Rolls Royce Trent 892. © Cory W. Watts (cc-by-sa-2.0)

Titanium

Titanium alloys are relatively corrosion resistant, but in the aerospace sector suffer stress corrosion cracking following degreasing in chlorine-containing agents, or even after handling by salty fingers! When titanium is used for medical implants, corrosion is a principal cause of failure; for example, localised wear of an implant exposes a small area of metal establishing a large anodic current density and localised metal wastage.