prohibits the mixing or combining of developers or solvent removers of different manufacturers.