Cleaning and Corrosion Control — FAA A&P Test Questions (ACS AM.I.G)
Cleaning and Corrosion Control (AM.I.G) is the General-bank subject area where the FAA checks whether you can name a corrosion type from its description, identify what it leaves behind, and pick a treatment that does not make the damage worse. The questions lean hard on definitions - galvanic, intergranular, exfoliation, fretting, filiform, stress corrosion - and on the conditions each one needs to start. Every AMTprep question published on this code carries a rationale and a handbook reference, so you can practice recognizing the corrosion from the wording of the stem.
Written by the AMTprep editorial team · Published · Last reviewed
Written against the FAA primary sources cited at the foot of this page.
What ACS AM.I.G covers
The material tracks the corrosion chapter of FAA-H-8083-30, and the test questions follow it closely. Start with the mechanism. Corrosion is an electrochemical reaction, and the galvanic form needs three things at once: two dissimilar metals, an electrolyte such as water carrying salt or exhaust residue, and an electrical path between them. Remove any one and the cell stops. The more anodic, chemically active member of the couple is the metal that gives up material. Then learn the types by description, because that is how the stems are written. Intergranular corrosion runs along the grain boundaries of an alloy and is often traced to improper heat treatment; exfoliation is its advanced form, lifting the metal in layers. Fretting appears between close-fitting parts subject to slight relative motion or vibration. Filiform shows up as worm-track lines under paint or a coating in humid conditions. Pitting and general surface attack are the everyday forms on aluminum. Then identification by product: aluminum leaves a white to gray powder over a pitted surface, magnesium a white powder that can lift the finish, iron and steel a reddish-brown rust, copper alloys a blue-green deposit. Prevention and treatment close the area out: Alclad sheet with its thin cladding of nearly pure aluminum, anodized and conversion-coated finishes, primer or sealant between dissimilar metals, and the cleaning rules that follow from all of it - approved cleaners only, no strong alkaline products on aluminum or magnesium, and no ferrous abrasives anywhere near aluminum structure.
Where this sits on the test
ACS AM.I.G is tested on the FAA General written test, one of 1,553 ACS-tagged questions in the General bank. Every question tagged to this area carries a worked rationale and its FAA handbook reference, so you can drill the code itself rather than the whole test.
FAA handbook references
- FAA-H-8083-30
Three traps candidates fall into
- Asked which metal corrodes in a galvanic couple, candidates pick the softer one or the more common one. It is the more anodic, chemically active member. An aluminum skin against a stainless steel fastener loses material at the aluminum, so the aluminum around the fastener is what you inspect.
- Grabbing the nearest abrasive. Steel wool and steel wire brushes leave ferrous particles embedded in aluminum, and every one of those particles becomes a new galvanic cell as soon as moisture returns. Aluminum wool, an aluminum wire brush, or an approved nonmetallic abrasive is the answer the test wants.
- Alclad gets treated as if it were primer. The cladding is a thin layer of nearly pure aluminum rolled onto the alloy core, and it protects sacrificially. Sand through it while polishing out a scratch and the corrosion protection is gone, even though the surface looks clean and bright.
50 free sample questions from ACS AM.I.G
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What two conditions must be present for galvanic corrosion to occur between two pieces of metal?
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Answer: Dissimilar metals in contact and the presence of an electrolyte
Why: Galvanic corrosion is an electrochemical action that requires two dissimilar metals in electrical contact and an electrolyte (such as moisture) to complete the circuit. The greater the difference in electrical potential between the two metals on the galvanic series, the faster the more active (anodic) metal corrodes. Identical metals have no potential difference, and without an electrolyte the corrosion cell cannot form.· FAA-H-8083-30 — Cleaning and Corrosion Control: galvanic (dissimilar-metal) corrosion
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When two dissimilar metals form a galvanic couple in the presence of an electrolyte, which metal corrodes?
