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Article Dans Une Revue Journal of Solid State Electrochemistry Année : 2015

Initial stages of multi-phased aluminium alloys anodizing by MAO: micro-arc conditions and electrochemical behaviour

Delphine Veys-Renaux
Emmanuel Rocca

Résumé

The electrochemical behaviour of AA1050 and AA2214 alloys was studied in a KOH/silicate in order to investigate the first stages of the coating formation during MAO process (by SEM and electrochemical measurements). Before the sparking initiation, occurring around 300 V for both alloys, a thin inner layer of aluminium oxide grows by a classical anodizing mechanism, and induces a great enhancement of the electrochemical resistance. Then, the micro-arc regime beyond 300 V leads to the formation of a dense, thicker but cracked external aluminium oxide layer. Afterwards, from 400 V, a sharp increase of current density named ``current wall'' and due to an increase of oxide conductivity, leads to a significant oxygen release and the occurrence of large and energetic sparks. Microscopic analyses reveal that the presence of copper-rich intermetallic phases in the multi-phased alloy (AA2214) induces the incorporation of copper nanoparticles in the gamma-alumina layer formed by the sparking phenomenon. These copper particles increase the reaction of water oxidation during the classical anodizing stage, and result in a delay of the sparking initiation during the galvanostatic anodizing and in a lower electrochemical resistance of the anodized layers.
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Dates et versions

hal-01295125 , version 1 (30-03-2016)

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Delphine Veys-Renaux, Emmanuel Rocca. Initial stages of multi-phased aluminium alloys anodizing by MAO: micro-arc conditions and electrochemical behaviour. Journal of Solid State Electrochemistry, 2015, 19 (10), pp.3121-3129. ⟨10.1007/s10008-015-2935-3⟩. ⟨hal-01295125⟩
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