346
H. Karakurkchi et al.
process, i.e., a value. An oxide film formation at aluminum oxidizing defines much
lower b value, and the oxygen immobilization in a film composition is characterized
by the positive fractional value of the shape parameter.
The other important peculiarity of studying aluminum alloys is the possibility
of electrochemical co-deposition of multi-component oxide systems MOS on their
surface [13, 26]. Such representations are formed within the limits of a hypothesis
that during PEO of Al alloys in electrolytes with additives of cations or/and oxoanions of the various natures, the requirements are created for thermo-chemical
and electrochemical reactions and conversions as the result of which one strongly
adherent coating is formed on a substrate. Proceeding from existing views about
the mechanism of aluminum alloys electrolytic oxidation in high-energy fields we
recognize four stages of oxide coatings formation at PEO:
(a) phase dielectric oxide forming obeying the faradeic mechanism before the
electrical breakdown;
(b) a film breakaway and occurrence of a plasmoid in the discharge canal (a cold
light and a sparking);
(c) thermo-chemical transformations and reactions involving gases, the electrolyte
components and metal (start of micro-electric arcs);
(d) condensation and polymorphic transformations of oxide phases (transition of a
micro-electric arc in the arc).
On the basis of the thermodynamic analysis of possible high-temperature chemical
reactions in the discharge canal, at an electrode layer and on the oxide/electrolyte
boundary the plurality of the processes proceeding in alkali solution at the oxo-anion
(MnO
−
4 ) presence, it is possible to introduce by the scheme (Fig. 10).
Aluminum and oxygen electrochemical oxidation is tracked by thermolysis of
water in a high-temperature area of the discharge canal with radicals OH· and
molecules O 2 formation. Last, in view of resonance capture of an electron possibility, dissociate on corpuscles O and O
− , diffusing in an oxide phase and oxidizing
a metal.
Simultaneously reactions of thermal manganate(VII)-ions intra-molecular
oxidation-reduction proceed
2MnO
−
4 → MnO
2−
4 + MnO 2 + O 2 , ,G
0
298 = −75.28kJ,
as well as disproportionation of unstable anions MnO
2−
4 (Fig. 10).
The manganese dioxide formed in both events can incorporate in Al 2 O 3 lattice as
Al
+3 and Mn
+4 ionic radiuses are closely related or according to [8] can go through
a series of high-temperature transformations:
MnO 2
900K
−−→ Mn 2 O 3
1300K
− −− → Mn 3 O 4
H. Karakurkchi et al.
process, i.e., a value. An oxide film formation at aluminum oxidizing defines much
lower b value, and the oxygen immobilization in a film composition is characterized
by the positive fractional value of the shape parameter.
The other important peculiarity of studying aluminum alloys is the possibility
of electrochemical co-deposition of multi-component oxide systems MOS on their
surface [13, 26]. Such representations are formed within the limits of a hypothesis
that during PEO of Al alloys in electrolytes with additives of cations or/and oxoanions of the various natures, the requirements are created for thermo-chemical
and electrochemical reactions and conversions as the result of which one strongly
adherent coating is formed on a substrate. Proceeding from existing views about
the mechanism of aluminum alloys electrolytic oxidation in high-energy fields we
recognize four stages of oxide coatings formation at PEO:
(a) phase dielectric oxide forming obeying the faradeic mechanism before the
electrical breakdown;
(b) a film breakaway and occurrence of a plasmoid in the discharge canal (a cold
light and a sparking);
(c) thermo-chemical transformations and reactions involving gases, the electrolyte
components and metal (start of micro-electric arcs);
(d) condensation and polymorphic transformations of oxide phases (transition of a
micro-electric arc in the arc).
On the basis of the thermodynamic analysis of possible high-temperature chemical
reactions in the discharge canal, at an electrode layer and on the oxide/electrolyte
boundary the plurality of the processes proceeding in alkali solution at the oxo-anion
(MnO
−
4 ) presence, it is possible to introduce by the scheme (Fig. 10).
Aluminum and oxygen electrochemical oxidation is tracked by thermolysis of
water in a high-temperature area of the discharge canal with radicals OH· and
molecules O 2 formation. Last, in view of resonance capture of an electron possibility, dissociate on corpuscles O and O
− , diffusing in an oxide phase and oxidizing
a metal.
Simultaneously reactions of thermal manganate(VII)-ions intra-molecular
oxidation-reduction proceed
2MnO
−
4 → MnO
2−
4 + MnO 2 + O 2 , ,G
0
298 = −75.28kJ,
as well as disproportionation of unstable anions MnO
2−
4 (Fig. 10).
The manganese dioxide formed in both events can incorporate in Al 2 O 3 lattice as
Al
+3 and Mn
+4 ionic radiuses are closely related or according to [8] can go through
a series of high-temperature transformations:
MnO 2
900K
−−→ Mn 2 O 3
1300K
− −− → Mn 3 O 4