corrosion

Question 1

inevitable result when metals are exposed to water, air, etc.

Answer 1

corrosion

Question 2

what aircraft needs since they contain some metal

Answer 2

constant inspection and cleaning to minimize the destructive effects of corrosion

Question 3

what can corrosion result to

Answer 3

significant decrease in the thickness of original load bearing material that can lead to loss of structural integrity and catastrophic failure

Question 4

what leads to the early detection of corrosion

Answer 4

routine in-service inspections and consequent rectification

Question 5

deterioration of the metal by chemical or electrochemical attack

Answer 5

metal corrosion

Question 6

effects of deterioration

Answer 6

change the smooth surface, weaken the interior, or damage or loosen adjacent parts

Question 7

main source of corrosion in an aircraft

Answer 7

water or water vapor containing salt with oxygen in the atmosphere

Question 8

two types of corrosion

Answer 8

direct chemical attack and electrochemical attack

Question 9

corrosion process always involves what

Answer 9

metal that is attacked or oxidized suffers (anodic change) and corrosive agent is reduced (undergoing cathodic change)

Question 10

attack resulting from a direct exposure of a bare surface to caustic liquid or gaseous agents

Answer 10

direct chemical attack

Question 11

common agents causing direct chemical attack on aircrafts

Answer 11

• spilled battery acid or fumes from batteries
• welding residual
• caustic cleaning solutions

Question 12

types of fluxes used in these are corrosive which attack the metals or alloys

Answer 12

brazing, soldering, and welding

Question 13

what are hygroscopic in nature and absorb moisture which causes severe pitting

Answer 13

flux residues

Question 14

should be kept tightly capped and as far from aircraft as possible

Answer 14

caustic cleaning solution

Question 15

may be likened chemically to the electrolytic reaction that takes place in electroplating, anodizing, or in a dry cell battery

Answer 15

electrochemical attack

Question 16

reaction in electrochemical attack requires what

Answer 16

medium, usually water

Question 17

capable of conducting a tiny current of electricity

Answer 17

water

Question 18

what happens during electrochemical attack

Answer 18

quantity of corrosive agent is reduced and is not renewed or removed, may completely react with metal, becoming neutralized

Question 19

basis for effective corrosion control

Answer 19

regular cleaning, surface refinishing, medium is removed and minute electrical circuit is eliminated

Question 20

responsible for most forms of corrosion on aircraft structure and component parts

Answer 20

electrochemical attack

Question 21

types of corrosion

Answer 21

intergranular corrosion, galvanic, exfoliation, oxidation, fretting, uniform surface, filiform surface, pitting or general surface, stress, concentration cell corrosion

Question 22

occurs any time two dissimilar metals make electric contact in the presence of an electrolyte

Answer 22

galvanic corrosion

Question 23

When metals of the same galvanic grouping are joined together, what happens?

Answer 23

show little tendency for galvanic corrosion

Question 24

an advanced form of intergranular corrosion and shows itself by lifting up the surface grains of a metal by the force of expanding corrosion products occurring at the grain boundaries just below the surface.

Answer 24

exfoliation corrosion

Question 25

what is the visible evidence of intergranular corrosion

Answer 25

most often seen on extruded sections where grain thickness is usually less than in rolled forms.

Question 26

difficult to detect in its initial stage

Answer 26

exfoliation corrosion

Question 27

One of the simpler forms of corrosion is “dry” corrosion

Answer 27

oxidation corrosion

Question 28

When a metal such as aluminum is exposed to a gas containing oxygen, a chemical reaction takes place on the surface between the metal and the gas.

Answer 28

oxidation corrosion

Question 29

best way to protect iron from dry corrosion

Answer 29

keep oxygen from coming into contact with its surface and temporarily by covering the surface with oil or grease, or permanently with a coat of paint.

Question 30

deterioration of material that occurs at the interface of two contacting surfaces due to small oscillatory movements arising between them in the presence of a corrosive medium.

Answer 30

fretting corrosion

Question 31

former involves the creation of localized pits / small holes in the material surface which can be deep and significant to structural integrity whilst the latter corrosion form starts with a more widely dispersed uniform surface etching that dulls the surface and can progress to generate a rougher or frosted surface appearance.

Answer 31

pitting or general surface

Question 32

This occur when the metal is subjection to tensile stress in the presence of a corrosive environment.

Answer 32

stress corrosion

Question 33

can occur only in the presence of tensile stresses

Answer 33

stress corrosion

Question 34

common place for stress corrosion

Answer 34

between rivets in a stressed skin, around pressed in bushing or tapered pipe fittings.

Question 35

is corrosion of metals in a metal-to-metal joint, corrosion at the edge of a joint even though the metals are identical, or corrosion of a spot on a metal’s surface covered by a foreign material.

Answer 35

concentration cell corrosion

Question 36

type of corrosion is an attack along the grain boundaries of an alloy and commonly results from a lack of uniformity in the alloy structure.

Answer 36

intergranular corrosion

Question 37

particularly susceptible to intergranular corrosion

Answer 37

aluminum alloys and stainless steels

Question 38

Where an area of unprotected metal is exposed to an atmosphere containing battery fumes, exhaust gases, or industrial contaminants, a uniform attack over the entire surface occurs.

Answer 38

uniform surface corrosion

Question 39

the corrosion presents as random threadlike filaments under the paint often with the paint bulging in blisters raised by the corrosion products.

Answer 39

filiform surface corrosion