6.4

Question 1

Corrosion Definition

Answer 1

Metals returning to thermodynamically stable state

Question 2

Anode

Answer 2

Attacked

Losses material

Question 3

Cathode

Answer 3

Corrosive

Gains material

Question 4

What is a neutral atom

Answer 4

Ion

Question 5

Oxidation is

Answer 5

The combination of a Metal with Oxygen of Atmosphere

Question 6

Oxide Film

Answer 6

Forms to protect against corrosion

Question 7

What metals is Oxide film present in

Answer 7

Pure Aluminium

Titanium

Chromium

Question 8

Oxidation Rate decreases as

Answer 8

Oxide film thickness increases

Question 9

If Oxides react with Water

Answer 9

Increased Oxidation

Question 10

Increases in temp Oxidation

Answer 10

Increases

Question 11

Corrosion in Steel

Answer 11

Rust

Question 12

Corrosion in Aluminium Alloy

Answer 12

White Powder

Question 13

Corrosion in Magnesium Alloy

Answer 13

Grey Powder

Question 14

Corrosion in Copper Alloys

Answer 14

Green Coating

Question 15

Corrosion in Cadmium and Zinc

Answer 15

White Powder

Question 16

Another Name for Galvanic Action

Answer 16

Electro Chemical

Dissimilar Metal Corrosion

Question 17

Rate of Galvanic Action

Answer 17

Slow

Low Current

Question 18

What is needed for Galvanic Action

Answer 18

2 Disimilar Metals

Electrolyte

Question 19

Crack Formation in a corrosive environment

Answer 19

Stress

Question 20

Stress is more common in

Answer 20

Alloys

Question 21

Stress can lead to failure below UTS but especially in

Answer 21

Elevated Temp

Question 22

Surface Corrosion

Answer 22

Direct Chemical Attack

EG: Battery Acid Or Waste

Question 23

Pitting

Answer 23

Localised

Small holes act as stress risers

Caused via

Non Metallic lnclusions
Poor Coating
Damage

Question 24

Crevice Corrosion

Answer 24

Aluminium Alloys

Localised

Bulges between fasteners

Due to changes in Local Chemistry of Crevice

Prevented via Primer and Sealent before Assy

Question 25

Intergranular Corrosion

Answer 25

Aluminium Alloys and Stainless Steels Cracks and Blisters Due to Improper Heat Treatment or Heat In Aircraft Must be scrapped

Question 26

Laminar / Exfoliation Corrosion

Answer 26

Extruded or Rolled Parts Extreme Intergranular Layers of corrosion

Question 27

Fretting Corrosion

Answer 27

2 Loaded Surfaces with Continuous Movement Removes Coating Causes Fatigue and Cracking

Question 28

Fretting Corrosion in Steel

Answer 28

Cocoa Powder

Question 29

Fretting Corrosion In Aluminium Alloys and Magnesium Alloys

Answer 29

Grey / Black Powder

Question 30

What is a Anti Fretting Corrosion Agent

Answer 30

Molybdenum Disulphide Grease

Question 31

Stress Corrosion

Answer 31

Caused by Tensile Stress in a Corrosion Environment Cracks Lengthen Rapidly

Question 32

Tensile Stress + Aluminium + _____ = Stress Corrosion

Answer 32

Hydrogen

Question 33

Tensile Stress + High strength steel + _____ = Stress Corrosion

Answer 33

Hydrogen

Question 34

Tensile Stress + Stainless + _____ = Stress Corrosion

Answer 34

Chlorides

Question 35

Filiform Corrosion

Answer 35

Oil or Grease Films Worm like Often starts and rivets and spreads

Question 36

Mercury Spillage

Answer 36

Aluminium Alloy Forms a Amalgam Soaks in and attacks grain boundaries Aircraft cannot be moved Cleaned X Ray

Question 37

How to Clean Mercury Spillage

Answer 37

Vacuum Syringe Nickel plated carbon fiber brush

Question 38

Microbial Corrosion

Answer 38

Fuel tanks Dormaint until water and temp Feeds of hydrocarbons in fuel Attaches and damages structure

Question 39

Hydrogen Embrittlement in Ferrous Metals

Answer 39

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

Question 40

Removal of Hydrogen Embrittlement in Ferrous

Answer 40

Bake Op at 191

Question 41

Hydrogen Embrittlement in Titanium

Answer 41

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

Question 42

Removal of Hydrogen Embrittlement in Ferrous

Answer 42

Relief Op at 524 °C for 6 hours

Question 43

Corrosion Fatigue

Answer 43

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

Question 44

Corrosion in Iron + Steel

Answer 44

Rust

Question 45

Corrosion in Aluminium Alloys

Answer 45

White Grey Powder

Question 46

Corrosion in Magnesium

Answer 46

White

Question 47

Corrosion in Copper

Answer 47

Blue Green Patina

Question 48

Corrosion in Chromium and Zinc

Answer 48

White

Question 49

Corrosion in Nickel and Chromium

Answer 49

Blue Green

Question 50

Nickel Plating is used for

Answer 50

Heat Resistance

Question 51

Chromium Plating is used for

Answer 51

Wear resistance

Question 52

What can improve Electrolyte Conductivity

Answer 52

Dirt Salts Acidic Gasses Exhaust Gasses

Question 53

What Battery Spillage is Acid Spillage

Answer 53

Lead Acid

Question 54

To Neutralise Acidic Spillage

Answer 54

10% By weight Sodium Bicarbonate

Question 55

What batteries can produce Alkaline Spillage

Answer 55

Nickel Cadmium (Patassium Hydroxide Spillage)

Question 56

How to neutralise Alkaline Spillage

Answer 56

Neutralised by 5% by weight Chromic Acid Crystals