-2 chapter 3 Flashcards
The
costs resulting from corrosion can be minimized
by early
detection, identification, and treatment.
within what ranges during scheduled or unscheduled maintenance actions on aviation equipment or components shall be visually inspected for corrosion.
the area involved as well as
those within 3 feet or 36 inches (18 inches on each side)
A general inspection
of aviation equipment or components is performed as
follows:
a. Clean the area thoroughly or, for water sensitive areas, wipe the area with a clean cloth dampened with an approved solvent.
b. If corrosion is suspected, examine the area with a
10X magnifying glass and flashlight. Examine edges of
skin panels, rivet heads, and corrosion prone areas. If
there are blisters, bubbles, or other coating irregularities
present, attempt to dislodge the paint by scraping with a
sharp plastic tool. If paint does not easily dislodge and
corrosion is not suspected, the irregularity is probably
confined to the paint film itself and no further action
should be taken. When corrosion is suspected but no
irregularities are present, apply a strip of ASTMD6123
Type II flatback masking tape over the clean, dry area.
Hand rub the tape for several strokes in order to assure
good adhesion, and remove the tape with an abrupt
lifting motion. Where paint is removed, inspect and
determine the degree of corrosion.
c. Remove corrosion, clean and treat
the surface , and paint.
Aluminum corrosion
white, gray, or black and may appear
as a paste when wet, or a hard, adherent film or easily
crumbled deposits (i.e., powder) when dry
Magnesium corrosion
white and form in large amounts
with significant losses to the base metal.
Steel corrosion
red, brown, or black rust deposits which
are easily detected
Copper corrosion
are blue
or blue‑green and are also easily detected.
Titanium
and stainless steels
do not produce significant amounts
of corrosion products but can exhibit stress corrosion
cracking.
VISUAL INSPECTION
Visual inspection is
the most widely used method for the detection and
evaluation of corrosion. It is very effective for detecting
surface, exfoliation, pitting, and galvanic corrosion
The following tools can be used to find and
evaluate the extent of corrosion damage:
a. Flashlight.
b. 10X Magnifying Glass.
c. Plastic Scraper.
d. Borescope.
e. Depth Gage, Pin Micrometer Type.
f. Optical Depth Micrometer.
DEGREES OF CORROSION.
Corrosion shall
be evaluated after the initial inspection and cleaning
to determine the nature and extent of repair or rework
needed.
LIGHT CORROSION
At this degree, the
protective coating is scarred or etched and the condition
of the metal is characterized by discoloration and
pitting to a depth of approximately one mil (0.001
inch) maximum. This type of damage can normally be
removed by light hand sanding.
MODERATE CORROSION
This appears similar
to light corrosion, with the addition of blistering or
evidence of scaling and flaking of the coating or paint
system. The pitting depths may be as deep as 10 mils
(0.010 inch). This type of damage is normally removed
by extensive hand sanding or light mechanical sanding.
SEVERE CORROSION
Its general appearance
is similar to moderate corrosion, with the addition of
severe intergranular corrosion, blistering, exfoliation,
scaling, or flaking. The pitting depths are deeper than
10 mils (0.010 inch). This damage must be removed by
extensive mechanical sanding or grinding.
COMMON CORROSION PRONE AREAS should be:
Corrosion prone areas should be cleaned, inspected,
and treated more frequently than less corrosion prone
areas
