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CLEANING & CORROSION CONTROL FINAL
COMPREHENSIVE STUDY GUIDE 2026
โ What is the main source of corrosion in aircraft? Answer: Water or water vapors containing salt that combines with oxygen in the atmosphere โ True or False: Aircraft operating in a marine environment or in areas where the atmosphere contains industrial fumes are NOT corrosive Answer: False, are particularly susceptible to corrosion โ True or False: On the surface of aluminum alloys and magnesium, corrosion appears as pitting and etching and is often combine with gray or white powdery deposits Answer: True โ True or False: On copper and copper alloys, the corrosion forms a reddish film Answer: False, greenish film โ True or false: Aluminum and aluminum alloys on steel, form a reddish corrosion byproduct known as rust
Answer: False, copper and copper alloys โ True or false: Some types of corrosion burrow between the surface coatings and the metal surface, and can spread until the part fails Answer: True โ What are the 2 general classifications of corrosion that cover most of the specific forms? Answer: Direct and Electro-chemical attacks โ True or False: The corrosion process always involves two simultaneous changes Answer: True โ A metal that is attacked or oxidized may be called? Answer: Anodic change โ The corrosive agent that is reduced, may be consider to be undergoing what? Answer: Cathodic change
โ True or false: Flux resides are hygroscopic in nature Answer: True โ Absorb moisture, and unless carefully removed tend to cause severe pitting Answer: Flux residues (hygroscopic) โ True or false: Fluxes used in brazing, soldering, and welding are corrosive, and they chemically attack the metals or alloys with which they are used. Answer: True โ What is important to remove from a metal surface immediately after a joining operation that uses a flux Answer: Remove the residual flux โ True or False: Where entrapment of a cleaning solution is likely to occur, use a noncorrosive cleaning agent, even thought it is less efficient Answer: True
โ True or False: Caustic cleaning solutions in concentrated form should NOT be kept tightly capped and as far away from aircraft as possible Answer: False โ True or False: Cleaning solutions used in corrosion removal are, in themselves, potentially corrosive agents Answer: True โ True or False: Electrochemical attack may be likened to the electrolytic reaction that takes place in electroplating, anodizing, or in a dry cell battery Answer: True โ The reaction in this corrosive attack requires a medium, usually water, which capable of conducting a tiny current of electricity Answer: Electrochemical Attack โ True or False: All metals are electrically active and have a specific electrical potential in a given chemical environment Answer: True โ The potential for a metal to be electrically active and have a specific electrical potential is called a metal's
โ What are the 7 forms of corrosion discussed in the book? Answer: Surface Corrosion Filiform Corrosion Dissimilar Corrosion Inter-granular Corrosion Stress Corrosion Fretting Corrosion False Brinelling โ Occurs as a result of the combined effect of sustained tensile stresses and a corrosive environment? Answer: Stress Corrosion โ True or false: stress corrosion cracking is found in most metal systems, however is particularly characteristic of aluminum, copper and certain stainless steels and high strength alloy steels with over 240,000 psi Answer: True โ Stress Corrosion may be trans-granular or inter-granular in nature Answer: True
โ This corrosion is particularly damaging form of corrosive attack that occurs when two mating surfaces, normally at rest with respect to one another, are subject to slight relative motion Answer: Fretting Corrosion โ Most fretting corrosion appears where? Answer: Rivets โ This corrosion is characterized by pitting of the surfaces and the generation of considerable quantities of finely divided debris Answer: Fretting Corrosion โ Since the restricted movements of two surfaces prevent debris from escaping very easily, an extremely localized abrasion occurs, the presence of water vapor greatly increases this type of deterioration, if the contact areas are small and sharp, deep grooves resembling pressure indentions may be worn in the rubbing surface, this type of corrosion is called what? Answer: False brinelling โ True or False: Extensive pitting damage may result from contact between dissimilar metal parts in the presence of a conductor Answer: True
Answer: Inter-granular Corrosion โ True or false: Lack of uniformity is caused by changes that occur in the alloy during heating and cooling during the material's manufacturing process Answer: True โ Very severe inter-granular corrosion may sometimes cause the surface of a metal to what? Answer: Exfoliate โ This is a lifting or flaking of the metal at the surface due to de- lamination of the grain boundaries cause by the pressure of corrosion residual product build up Answer: Exfoliation โ Appears as a general roughening, etching, or pitting of the surface of a metal, frequently accompanied by a powdery deposit of corrosion products Answer: Surface Corrosion โ True or False: Surface corrosion may be caused by either direct or electrochemical attack Answer: True
