THE PASSIVE BEHAVIOR OF 304-STAINLESS-STEEL IN PC-H2O AND DME-H2O MIXTURES

The passivation and breakdown behavior of 304 stainless steel in propylene carbonate (PC) or dimethoxyethane (DME) mixtures with water and containing 0.5 M LiAsF6 were studied. The air-formed film of 304 stainless steel provides a good passive film that resists breakdown. No pitting was observed in either PC-H2O-0.5 M LiAsF6 mixtures or mixed DME-H2O-0.5 M LiAsF6 solutions if the polarizations were conducted below the oxidation potential [1800 mV (sce)] of the hexafluoroarsenate electrolyte. It is apparent that even small amounts of water were sufficient to stabilize the passive film on stainless steel through a probable oxide-oxyhydroxide formation. Fitting of the 304 stainless steel was observed in both mixed organic-water solutions at potentials above the oxidation potential of AsF6- because of the lack of passivating mechanisms such as salt film formation, electropolymerization, or oxide-oxyhydroxide formation.