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Hard X –Ray Photoelectron Spectroscopy (HAXPES) characterisation of electrochemical passivation oxide layers on Al-Cr-Fe Complex Metallic Alloys (CMA)

Alessandra Beni (1,*), Noémie Ott (1), Magdalena Pawelkiewicz (1), Micheline Wardé (2), Kirsty Young (3), Birgitta Bauer (4), Parasmani Rajput (5), Blanka Detlefs (5), Jörg Zegenhagen (5), Ronan McGrath (3), Marie-Geneviève Barthés-Labrousse (2), Lars P. H. Jeurgens (1), Patrik Schmutz (1,*)

(1) Empa, Swiss Federal Laboratories for Materials Science & Technology, Ueberlandstrasse 129, 8600, Duebendorf, Switzerland.

(2) ICMMO, CNRS UMR 8182 Université Paris Sud, 91404, Orsay Cedex, France.

(3) Department of Physics, University of Liverpool, Liverpool L69 3BX, United Kingdom.

(4) Department of Earth and Environmental Sciences, Ludwig Maximilians University, Theresienstrasse 41, 80333 Munich, Germany.

(5) European Synchrotron Radiation Facility, ESRF, 6 rue Jules Horowitz, 38043 Grenoble Cedex, France.


* alessandra.beni@empa.ch, patrik.schmutz@empa.ch

 

A non-destructive Hard X-Ray Photoelectron Spectroscopy (HAXPES) characterisation of the passivation layers formed by electrochemical polarisation of Al-Cr-Fe complex metallic alloys has been performed to unveil the oxide growth/dissolution mechanisms of these high corrosion resistant intermetallic phases. By employing X-ray excitation energies from 2.3 to 10.0 keV, the depth distributions of Al- and Cr- oxide and hydroxide species in the nm-thick  (Al,Cr)-passive layers have been determined. High resolution core level spectra allowed distinguishing the presence of Al oxide and Al hydroxide species. Moreover, simultaneous analyses of the shallow Al 2s and deep Al 1s core level lines (respectively, more bulk- and surface-sensitive) provided complementary information to effectively determine the depth-resolved contributions of hydroxide and oxide species within the passivation layer. A Cr threshold concentration of 18 (at %) was found for effective passivation at pH 1, thus indicating the potential use of these intermetallic for coating of Al alloys and steels which are not stable in this lower pH range.


DOI link: http://dx.doi.org/10.1016/j.elecom.2014.05.024 


a) High-resolution spectra recorded at 6 keV for theAl78.7Cr20.6Fe0.7 alloy after electrochemical polarisation in sulphuric acid (pH 1) for 24 hours at 0VSCE. b) Al intensity ratios at various energies as a function of the alloy Cr content (pH 1).
a) High-resolution spectra recorded at 6 keV for theAl78.7Cr20.6Fe0.7 alloy after electrochemical polarisation in sulphuric acid (pH 1) for 24 hours at 0VSCE. b) Al intensity ratios at various energies as a function of the alloy Cr content (pH 1).