PROTECTION OF DUPLEX STAINLESS-STEEL FROM LOCALIZED CORROSION BY SURFACE SUPERPASSIVATION

So-called superpassivation surface treatment was conducted on a 22Cr-5 Ni-3Mo-N duplex stainless steel, and its pitting and stress corrosion cracking (SCC) behaviour is studied in hot concentrated chloride solut ions using cyclic polarization measurements and potential-controlled c onstant load tests. The results indicate that ''superpassivated'' stee l has an excellent pitting resistance and - consequently - also a very good resistance to SCC since SCC of the duplex stainless steel initia tes from pitting in the studied environments. Auger electron spectrosc opy analyses show that the passivation treatment leads to a thick high ly chromium-enriched passive film. Improved resistance of the duplex s tainless steel to pitting and SCC is attributed to the existence of th is him.