Materials and Hardware
Metals
Separate ferrous (steels, corrosion-resistant steel) from non-ferrous (aluminium, magnesium, titanium, copper alloys). Know the aluminium alloys: 2024 (copper-bearing, good fatigue strength, poor corrosion resistance, often clad) versus 7075 (zinc-bearing, high strength) versus 6061. Heat treatments: annealing, normalising, hardening, tempering, solution treatment and precipitation ageing.
Corrosion
Recognise surface, galvanic, pitting, intergranular, exfoliation, fretting and stress corrosion. The galvanic rule is simple: two dissimilar metals plus an electrolyte gives galvanic attack, and the further apart they sit in the galvanic series, the faster the attack. Stainless steel is corrosion-resistant, not corrosion-proof.
Composites and hardware
In fibre/resin composites the fibre direction controls strength, so impact damage can be invisible; delamination is the classic defect. Fasteners include AN, MS and NAS bolts, solid and blind rivets, and hi-loks; also know thread types, lockwire, self-locking nuts, bearings, bushes and seals.
The traps
Selecting a rivet by diameter instead of grip length; muddling AN (aircraft) and MS (military standard) designations; assuming a washer does not change grip requirements; thinking composites fail visibly.
Worked example
Rule of thumb for solid rivets: diameter ≈ 3 × the thickness of the thickest sheet. For two 1.0 mm sheets, d ≈ 3 mm, so select a 3.2 mm (1/8 in) rivet whose grip length spans the 2.0 mm stack plus the allowances in the table.