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Answer: The more anodic (more active) metal
Why: In a galvanic couple the more active metal becomes the anode and corrodes, while the less active metal becomes the cathode and is protected. This is why coupling a small area of anodic metal to a large cathodic area produces rapid, severe attack on the anode. Identifying the anodic member of the pair on the galvanic series predicts which part will deteriorate.· FAA-H-8083-30 — Cleaning and Corrosion Control: anodic vs. cathodic behavior
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Corrosion that attacks along the grain boundaries of an alloy, often from improper heat treatment, is called
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Answer: intergranular corrosion
Why: Intergranular corrosion is an attack along the grain boundaries of an alloy, frequently the result of a lack of uniformity in the alloy structure caused by improper or interrupted heat treatment. Because it follows the boundaries between grains, it can progress deep into the metal with little visible surface evidence, making it especially dangerous.· FAA-H-8083-30 — Cleaning and Corrosion Control: forms of corrosion (intergranular)
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The corrosion that occurs between two close-fitting surfaces subject to slight vibration or relative motion is known as
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Answer: fretting corrosion
Why: Fretting corrosion occurs between two mating surfaces normally at rest with respect to each other that are subjected to slight relative motion or vibration. The motion prevents protective films from re-forming and traps abrasive corrosion products, producing pits and a discolored, mottled texture at the contact area.· FAA-H-8083-30 — Cleaning and Corrosion Control: forms of corrosion (fretting)
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A thread-like or worm-track corrosion found under painted or coated surfaces in humid conditions is called
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Answer: filiform corrosion
Why: Filiform corrosion is a distinctive thread-like or wormtrack attack that occurs under organic coatings (paint or film) when the relative humidity is high and the surface is slightly acidic. It is recognized by the random thread-like filaments visible beneath the finish and indicates the coating has been undercut.· FAA-H-8083-30 — Cleaning and Corrosion Control: forms of corrosion (filiform)
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On a bare magnesium part, the corrosion products that form are typically
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Answer: a white or gray powder
Why: Magnesium is the most chemically active metal used in aircraft, and its corrosion products appear as a white or gray powdery deposit. Reddish-brown scale identifies ferrous (iron and steel) corrosion, while blue-green deposits are characteristic of copper-based alloys, so the color of the corrosion product helps identify the base metal involved.· FAA-H-8083-30 — Cleaning and Corrosion Control: corrosion of magnesium
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Which corrosion product is characteristic of corroding iron and steel parts?
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Answer: A reddish-brown rust or scale
Why: Iron and steel form a characteristic reddish-brown oxide commonly known as rust. Unlike the protective oxide on aluminum, this scale is porous and does not stop further attack; it flakes away and exposes fresh metal. White powder indicates aluminum or magnesium, and blue-green film indicates copper alloys.· FAA-H-8083-30 — Cleaning and Corrosion Control: corrosion of ferrous metals
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Alclad aluminum resists corrosion better than bare alloy sheet because it has
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Answer: a thin coating of pure aluminum rolled onto each surface
Why: Alclad sheet consists of a high-strength aluminum alloy core with a thin coating of comparatively pure aluminum metallurgically bonded to each surface. The pure aluminum cladding forms a protective oxide and is anodic to the core, sacrificially protecting it. This is a metallurgical coating, not a primer or a chemically deposited film.· FAA-H-8083-30 — Cleaning and Corrosion Control: Alclad surfaces
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Alodine (a chemical conversion coating) is applied to aluminum primarily to
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Answer: increase corrosion resistance and improve paint adhesion
Why: Alodizing is a simple chemical (conversion) treatment for aluminum alloys that forms a protective film to increase corrosion resistance and provides a good bonding surface for paint. It does not appreciably harden the metal for wear resistance, and it does not add structural thickness or fill pitting—it is a thin conversion coating.· FAA-H-8083-30 — Cleaning and Corrosion Control: chemical conversion coatings (Alodine)
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What is the proper action when corrosion is found on a stressed structural member or its depth exceeds allowable limits?
