WARNING: AVOID EXCESSIVE INHALATION OF ABRASIVE DUST. PROVIDE VENTILATION AS
REQUIRED.
(a) In-cabinet Blasting. In-cabinet blasting is preferred. External gun
blasting may be used if adequate confinement and recovery are pro-vided for the abrasives.
1) For the abrasive, use glass beads (150 mesh or finer).
2) If possible, remove the part from the component. If this is not
possible, give areas adjacent to the part protection from scale,
chips, corrosion products and the abrasive blast.
3) If you find grease or dirt, clean the area per par. 5.
4) Give protection from the blast to such close tolerance surfaces as
bushings, bearings, close tolerance shafts and threads.
5) Remove only the corrosion products by abrasive blasting with glass
beads.
(b) External Gun Blasting. The frequency of occurrence of filiform cor-rosion has led to the development of portable abrasive blasters. A
typical external gun blasting procedure for removing filiform corro-sion on aluminum skin follows:
1) Remove any heavy soils with alkaline emulsion cleaner.
2) Strip the protective finish (both enamel and primer).
3) Mechanically remove the filiform corrosion by blasting with glass
beads (approximately 150 mesh).
4) After blasting, remove any enamel or primer that may remain in the
corrosion cleanup area. Flush with water and clean the surface in
preparation for surface treatment.
(c) Portable Abrasive Blaster. Filiform corrosion can be quickly removed
by use of a portable abrasive blaster. An example is the Model E-10A
Clemco Eductomatic Portable Blast Cleaner (Clemco Industries,
V86192) (Fig. 7).
1) The unit weighs 7 pounds and includes an abrasive reservoir (which
holds up to 4 pounds of glass beads)., suction abrasive pickup,
swivel blast nozzle and vacuum abrasive return.
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20-40-00
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OCT 01/01
2) The blast head has a concentric arrangement. The inner tube blasts
the glass beads against the airplane surface, and the outer passage
retrieves the beads and dust and separates them. A double-acting
control valve regulates both the blast and the suction. The blast
head is connected by a swivel joint to the body of the unit. This
feature lets you turn the blast in any direction and keep the main
body of the machine vertical.
3) During operation, control the air source to 80 pounds pressure max-
imum. Hold the blast nozzle on the surface to remove corrosion in
an approximate one-inch diameter path. Try the equipment on a test
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