Analysis of the electrochemical reaction behavior of alloy AZ91 by EIS technique in H₃PO₄/KOH buffered K₂SO₄ solutions
By Anik, Mustafa & Celikten, Gizem
Published in Corrosion Science
2007
Abstract
The EIS technique was used to analyze the electrochemical reaction behavior of Alloy AZ91 in H₃PO₄/KOH buffered K₂SO₄ solution at pH 7. The corrosion resistance of Alloy AZ91 was directly related with the stability of Al2O3 · ₓH₂O rich part of the composite oxide/hydroxide layer on the alloy surface. The break down of the oxide layer was estimated to occur mainly on the matrix solid solution phase in Alloy AZ91. The mf capacitive loop arose from the relaxation of mass transport in the solid oxide phase in the presence of Al2O3 · ₓH₂O rich part and from Mg⁺ ion concentration within the broken area in the absence of Al2O3 - ₓH₂O rich part in the composite oxide structure on the alloy surface. The lf inductive loop had tendency of disappear when the dissolution rate of the alloy decreased as a result of the formation of the protective oxide layer.