80 Questions
What is the most common form of corrosion?
Surface corrosion
How does surface corrosion appear?
General roughening, etching, or pitting
What may happen when corrosion spreads under the surface coating?
The paint or plating is lifted off the surface in small blisters
What conditions are conducive to the occurrence of filiform corrosion?
High humidity and slightly acidic surface
Which type of finish is particularly vulnerable to filiform corrosion?
Polyurethane
How does filiform corrosion behave differently on steel and aluminum surfaces?
Traces never cross on steel, but they cross under one another on aluminum
What is exfoliation corrosion?
An advanced form of intergranular corrosion lifting up the surface grains of a metal
Where is exfoliation corrosion most often seen?
On extruded sections where grain thickness is usually less than in rolled forms
What inspection methods are being used with a great deal of success to detect exfoliation corrosion?
Ultrasonic and eddy current inspection methods
What type of corrosion is particularly susceptible to high-strength aluminum alloys, such as 2014 and 7075, if they have been improperly heat-treated?
Intergranular corrosion
What causes lack of uniformity in the alloy structure, leading to intergranular corrosion?
Changes occurring during the heating and cooling process
Which alloys are particularly susceptible to a form of electrochemical attack that commonly results from a lack of uniformity in the alloy structure?
Aluminum alloys and some stainless steels
What tools are useful in observing obscure areas during inspections?
Mirrors, borescopes, and fiber optics
Which NDI methods may be of value in the detection of corrosion?
Liquid penetrant, magnetic particle, eddy current, x-ray, ultrasonic, and acoustical emission
What is required for eddy current, x-ray, and ultrasonic inspection methods to obtain reliable results?
Properly calibrated equipment and a controlling reference standard
How often must routine maintenance inspections be performed on amphibians or seaplanes?
Daily
What is the first step in all corrosion inspections?
Thorough cleaning of the area to be inspected
What should be used as a general guide when an area is to be inspected for corrosion?
Scheduled maintenance checklists
Which sense is also an effective inspection method for the detection of hidden, well-developed corrosion?
Sense of touch
What is a prime spot for corrosion due to dissimilar metal contact?
Piano-type hinges
What is the result of the entrance and entrapment of corrosive agents between the layers of metal in spot welding?
Corrosion products at crevices
What is a natural trap for dirt, salt, and moisture?
Piano-type hinges
What must include lubrication and actuation through several cycles to ensure complete lubricant penetration?
Inspection of hinges
What must be assured if inside paint removal is necessary?
Adequate ventilation
What should be worn when using paint remover due to its toxic nature?
Rubber gloves, aprons of acid repellent material, and goggle type eyeglasses
What should be used to assist in removing persistent paint finishes?
Only nonmetallic scrapers
What should not be used on aluminum parts during cleaning?
Steam cleaning equipment
What is the depth of cover of stripper recommended during the stripping procedure?
1 ⁄32" to 1 ⁄16"
What is the recommended method for disposal of the stripped residue?
In accordance with environmental laws
In what circumstances may dry cleaning solvent (P-D-680) be used?
For removing oil, grease, or soft preservative compounds
What type of cleaning compounds do modern environmental standards encourage the use of?
Water-based, non-toxic cleaning compounds
What is the purpose of the preliminary cleaning operation in the removal of corrosion?
To determine the extent of the spread of the corrosion
What type of cleaning compounds are encouraged by modern environmental standards?
Water-based, non-toxic cleaning compounds
What may be used for heavy-duty removal of thick or dried preservatives?
Solvent emulsion type compounds
What is the result of the presence of rust on steel surfaces?
Promotes additional corrosion by attracting moisture and acting as a catalyst
Where does rust first appear on steel surfaces?
Bolt heads, hold-down nuts, or other unprotected aircraft hardware
What is the danger associated with even the smallest amount of rusting in areas with paint failures or mechanical damage?
Potentially dangerous and must be removed and controlled
What is the significance of rust on structural components in terms of maintenance?
Indicates a need for maintenance and possible corrosive attack in critical areas
What is the most practicable means of controlling the corrosion of steel?
Complete removal of corrosion products by mechanical means and restoring corrosion preventive coatings
What is the difficulty associated with removing all corrosion products using abrasive or polishing methods alone?
Residual rust usually remains in small pits and crevices, making complete removal practically impossible
What is the easiest type of corrosion to detect in its early stages?
Magnesium attack
What is the initial sign of magnesium attack?
Lifting of the paint film and white spots on the magnesium surface
What does re-protection of magnesium involve?
Removal of corrosion products, partial restoration of surface coatings, and reapplication of protective coatings
What are the most common magnesium castings mentioned in the text?
