A.
This section provides general guidance on the repair of corroded area. The
procedure presented is:
(1)
Gain access to the entire corroded area.
(2)
Mechanically remove the corrosion products
(3)
Determine the extent of the corrosion damage
(4)
Repair or replace the damaged components
(5)
Finish the new or repaired parts.
(6)
Replace removed components
B.
Gain access to the entire corroded area.
(1)
Corrosion products typically retain moisture. If those products are not
removed, corrosion will continue. Corrosion can take place within layered
construction or under (behind) equipment fastened in place.
C.
Mechanically remove the corrosion.
(1)
Chemicals will not remove corrosion. The best chemicals can do is interrupt the
corrosion cell by either displacing water or shielding corrosion products from
oxygen. In either case, the effect is temporary and will need to be renewed.
(2)
Sand mild corrosion.
(3)
Use rotary files or sanding disks for heavier corrosion. Finish up with fine
sand paper.
NOTE:
Do not use metallic wool. Metal particles will be embedded in the surface,
which will initiate additional corrosion.
D.
Determine the extent of corrosion damage.
(1)
Direct measurement is simplest.
(2)
Indirect measurement may be necessary
(a)
Eddy Current or ultrasound tools can be used for thickness measurement away
from part edges.
E.
Repair or replace corrosion damaged components
(1)
Replace damaged or corroded steel or aluminum fasteners.
(2)
If the material is sheet or plate, the thickness is allowed to be as little as
90% of the nominal thickness.
(3)
This general allowance is not allowed if:
(a)
The area of the part contains fasteners.
(b)
The reduced thickness compromises the fit or function of a part.
F.
Finish the new or repaired parts
(1) Apply Alodine or similar anticorrosion
compounds to new or repaired parts or
(2)
Apply zinc chromate or
(3)
Apply epoxy fuel tank primer.
(4)
Paint the exterior or visible interior parts
G.
Replace Removed Components.
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