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Mod 6 > 6.4 > Flashcards

6.4 Flashcards

1
Q

Corrosion Definition

A

Metals returning to thermodynamically stable state

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2
Q

Anode

A

Attacked

Losses material

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3
Q

Cathode

A

Corrosive

Gains material

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4
Q

What is a neutral atom

A

Ion

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5
Q

Oxidation is

A

The combination of a Metal with Oxygen of Atmosphere

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6
Q

Oxide Film

A

Forms to protect against corrosion

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7
Q

What metals is Oxide film present in

A

Pure Aluminium

Titanium

Chromium

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8
Q

Oxidation Rate decreases as

A

Oxide film thickness increases

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9
Q

If Oxides react with Water

A

Increased Oxidation

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10
Q

Increases in temp Oxidation

A

Increases

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11
Q

Corrosion in Steel

A

Rust

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12
Q

Corrosion in Aluminium Alloy

A

White Powder

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13
Q

Corrosion in Magnesium Alloy

A

Grey Powder

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14
Q

Corrosion in Copper Alloys

A

Green Coating

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15
Q

Corrosion in Cadmium and Zinc

A

White Powder

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16
Q

Another Name for Galvanic Action

A

Electro Chemical

Dissimilar Metal Corrosion

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17
Q

Rate of Galvanic Action

A

Slow

Low Current

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18
Q

What is needed for Galvanic Action

A

2 Disimilar Metals

Electrolyte

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19
Q

Crack Formation in a corrosive environment

A

Stress

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20
Q

Stress is more common in

A

Alloys

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21
Q

Stress can lead to failure below UTS but especially in

A

Elevated Temp

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22
Q

Surface Corrosion

A

Direct Chemical Attack

EG: Battery Acid Or Waste

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23
Q

Pitting

A

Localised

Small holes act as stress risers

Caused via

Non Metallic lnclusions
Poor Coating
Damage

24
Q

Crevice Corrosion

A

Aluminium Alloys

Localised

Bulges between fasteners

Due to changes in Local Chemistry of Crevice

Prevented via Primer and Sealent before Assy

25
Q

Intergranular Corrosion

A

Aluminium Alloys and Stainless Steels

Cracks and Blisters

Due to Improper Heat Treatment or Heat In Aircraft

Must be scrapped

26
Q

Laminar / Exfoliation Corrosion

A

Extruded or Rolled Parts

Extreme Intergranular

Layers of corrosion

27
Q

Fretting Corrosion

A

2 Loaded Surfaces with Continuous Movement

Removes Coating

Causes Fatigue and Cracking

28
Q

Fretting Corrosion in Steel

A

Cocoa Powder

29
Q

Fretting Corrosion In Aluminium Alloys and Magnesium Alloys

A

Grey / Black Powder

30
Q

What is a Anti Fretting Corrosion Agent

A

Molybdenum Disulphide Grease

31
Q

Stress Corrosion

A

Caused by Tensile Stress in a Corrosion Environment

Cracks Lengthen Rapidly

32
Q

Tensile Stress + Aluminium + _____

= Stress Corrosion

A

Hydrogen

33
Q

Tensile Stress + High strength steel + _____

= Stress Corrosion

A

Hydrogen

34
Q

Tensile Stress + Stainless + _____

= Stress Corrosion

A

Chlorides

35
Q

Filiform Corrosion

A

Oil or Grease Films

Worm like

Often starts and rivets and spreads

36
Q

Mercury Spillage

A

Aluminium Alloy

Forms a Amalgam

Soaks in and attacks grain boundaries

Aircraft cannot be moved

Cleaned

X Ray

37
Q

How to Clean Mercury Spillage

A

Vacuum

Syringe

Nickel plated carbon fiber brush

38
Q

Microbial Corrosion

A

Fuel tanks

Dormaint until water and temp

Feeds of hydrocarbons in fuel

Attaches and damages structure

39
Q

Hydrogen Embrittlement in Ferrous Metals

A

Can occur at loads 30% of UTS

Hydrogen from Corrosion

Attaches to Surfaces under sustained load

Embrittlement Occurs

Harder the metal more likely for HE

40
Q

Removal of Hydrogen Embrittlement in Ferrous

A

Bake Op at 191

41
Q

Hydrogen Embrittlement in Titanium

A

Can be bonded

Room Temp; Acids

288 °C ; Steam Oil or Other Hydrogen
Stubstances

Hydrogen gathers at areas of high stress

HE reduces impact and tensile strength

42
Q

Removal of Hydrogen Embrittlement in Ferrous

A

Relief Op at 524 °C for 6 hours

43
Q

Corrosion Fatigue

A

Combination of Corrosion and Fatigue

Mechanical degradation due to cyclical loading and corrosion

Normal Fatigue
90% Nucleation 10% Propagation

Corrosion Fatigue
10% Nucleation 90% Propagation

44
Q

Corrosion in Iron + Steel

A

Rust

45
Q

Corrosion in Aluminium Alloys

A

White Grey Powder

46
Q

Corrosion in Magnesium

A

White

47
Q

Corrosion in Copper

A

Blue Green Patina

48
Q

Corrosion in Chromium and Zinc

A

White

49
Q

Corrosion in Nickel and Chromium

A

Blue Green

50
Q

Nickel Plating is used for

A

Heat Resistance

51
Q

Chromium Plating is used for

A

Wear resistance

52
Q

What can improve Electrolyte Conductivity

A

Dirt
Salts
Acidic Gasses
Exhaust Gasses

53
Q

What Battery Spillage is Acid Spillage

A

Lead Acid

54
Q

To Neutralise Acidic Spillage

A

10% By weight Sodium Bicarbonate

55
Q

What batteries can produce Alkaline Spillage

A

Nickel Cadmium (Patassium Hydroxide Spillage)

56
Q

How to neutralise Alkaline Spillage

A

Neutralised by 5% by weight Chromic Acid Crystals

Mod 6 (8 decks)

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