T.O. 33B-1-1
2-19
Pretesting SHALL be performed as follows:
a. If spare or extra parts are available, the entire surface to be inspected may be pretested. If the part to be
inspected must be reused, the pretest should be performed on a small area where possible damage can
be tolerated.
b. The part to be pretested SHALL be cleaned and visually examined for evidence of pre-existing damage.
c. Apply the penetrant to be used to the area selected and allow it to remain on the surface for at least
twice the proposed dwell time. Wipe excess penetrant from the area and closely examine for any
surface changes.
d. Repeat Step c with the remover and developer to be used, examining the part surface for any evidence of
change between each process step.
e. If any evidence of adverse effects is noted, the penetrant inspection method should not be used.
2.3.3
Cleaning.
2.3.3.1
Responsibility for Cleaning.
Properly performing surface treatment operations, such as paint stripping and cleaning of military system metals and
alloys, requires skill and knowledge. Improper methods, materials, or procedures can result in severe damage to
surfaces and parts. Nondestructive inspection personnel are neither trained nor experienced in performing paint
stripping or cleaning. Surface treatment processes SHALL be accomplished only by qualified personnel.
2.3.3.2
Need For Clean Surfaces.
The proper preparation of parts prior to inspection is critical. Successful detection of discontinuities by penetrant
inspection depends upon the ability of the penetrant to enter and exit from the discontinuity, and the resulting
indication must be readily distinguishable from the background. Surface conditions, such as coatings or soil
contamination, can reduce the effectiveness of the inspection by interfering with the entry and exit process or producing
a high residual background. Penetrant inspection is reliable only when the parts to be inspected are free of
contaminants. Foreign material, either on the surface or within the discontinuity, can produce erroneous results. Any
interfering conditions must be removed by proper cleaning or surface treatment prior to penetrant application.
2.3.3.3
Factors In Selecting A Cleaning Process.
CAUTION
Improper cleaning methods can cause severe damage or degradation of parts.
Selection and application of cleaning processes SHALL be accomplished only by
qualified personnel.
Cleaning is a broad term covering methods and materials used to remove contaminants or soils from a surface.
Cleaning is routinely used for corrosion control and to prepare surfaces for other treatments. There are no special
methods or materials specifically dedicated to penetrant inspection. Different materials and parts require separate or
individual cleaning processes. No one cleaning method is equally effective on all contaminants. The selection of a
suitable cleaning process is complex and depends on a number of factors, such as:
a. Type of soil(s) or contaminant(s) to be removed.
b. Part material. Some nonferrous metals, such as aluminum and magnesium, present problems because
strong alkaline or acid cleaners attack the metals. Steels, especially in the heat treated condition, are
likely to become embrittled by acid cleaners. Other metals, such as titanium and high nickel alloys, can
