The behavior of stainless steels in physiological solution containing complexing agent studied by X-ray photoelectron spectroscopy

The passive film formed by electrochemical oxidation on two different stain less steels differing in molybdenum (Mo) content in physiological solution with and without the addition of complexing agent, i.e., citrate, ct as stu died using X-ray photoelectron spectroscopy. The alloys were polarized at d ifferent oxidation potentials in the electrochemical chamber attached to th e spectrometer. Thus, the composition of the film formed by oxidation was a nalyzed by X-ray photoelectron spectroscopy without prior exposure to air ( quasi in situ). The passive film formed in physiological solution consists of two predominant oxides, i.e.i chromium and iron oxides. Oxides of alloyi ng elements nickel and Mo are also detected in the film. It seems that the strong enrichment of oxidized chromium and Mo in the passive layer, and str ong enrichment of Mo and depletion of iron at the metal surface underneath the passive layer, are responsible for the outstanding corrosion resistance of orthopedic stainless steel in physiological solution. Commercial AISI 3 04 is not suitable for orthopedic applications. The addition of complexing agent affects significantly the passivation behavior of orthopedic stainles s steel, because it changes the distribution of the elements within the pas sive layer and at the metal surface underneath. (C) 2000 John Wiley & Sons, Inc.