Repassivation Investigations on Aluminium: Physical Chemistry of the Passive State

Tristan Oliver Nagy 1 , Morris Jhängi Joseph Weimerskirch 2 , Ulrich Pacher 1  and Wolfgang Kautek 1
  • 1 Department of Physical Chemistry, University of Vienna, Währingerstraße 42, A-1090 Vienna, Austria
  • 2 Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Vienna, Austria

Abstract

We show the temporal change in repassivation mechanism as a time-dependent linear combination of a high-field model of oxide growth (HFM) and the point defect model (PDM). The observed switch in transient repassivation current-decrease under potentiostatic control occurs independently of the active electrode size and effective repassivation time for all applied overpotentials.

For that, in situ depassivation of plasma electrolytically oxidized (PEO) coatings on aluminium was performed with nanosecond laser pulses at 266 nm and the repassivation current transients were recorded as a function of pulse number.

A mathematical model combines the well established theories of oxide-film formation and growth kinetics, giving insight in the non linear transient behaviour of micro-defect passivation.

According to our findings, the repassivation process can be described as a charge consumption via two concurrent channels. While the major current-decay at the very beginning of the fast healing oxide follows a point-defect type exponential damping, the HFM mechanism supersedes gradually, the longer the repassivation evolves. Furthermore, the material seems to reminisce former laser treatments via defects built-in during depassivation, leading to a higher charge contribution of the PDM mechanism at higher pulse numbers.

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Founded in 1887, the Zeitschrift für Physikalische Chemie covers the main developments in physical chemistry, placing with an emphasis on experimental research. It represents a combination ofdiscusses reaction kinetics and spectroscopy, surface research and electrochemistry, thermodynamics and the structure analysis of matter in its various conditions, among other topics.

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