SURFACE-COMPOSITION OF RU CONTAINING DUPLEX STAINLESS-STEEL AFTER PASSIVATION IN NONOXIDIZING MEDIA

In this paper, results obtained by surface analysis (Auger Electron Sp ectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS)) studies p erformed on the passive layers that formed spontaneously on duplex sta inless steels (DSSs) and Ru containing (0.3%) duplex stainless steel ( DSS:Ru) in HCl and H2SO4 solutions are presented in order to explain t he roles of the different alloying elements in the passivation process . From the AES studies, it followed that the Cr concentrations were sl ightly higher (about 3%) in the passive layers of both materials, comp ared to their bulk concentrations, whereas the Ni concentrations were reduced to less than half their bulk concentrations at the outer surfa ces of the passive layers, with an increasing concentration gradient t owards the hulk of the material. Enrichment of Mo at outer surface of the passive layer was only observed in the case of the DSS:Ru samples which were passivated in HCl. The XPS results indicated that the passi ve layer on the DSS:Ru samples contained more Cr2O3 and Fe2+ than Cr(O H)(3) and Fe3+, respectively, in the passive layer, compared to the DS S samples without Ru. (C) 1998 Elsevier Science B.V. All rights reserv ed.