(2)Livestock cargo. Subsequent to livestock hauling on an airplane, spe-cific areas should inspected for signs of contaminants that cause corro-sion. Detailed procedures are given in 20-61-00.
Volume 1
20-20-00
Page 2
OCT 01/01
CORROSION PREVENTION MANUAL
GENERAL INFORMATION
INSPECTION AND DETECTION
D. Methods of Inspection. Visual or nondestructive inspection (NDI) procedures
are used for identifying the existence of corrosion. For general inspection,
the visual means aided by magnifying glasses, borescopes, etc., is used
extensively. The NDI techniques have limited capability to locate or detect
corrosion because of complexity of instrumentation, complexity of areas
being inspected and time consumed to make the inspection. In specific local-ized areas where inspection by visual means is impossible or where extent of
corrosion has to be determined after visual detection, the NDI technique may
be used. The following NDI techniques are used to inspect the localized
areas; however, the method employed should be at the judgment of the NDI
technician.
(1)Eddy current. Eddy current can be used to locate corrosion in skin, dou-bler and spar areas. The method is also used to determine if corrosion
visible by corrosion products, skin bulging or joint dislocation has
generated microcracks.
(2)Ultrasonic. Ultrasonic inspection technique is used for flaw detection
in honeycomb sandwich constructions or bonded panels. Corrosion can be
detected by measurement of panel thickness by ultransonic means.
(3)Radiographic. Radiography (X-ray) is used for flaw detection in areas
not accessible for visual inspection without major disassembly. This
method is also used for backup method to other NDI techniques (i.e.,
detect core corrosion in sandwich panels located by the ultransonic
method). Severe corrosion can be detected by radiographic means if the
depth or metal loss is 20% of the panel thickness or greater.
(4)Penetrant. The penetrant technique can be used on nonmagnetic parts such
as thick skins, forgings, etc., after paint stripping and removal to
determine the presence of cracks. This technique is also used to detect
surface and intergrandular corrosion.
(5)Magnetic particle. This technique may be used on low alloy steel parts.
The presence of microcracks, after paint stripping and corrosion
removal, can be detected
2. Corrosion Detection
A. General. Painted metals, plated surfaces, or aluminum clad normally will not
be susceptible to corrosion as unpainted, unplated or nonclad surfaces. The
metals in the corrosion-affected areas are characterized by a scaly or blis-tered appearance, or at times by discoloration or blistering of the paint.
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