01-1A-509-1 Ch3

Question 1

What is the s the chemical
or electrochemical deterioration of a material?

Answer 1

Corrosion

Question 2

What type of corrosion product does Aluminum and magnesium form?

Answer 2

white oxides or hydroxides

Question 3

What is the most common type of corrosion and the one that can be treated effectively by maintenance personnel?

Answer 3

Electrochemical corrosion

Question 4

Can corrosion occur in the absence of water?

Answer 4

Yes but only at high temperatures found in gas turbine
engines.

Question 5

What is the smallest unit of an element, made up of positively charged nucleus surrounded by a system of negatively charged electrons?

Answer 5

Atom

Question 6

What is a negatively charged subatomic particle?

Answer 6

Electron

Question 7

What is an atom or group of atoms or molecules which have acquired a net electric charge by gaining or losing electrons?

Answer 7

ION

Question 8

If an ION gains electrons, is it positive or negative?

Answer 8

It is a negative ION

Question 9

If an ION loses electrons, is it a positive or negative ION?

Answer 9

It is a positive ION.

Question 10

Ions are forced to move through liquid solutions, what can ions not move through?

Answer 10

metal conductors

Question 11

What is a liquid (usually water) solution containing ions?

Answer 11

Electrolyte

Question 12

In the theory of corrosion, when a metal corrodes, the atoms ______ electrons and become _______ charged?

Answer 12

lose, positively

Question 13

How many conditions are necessary for metal corrosion to occur?

Answer 13

4
a. a metal which has tendency to corrode must be present
b. a dissimilar conductive material must be present
c. a conductive liquid (electrolyte) must connect the anode and cathode
d. electrical contact between the anode and cathode must exist

Question 14

What is the corroding metal called?

Answer 14

anode

Question 15

Filiform corrosion can be prevented by storing equipment and aircraft in an environment with a relative humidity below ___%, by using coating systems having a low rate of diffusion for oxygen and water vapors, and maintaining coatings in good condition, and applying corrosion preventive compounds(CPCs) when coating is damaged.

Answer 15

65%

Question 16

Filiform corrosion is a form or ____ corrosion.

Answer 16

Crevice corrosion

Question 17

Methods to minimize crevice corrosion include closing the crevice by welding, sealant, or soldering, and use of ______.

Answer 17

nonabsorbent gaskets (such as Teflon)

Question 18

Crevice corrosion may occur in?

Answer 18

In any crevice where a stagnant solution has pooled. Crevices are usually found at gasket surfaces, lap joints, and under bolt or rivet heads.

Question 19

Exfoliation Corrosion is an advanced form of what type of corrosion?

Answer 19

intergranular corrosion

Question 20

What is intergranular corrosion?

Answer 20

Is an attack on the grain boundaries of the metal

Question 21

Pitting corrosion failures are common in ____ electrolytes.

Answer 21

electrolytes containing chloride or chlorine containing ions such as sea water

Question 22

______ corrosion is a form of extremely localized attack that results in holes in the metal.

Answer 22

Pitting corrosion

Question 23

Galvanic occurs when ______ are in contact with each other and an electrolyte such as sea water.

Answer 23

different metals

Question 24

What is the most common type of corrosion?

Answer 24

Uniform surface corrosion.

Question 25

What is uniform surface corrosion?

Answer 25

it is a direct chemical attack on a metal surface that proceeds uniformly over the entire exposed surface

Question 26

What type of corrosion it this: the surface becomes rough and possibly frosted in appearance. Magnesium and low alloy steels are most susceptible to this type of corrosion.

Answer 26

Uniform surface corrosion

Question 27

Which corrosion type is : due to impingement or cavitation can be accelerated due to the action of a corrosive fluid against the metal surface.

Answer 27

Erosion Corrosion

Question 28

How is erosion corrosion characterized?

Answer 28

by grooves, gullies, waves, rounded holes, and or valleys in the metal surface.

Question 29

What is the difference between hydrogen embrittlement and Stress Corrosion Cracking(SCC)?

Answer 29

Hydrogen embrittlement is very similar to SCC. They are distinguished by the interaction of an applied electrical current with the base metal. -if the current makes the metal more anodic and cracking is accelerated the failure mechanism is SCC. -If the current makes the metal more cathodic, which accelerates hydrogen generation, the failure is hydrogen embrittlement.

Question 30

What is corrosion fatigue?

Answer 30

is the cracking of metals caused by the combined effects of cyclic stress and corrosion.

Question 31

Since pure aluminum is more corrosion resistant that most alloys, aluminum alloys are often covered with a thin layer of what?

Answer 31

a thin layer of nearly pure aluminum called cladding or Alclad.