Formation and Stability of Protective Passive Films formed on the New Generation of Stainless Steel Rebar Alloys

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Title: Formation and Stability of Protective Passive Films formed on the New Generation of Stainless Steel Rebar Alloys

Author(s): B.P. Bergsma and C.M. Hansson

Publication: Special Publication

Volume: 291

Issue:

Appears on pages(s): 1-16

Keywords: Stainless steel reinforcing bars, synthetic pore solution, cyclic polarization, Raman spectroscopy

Date: 3/29/2013

Abstract:
Electrochemical polarization and Raman spectroscopy were used to investigate the passive film formation of four grades of stainless steels in concrete and synthetic concrete pore solutions. Steels tested were austenitic grades UNS S24100 and UNS S31603, and duplex grades UNS S32101 and UNS S32304. These techniques have identified both similarities and differences in the protective films. The air-formed Cr2O3 film is not stable on any of the steels at potentials more anodic than approximately -100 mV SCE. In its stead, CrO3 and mixed spinels form at more anodic potentials. The manganese-bearing grades (S24100 and S32101) exhibited Raman peaks attributed to manganese-bearing spinels, indicating that these steels form unique passive films. These films show similar stability and breakdown behaviour in chloride-free pore solutions; studies in chloride-bearing solutions are on-going.