SkyDrill

Deadline for painting over a chromic acid inhibitor treatment

Aviation Mechanic General (AMG) practice question 34 of 36 on Cleaning and Corrosion Control. ACS element AM.I.G.R8 · 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 treats a corroded aluminum surface with chromic acid inhibitor. By when must the regular paint finish be applied over the treated surface?

  1. ANo later than 7 days afterward
  2. BNo later than the same day
  3. CWithin 72 hours of the treatment
Show the answer and explanation

Correct answer: B. No later than the same day

  • A — incorrect A week is far beyond the stated limit, which ends on the day the chromic acid treatment is applied.
  • B — correct The treatment must be followed by regular paint finishes as soon as practicable, and never later than the same day as the latest chromic acid treatment.
  • C — incorrect No 72-hour allowance is given; leaving the treated surface unpainted past that day exceeds the handbook's limit.

BACKGROUND

A 10 percent solution by weight of chromic acid, activated by a small amount of sulfuric acid, is particularly effective in treating exposed or corroded aluminum surfaces, and it may also be used on corroded magnesium. The treatment tends to restore the protective oxide coating on the metal surface, but that restored film is meant to be sealed under paint promptly. The handbook requires such treatment to be followed by regular paint finishes as soon as practicable and never later than the same day as the latest chromic acid treatment. Chromium trioxide flake is a powerful oxidizing agent and a fairly strong acid, so it must be stored away from organic solvents and other combustibles. Wiping cloths used in chromic acid pickup must be thoroughly rinsed or disposed of.

STUDY TIP

Plan corrosion work so the finish can be applied the same day the inhibitor goes on, and do not treat a surface you cannot paint before the shift ends.

KEY POINTS

  • Chromic acid inhibitor is a 10 percent chromic acid solution activated by a small amount of sulfuric acid, used on exposed or corroded aluminum.
  • It partially restores the protective oxide film, so the paint finish must follow as soon as practicable and never later than the same day.
  • Chromium trioxide flake is a strong oxidizer, stored away from organic solvents, and its wiping cloths are rinsed or discarded.

SOURCES

  • FAA-H-8083-30B ch08 "Chromic Acid Inhibitor"
Practice the Aviation Mechanic General (AMG) test →Timed 60-question exam, by ACS area, or review your misses. Free.
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.