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Metal polish on anodized aluminum

Aviation Mechanic General (AMG) practice question 21 of 31 on Cleaning and Corrosion Control. ACS element AM.I.G.R2 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONA mechanic plans to use a metal polish intended for clad aluminum surfaces on an anodized aluminum part. Why is this prohibited?

  1. AThe polish reacts chemically with the anodic coating and dissolves it
  2. BThe polish leaves an oily film that prevents the paint from bonding
  3. CThe polish is abrasive enough to remove the anodized film
Show the answer and explanation

Correct answer: C. The polish is abrasive enough to remove the anodized film

  • A — incorrect The damage mechanism described is mechanical abrasion of the soft oxide coating, not a chemical reaction.
  • B — incorrect The handbook's objection is that the polish removes the oxide coat; it does not cite a paint-bonding problem from residue.
  • C — correct Metal polish intended for clad aluminum must not be used on anodized aluminum because it is abrasive enough to actually remove the protective anodized oxide film.

BACKGROUND

Anodizing thickens the natural aluminum oxide film, giving excellent corrosion resistance and a good bond for paint, but the coating is soft and easily scratched, and once damaged it can only be partially restored by chemical surface treatment. For that reason metal polish intended for clad aluminum surfaces must not be used on anodized aluminum, since it is abrasive enough to remove the protective film. Approved tools for cleaning anodized surfaces are aluminum wool, nylon webbing impregnated with aluminum oxide abrasive, fine nonwoven abrasive pads, or fiber bristle brushes; steel wool, steel wire brushes, and harsh abrasives are prohibited on any aluminum surface.

STUDY TIP

Before cleaning any aluminum part, identify whether it is Alclad or anodized; the polish that is correct for one destroys the protection on the other.

KEY POINTS

  • Aluminum metal polish is for unpainted Alclad, not anodized surfaces
  • The polish is abrasive enough to remove the anodized oxide coat
  • Damaged anodizing can only be partially restored in the field

SOURCES

  • FAA-H-8083-30B ch08 "Treatment of Unpainted Aluminum Surfaces"
  • FAA-H-8083-30B ch08 "Mild Abrasive Materials"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.