โ Gives the appearance of a series of small worms under the paint surface, it is often sen on surfaces that have been improperly chemically treated prior to painting Answer: Filiform Corrosion โ True or False: Sometimes corrosion will spread under the surface coating and cannot be recognized by either the roughening of the surface of the powdery deposit, instead paint of playing is lifted off the surface in small blisters Answer: True โ Name two types of factors affecting corrosion Answer: Climate and Foreign Material โ What are the types of foreign material that are controllable in the spread of corrosive attacks Answer: Soil and atmospheric dust Oil grease, and engine exhaust residues Salt water and salt moisture condensation Spilled battery acid and caustic cleaning solutions Welding or brazing flux residues
โ Are both jet and reciprocating engine exhaust deposits very corrosive? Answer: Yes, give particular attention where gaps, seams, hinges, and fairings โ What will minimize corrosion of acid deposits? Answer: Regular cleaning and neutralization of acid deposits โ These are natural sumps for waste hydraulic fluids, dirt, and odds and ends of debris. Residual oil quite often masks small quantities of water that settle to the bottom ad set up a hidden chemical cell Answer: Bilge Areas โ Instead of using chemical treatments for the bilge water, current floor manufacturers recommend what? Answer: - Diligent maintenance of the internal coatings
- Interior compartments are painted to protect โ Inspection procedures should include particular attention paid to areas located under what? Answer: Galleys and Lavatories
โ More than any other area in the aircraft, this area probably receives more punishment due to mud, water, salt, gravel, and other flying debris Answer: Wheel well and Landing geat โ True or False: Due to heat generated by braking action, preservatives CAN be used on some main landing gear Answer: False โ What tends to mask corrosion rather than prevent it? Answer: Partially applied preservative โ Design specifications require that aircraft have what installed in all areas where water may collect Answer: Drains? โ True or False: daily inspection of low point drains is NOT a standard requirement Answer: False โ These areas are being constantly abraded with airborne dirt and dust, bits of gravel from runways, and rain erosion, which tends to remove the protective finish
โ What type of lubricants are used when servicing piano hinges? Answer: Water-displacing โ True or false: Inspection of hinges should include lubrication and actuation through several cycles to ensure complete lubricant penetration Answer: True โ Corrosion of metal skins joined by spot welding is the result of what? Answer: Entrance and entrapment of corrosive agents between layers of metal โ What should be done to control cables that have internal corrosion? Answer: Removed โ True or false: Replace light external corrosion Answer: False,remove corrosion with a non-woven abrasive pad lightly soaked in oil or steel wire brush โ In general any complete corrosion treatment involves?
Answer: 1) Cleaning and stripping corrosion
- Removing corrosion
- Neutralizing residual materials
- Restoring protective surface film
- Applying temporary/permanent paint finishes โ VOCs Answer: Volatile Organic Compounds โ Modern environmental standards encourage the use of what type of cleaning compounds whenever possible? Answer: Water-based, non toxic cleaning compounds โ The general use of what can be used for MOST applications? Answer: General purpose water rinsable stripped โ How long should paint stripper remain on the surface before being washing and scrubbing? Answer: A sufficient length of time to wrinkle and lift the paint โ What type of scrapers should be used to assist in removing persistent paint finishes?
โ True or False: Mechanical means and restoring corrosion preventive coating are practicable means of control corrosion on HIGHLY STRESSED STEEL Answer: False, use of abrasive papers and compounds, small power buffers and buffing compounds, hand wire brushing, or steel wool are all acceptable cleanup procedures โ True or False: Generally speaking, if at all possible, the steel part should be removed from the airframe for treatment, as it can be nearly impossible to remove all residues Answer: True โ It is essential that that steel surfaces not be what during buffing? Answer: Overheated โ What type of extensive damage may result from a contact between dissimilar metal parts in the presence of a conductor? Answer: Pitting damage โ What form of corrosion may exist without visible surface evidence? Answer: Inter-granular Corrosion
โ Is the formation of an oxide on the surface of aluminum sheet necessarily detrimental? Answer: No, the coating provide a hard shell barrier to the introduction of corrosive elements, such oxidation should not be confused with corrosion โ At least 3 forms of attack on aluminum alloys are particularly serious, what are they? Answer: 1 - Penetrating pit-type corrosion 2 - Stress corrosion cracking 3 - Inter-granular corrosion โ A thin layer coating of relatively pure aluminum is applied over the base aluminum alloy, protection is good, and can be maintained in a polished condition Answer: Alcald aluminum โ During a typical aluminum corrosion treatment sequence, what type of cleaner should you use? Answer: Ph neutral product โ True or false: Metal polish intended for use of clad aluminum aircraft surfaces must not be used on anodized aluminum since it is abrasive enough to actually remove the protective anodized film
