T.O. 1-1-691 and NAVAIR 01-1A-509, TM 55-1500-334-23 prohibits the use of
raw steam for cleaning aircraft and missile surfaces.
Steam cleaning is a form of alkaline or detergent cleaning. Diluted solutions of alkaline cleaners, detergent cleaners, or
mixtures of both are injected into a live steam spray. The steam/cleaner mixture is under pressure and the jet is
directed at the surface to be cleaned by a spray wand. Steam cleaning provides both chemical and strong mechanical
action at elevated temperatures. Mobile steam generators permit application on parts and structures that cannot be
brought into the cleaning shop.
Detergent cleaners are water base chemicals called surfactants, which surround and attach themselves to particles of
surface soil. The particles of soil and detergent are then washed away by solution agitation, pressure spray, or hand
wiping. The action is identical to hydrophilic removers in the penetrant process described in paragraph 184.108.40.206.2.
Detergent cleaners may be alkaline, acidic or neutral but must be noncorrosive to the material being inspected. The
cleaning properties of detergent solutions facilitate complete removal of light soils from the part surface, preparing it
for penetrant inspection.
Emulsion cleaners consist of an organic solvent and a detergent in water based solution. The organic solvent may be a
petroleum base liquid. The soils are removed through a combination solvent-detergent action. The cleaner is lightly
alkaline and is usually sprayed on the part. Emulsion cleaning can leave a light oil film on the part surface that is the
residue of the solvent. Emulsion cleaned parts must be hot water rinsed or wiped with a solvent to remove the oily
residue prior to penetrant inspection.
This type of process removes soils by dissolving them. Solvents can be used on oils, greases, waxes, sealants, paints
and general organic matter. The resulting solution may leave a thin film or residue of an oily nature. This oily film
must be removed with another solvent, vapor degreasing, alkaline or detergent cleaning prior to penetrant inspection.
Solvent cleaning may be accomplished by tank immersion, but is more often applied by spraying or hand wiping when
alkaline, detergent or vapor degreasing is impractical.
Methyl chloroform, the most commonly used solvent in vapor degreasers, is no
longer available to government facilities because of its detrimental effect on the
ozone layer. Other solvents that can be used are generally too toxic or expensive to
be practical substitutes. Consequently, utilization of vapor degreasing is generally
no longer available to government facilities.
This method adds ultrasonic agitation to solvent or detergent cleaning. The agitation is the result of cavitation of the
liquid when subjected to the high and low pressure (partial vacuum) of the ultrasonic waves. The formation and
collapse of the cavities in the liquid provides a scrubbing action to the surface of the part. The agitation increases
action of the cleaning solution and decreases cleaning time. It is particularly effective in removing contaminants
trapped in discontinuities. However, its effectiveness is dependent upon the cleaning medium. It should be used with
water and detergent on inorganic soils, such a rust, dirt, salts and corrosion products. It should be used with an
aromatic or halogenated solvent if the soil to be removed is organic, such as oil or grease; see paragraph 220.127.116.11.