Materials and Hardware: Properties, Corrosion and Fasteners
Materials
Understand the properties that matter in airworthiness: strength, stiffness, ductility, fatigue resistance, and corrosion resistance. Know the common aircraft materials (aluminium alloys, titanium, steel, composites) and where each is used and why. Understand heat treatment and the difference between annealing and hardening, and the meaning of temper designations.
Corrosion
Know the types of corrosion: surface, galvanic, pitting, intergranular, exfoliation, stress-corrosion cracking and fretting. Understand the conditions that promote each and the inspection and prevention methods, including protective coatings, sealants, drainage and the avoidance of dissimilar metal contact.
Hardware
Know the types of fasteners (solid rivets, blind rivets, bolts, screws), their identification markings, and the meaning of grip length and thread engagement. Understand lockwiring, self-locking nuts, and the difference between a close-tolerance and an interference-fit fastener. Know the correct handling of composite materials, including moisture and contamination control.
Traps
- Confusing galvanic corrosion (dissimilar metals plus electrolyte) with pitting (localised breakdown of the passive layer).
- Assuming all rivets are interchangeable; head type and alloy markings matter.
- Forgetting that composites can hide damage that is invisible externally.
Rule of thumb
For corrosion questions, identify the three ingredients: a susceptible material, an electrolyte, and a driving potential. Remove any one and corrosion stops.