Corrosion

Question 1

Corrosion that occurs when different metals are in contact with each other and an electrolyte. Recognizable by the presence of a buildup of corrosion deposits at the joints between metals

Answer 1

Galvanic

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Question 2

Intergranular

Answer 2

grain boundaries of the metals(cross sections), high strength aluminum alloys are most susceptible

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Question 3

Exfoliation

Answer 3

An advanced form of intergranular, surface grains of the metal are lifted up by the force of expanding corrosion, lifting up or swelling is visible evidence of exfoliation corrosion

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Question 4

Crevice

Answer 4

electrolyte inside crevice contains less O2 and more metal ions than electrolyte just outside the crevice(stagnant solution has pooled). This is common around gasket surfaces, lap joints, and under bolt or rivet heads

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Question 5

Stress corrosion cracking

Answer 5

Intergranular or transgranular cracking of a metal caused by the combined effects of constant tensile stress and corrosion.

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Question 6

Fillform

Answer 6

O2 concentration cell corrosion or crevice corrosion occurs on metal surfaces having a thin organic coating system, wormlike trace of corrosion beneath the paint film. Starts at breaks in the coasting system such as scratches and cracks around fasteners and seams, Affected by humidity, keep aircraft below 65%

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Question 7

What are the two most important factors of preventing corrosion and the only which can be controlled by field personnel

Answer 7

1. the removal of the electrolyte
2. application of protective coatings

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Question 8

Iron in the presence of moisture and air will return to its natural state which is what

Answer 8

iron oxide rust

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Question 9

Aluminum and magnesium form corrosion products that are what

Answer 9

White oxides or hydroxides

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Question 10

What is the most common type of corrosion and is also can be the most effectively treated by maintenance personal is what

Answer 10

Electrochemical corrosion

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Question 11

What type of corrosion commonly occurs at the edge of aircraft skin sections or next to countersunk fasteners

Answer 11

Exfoliation

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Question 12

What type of corrosion happens with a flashlight battery

Answer 12

Galvanic

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Question 13

What metal has the highest potential to corrode

Answer 13

Lithium

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Question 14

The most common type of corrosion, resulting from direct chemical attack on a metal surface that proceeds uniformly over the entire exposed surface. May show up as general dulling, etching, rough, frosted.

Answer 14

Uniform surface corrosion

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Question 15

This type of corrosion most often occurs on extruded sections of metal and is found primarily in aluminum sheet around steel fasteners.

Answer 15

Exfoliation

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Question 16

This corrosion is characterized by grooves, gullies, waves, rounded holes and/or valleys in the metal surface.

Answer 16

Erosion

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Question 17

What can cause stress corrosion

Answer 17

Welding, cold working, forming, and heat treatment operations

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Question 18

Corrosion occurs at contact areas between materials under load subject to repeated vibration, has a general appearance of galling, in which chunks of metal are torn from the surface. Occurs commonly in landing gear component attachment areas or engine blade roots

Answer 18

Fretting

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Question 19

Also called high temperature oxidation, absence of water can occur at high temperatures such as those found in turbine engine combusters, turbine sections, and afterburners

Answer 19

Hot Corrosion

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Question 20

What type of corrosion attacks aluminum alloy

Answer 20

surface pitting, intergranular, exfoliation, stress, and fretting- white to gray powder

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Question 21

What type of corrosion attacks magnesium alloy

Answer 21

Pitting- white powdery, snowlike mounds, and white spots on surface

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Question 22

How does corrosion usually present

Answer 22

Chalky white powder or green discoloration

CGTO PG-85-00-310-A 7-91

Question 23

Pitting

Answer 23

most common on stainless steels but common on aluminum and magnesium alloys, white or grey powdery deposits, similar to dust which botch the surface, tiny pits or holes can be seen on the surface

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