Titanium alloys generally have a tenacious oxide film which gives them resistance to corrosion in most applications involving marine conditions and salts at near ambient temperature. Titanium alloys can exhibit sensitivity to both oxygen and hydrogen environments. If the oxide film is breached while in oxygen service, pyrophoric behavior can occur. Commercially pure and alpha titanium alloys can also form hydrides when exposed to hydrogen charging environments such as from galvanic coupling, exposure to hot acids or hydrogen gas. These hydrides in the microstructure can lead to catastrophic loss in ductility and fracture toughness.
Stainless steels are probably the most widely used materials for corrosion resistant applications.
Alloying additions of Cr, Ni, Mo and sometimes N are used to enhance corrosion and pitting resistance in aqueous environments containing chlorides and possibly sulfide at moderate to low pH. The main concern in these materials is to have a high enough alloy content to resist localized corrosion and stress corrosion cracking due to chlorides. For many applications nickel base alloys are primarily used for their high strength and good high temperature corrosion resistance. In other applications, they may encounter exposure to hydrogen charging environments.