Flow microcapillary plasma mass spectrometry-based investigation of new Al–Cr–Fe complex metallic alloy passivation

• Published in: Talanta (Oxford) 2014-03, Vol.120, p.230-238
• Main Authors: Ott, N., Beni, A., Ulrich, A., Ludwig, C., Schmutz, P.
• Format: Article
• Language: English
• Subjects: Alloys - chemistry; Aluminum; Aluminum - chemistry; Aluminum base alloys; Al–Cr–Fe complex metallic alloys; Chromium - chemistry; Corrosion; Corrosion resistance; Dissolution; Electrolytes; Electrolytes - chemistry; Equipment Design; Flow cell; Gamma phase; ICPMS analysis; Iron - chemistry; Mass Spectrometry - instrumentation; Microcapillary; Microfluidic Analytical Techniques - instrumentation; Passivation; Passivity; Potentiostatic polarization; Surface Properties
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2013.11.091

Al–Cr–Fe complex metallic alloys are new intermetallic phases with low surface energy, low friction, and high corrosion resistance down to very low pH values (0–2). Flow microcapillary plasma mass spectrometry under potentiostatic control was used to characterize the dynamic aspect of passivation of an Al–Cr–Fe gamma phase in acidic electrolytes, allowing a better insight on the parameters inducing chemical stability at the oxyhydroxide–solution interface. In sulfuric acid pH 0, low element dissolution rates (in the µgcm−2 range after 60min) evidenced the passive state of the Al–Cr–Fe gamma phase with a preferential over-stoichiometric dissolution of Al and Fe cations. Longer air-aging was found to be beneficial for stabilizing the passive film. In chloride-containing electrolytes, ten times higher Al dissolution rates were detected at open-circuit potential (OCP), indicating that the spontaneously formed passive film becomes unstable. However, electrochemical polarization at low passive potentials induces electrical field generated oxide film modification, increasing chemical stability at the oxyhydroxide–solution interface. In the high potential passive region, localized attack is initiated with subsequent active metal dissolution. [Display omitted] •Development of flow microcapillary-based setup coupled to electrochemical control.•Local, time-resolved and element-specific ionic release investigations.•Simultaneous characterization of passive film growth and dissolution processes.•Development of micro salt-bridges stable in acidic solutions.•Anodic polarization enhances the passive film stability of Al–Cr–Fe gamma phase.