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AIRFRAME REPAIR > CHAPTER 6 - MATERIALS AND CORROSION > Flashcards

CHAPTER 6 - MATERIALS AND CORROSION Flashcards

1
Q

GENERAL INTRODUCTION
What two categories are metals and alloys separated into?

A

Ferrous and Non-ferrous

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2
Q

GENERAL INFOMATION
How would you define an alloy?

A

The addition of other metals, or substances, to a basic metal, in order to obtain desirable properties

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3
Q

STANDARD AND SPECIFICATIONS
Why are standards beneficial to business and to individuals?

A

Defines accurate measurement, lowering production costs, improves product performance, quality, uniformity, interoperability and functionality
Many benefits

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4
Q

STANDARDS AND SPECIFICATIONS
How do British, French and American Standards each measure a metal’s thickness?

A

British: Standard Wire Gauge
French: Millimetres
American: Thousands of an inch

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5
Q

STANDARDS AND SPECIFICATIONS
State which standards are oldest to newest between British, French and American..

A

British 1901
American 1904
French 1943

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6
Q

STANDARDS AND SPECIFICATIONS
Who produces the International Standards? And their correct abbreviation..

A

ISO
International Organisation for Standardisation

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7
Q

STANDARDS AND SPECIFICATIONS
Which standard system is most frequently used in MOD?

A

Defence Standard

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8
Q

STANDARD AND SPECIFICATIONS
Why do we need Proof of Conformity for metallic and non-metallic materials?
Where is this from?

A

To show it is safe to be used on an aircraft
Give directly from the contractor

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9
Q

STANDARDS AND SPECIFICATIONS
What materials do not require Certificate of Conformity?

A

Materials supplied under Federal Military Stock (FMS)

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10
Q

COLOUR CODING
What scheme is used for rapid identification but should not be used as sole means of identifications?

A

Colour coding

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11
Q

COLOUR CODING
What material pieces are not colour coded?

A

Thin gauge sheets

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12
Q

FERROUS METALS
What is the difference between ferrous and non-ferrous metals?

A

Ferrous metals contain mostly iron

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13
Q

HEAT TREATMENT OF SHEET ALLOYS
Which treatment is used to change the metal into a very soft and malleable condition?

A

Annealing

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14
Q

HEAT TREATMENT OF SHEET ALLOYS
Which treatment changes the metal into a soft condition? It also gives the metal some specified qualities when it has aged?

A

Heat treatment

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15
Q

HEAT TREATMENT OF SHEET ALLOYS
Why is Refrigerated Storage used as a treatment?

A

Slows down the natural age process to keep the metal in its heat treated or quenched condition for longer

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16
Q

HEAT TREATMENT OF SHEET ALLOYS
What is another term for precipitation (accelerated) treatment?

A

Artificial Age Treatment

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17
Q

HEAT TREATMENT OF SHEET ALLOYS
What is the benefits of Artificial Age Treatment?

A

Maximum strength of an alloy which can be heat treated
It is necessary to artificially age the material

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18
Q

HEAT TREATMENT OF SHEET ALLOYS
What process occurs are room temperature?

A

Natural Age Process

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19
Q

HEAT TREATMENT OF SHEET ALLOYS
What happens to all alloys which go through the natural age process?

A

Their strength begins to increase immediately when they begin to cool

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20
Q

AIRCRAFT ENVIRONMENTAL DAMAGE PREVENTION AND CONTROL
What does the term Environmental Damage mean?

A

Describes the physical degradation of material properties as a direct result of interaction with the climate or environment

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21
Q

AIRCRAFT ENVIRONMENTAL DAMAGE PREVENTION AND CONTROL
What three major factors are included with ED?

A

Corrosion
Erosion
Degradation of surface finish and composite material properties

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22
Q

AIRCRAFT ENVIRONMENTAL DAMAGE PREVENTION AND CONTROL
What is the most significant form of ED?

A

Corrosion

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23
Q

AIRCRAFT ENVIRONMENTAL DAMAGE PREVENTION AND CONTROL
What are the 4 major effects of corrosion?

A

Reduce static strength
Initiate stress corrosion cracking
Shorten fatigue life
Detrimentally affects avionics and mechanical equipment

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24
Q

AIRCRAFT ENVIRONMENTAL DAMAGE PREVENTION AND CONTROL
What should a permanent protective metallic coating have in comparison to the metal

A

A higher resistance to corrosion

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25
Q

AIRCRAFT ENVIRONMENTAL DAMAGE PREVENTION AND CONTROL
What are the three general classes of coatings?
Explain how the work..

