TO 35-1-3 - Robins Air Force Base
TO 35-1-3 - Robins Air Force Base
TO 35-1-3 - Robins Air Force Base
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<strong>TO</strong> <strong>35</strong>-1-3<br />
CHAPTER 5<br />
CORROSION PREVENTION AND CONTROL OF HUSH HOUSES<br />
5.1 MATERIALS.<br />
There are three basic materials used in the construction of<br />
Hush Houses. The primary material being galvanized steel, the<br />
galvanizing will offer improved corrosion protection over the<br />
plain carbon steel. The second material used is carbon steel,<br />
which is susceptible to a corrosion environment. The third<br />
material used are Types 321 and 409 stainless steel that may<br />
be specified in numerous rework contracts for use in the hot<br />
section. Types 321 and 409 stainless steel is weldable and will<br />
offer adequate corrosion protection.<br />
5.1.1 Fastener Replacement. Any fastener replacement<br />
should be accomplished using either stainless steel fasteners or<br />
hot dip galvanized fasteners.<br />
5.2 REPAIR.<br />
To prevent dissimilar metal related problems, do not<br />
use zinc plated or hot dipped zinc fasteners on stainless<br />
or corrosion resistant steel parts.<br />
5.2.1 Galvanized Steel. The amount of corrosion present<br />
will determine what is required for repair. If the corrosion is<br />
minor, then either abrasively grind the corrosion or chemically<br />
treat with pretreatment compound. If the corrosion is severe or<br />
widespread, abrasive blasting may be required.<br />
5.2.1.1 If an entire galvanized steel component is replaced,<br />
then every side of that component must be primed prior to<br />
installation. If any part of the installation process, such as<br />
welding, damages the paint, the exposed damaged area will be<br />
cleaned and repainted with thinned organic zinc-rich primer.<br />
5.2.1.2 Hush House galvanized sheet should be hot dip galvanized<br />
per ASTM A446 Grade C, coating G-210.<br />
5.2.2 Carbon Steel. All accessible carbon steel items<br />
require sandblasting prior to application of the respective zincrich<br />
paints. The sandblasting and subsequent painting of an<br />
assembled structure will provide protection to the exposed<br />
portion of the structure. If there is corrosion in a seam or joint,<br />
refer to Paragraph 5.2.2.2.<br />
5.2.2.1 If an entire component (panel, plate, beam, support)<br />
is replaced. Then every side of that component must be primed<br />
prior to installation. If any part of the installation process, such<br />
as welding, damages the paint, the exposed damage area will<br />
be cleaned and repainted with thinned inorganic zinc-rich<br />
primer.<br />
Failure to prime faying (back to back) surfaces of<br />
carbon steel will result in corrosion that cannot be<br />
treated without extensive repair or disassembly.<br />
5.2.2.2 Carbon Steel (Angle Iron) seams, such as a T-angle,<br />
having corrosion, will require the following procedure to<br />
remove and treat corrosion.<br />
a. Apply phosphoric acid corrosion removing compound.<br />
Allow the material to dwell on the surface for 30-45<br />
minutes - add additional material to keep the surface<br />
wet. Agitate with thin bristled steel brush, if necessary,<br />
to remove heavier rust.<br />
b. Rinse area and check for rust; metal conditioner if necessary.<br />
c. Allow area to dry.<br />
d. Mask gaps at lower sides of “angle iron” T's with masking<br />
tape per SAE-AMS-T-23397 or equivalent.<br />
e. Fill entire gap using sealant MIL-PRF-81733, Type IV.<br />
5.2.3 Stainless Steel. Characteristics of stainless steel are<br />
as follows.<br />
NOTE<br />
• Use of sealant gun is recommended for injecting<br />
sealant into entire gap.<br />
• Above procedure should only be accomplished for<br />
treating existing corrosion problems in this area.<br />
Change 4 5-1