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Corrosion identification and inspection

One of the topics candidates miss most on the Aviation Mechanic General written test. It sits under General: Cleaning and Corrosion Control (Task G) in the FAA standards, code AM.I.G.K6.

Updated September 2026 · Reporting window: 2nd Quarter CY2025 (Jul 2024 to Jun 2025)

78.49%
of A&P General candidates miss this code
6th
most-missed of 9 codes the FAA lists
Severe
threat level

What this topic actually is

Corrosion is metal returning to its natural, oxidized state. On an airframe it shows up in predictable forms: surface corrosion (a dull, powdery film), pitting (small deep holes), intergranular corrosion (along grain boundaries inside the metal, often invisible from outside), and galvanic corrosion where two different metals touch with moisture between them.

The exam wants you to identify the type from a description, name where it hides (lap joints, battery boxes, bilge areas, anywhere water collects), and pick the right inspection method. The rule under most questions: the more active (anodic) metal always corrodes first, and magnetic particle inspection only works on steel, never aluminum or magnesium.

Where to study this
Aviation Maintenance Technician Handbook, General (FAA-H-8083-30), cleaning and corrosion control chapter; AC 43.13-1B.
Read Aviation Maintenance Technician Handbook, General on Aviator IQ →

Why most candidates miss it

Candidates memorize the names but not the ranking. They assume the stronger or more expensive metal survives, when galvanic corrosion sacrifices whichever metal is more chemically active, regardless of strength. The trap that catches people: mixing up which metal corrodes first. Try it yourself.

Sample trap question

A steel bolt is installed in a magnesium casting and the joint stays damp. Which metal corrodes first, and why?

How to master it

Learn the galvanic activity order once (magnesium most active, then aluminum, then steel), and pair each corrosion type with one place it hides and one way to catch it. Then drill until the type-to-method match is automatic.

Then lock it in with repetition. The A&P General written test practice on Aviator IQ is built from the same FAA handbooks and figures, and every answer cites its source.

The one thing to remember

The more active metal corrodes first, every time. Strength does not protect it.

More questions people miss on the A&P General

This code is one of several the A&P General catches people on. Here are example questions across the topics candidates miss most. Try each for an instant breakdown.

1. Ohm's law

A circuit has 12 volts applied across 4 ohms of resistance. The current flowing is:

2. Series and parallel circuits

In a series circuit, which quantity is the same through every component?

3. Galvanic corrosion

When two dissimilar metals are joined with an electrolyte present, the metal that corrodes is the one that is more:

4. Static-sensitive components

Before handling a static-sensitive electronic component, the technician should:

5. Aircraft weight and balance

Removing weight from a point forward of the datum will move the center of gravity:

6. Ratios and mixtures

A mixture calls for 3 parts of fluid A to 1 part of fluid B. To make 8 gallons of mixture, how much of fluid A do you need?

7. Bernoulli's principle

According to Bernoulli's principle, as the velocity of a moving fluid increases, its static pressure:

8. Fueling safety

When fueling an aircraft, bonding and grounding are used to:

9. Maintenance records

A maintenance record entry approving an aircraft for return to service must include the date, a description of the work, and:

10. Aircraft hardware

The grip length of an AN bolt should be chosen so that:

Sources & data notes
  • Pass rates, volumes, and average scores are the FAA's published figures. Difficulty rankings and threat levels are Aviator IQ's analysis of that public data, not official FAA ratings.
  • Aviator IQ is not affiliated with, endorsed by, or associated with the Federal Aviation Administration.

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