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Answer: Refer to the manufacturer's data to repair or replace the part
Why: When corrosion penetrates a structural member beyond the limits established by the manufacturer, simply cleaning or coating the area is not acceptable because load-carrying capability has been reduced. The mechanic must consult the manufacturer's maintenance or structural repair manual to determine whether the part can be reworked within limits or must be replaced. Painting over corrosion seals in the damage and is never acceptable.· FAA-H-8083-30 — Cleaning and Corrosion Control: assessment and limits of corrosion damage
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When bare aluminum is exposed to air, the oxide film that forms is
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Answer: an electrical insulator that protects the metal beneath.
Why: Aluminum reacts with air to form a thin, tough, nonconductive oxide film. This layer is an electrical insulator, which is why aluminum bonding and grounding surfaces must be cleaned back to bright metal. The oxide actually protects the metal beneath, so the part does not become weaker.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Besides improving corrosion resistance, anodizing an aluminum surface also
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Answer: provides a good surface for paint to adhere to.
Why: Anodizing thickens the natural oxide into a hard, slightly porous film. Besides improving corrosion protection, that controlled porosity provides an excellent key for paint and primer to adhere to. A fully sealed, nonporous surface would actually be a poorer base for paint.· FAA-H-8083-30 — Cleaning and Corrosion Control
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If caustic soda (sodium hydroxide) leaves a black stain on a metal surface, the metal is most likely
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Answer: an aluminum alloy.
Why: Caustic soda (sodium hydroxide) attacks the alloying elements in aluminum alloy and leaves a dark or black smut on the surface. Pure aluminum and the pure-aluminum clad layer of Alclad react much less and stay light, so a black stain identifies the material as an aluminum alloy.· FAA-H-8083-30 — Cleaning and Corrosion Control
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When diluting a concentrated acid with water, the correct and safe procedure is to
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Answer: add the acid slowly to the water.
Why: Always add the acid slowly to the water while stirring. Dilution releases considerable heat, and the large volume of water absorbs it safely; pouring water onto concentrated acid causes a localized boiling reaction that can spatter corrosive acid out of the container.· FAA-H-8083-30 — Cleaning and Corrosion Control
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A suitable solvent for degreasing aluminum alloy parts is
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Answer: mineral spirits or naphtha.
Why: Aluminum alloys are degreased with petroleum-based solvents such as mineral spirits and naphtha, which dissolve oils and grease without attacking the metal. Dilute sulfuric acid would corrode the alloy and is an etchant rather than a degreaser, so it is not a safe substitute, per FAA-H-8083-30 cleaning practice.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Aircraft transparent plastic (acrylic) windows and windshields should be cleaned with
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Answer: warm soapy water, then rinsed and dried.
Why: Acrylic transparencies scratch and craze easily, so FAA-H-8083-30 directs cleaning with plenty of warm soapy water and a soft cloth, then rinsing and drying, to float off grit without abrasion or chemical attack. Solvents and dry rubbing with leather risk crazing or scratching, so the warm soapy water method is correct.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Abrasive blasting media that were used on an aluminum component and are then re-used on a steel component will
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Answer: cause corrosion of the steel component.
Why: Blasting media used on aluminum pick up aluminum particles; if those same media are then used on a steel part, they embed dissimilar-metal residue that sets up galvanic action and corrosion of the steel. To avoid this contamination, media used on aluminum must not be re-used on steel components.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Intergranular corrosion is generally caused by
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Answer: improper heat treatment of the metal.
Why: Intergranular corrosion is selective attack along the grain boundaries of an alloy. It typically results from improper heat treatment, which leaves the grain-boundary regions chemically different and anodic relative to the grain interiors. Dissimilar-metal contact causes galvanic corrosion instead, and improper assembly is unrelated to this grain-boundary mechanism.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Corrosion caused by electrolytic (galvanic) action is the result of
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Answer: contact between two unlike metals.
Why: Electrolytic (galvanic) corrosion requires an anode, a cathode, and an electrolyte. Joining two unlike metals creates a potential difference that drives current through any moisture present, so the more anodic metal corrodes. Anodizing is a protective film and a wrong quenchant affects heat-treatment properties — neither sets up the galvanic cell described here.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Corrosion may best be described as the destruction of metal by
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Answer: electrochemical action.
