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Residual treatment salts under paint

Aviation Mechanic General (AMG) practice question 7 of 31 on Cleaning and Corrosion Control. ACS element AM.I.G.K19 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONSoluble salts from a chromic acid or dichromate surface treatment were not completely removed before the surface was painted. What effect does this have on the paint coating?

  1. AThe salts harden and improve paint adhesion
  2. BThe salts liquefy and promote blistering
  3. CThe salts prevent the paint from curing at all
Show the answer and explanation

Correct answer: B. The salts liquefy and promote blistering

  • A — incorrect Residual salts are harmful, not beneficial; the handbook emphasizes that all residues must be removed.
  • B — correct The handbook states that soluble salts from chemical surface treatments such as chromic acid or dichromate treatment liquefy and promote blistering in the paint coatings.
  • C — incorrect The stated effect is blistering of the coating from liquefied salts, not a failure of the paint to cure.

BACKGROUND

Chemical cleaners and surface treatments must be used with great care on assembled aircraft because corrosive materials can become entrapped in faying surfaces and crevices. Any materials used must be relatively neutral and easy to remove, and all residues must be removed. Soluble salts left behind by chemical surface treatments such as chromic acid or dichromate treatment liquefy and promote blistering in the paint coatings. For magnesium, the handbook similarly warns not to let excess chromic acid solution dry on the surface, because such deposits cause paint lifting.

STUDY TIP

Whenever a treatment chemical is used before painting, the exam expects you to know that incomplete removal shows up later as blistering or lifting of the finish.

KEY POINTS

  • All chemical treatment residues must be removed before painting
  • Soluble chromate salts liquefy and cause paint blistering
  • Dried excess chromic acid on magnesium causes paint lifting

SOURCES

  • FAA-H-8083-30B ch08 "Chemical Cleaners"
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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.