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M6 Resit > 6.4 Corrosion✅(6) > Flashcards

6.4 Corrosion✅(6) Flashcards

1
Q

How does corrosion occur?

A

chemical or electrochemical reactions cause metals to be oxidised, forming salts and oxides of the metal

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2
Q

What is erosion

A

destruction through mechanical action

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3
Q

What is the advantage of a passive film produced on the surface of aluminium and titanium

A

-prevents further surface oxidisation

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4
Q

Can corrosion be prevented?

A

No

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5
Q

Corrosion is a natural process, and its prevention is almost impossible, but it can be controlled (T or F)

A

T

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6
Q

What is the best way to control corrosion?

A
  • Cleanliness
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7
Q

What is galvanic corrosion?

A
  • When 2 dissimilar metals (more noble & less noble) make electrical contact in the presence of an electrolyte
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8
Q

Metals from the less noble group corrode easier when they are in contact with more noble metals (T or F)

A

T

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9
Q

What is electrolytic corrosion?

A

Due to an electrolyte and the flow of an electrical current between the 2 metals, caused by an externally induced electromotive force (EMF)

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10
Q

Galvanic corrosion describes the interaction between two different metals (T or F)

A

T

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11
Q

Electrolytic corrosion is caused by an external source of current (T or F)

A

T

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12
Q

Bacteria can be classified into 2 categories which are

A
  • aerobic
  • anaerobic
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13
Q

What is a microbial attack?

A
  • includes actions of bacteria, fungi or moulds (commonly found in aircraft fuel tanks)
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14
Q

Microbial growth occurs at the interface of water and fuel (T or F)

A

T

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15
Q

How can microbial composition be minimised

A
  • scheduled water drainage from fuel tanks
  • Inspection for milky white substance
  • application of biocide to prevent further growth
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16
Q

What are the two main areas that are susceptible to corrosion on an aircraft

A
  • toilets
  • galleys
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17
Q

What is stress corrosion cracking (SCC)

A
  • growth of crack formation in a corrosive environment
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18
Q

What is a common place for stress corrosion

A
  • between rivets in a stressed skin
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19
Q

What is Filiform corrosion

A

special form of oxygen-concentration cell corrosion or crevice corrosion that occurs on metal surfaces with organic coating system

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20
Q

Filiform corrosion occurs when the relative humidity of the air is what?

A

78%-90%

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21
Q

What occurs if filiform corrosion is not removed

A

leads to intergranular corrosion (especially around fasteners and seams)

22
Q

What is pitting corrosion

A

localised form of corrosion that produces holes in the material

23
Q

What is the most common type of corrosion on aluminium and magnesium

A

pitting corrosion

24
Q

Pitting corrosion is dangerous because of the vertical extension, which decreases the materials strength (T or F)

A

T

25
Q

What is intergranular corrosion

A

usually presents itself as cracking and tends to accelerate over time

26
Q

What is exfoliation corrosion

A

advanced form of intergranular corrosion

27
Q

Exfoliation is most prone to occur in what products

A

wrought products

28
Q

What is fretting corrosion

A

special type of erosion-corrosion which occurs due to vibration and slipping

29
Q

How is fretting identified

A
  • black or grey-brown powder/paste
30
Q

What can help reduce rubbing friction and prevent fretting corrosion

A

lubricant or sealant

31
Q

What is a crevice corrosion?

A
  • attacks metal surface through a stagnant solution in the crevices
32
Q

Even small amounts of mercury can lead to serious corrosion problems for various metals and alloys (T or F)

A

T

33
Q

Mercury attacks aluminium through a chemical reaction known as what?

A

amalgamation

34
Q

Disadvantages of mercury

A
  • damaging to aircraft structures
  • mercury vapours is dangerous for people
35
Q

Why are noble metals such as silver, gold and platinum used in aircraft assemblies

A
  • because of their resistance to surface attack
  • and improved electrical and thermal conductivity
36
Q

Copper and copper alloys are also relatively corrosion resistant (T or F)

A

T

37
Q

How is severe copper corrosion evident by

A

accumulation of green to blue copper salts

38
Q

What is dry corrosion

A
  • metals form a thin oxide layer due to the reaction of metals with oxygen
39
Q

What is wet corrosion

A
  • takes place in humidity exceeds 60%
40
Q

If an alkaline or acidic liquid contacts metal, corrosion forms. This is known as?

A

direct chemical attack

41
Q

Examples of corrosion prone areas?

A
  • exhaust areas
  • battery compartment
  • lavatories and galley access
  • bilge areas
  • wheel well (LG area)
42
Q

Aluminium is generally corrosion resistant (T or F)

A

T

43
Q

When a anodised coating is damaged, how can it be partially restored?

A

by chemical surface treatment

44
Q

What is the corrosion product of aluminium

A

white-to-grey powdery material

45
Q

What is the corrosion product of copper

A

bluish-green coating on surface of material

46
Q

Is magnesium highly susceptible to corrosion

A

yes

47
Q

magnesium is particularly susceptible to what type of corrosion

A

pitting corrosion

48
Q

What material is highly corrosion resistant?

A

titanium

49
Q

If titanium is in contact with zinc and cadmium plated parts, what can occur

A

promote cracking

50
Q

Thicker structural components are more prone to corrosive attacks due to variations in their composition (T OR F)

A

T

51
Q

What attacks can occur on copper components

A
  • staining
  • tarnish

M6 Resit (10 decks)

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