Effects of AC-Modulated Passivation and Post-Treatment on Composition and Stability of Passive Films
Abstract An investigation of the effects of alternating voltage modulated passivation (AC-modulated passivation) and post-treatment on the composition and stability of passive films on 302 and 316 stainless steels by ellipsometry, electrochemistry, and surface Auger electron spectroscopy analysis was carried out. AC-modulated passivation increases the concentration of elements O, and the ratio Cr/ (Cr + Fe) in the passive film, changes the depth composition profile of the film, roughens the surface of the passive film and makes it more favorable to the adsorption of molybdenum-containing ions during post-treatment. Hence, the resistance against the chemical dissolution of the passive film increased and the stability of the passive film improved.
We propose an innovative procedure for extracting decay regions from color images of stony materials. The use of appropriate image analysis techniques can offer an important contribution to be used together with the traditional methodologies for studying and diagnosing the decay of stony materials that constitute ancient monuments. The presented approach is constituted by the PDE (Partial Differential Equations) model of anisotropic diffusion and by the level set/fast marching method. The anisotropic diffusion is applied in order to limit the smoothing at the zones of high gradient. In the segmentation process, the numerical technique of the level set/fast marching is applied in order to extract from the image only the color region examined. The study case concerns impressive remains of the city of Aosta (Italy).