TO 1-1-700 - Robins Air Force Base

TO 1-1-700
MIL-PRF-81733, SEALING AND COATING COMPOUND,
CORROSION INHIBITIVE 48
SAE AMS-S-8802, SEALING COMPOUND
(POLYSULFIDE) 62
10.4 RIVETS.
Rivets are commonly used fasteners in construction of shelters
and electronic and electrical boxes for attaching panels, braces
and mounting parts. Those rivets shall be installed wet with
MIL-PRF-81733, Type I or IV, Class 1 or 2, Grade A sealant.
The exposed rivet head and approximately 1/4 inch of the
adjacent structure shall be brush-over-coated with SAE AMS-
S-8802 (MIL-S-8802), Class A sealant.
10.5 MATING SURFACES AND CREVICES.
Similar to corrosion around fasteners, corrosion in faying surface
areas, crevices, seams, and joints is caused by the intrusion
of salt water and/or other corrosive fluids or agents. Entry
of fluids by capillary action causes corrosive liquids to flow
into the tightest of joints. The effect of corrosion resulting
from fluid intrusion into joint areas is usually detectable as
bulging of the skin surface. There are several methods to prevent
fluid intrusion and corrosion in the mating of metal surfaces
or at crevices, joints, and seams.
10.5.1 Faying Surface Sealing. Faying surfaces are sealed
by applying a sealant to the connecting surfaces of two or
more parts and then assembling the parts while the sealant is
still wet. It is a very effective seal and should be used for all
assembly or reassembly. When possible, it should be used in
conjunction with fillet sealing. There are two types of faying
surface seals: removable and permanent. Removable seals are
used around access doors, removable panels, inspection plates,
etc. A removable seal can be formed using a low adhesion
sealant that adheres to both surfaces, or by using a high adhesion
sealant that adheres to one surface and a parting agent on
the mating surface. Permanent seals are created using high
adhesion sealants between permanently fastened structures
(see Figure 10-4). To create a permanent seal, coat either one
or both mating surfaces with a high adhesion sealant before
assembling the parts and then assembling them while the sealant
is still wet. Apply enough sealant to force a bead to
squeeze out along the joint after assembly. Install all fasteners
wet with the sealant. Assemble parts within the rated application
life and/or assembly life of the sealant while taking into
account the effects of temperature and humidity on these times
(see Chapter 12 of this manual).
10.5.2 Fillet Sealing. Fillet or seam sealing is the most
common type of sealing used on support equipment. Fillet
seals are used to cover the edges or seams of structural joints
along stiffeners or beams, skin panel and wall butt joints, areas
where mating surfaces require electrical contact (e.g. antenna
to a shelter roof surface), and to seal around fittings and fasteners.
This type of sealing is the most easily repaired. It
should be used in conjunction with faying surface sealing if
possible and in place of it if the assembly sequence restricts
the use of faying surface sealing (see Figure 10-5 and Chapter
12 of this manual).
Figure 10-4. Faying Surface Sealing
10-3