Definition
A form of corrosion that occurs when a metal part is under sustained tensile stress and is also exposed to a corrosive environment at the same time. The combination causes cracks to form and grow along grain boundaries in the metal, often progressing without any visible surface damage until the part fails.
Plain English
A type of metal damage that happens when a part is being pulled or stretched while also sitting in something corrosive, like moisture or salt air. The two conditions together cause hidden cracks that can lead to sudden failure.
Context Anchor
Seen in aircraft maintenance inspections, especially around metal structure, fasteners, landing gear parts, and areas that carry load and can trap moisture or chemicals.
Derivation
‘Stress’ comes from Latin strictus, meaning ‘drawn tight.’ ‘Corrosion’ comes from Latin corrodere, ‘to gnaw away.’ The name captures the mechanism well: the metal is being pulled tight while something is gnawing at it, and the two effects together cause damage neither would cause alone.
Why Pilots Care
Undetected stress corrosion can lead to catastrophic structural failure in flight-critical components.
Analogy
It is like a metal coat hanger that is held bent while rust attacks it. The bend puts the metal under load, and the rust weakens it, so a crack can start sooner than it would from either problem alone.
Intuition Check
Do not read this as simple surface rust. Stress corrosion specifically means corrosion acting together with load in the part, often leading to cracking.
Example Sentence 1
The mechanic flagged the landing gear fitting for stress corrosion inspection because it sits under constant load and is regularly exposed to moisture.
Example Sentence 2
High-strength aluminum alloys are particularly susceptible to stress corrosion in marine environments.