Buried underground pipelines made of various grades of austenitic stainless steel tubing are commonly used in many applications in the petrochemical industry, e.g., hydraulic lines,
utility water, and transporting hydrocarbons (Ref 1).
This is because of their potentially useful combination of mechanical properties and corrosion resistance. It is well known that these steels derive their corrosion resistance from a thin tenacious surface layer of Cr2O3.
Passivity is maintained in most natural environments; however, a transition to an active state occurs in environments containing high chloride concentrations as in seawaters or in reducing solutions. In this case, the protective oxide film is degraded by the chloride ions.
Although pitting
remains to be a problem in these environments (Ref 2-4), steel
grades with lower pitting resistance can still be used provided
that they are protected by insulating organic coatings (Ref 3, 5).
However, pitting can still occur if the coating is damaged or
cracked (Ref 6). The problem is compounded by the presence
of residual tensile stress, e.g., in a weld heat-affected zone,
causing stress corrosion cracking (Ref 7). Experiment shows
that a correlation exists between stacking fault energy and the
susceptibility to stress corrosion cracking, e.g., (Ref 1, 8).