Cleaning, Corrosion and Finishes — practice questions

14% of the exam ≈8 real questions 8 free questions here

Fourteen percent of the weighting, and its identification-and-inspection item (AM.I.G.K6) was the FAA's most-missed General code from April 2024 to March 2025. Corrosion theory and forms, galvanic action, removal and treatment, protective coatings, cleaning, and paint finish defects.

Where people lose points

• In a concentration cell, corrosion happens where oxygen (or metal ions) is LOWEST, under gaskets and in crevices.
• Exfoliation is advanced intergranular corrosion, most often on extruded sections; intergranular can exist with no visible sign.
• In a dissimilar-metal couple the more anodic metal corrodes; magnesium is the most anodic of the common aircraft metals.
• Never use steel wool or steel brushes on aluminum or magnesium, and never move abrasive pads between metals.
• Fisheyes come from contamination such as silicone; blushing comes from humidity while dope dries.

Questions and answers, explained

All 3 questions above, with the correct answer and why it is correct. Everything here is on cleaning, corrosion and finishes.

1. What is the correct general sequence for treating corrosion?

   • ARemove products, neutralize residue, restore protective film, apply coatingCorrect
   • BPaint over it to seal it, then inspect it at the next annual inspection
   • CApply primer first, then remove the products, then neutralize the pits
   • DNeutralize, apply topcoat, then remove products

   Why: The handbook describes corrosion treatment as removing as much of the corrosion products as practicable, neutralizing residual materials in pits and crevices, restoring protective surface films, and applying temporary or permanent coatings or paint finishes.

   Reference AM.I.G.K7 · FAA-H-8083-30B, Ch. 8 (Treatment of Corrosion)

2. Small craters called fisheyes in a fresh paint finish are most often caused by

   • Aapplying the paint in coats that are too thin
   • Bspraying when the hangar is below freezing temperature
   • Cusing too much thinner in the topcoat
   • Dcontamination such as silicone on the surfaceCorrect

   Why: Fisheyes form where the paint will not wet a contaminated spot, typically silicone, wax or oil. The Airframe handbook says the most effective prevention is a clean, contamination-free surface, checked with a water break test before painting.

   Reference AM.I.G.K19 · FAA-H-8083-31B, Ch. 8 (Fisheyes)

3. When a fixed-wing airplane in the standard category is repainted, its nationality and registration marks must generally be at least how high?

   • A2 inches
   • B3 inches
   • C6 inches
   • D12 inchesCorrect

   Why: 14 CFR 45.29(b)(1): marks on fixed-wing aircraft must be at least 12 inches high. The smaller sizes are exceptions, such as 3 inches for gliders and certain experimental aircraft, and older 2-inch marks only until the aircraft is repainted.

   Reference AM.I.G.K20 · 14 CFR 45.29(b)(1)

Topics inside this domain

• Aircraft corrosion types for the A&P General: how to tell them apart

Drill other domains

• Electricity and Electronics (16%)
• Aircraft Drawings (4%)
• Weight and Balance (6%)
• Fluid Lines and Fittings (4%)
• Materials, Hardware and Processes (8%)
• Ground Operations and Servicing (9%)

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