Why: Corrosion is fundamentally the electrochemical destruction of a metal, in which the metal gives up electrons (oxidizes) at anodic sites while a reduction reaction occurs at cathodic sites through an electrolyte. The other terms are not recognized corrosion mechanisms; corrosion is an electrochemical, not a mechanical or hydroelectric, process.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Exfoliation corrosion is sometimes also referred to as
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Answer: layer corrosion.
Why: Exfoliation is a form of intergranular corrosion that progresses along planes parallel to the surface, forcing the metal apart into leaf-like layers — hence it is also called layer corrosion. Filiform is a thread-like attack under coatings and subsurface corrosion is a more general term, so neither is the recognized alternative name for exfoliation.· FAA-H-8083-30 — Cleaning and Corrosion Control
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When dissimilar metals are joined in the presence of an electrolyte, one metal forms the anode and the other the cathode. Which one will suffer from corrosion?
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Answer: The anode.
Why: In any corrosion cell the anode is the electrode that loses electrons and dissolves, so it is the part that corrodes. The cathode is protected by the current flow. When dissimilar metals are coupled, the more active (anodic) member sacrifices itself while the cathodic member is preserved.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Stress corrosion is best described as corrosion occurring in an area that is under
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Answer: continuous (sustained) loading.
Why: Stress corrosion is the combined action of a sustained (continuous, static) tensile stress and a corrosive environment, which together produce cracking that neither would cause alone. Cyclic loading with corrosion is corrosion fatigue, and rubbing between mating surfaces is fretting — so the distinguishing feature here is the continuous, not cyclic, load.· FAA-H-8083-30 — Cleaning and Corrosion Control
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An electrochemical corrosion reaction on an airframe is made possible by the contact of
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Answer: moisture on the surface of the metal.
Why: An electrochemical corrosion reaction needs an electrolyte to carry current between anodic and cathodic sites; on an airframe this is supplied by moisture on the metal surface. Dissimilar metals or a bond merely set up or control the potential difference, but without surface moisture acting as the electrolyte the reaction cannot proceed.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Galvanic corrosion is caused by
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Answer: joining two dissimilar metals.
Why: Galvanic corrosion arises when two dissimilar metals are joined in the presence of an electrolyte, the potential difference driving the more anodic metal to corrode. Incorrect heat treatment causes intergranular attack, and cyclic stress with section loss relates to fatigue, so the defining cause of galvanic corrosion is the dissimilar-metal couple.· FAA-H-8083-30 — Cleaning and Corrosion Control
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In the galvanic series, when the most noble metal is joined to a less noble metal, the noble metal will
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Answer: allow the less noble metal to corrode first.
Why: The most noble metal is cathodic and corrosion-resistant, so when coupled it stays protected and forces the less noble (anodic) metal to corrode preferentially. It does not corrode before the less noble metal; the key effect is that the less noble partner sacrifices itself first.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Stress corrosion cracking is associated with
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Answer: a corrosion pit in a member under sustained tensile stress.
Why: Stress corrosion needs a sustained tensile stress acting together with a corrosive condition; a corrosion pit in a stressed member provides the stress raiser from which cracking initiates and grows. A pit under a purely compressive load will not propagate a stress-corrosion crack, and adding cyclic loading describes corrosion fatigue instead.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Where on a poorly fabricated structural skin repair is stress-corrosion cracking most likely to begin?
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Answer: Radiating from corners or sharp edges where stress is concentrated.
Why: Stress-corrosion cracking initiates where sustained tensile stress is highest. A poorly made repair concentrates stress at corners and sharp edges, so cracks start and radiate outward from those stress raisers. Good repairs use smooth, generous radii precisely to avoid these high-stress points.· FAA-H-8083-30 — Cleaning and Corrosion Control
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A metal that is described as inherently stable (noble) will tend to
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Answer: Strongly resist corrosion in normal environments.
