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- Electrochemical noise (2) (entfernen)
Electrochemical noise (EN) enables corrosion research and monitoring in real time and with high sensitivity. In the case of submicroscopic nucleation events of pitting corrosion it has been observed that the cathodic process plays a decisive role in the mechanism as well as in the origin of EN signals, which depend not only on the metallic dissolution reaction but also on the electron-consuming process. EN signals arising from the nucleation process of localized corrosion on stainless steels can only be recorded due to the inhibition effect on the cathodic process achieved by the spontaneous formation of the passive layer. In consequence, passive layer stability becomes a significant factor in influencing EN signals. The way in which the passive layer stability affects the acquisition and analysis of EN signals arising from pitting corrosion on stainless steels is discussed in detail.
Pitting corrosion is one of the most common mechanisms of surface damage on stainless steels. Electrochemical methods have been preferentially applied for the evaluation of the pitting corrosion resistance of stainless steels in the laboratory. Nevertheless, some of them are not reliable enough and in general the application of electrochemical methods in the field becomes difficult because of required deep understanding of corrosive phenomena and measurement technology. Therefore, new approaches for the evaluation of the pitting corrosion susceptibility of stainless steel surfaces in the laboratory as well as in the field are necessary. In the present paper two novel strategies including electrochemical noise measurements under anodic polarization for laboratory testing, and an indicator test to assess the susceptibility of stainless steel surfaces to pitting corrosion in the field are introduced. Experimental results concerning the influence of surface treatments on the pitting corrosion resistance on stainless steels have confirmed that final surface condition has a significant effect on their future pitting corrosion susceptibility. In addition, the pitting corrosion resistance of stainless steel surfaces was observed being specifically dependent on the achieved surface topography and in some cases independent on the roughness parameters of the surface.