Cleaning & Corrosion

Question 1

What is meant by metal corrosion?

Answer 1

The deterioration of the metal by chemical or electrochemical attack

Question 2

What material forms a greenish film when corroded?

Answer 2

Copper and Copper Alloys

Question 3

What are two general classifications of corrosion?

Answer 3

1. Direct chemical attack
2. Electrochemical attack

Question 4

Name three common agents that cause direct chemical attack on aircraft metal structure:

Answer 4

1. Spilled battery acid
2. Residual flux deposits
3. Entrapped caustic cleaning solutions

Question 5

What is meant by an electrochemical attack on aluminum alloy?

Answer 5

A natural attack occurrence that attacks metal converting back to a metallic compound in which 4 conditions must exist.
Anode
Cathode
Electrolyte
Electrical contact between anode and cathode

Question 6

What type of corrosion is most common on aircraft structures?

Answer 6

Surface Corrosion

Question 7

How does surface corrosion appear on the surface of an alloy?

Answer 7

As general roughening, etching, or pitting on the surface of a metal

Question 8

Does all corrosion appear on the surface of an alloy?

Answer 8

No, sometimes corrosion spreads under the surface coating

Question 9

What is meant by dissimilar metal corrosion?

Answer 9

Contact between dissimilar metal parts in the presence of a conductor

Question 10

How may intergranular corrosion be detected?

Answer 10

Ultrasound
Eddy Current
X-ray

Question 11

Where does fretting corrosion generally occur?

Answer 11

Between two mating surfaces

Question 12

Name six operations which are good corrosion-preventative measures:

Answer 12

1. Adequate cleaning
2. Periodic lubrication
3. Detailed inspection
4. Prompt treatment of corrosion
5. Daily wipe down
6. Sealing of aircraft against water

Question 13

How often should aircraft be checked for corrosion?

Answer 13

During routine maintenance inspections. Seaplanes must be checked daily.

Mild zones: Every 90 days
Moderate zones: Every 45 days
Severe zones: Every 15 days

Question 14

Are exhaust gases considered to be corrosive?

Answer 14

Yes
Both jet and reciprocating engine exhaust deposits are very corrosive

Question 15

How is corrosion around battery boxes minimized?

Answer 15

Regular cleaning and neutralization of acid deposits

Question 16

How are the bilge areas of a seaplane protected from corrosion?

Answer 16

•Chemical conversion coating applied to the surfaces of the sheet material •Sealants are installed at the lap joints •Interior compartments are painted

Question 17

What is done to prevent water entrapment in aircraft?

Answer 17

Drains are installed in all areas where water may collect

Question 18

Where would corrosion most likely occur on an aircraft skin?

Answer 18

•Edges
•Areas around fasteners
•Cracked, chipped, or areas with missing paint

Question 19

What is the proper treatment for a control cable found to have internal corrosion?

Answer 19

Replace cables that have internal corrosion

Question 20

Name nine steps for complete corrosion preventative maintenance:

Answer 20

1. Keep drain holes free from obstructions
2. Adequate cleaning
3. Thorough periodic lube
4. Drain fuel cell sumps
5. Maximum use of protective covers while parked…….
   I doubt they will ask us all of this i’m not writing them all out lol

Question 21

What type of paint stripper is recommended for aircraft structure?

Answer 21

Water soluble stripper can be used for most applications

Question 22

How long should paint remover remain on the surface before it is washed off?

Answer 22

Between 10 minutes to several hours depending on the temperature, humidity, and the condition of the paint.

Question 23

If steel rust is allowed to remain on the surface, will it prevent further attack?

Answer 23

It’s presence actually promotes additional attack by attracting moisture from the air and acting as a catalyst for corrosion

Question 24

What is the most practical way of removing corrosion products from steel?

Answer 24

By mechanical means and restoring corrosion preventive coatings

Question 25

Name three types of corrosion considered serious in aluminum alloy structure:

Answer 25

1. Penetrating pit type
2. Stress corrosion
3. Intergranular

Question 26

What treatment is recommended for removing corrosion from clad aluminum surfaces?

Answer 26

Hand polish the corroded areas with fine abrasives or with polish material

Question 27

What treatment is recommended for removing corrosion from aluminum surfaces which are to be painted?

Answer 27

Treat superficially corroded areas with a 10% solution of chromic acid and sulfuric acid

Question 28

Is steel wool suitable for removing corrosion products from aluminum structures?

Answer 28

No, do not use severe abrasive materials or materials of different metal

Question 29

How is corrosion recognized on magnesium structures?

Answer 29

•Lifting of paint film
•White spots
•Snow-like mounds
•White whiskers

Question 30

What are the steps in treating magnesium sheets for corrosion?

Answer 30

1. Clean and strip paint
2. Use stiff hog-bristle brush or non woven abrasive pad to clear corrosion
3. Treat with chromic acid solution with sulfuric acid
4. Allow chromic acid to sit for 5-20 minutes then wipe off
5. Restore protective paint

Question 31

How should joints between steel and aluminum be protected?

Answer 31

Lubrication and actuation through several cycles to ensure complete lubricant penetration

Question 32

How should joints between magnesium and aluminum be protected against corrosion?

Answer 32

Insulate each surface with at least two coats of zinc chromate or epoxy and then add a layer of pressure sensitive vinyl tape

Question 33

What type of cleaning, chemical or mechanical, is preferred for removing corrosion from a metal surface?

Answer 33

Chemical cleaning is preferred over mechanical

Question 34

What is meant by pickling steel?

Answer 34

The process of treating steel parts for the removal of rust before plating by using a solution of either muriatic or sulfuric acid

Question 35

Electro cleaning is another type of chemical cleaning similar to what?

Answer 35

Electroplating

Question 36

Give three examples of how we protect metal from dissimilar metal contact:

Answer 36

Zinc Chromate
Bonding Strap
Vinyl Tape

Question 37

If you want a high lust what should you do prior to electroplating?

Answer 37

Polishing, buffing, and coloring of metal surfaces

Question 38

What is the main purpose of metal finishing?

Answer 38

Corrosion Resistance

Question 39

What are two reasons for anodizing an aluminum structure?

Answer 39

1. increase the thickness and density of the natural oxide film
2. Corrosion resistance

Question 40

What is meant by alodizing?

Answer 40

When an aluminum alloy is chemically treated to increase corrosion resistance and improve paint bonding qualities

Question 41

How is alodizing applied to an aluminum surface?

Answer 41

Surface is pre-cleaned with an acidic or alkaline metal cleaner and then alodine is applied by dipping or spraying

Question 42

What precaution should be taken before scrubbing a plastic windshield?

Answer 42

Rinse with fresh water and dry with chamois/synthetic wipes or absorbent cotton

Question 43

Should a plastic window be wiped with a cloth to clean it?

Answer 43

No, do not rub plastic with dry cloth as it will likely create scratches

Question 44

What should be used to wash grease, oil, and hydraulic fluid from aircraft tires?

Answer 44

wash with mild soap solution

Question 45

What is the difference between aliphatic and aromatic naphtha?

Answer 45

Aromatic naphtha must not be confused with aliphatic material as it is toxic (attacks acrylics and rubber) and must be used with adequate controls

Question 46

What corrosion is associated with a deficiency of oxygen?

Answer 46

Concentration Cell corrosion