Stainless steels are susceptible to stress corrosion cracking (SCC) in wide range of
environments. SCC occurs predominantly when stainless steels are exposed to chloride
containing environments. The concentration of these chloride ions vary with different industrial
applications from 10ppm in cooling water to 22,000ppm (seawater). This study was focused on
low chloride concentrations and is relevant to steam turbines and cooling water systems.
The effect of applied potential (Eapp) on (SCC) behaviour of stainless steels (12%Cr -
25%Cr, PREN 11- 43) was investigated using the slow strain rate technique (SSRT) in an
autoclave with controlled potentials, using a three electrode cell and potentiostat. The tests
were conducted at 1300C in a solution containing 15-30ppm chloride and 8ppm dissolved
oxygen. The results showed that the reduction in ultimate tensile strength (UTS) and the
reduction of area (ROA) varied with the applied potential. A critical SCC potential (ESCC) was
found to exist in a narrow potential range for each of the materials tested.
Fractographic observations on fractured specimens in the scanning electron microscope
(SEM) showed that the loss of ductility, indicated by the decrease in ROA was linked to the
initiation, coalescence and propagation of cracks for all materials. Depending on the microstructure the forms and causes of SCC in all these materials was different. Safe
operating limits in dilute chloride conditions were fully determined for all grades investigated in
this study.