Why: An inherently stable, noble metal is reluctant to react with its environment and therefore strongly resists corrosion. Unstable metals readily revert toward their natural oxide or ore state and are corrosion-prone, which is the opposite condition.· FAA-H-8083-30 — Cleaning and Corrosion Control
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The natural oxide film that forms on the surface of aluminum is best described as
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Answer: Tightly adherent and non-porous, sealing the surface.
Why: Aluminum's corrosion resistance comes from a thin, tightly adherent, non-porous oxide film that forms naturally on its surface. Because the film is non-porous it seals the underlying metal from further attack; a porous film would let the electrolyte through and would not be self-protecting.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Effective corrosion control of an aircraft structure most properly begins at the
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Answer: Original design stage, before manufacture begins.
Why: Corrosion control begins at the design stage, where material selection, dissimilar-metal isolation, drainage, sealing, and accessibility for inspection are built in. Decisions made later can only work within the design already chosen, so preventing corrosion is most effective when addressed in the original design.· FAA-H-8083-30 — Cleaning and Corrosion Control
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In a galvanic corrosion cell formed by two dissimilar metals, which metal corrodes?
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Answer: The anode, which is the more active (less noble) metal.
Why: In a galvanic couple the anode — the more active, less noble metal — gives up electrons and corrodes, while the cathode is protected. The anode is therefore always the part that corrodes in a dissimilar-metal cell.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Galvanic corrosion is the direct result of
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Answer: Contact between two dissimilar metals in the presence of an electrolyte.
Why: Galvanic corrosion is set up by contact between two unlike (dissimilar) metals in the presence of an electrolyte; the resulting potential difference drives the anodic metal to corrode. Surface-treatment faults do not create the dissimilar-metal cell that defines galvanic corrosion.· FAA-H-8083-30 — Cleaning and Corrosion Control
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What are the characteristic signs of fretting corrosion at a tight, slightly moving joint?
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Answer: Fine black powder on aluminum or reddish-brown staining on steel.
Why: Fretting corrosion occurs at tight mating surfaces with slight relative movement and produces fine oxidized debris — a black powder on aluminum or a reddish-brown (cocoa-colored) staining on steel. Intergranular cracking and flaking are signs of other corrosion forms.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Black streaks tracking back from a riveted joint most likely indicate
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Answer: Fretting corrosion at the working joint.
Why: Black streaks tracking back from a rivet hole are oxidized debris worked out from between two surfaces micro-moving against each other under load — the classic signature of fretting corrosion. Galvanic and intergranular corrosion produce different indications.· FAA-H-8083-30 — Cleaning and Corrosion Control
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After a steel part is welded, the weld region may corrode preferentially because
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Answer: The heat-affected zone becomes anodic to the surrounding metal.
Why: Welding heats a band of the parent metal and changes its metallurgical condition, leaving the heat-affected zone anodic relative to the surrounding unaffected metal. That potential difference makes the weld region corrode preferentially. Spatter and paint loss are secondary effects.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Intergranular corrosion is particularly hazardous because it
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Answer: May progress extensively with little or no visible surface indication.
Why: Intergranular corrosion attacks along internal grain boundaries and can progress extensively with little or no sign on the surface, making it dangerous and hard to detect. Visible gray or white powder and flaking are characteristic of surface or exfoliation corrosion, not the hidden intergranular form.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Jointing (sealing) compound applied between mating structural surfaces is used to
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Answer: Prevent dissimilar-metal (galvanic) corrosion at the interface.
Why: Jointing compound is applied between mating surfaces to seal out moisture and electrically separate dissimilar metals, breaking the galvanic cell that would otherwise drive corrosion at the joint. It is not a structural adhesive and is not intended to ease disassembly.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Galvanic corrosion from dissimilar-metal contact is best prevented by
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Answer: Placing a non-porous dielectric material between the surfaces.
