Piper Malibu Meridian PA-46-500TP Airplane Maintenance Manual page 1192

Type of Material
Steel
Aluminum
Magnesium (highly susceptible
to corrosion)
Cadmium (plating)
Chromium (plating)
* Red rust generally shows on bolt heads, hold-down nuts and other aircraft hardware. Its presence in
these areas is generally not dangerous. However, it is indicative of a need for maintenance and also of
the possibility of corrosive attack in more critical areas. Any corrosion on the surface of a highly
stressed steel part is potentially dangerous. A careful removal of corrosion products using mild
abrasives (rough or fine grit aluminum oxide paper) is necessary, using care not to overheat the metal
when removing the corrosion.
** For abrasion, do not use dissimilar material (i.e. steel wool on aluminum). Remove only the material
required to clean up the affected area.
After cleaning, ensure that no cleaning solution remains in any holes, crevices or joints, as it may
lead to increased corrosion. Also, all exposed areas (landing gear, flap tracks, control surface, hinge
parts, etc) should be lubricated after cleaning.
C. Corrosion Inspections
NOTE: Some areas of the airplane have been treated with a corrosion inhibiting compound which
requires re-treatment at 5 year intervals. See 5-30-00.
Corrosion should be inspected for at every inspection. In trouble areas, the inspection frequency
should be increased.
In addition to routine inspections:
(1) Aircraft operating around a marine environment should be given special checks on a weekly
basis.
(2) Aircraft operating in a semi-acid condition should be inspected monthly. A semi-acid condition
is likely to occur in industrialized areas where sulfur bearing particles in dust, smoke and smog
attack painted surfaces.
51-10-00
PAGE 2
Apr 15/07
PIPER AIRCRAFT, INC.
PA-46-500TP, MALIBU MERIDIAN
MAINTENANCE MANUAL
CHART 1
TYPES OF METAL CORROSION
Type of Corrosion
Rust*
White to grey powdery material.
White powdery snow-like
mounds and white spots.
White to brown to black
mottling of surface (plating
is still protecting until iron
appears).
May pit in chloride
environment.
Remedy**
Complete removal of
corrosion by mechanical
means.
Mechanical polishing or
brushing with material
softer than aluminum.
Mechanical removal of
corrosion should be limited
to metal surfaces from
which the cadmium has
been depleted.
Promotes rusting of steel
where pits occur in the
coating.
6F12