Stainless Steels and Alloys: Why They Resist Corrosion
and How They Fail*
Localized Corrosion
Breakdown of passive film often leads to localized corrosion
such as pitting and crevice corrosion. Figure 9 shows pitting corrosion
in a Duplex stainless steel after exposure to NaCl solution [7].
Figure 9 Pitting corrosion of Duplex stainless steel (SAF2304)
in NaCl solution. The pitting events can sometimes be indicated by an electrochemical
potential noise as illustrated in Figure 10 where the potentials for 3
different grades of duplex stainless steels are being monitored. SAF2304
showed clear pitting signals compared with SAF2507 and SAF 2205.
Figure 10
The susceptibility to pitting corrosion can be quantified
with the electrochemical technique - the cyclic pitting scan. Figure 11
showed the comparison between three duplex steels in NaCl solution.
Figure 11
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