Formation of Manganese-Containing PEO Coatings on Aluminum Alloys
347
Fig. 10 The scheme of transformations at aluminum PEO treatment in a potassium permanganate
(VII) solution
Thus, manganese dioxide, in our opinion, is formed predominantly in the lowtemperature area and on the oxide/electrolyte boundary, and double manganese oxide
of the mixed valence—in the high-temperature area of discharge canal.
Since specific electrical conductivity of MnO 2 and Mn 3 O 4 on some orders exceed
Al 2 O 3 conductivity the voltage of sparking and forming in permanganate (VII) solution are less than in aluminum oxide formation in an alkaline electrolyte. Due to
the crystallization of both oxides simultaneously with the Al 2 O 3 which undergoing
347
Fig. 10 The scheme of transformations at aluminum PEO treatment in a potassium permanganate
(VII) solution
Thus, manganese dioxide, in our opinion, is formed predominantly in the lowtemperature area and on the oxide/electrolyte boundary, and double manganese oxide
of the mixed valence—in the high-temperature area of discharge canal.
Since specific electrical conductivity of MnO 2 and Mn 3 O 4 on some orders exceed
Al 2 O 3 conductivity the voltage of sparking and forming in permanganate (VII) solution are less than in aluminum oxide formation in an alkaline electrolyte. Due to
the crystallization of both oxides simultaneously with the Al 2 O 3 which undergoing