Conditions required for electrochemical corrosion

Aviation Mechanic General (AMG) practice question 2 of 31 on Cleaning and Corrosion Control. ACS element AM.I.G.K2 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONWhich condition is one of the four that must exist before electrochemical corrosion can occur?

ADirect exposure of a bare surface to a caustic gas at a single point
BA continuous, conductive liquid path (electrolyte)
CA surface temperature above 700 °F

Show the answer and explanation

Correct answer: B. A continuous, conductive liquid path (electrolyte)

A — incorrect This describes direct chemical attack, in which the anodic and cathodic changes occur at the same point; it is a separate classification from electrochemical attack.
B — correct The handbook lists four conditions for electrochemical corrosion: an anode, a cathode, a continuous conductive liquid path (electrolyte), and electrical contact between anode and cathode. Eliminating any one of them stops the corrosion.
C — incorrect The 700 °F figure is the temperature above which titanium develops colored surface oxides; it is not one of the conditions for electrochemical corrosion.

BACKGROUND

The handbook divides corrosion into two general classifications: direct chemical attack and electrochemical attack. Electrochemical attack requires four conditions: a metal subject to corrosion (the anode), a dissimilar conductive material with less tendency to corrode (the cathode), a continuous conductive liquid path (the electrolyte), and electrical contact between the anode and cathode, usually metal-to-metal contact such as rivets or bolts. Elimination of any one of these conditions stops electrochemical corrosion, which is the basis of effective corrosion control. The electrochemical attack is responsible for most forms of corrosion on aircraft structure.

STUDY TIP

Memorize the four conditions as a set and remember that removing any single one stops the process; that idea underlies most corrosion-control questions.

KEY POINTS

Electrochemical corrosion needs anode, cathode, electrolyte, and electrical contact
Removing any one condition stops electrochemical corrosion
Direct chemical attack occurs at a single point and is a different classification

SOURCES

FAA-H-8083-30B ch08 "Electrochemical Attack"

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