Why: Galvanic corrosion between dissimilar metals is best prevented by inserting a non-porous, non-conducting (dielectric) barrier between them, which interrupts the electrical path and keeps electrolyte out so no corrosion cell can form. Bonding connects the metals electrically, and primer alone is not a reliable insulating separation.· FAA-H-8083-30 — Cleaning and Corrosion Control
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When certain stainless steels are welded, the sensitized zone near the weld becomes susceptible to a form of corrosion known as
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Answer: Weld decay.
Why: When some stainless steels are welded, chromium near the weld combines with carbon to form chromium carbides at the grain boundaries, locally depleting the chromium that gives corrosion resistance. The sensitized zone then corrodes intergranularly — a condition known as weld decay.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Corrosion that lifts and flakes the metal surface as corrosion products force grain layers apart parallel to the surface is called
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Answer: Exfoliation corrosion.
Why: Exfoliation corrosion progresses along grain boundaries lying parallel to the surface; the bulky corrosion products force the layers apart, lifting and flaking the metal like the leaves of a book. Electrolysis is the electrochemical process itself, and 'transgranulation' is not a corrosion term.· FAA-H-8083-30 — Cleaning and Corrosion Control
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On aluminum alloy, the typical indication of fretting corrosion is
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Answer: A fine black powder at the working interface.
Why: Fretting corrosion on aluminum alloy produces fine, dark oxidized debris that appears as a black powder at the working interface. On steel the equivalent debris is reddish-brown, so white or brown powder points to other corrosion forms.· FAA-H-8083-30 — Cleaning and Corrosion Control
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What action protects integral fuel tanks from corrosion caused by microbiological growth?
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Answer: A biocidal additive is used in the fuel.
Why: Microbiological growth in integral fuel tanks lives at the fuel/water interface, and its by-products cause corrosion of the tank structure. The accepted protection is to add an approved biocidal additive to the fuel that kills the organisms. Chromate coatings and liners address other concerns and do not control the microbial growth that drives this corrosion.· FAA-H-8083-30 — Cleaning and Corrosion Control
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What type of corrosion attacks the grain boundaries of aluminum alloys that have been improperly or inadequately heat treated?
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Answer: Intergranular corrosion.
Why: Improper or inadequate heat treatment leaves the grain boundaries in an electrochemically more anodic state, so corrosion attacks preferentially along those boundaries — the definition of intergranular corrosion. Stress corrosion additionally requires sustained tensile stress, and surface corrosion is general rather than grain-boundary selective.· FAA-H-8083-30 — Cleaning and Corrosion Control
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The artificial production of an oxide film on the surface of aluminum or its alloys by an electrolytic process is commonly called
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Answer: anodizing.
Why: Deliberately growing a protective oxide film on aluminum or its alloys by an electrolytic process is called anodizing. Alodizing (chromate conversion coating) is a chemical process and parco-lubrizing is a phosphate process for steel, so the artificially produced electrolytic oxide film is anodizing.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Intergranular corrosion in structural aluminum alloy parts
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Answer: cannot always be detected by surface indications.
Why: Because intergranular corrosion runs along internal grain boundaries, it can be well advanced before any sign reaches the surface, so it cannot always be detected by surface indications. It is not confined to non-heat-treated material, and a white powdery deposit is typical of surface corrosion rather than the hidden intergranular form.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Corrosion will generally spread more rapidly when metals are exposed to
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Answer: high temperatures.
Why: Corrosion is an electrochemical reaction whose rate increases with temperature, and warm conditions usually bring the moisture needed to act as an electrolyte. Dry and cold climates both slow the reaction and reduce available moisture, so corrosion spreads most rapidly at high temperatures.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Magnesium alloy components are generally protected against corrosion by
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Answer: a chemical conversion process.
Why: Magnesium alloys are highly anodic and are protected by a chemical conversion treatment such as chromating, which forms a corrosion-resistant film and a good base for paint. An electrolytic deposit or paint alone is not the primary protection — the basic protection is the chemical conversion coating.· FAA-H-8083-30 — Cleaning and Corrosion Control
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When it is necessary to remove corrosion from a steel component in place, a suitable removing solution is based on
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Answer: phosphoric acid.
