Definition
An electrochemical form of corrosion that occurs when two different metals are in direct contact in the presence of an electrolyte (such as water or moisture), causing the more chemically active metal to corrode at an accelerated rate. Also known as galvanic corrosion.
Plain English
When two different metals touch and get wet, one of them eats away faster than it normally would. The moisture acts like a battery, and the weaker metal slowly wears down.
Context Anchor
Seen in aircraft maintenance, especially during inspections of fasteners, sheet metal, fittings, joints, and areas where moisture can collect.
Derivation
Dissimilar means 'not alike,' from Latin dis- (not) and similis (alike). The name simply describes the cause: corrosion that happens because the two metals are not the same kind.
Why Pilots Care
Unchecked corrosion at mixed-metal joints weakens airframe strength and can lead to component failure.
Analogy
Think of two different metals and moisture making a tiny battery. That small electrical action can cause one metal to waste away over time.
Grounding Statement
Picture a steel screw installed in an aluminum aircraft panel where rainwater sits; over time, the area around the contact point can begin to corrode.
Intuition Check
Dissimilar metal corrosion is not just ordinary rust, and it is not caused only by age. The key idea is unlike metals connected together with moisture or another conductive liquid present.
Example Sentence 1
The mechanic found dissimilar metal corrosion where the steel fastener met the aluminum skin.
Example Sentence 2
During the annual inspection, the technician found white powder indicating dissimilar metal corrosion around the rivets joining two different alloys.