Engine cases, bellcranks, fittings, covers, plates, and handles
What is recommended if dangerous corrosive penetration is to be avoided on magnesium castings?
Earliest practicable treatment
When is a decision from the manufacturer necessary for evaluating the adequacy of structural strength in a structural casting?
If extensive removal of corrosion products is involved
What is the main purpose of providing surface finishes to aircraft parts?
To provide corrosion resistance
Which cleaning method is preferred over mechanical cleaning for steel parts?
Chemical cleaning
What are steel parts pickled for before plating?
To remove scale, rust, or other foreign matter
Why is an understanding of various types of metal finishes necessary for proper maintenance in the field?
To ensure effective corrosion control
What type of acid is more effective in removing certain types of scale in the pickling solution?
Muriatic (hydrochloric) acid
What is the method used for cleaning aluminum and magnesium parts?
Electrocleaning in a hot alkaline solution
What type of cleaning is not applicable to thin aluminum sheets, particularly Alclad?
Blast cleaning with abrasive media
What process involves passing an electric current through a solution similar to electroplating?
Electrocleaning
What is the purpose of anodizing nonclad aluminum alloy surfaces?
To increase the thickness and density of the natural oxide film
What is the recommended tool for cleaning anodized surfaces?
Aluminum wool
What is prohibited when treating anodized surfaces?
Using steel wool or steel wire brushes
What is the purpose of Alodizing in aircraft work?
To increase corrosion resistance and improve paint bonding qualities
What is the purpose of the Deoxylyte® bath in the Alodizing process?
To counteract alkaline material and make the Alodine® aluminum surface slightly acid on drying
What color does the Alodine® coating result in on copper bearing alloys?
Olive green
What is the flashpoint requirement for solvent cleaners used in aircraft cleaning?
Not less than 105 °F
Which solvent is mentioned as the most common petroleum base solvent used in aircraft cleaning?
Stoddard solvent
Which solvents meet the nonflammable requirement but are toxic?
Chlorinated solvents
What is the potential danger of active solvents like methyl ethyl ketone (MEK) and acetone?
Harmful or fatal if swallowed, inhaled, or absorbed through the skin
What is the main purpose of safety solvent, trichloroethane (methyl chloroform)?
General cleaning and grease removal
What is the potential danger associated with methyl ethyl ketone (MEK) when inhaled?
Toxicity
What is the result of using kerosene for general solvent cleaning without a protective agent?
Leaves an appreciable film on cleaned surfaces
What type of cleaning compounds are recommended for use in the oxygen system?
Anhydrous (waterless) ethyl alcohol or isopropyl alcohol
What is the purpose of solvent and water emulsion compounds used in general aircraft cleaning?
Removal of heavy deposits like carbon, grease, oil, or tar
What safety precautions should be observed when using phenolic-based solvent emulsion cleaners?
Wear rubber gloves and goggles
What is the recommended cleaning compound for removal of heavy preservative coatings?
Kerosene
What type of cleaning compounds are encouraged by modern environmental standards?
Solvent and water emulsion compounds
What is the potential danger of using aromatic naphtha for cleaning acrylics and rubber products?
Toxicity and attacks on acrylics and rubber products
What is the potential danger associated with prolonged use of safety solvent?
Can cause dermatitis on some persons
What type of soils can MIL-C-5410 Type I and II materials effectively remove from aircraft surfaces?
Light to medium soils, operational films, oils, or greases
What is the caution regarding the cleaning of nonionic (flat) finishes on aircraft surfaces?
They are not to be cleaned more than necessary and must never be scrubbed with stiff brushes
Direct chemical attack and electrochemical attack. In both types of corrosion, the metal is converted into a metallic ______, such as an oxide, hydroxide, or sulfate.
compound
The corrosion process involves two simultaneous changes: the metal that is attacked or oxidized suffers what is called anodic ______, and the corrosive agent is reduced and is considered as undergoing cathodic ______
change
An oxygen cell can develop at any point where the oxygen in the air is not allowed to diffuse into the solution, thereby creating a difference in oxygen concentration between two points. Typical locations of oxygen concentration cells are under gaskets, wood, rubber, and other materials in contact with the metal surface. [Figure 8-12]. Corrosion occurs at the area of low oxygen concentration ______
anode
From the moment the metal is manufactured, it must be protected from the deleterious effects of the environment that surrounds it. This protection can be the introduction of certain elements into the base metal, creating a corrosion-resistant alloy, or the addition of a surface coating of a chemical conversion coating, metal, or ______
paint
Test your knowledge of surface corrosion with this quiz! Learn about the common characteristics and causes of surface corrosion, including roughening, etching, pitting, and powdery deposits of corrosion products. Explore the factors that contribute to direct chemical or electrochemical attack leading to surface corrosion.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
