A Novel In Situ Scratching EC-ICP-MS Setup for Real Time Monitoring of Tribocorrosion and Repassivation Dynamics

Abstract

Tribochemical processes occur in various environments, where the combination of mechanical stress and chemical reactions can lead to significant changes in material properties, surface composition, roughness and technological performance. A detailed observation of chemical and mechanical tribodegradation, as well as materials repassivation are difficult to asses in-situ. Here, we developed a novel electrochemical flow cell to enable in-situ surface scratching followed by elemental analysis using inductively coupled plasma mass spectrometry (ICP-MS). The cell features an eccentrically positioned rotating sphere that scratches the surface, while ICP-MS analyzes material degradation downstream. This facilitates both qualitative and quantitative assessments of the electrochemical and mechanical removal of material, and allows a quantitative characterization of repassivation. Experiments conducted on a stainless steel sample, Fe(82.5)Cr(17.5), demonstrated excellent reproducibility. Due to tribomechanical damaging, repassivation of damaged areas showed considerably faster first order reaction kinetics and higher dissolution rates, compared to electrochemical passivation. During the scratching process, both ions and particles were observed to dissolve. While high Cr-content (≥12%) facilitates full repassivation, low Cr-content (< 12%) samples are unable to form a stable passive layer under tribocorrosive conditions. This technique is directly applicable for analyzing complex tribochemical processes, which can apply to a wide range of available engineering materials.