A
  1. Metallic Coatings - protects by preventing access of the corrosive agent - protects sacrificially
  2. Metallic Coatings - protects by exclusion but do not protect sacrificially so could accelerate corrosion once underlying metal is exposed
  3. Surface Conversion Coatings - provide a reservoir of corrosion inhibitor - acts as a good base for paint
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26
Q

AIRCRAFT ENVIRONMENTAL DAMAGE PREVENTION AND CONTROL
Why are supplementary protectives important?

A

Provide short and long term temporary protectives that are easily removed by solvent action and semi-permanent materials

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27
Q

TYPES OF CORROSION
Define corrosion..

A

Tendency for a metal to revert to their thermodynamically more stable oxidised state

28
Q

TYPES OF CORROSION
Which metals are strongly resistant to corrosion?

A

Gold and Platinum

29
Q

TYPES OF CORROSION
What two types of reaction may occur between metals and their environments?

A

Either dry or in an aqueous environment

30
Q

TYPES OF CORROSION
What is the term oxidation usually describing?

A

The direct combination of a metal with the oxygen of the atmosphere

31
Q

TYPES OF CORROSION
What physical changes show oxidation in the materials below?
1. Iron/Steel
2. Aluminium Alloys
3. Magnesium Alloys

A
  1. Red Rust
  2. White to grey powdery deposits
  3. Same as above however give a fluffy or granular appearance
32
Q

TYPES OF CORROSION
Before the specific signs, what are the early signs of corrosion?

A

Flakes or blisters in the paint finish

33
Q

TYPES OF CORROSION
What is the most usual type of corrosion? Which contaminants usually cause this?

A

Surface Corrosion

Sea-air
Aircraft exhaust gases
Funnel smoke

34
Q

TYPES OF CORROSION
State the type of corrosion..

Frequently occurs where there is a leakage of a highly corrosive fluid, such as battery acid. Usually found on metals which have a natural oxide skin.

A

Pitting Corrosion

35
Q

TYPES OF CORROSION
State the type of corrosion…

Damage is in the grain boundaries in the metal. Showed as a group of corrosion areas or cracks on the metal surface - doesn’t always occur. Gives very little, or no, external indication

A

Intergranular corrosion

36
Q

TYPES OF CORROSION
State the type of corrosion…

A type of metal failure can occur and cause cracks from the internal or external structural or operational loads causing stress

A

Stress corrosion

37
Q

TYPES OF CORROSION
State the type of corrosion…

Cyclic stresses from an external loads cause this type of stress corrosion. Cracks start as small pits

A

Fatigue Corrosion

38
Q

TYPES OF CORROSION
State the type of corrosion…

Very small movements between two heavily loaded surfaces, one of which must be metal. Shows at an early stage as a change of the surface colour. Steel shows as a brown stain

A

Fretting Corrosion

39
Q

TYPES OF CORROSION
State the type of corrosion…

Areas which are liable to preferential attacks, usually by a differential aeration form of corrosion intensified by the high ratio of cathode to anode area involved

A

Crevice Corrosion

40
Q

TYPES OF CORROSION
State the type of corrosion…

Occurs beneath thin protective coatings on aluminium and steel alloys. Often starts at fasteners and extends as thread-like lines of corrosion under paint. Usually very shallows and not structurally dangerous

A

Filiform Corrosion

41
Q

TYPES OF CORROSION
State the type of corrosion…

A form of intergranular corrosion in which the attack occurs in layers parallel to the surface. The wedging action causes lifting of the metal surface at an early stage when the corrosion is close to/on the surface. The further down this starts, the more detrimental it shall be

A

Exfoliation or Layer Corrosion

42
Q

TYPES OF CORROSION
What is another term for layer corrosion?

A

Exfoliation Corrosion

43
Q

TYPES OF CORROSION
How does Electrochemical Corrosion occur?
IF this occurred between Zinc and Copper, which one would be the anode? Which is the cathode?

A

Caused by an electrolytic effect between two different metals which touch via liquid

Anode: Zinc (progressively decreases in size)
Cathode: Copper ( progressively increases in size)

44
Q

CORROSION PRONE AREAS
What are the the key watchwords for all husbandry procedures?

A
  1. Keep aircraft CLEAN
  2. Keep aircraft DRY
  3. Maintain aircraft PROTECTIVE COATINGS
45
Q

CORROSION PRONE AREAS
List the top 7 areas prone to corrosion…

A

External surfaces
Undercarriages
Helicopter Rotating Assemblies
Engine Intakes, Cooling Air Vents
Electrical Equipment
Exhaust Areas
Cargo Floors

46
Q

EROSION PREVENTION AND CONTROL
What is Erosion?