Why: For removing corrosion from a steel component in situ, a phosphoric-acid-based solution is used because it dissolves the rust and leaves a passivating phosphate film that resists further attack. Chromic and nitric acid treatments are associated with other metals and processes, so phosphoric acid is the suitable base for steel.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Heavy corrosion deposits on clad aluminum alloy should be removed
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Answer: chemically, using a phosphoric acid solution.
Why: On clad aluminum the thin pure-aluminum cladding must be preserved, so heavy corrosion is removed chemically with a phosphoric-acid-based treatment that dissolves the corrosion and passivates the surface without cutting into the protective cladding. A mechanical vibrator risks removing the cladding, and trichloroethylene is a degreaser, not a corrosion remover.· FAA-H-8083-30 — Cleaning and Corrosion Control
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Frequently asked questions
- What conditions are required for galvanic corrosion?
- Three, and all of them at the same time: two dissimilar metals, an electrolyte such as moisture carrying salts or contaminants, and an electrical connection between the metals. That is why the standard prevention is a barrier. Primer, sealant, or a nonconductive separator placed between dissimilar parts breaks either the electrical path or the electrolyte film, and the cell cannot run.
- How do I tell intergranular corrosion from surface corrosion?
- Surface corrosion appears as a powdery deposit with visible pitting you can clean and treat. Intergranular corrosion runs along the grain boundaries below the surface, so a part can look nearly clean while the material underneath has lost strength. Advanced cases exfoliate and lift the metal in layers. It is usually confirmed by nondestructive inspection rather than by eye.
- What color are the corrosion products on each metal?
- Aluminum gives a white to gray powder over a roughened, pitted surface. Magnesium gives a white powder that can push the finish up off the part. Iron and steel give reddish-brown rust. Copper and its alloys give a blue-green deposit. The test asks this in both directions, so learn metal to product and product to metal.
- Can I use a steel wire brush to clean corrosion off aluminum?
- No. Steel bristles and steel wool embed ferrous particles in the softer aluminum, and each particle forms a dissimilar-metal couple that starts corroding again with the next exposure to moisture. Use aluminum wool, an aluminum wire brush, a fiber bristle brush, or an approved nonmetallic abrasive pad, and follow the manufacturer's corrosion removal procedure for that part.
- What is Alclad and why does it resist corrosion?
- Alclad is aluminum alloy sheet with a thin layer of nearly pure aluminum rolled onto each surface during manufacture. The pure aluminum is anodic to the alloy core, so it corrodes first and shields the structural material underneath. That protection only lasts while the cladding is intact, which is why aggressive sanding and hard abrasives are avoided on clad sheet.
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- Regulations, Maintenance Forms, Records, and Publications
- Physics for Aviation
- Inspection Concepts and Techniques
- Human Factors
Airframe
- Metallic Structures
- Non-Metallic Structures
- Flight Controls
- Airframe Inspection
- Landing Gear Systems
- Hydraulic and Pneumatic Systems
- Environmental Systems
- Aircraft Instrument Systems
- Communications, Light Signals, and Runway Lighting Systems
- Aircraft Fuel Systems
- Aircraft Electrical Systems
- Ice and Rain Control Systems
- Airframe Fire Protection Systems
- Rotorcraft Fundamentals
- Water and Waste Systems
Powerplant
- Reciprocating Engines
- Turbine Engines
- Engine Inspection
- Engine Instrument Systems
- Engine Fire Protection Systems
- Engine Electrical Systems
- Engine Lubrication Systems
- Ignition and Starting Systems
- Engine Fuel and Fuel Metering Systems
- Reciprocating Engine Induction and Cooling Systems
- Turbine Engine Air Systems
- Engine Exhaust and Reverser Systems
- Propellers
Primary sources
Drill ACS AM.I.G inside the full General bank
Adaptive engine, timed exam simulator, ACS-code remediation, and oral prep — everything you need to pass.