Stainless Steels and Alloys: Why They Resist Corrosion
and How They Fail*
Stress Corrosion Cracking
Stainless steels are susceptible to stress corrosion cracking
in environments containing certain chemical species such as chloride. Welding
of unstabilised stainless steel may cause sensitization and result in weld
decay - a form of intergranular stress corrosion cracking. Figures 12 and
13 showed two structures with and without sensitization.
Figure 12 Unsensitized structure for 304 stainless
steel
Figure 13 Sensitized structure of 304 stainless
steel
The degree of sensitization can be rapidly quantified
with the double-loop electrochemical potentiokinetic reaction method (DL-EPR).
Figure 14 showed the DL-EPR for a 304 stainless steel sensitized at 700oC
with and without protection by ceramic insulating paste [6].
Figure 14 DL-EPR measurements on 304 stainless steels
The section protected by ceramic heat insulating paste
(green curve) showed similar current density peaks as the control sample
(blue curve) indicating the effectiveness of the paste in reducing the
degree of sensitization.
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