TM 1-1520-238-23
1-158
Change 9
1.49.
CORROSION CONTROL/INSPECTION – continued
d. Remove corrosion where it is found.
(1) Be sure ALL corrosion is removed. Remove paint to make sure.
(2) Treat area, then paint or protect as directed in paragraphs 1.49.15 and 1.49.16.
e. There are three general types of metal in the helicopter: aluminum, steel (ferrous alloys), and magne-
sium.
(1) Metal identification kit can be used to find the type of metal you are working with.
(2) A simple check will tell you if the material is steel. Use a magnet: if it holds it is on steel.
(3) If required, go to TM 1-1500-344-23 for further corrosion information.
1.49.4. Corrosion Identification
a. Aluminum.
(1) Look for a white-to-gray powdery metal. Check if it can be removed by using something softer than the
metal part.
(2) Look to see if the part is slightly yellow. This is caused by an anodize coating used on some aluminum
parts.
(3) Go to paragraph 1.49.15 for corrosion removal.
b. Steel (ferrous alloys).
(1) Look for rust. It should be reddish brown scaling or flaking on the surface.
(2) Steel is painted to prevent corrosion. Look for breaks in the painted surface.
(3) Check the part with a magnet if in doubt: if it holds, it is steel.
(4) Go to paragraph for 1.49.15 for corrosion removal.
c. Magnesium.
(1) If the part is not steel or aluminum (nose gearboxes, main transmission, tail rotor gearboxes, and genera-
tors) go to TM 1-1500-344-23 for information on positive identification.
(2) TM 1-1500-344-23 gives a chemical procedure that will identify the metal.
(3) Go to paragraph 1.49.15 for corrosion removal.
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