A

Erosion is the loss of material from aircraft components by the action of small particles such as grit, sand, stones, ice and water

47
Q

EROSION PREVENTION AND CONTROL
State the issues which erosion causes…

A

Destroys component corrosion protection
Introduces wear to mechanical and avionics system
Degrades optical quality and strength of transparencies
Affect intake and airframe aerodynamics
A source of fatigue crack initiation

48
Q

EROSION PREVENTION AND CONTROL
What can significantly reduce the risk of erosion?

A

Effective use of tap
Abrasion-resistant or anti-erosion paints
Suitable operating procedures

49
Q

EROSION PREVENTION AND CONTROL
Who must authorise the specific process and materials used to protect and control against erosion?

A

Type Airworthiness Authority and detailed within the Aircraft Document Set

50
Q

MAINTENANCE IN EXTREME ENVIROMENTS
What are the two extreme environments?

A

Artic Conditions
High Temperature environments

51
Q

MAINTENANCE IN EXTREME ENVIRONMENTS
List the three high temperature environments..

A

Desert
Arid Salt Laden
Hot and Humid

52
Q

MAINTENANCE IN EXTREME ENVIRONMENTS
What are the three major consequences of corrosion?

A
  1. Reduction in static strength
  2. Stress corrosion cracking
  3. Shortening of fatigue life
53
Q

DISCOVERING AND RECTIFYING CORROSION
What are the two types of ways corrosion can be removed?

A

Mechanical and Chemical

54
Q

DISCOVERING AND RECTIFYING CORROSION
What mechanical methods are used to remove corrosion?

A

Grinding with abrasive wheels
Manual grinding
Abrasive blasting using a Vacu-Blast

55
Q

DISCOVERING AND RECTIFYING CORROSION
State 3 essential requirements when removing corrosion..

A

Remove all corrosion, hidden and visible
Leave surface smooth
Leave surface uncontaminated by the removal process
Do not blend material into a crack
Do not exceed any metal removal limits that may apply

56
Q

DISCOVERING AND RECTIFYING CORROSION
What materials usually require chemical removal of corrosion products?

A

Aluminium and magnesium alloys

57
Q

DISCOVERING AND RECTIFYING CORROSION
Where is chemical removal methods potentially dangerous?

A

Where residues cannot be completely removes eg crevices, laps and enclosed areas

58
Q

RESTORATION OF PROTECTIVE FINISH
Why do we use Pre-treatment?

A

To provide protection and give a suitable base for the adhesion of the primer

59
Q

REMOVAL AND NEUTRALISING CORROSIVE AGENTS
What should be used to clean up in the event of a acid spillage?

A

Use a clean rag to soak up as much as possible
Neutralise the area with an aqueous solution of 10% by weight of sodium carbonate

60
Q

REMOVAL AND NEUTRALISING CORROSIVE AGENTS
How do you know when cleaning is adequate?

A

Universal paper will give a PH value between 5 and 9
Paying close attention to to positions where the spill could be trapped

61
Q

REMOVAL AND NEUTRALISING CORROSIVE AGENTS
How often after a acid or alkali spill should the aircraft be reexamined?

A

Re-examine the area at weekly intervals
If there is no contamination in the first week, still re-examine a week later

62
Q

REMOVAL AND NEUTRALISING CORROSIVE AGENTS
What actions should be took after an alkali spill?

A

Use a clean rag to help soak up the spillage
Use a 5% (by weight) solution of chromic acid in water

63
Q

REMOVAL AND NEUTRALISING CORROSIVE AGENTS
What should be noted when using chromic acid?

A

Chromic acid is poisonous an corrosive t some metals at high concentration. Rags contaminated are at fire risk and should be disposed of as industrial waste

64
Q

REMOVAL AND NEUTRALISING CORROSIVE AGENTS
How should micro-organisms be removed?

A

Removed with a bristle brush and a solution of one part (by volume) of cleaning compound and five-parts hot water at about 50 degrees. Area must be rinsed with copious quantities of clean water

65
Q

REMOVAL AND NEUTRALISING CORROSIVE AGENTS
After removal of micro-organisms, what areas should be carefully inspected for remaining contamination and corrosion?

A

Tank surfaces and plumbing

AIRFRAME REPAIR (13 decks)

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