TO 35-1-3 - Robins Air Force Base

TO 35-1-3
CHAPTER 5
CORROSION PREVENTION AND CONTROL OF HUSH HOUSES
5.1 MATERIALS.
There are three basic materials used in the construction of
Hush Houses. The primary material being galvanized steel, the
galvanizing will offer improved corrosion protection over the
plain carbon steel. The second material used is carbon steel,
which is susceptible to a corrosion environment. The third
material used are Types 321 and 409 stainless steel that may
be specified in numerous rework contracts for use in the hot
section. Types 321 and 409 stainless steel is weldable and will
offer adequate corrosion protection.
5.1.1 Fastener Replacement. Any fastener replacement
should be accomplished using either stainless steel fasteners or
hot dip galvanized fasteners.
5.2 REPAIR.
To prevent dissimilar metal related problems, do not
use zinc plated or hot dipped zinc fasteners on stainless
or corrosion resistant steel parts.
5.2.1 Galvanized Steel. The amount of corrosion present
will determine what is required for repair. If the corrosion is
minor, then either abrasively grind the corrosion or chemically
treat with pretreatment compound. If the corrosion is severe or
widespread, abrasive blasting may be required.
5.2.1.1 If an entire galvanized steel component is replaced,
then every side of that component must be primed prior to
installation. If any part of the installation process, such as
welding, damages the paint, the exposed damaged area will be
cleaned and repainted with thinned organic zinc-rich primer.
5.2.1.2 Hush House galvanized sheet should be hot dip galvanized
per ASTM A446 Grade C, coating G-210.
5.2.2 Carbon Steel. All accessible carbon steel items
require sandblasting prior to application of the respective zincrich
paints. The sandblasting and subsequent painting of an
assembled structure will provide protection to the exposed
portion of the structure. If there is corrosion in a seam or joint,
refer to Paragraph 5.2.2.2.
5.2.2.1 If an entire component (panel, plate, beam, support)
is replaced. Then every side of that component must be primed
prior to installation. If any part of the installation process, such
as welding, damages the paint, the exposed damage area will
be cleaned and repainted with thinned inorganic zinc-rich
primer.
Failure to prime faying (back to back) surfaces of
carbon steel will result in corrosion that cannot be
treated without extensive repair or disassembly.
5.2.2.2 Carbon Steel (Angle Iron) seams, such as a T-angle,
having corrosion, will require the following procedure to
remove and treat corrosion.
a. Apply phosphoric acid corrosion removing compound.
Allow the material to dwell on the surface for 30-45
minutes - add additional material to keep the surface
wet. Agitate with thin bristled steel brush, if necessary,
to remove heavier rust.
b. Rinse area and check for rust; metal conditioner if necessary.
c. Allow area to dry.
d. Mask gaps at lower sides of “angle iron” T's with masking
tape per SAE-AMS-T-23397 or equivalent.
e. Fill entire gap using sealant MIL-PRF-81733, Type IV.
5.2.3 Stainless Steel. Characteristics of stainless steel are
as follows.
NOTE
• Use of sealant gun is recommended for injecting
sealant into entire gap.
• Above procedure should only be accomplished for
treating existing corrosion problems in this area.
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