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Smoking rivet identification

Aviation Mechanic General (AMG) practice question 16 of 31 on Cleaning and Corrosion Control. ACS element AM.I.G.K6 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONDuring inspection of an engine cowling, a mechanic finds a black ring around a rivet head. This is the identifying mark of what form of corrosion?

  1. AFiliform corrosion beneath the paint film
  2. BExfoliation corrosion of the skin
  3. CFretting corrosion (a smoking rivet)
Show the answer and explanation

Correct answer: C. Fretting corrosion (a smoking rivet)

  • A — incorrect Filiform corrosion is recognized by worm-like traces of corrosion products beneath an organic coating, not by a black ring around a rivet.
  • B — incorrect Exfoliation shows as surface grains lifted by expanding corrosion products and is most often seen on extruded sections, not as a ring around a rivet.
  • C — correct The handbook states that the most common example of fretting corrosion is the smoking rivet found on engine cowlings and wing skins, identified by a black ring around the rivet.

BACKGROUND

Fretting corrosion occurs when two mating surfaces that are normally at rest are subject to slight relative motion. It produces pitting and large quantities of finely divided debris that cannot escape, causing localized abrasion. On bearing surfaces it is also called false brinelling. The most common example on aircraft is the smoking rivet found on engine cowlings and wing skins, identified by a black ring around the rivet. Unusually, this reaction is not driven by an electrolyte, and moisture may even inhibit it.

STUDY TIP

Link each form of corrosion to its one visual signature: black ring for fretting, worm-like traces for filiform, lifted grains for exfoliation, white powder for aluminum and magnesium.

KEY POINTS

  • Fretting: slight relative motion between mating surfaces
  • Smoking rivet = black ring around the rivet head
  • Fretting is not driven by an electrolyte

SOURCES

  • FAA-H-8083-30B ch08 "Fretting Corrosion"
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MORE ON CLEANING AND CORROSION CONTROL

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.