356
H. Karakurkchi et al.
Table 7 Corrosion indicators of PEO coatings
Corrosion medium
Coating
Current index, j c ·10 6 ,
A/cm 2
Deep index, k h ·10 3 ,
mm/year
1 day
30 days
1 day
30 days
0,1 M Na 2 SO 4
Al|Al 2 O 3 *
3.40
0.39
37.03
4.25
Al|Al 2 O 3 , MnO x
0.03
0.02
0.32
0.22
0,01 M NaOH
Al|Al 2 O 3 *
3.54
10.36
38.55
112.8
Al|Al 2 O 3 , MnO x
2.12
0.52
23.09
5.66
*Oxide formed in sulfate acid
Table 8 Characteristics of the CO conversion to CO 2
Material
Active metal content,
at.%
Ignition temperature T i ,
K
Complete conversion
temperature T c , K
Pt
100
490
570
Al|Al 2 O 3
30.8
595
670
Al|Al 2 O 3 ·MnO x
Mn—33
345
505
which is favorable for redistribution of negative charge density and bond breakdown.
Secondly, MnO x also exhibits donor properties, being a source of mobile oxygen
for the oxidation of intermediates. Ultimately the branched micro-porous globular
surface of mixed oxides contains a large number of high-energy catalytic centers
[31] that provides an increase in the number of elementary collisions and reactions
[32].
Mixed conversion coatings Al 2 O 3 ·MnO x were applied on the surface of the piston
of the combustion chamber which was the part of a single-cylinder diesel engine. It
was established that fuel economy when operating a diesel engine with a piston, the
surface of which is coated with Al 2 O 3 ·MnO x , reaches 3%. The toxic emissions such
as nitrogen oxides from engine operating under forced modes decrease significantly
as was shown in [33]. So, mixed oxide systems applied on the aluminum alloys by
PEO are promising in the environmental technologies for both air and water media
purification [10, 11]. Also, such catalytic systems may be used for the intra-cylinder
catalysis in order to reduce toxicity of engine emissions [33].
5 Conclusions
1. The plasma electrolytic oxidizing technique for producing mixed oxide coatings
on aluminum alloys was developed. The composition of alkaline electrolytes
containing potassium permanganate as well as oxidizing current density and
regime was proposed to enrich the surface layer with manganese. It was shown
that the designed method to be the most technologically advanced for producing
H. Karakurkchi et al.
Table 7 Corrosion indicators of PEO coatings
Corrosion medium
Coating
Current index, j c ·10 6 ,
A/cm 2
Deep index, k h ·10 3 ,
mm/year
1 day
30 days
1 day
30 days
0,1 M Na 2 SO 4
Al|Al 2 O 3 *
3.40
0.39
37.03
4.25
Al|Al 2 O 3 , MnO x
0.03
0.02
0.32
0.22
0,01 M NaOH
Al|Al 2 O 3 *
3.54
10.36
38.55
112.8
Al|Al 2 O 3 , MnO x
2.12
0.52
23.09
5.66
*Oxide formed in sulfate acid
Table 8 Characteristics of the CO conversion to CO 2
Material
Active metal content,
at.%
Ignition temperature T i ,
K
Complete conversion
temperature T c , K
Pt
100
490
570
Al|Al 2 O 3
30.8
595
670
Al|Al 2 O 3 ·MnO x
Mn—33
345
505
which is favorable for redistribution of negative charge density and bond breakdown.
Secondly, MnO x also exhibits donor properties, being a source of mobile oxygen
for the oxidation of intermediates. Ultimately the branched micro-porous globular
surface of mixed oxides contains a large number of high-energy catalytic centers
[31] that provides an increase in the number of elementary collisions and reactions
[32].
Mixed conversion coatings Al 2 O 3 ·MnO x were applied on the surface of the piston
of the combustion chamber which was the part of a single-cylinder diesel engine. It
was established that fuel economy when operating a diesel engine with a piston, the
surface of which is coated with Al 2 O 3 ·MnO x , reaches 3%. The toxic emissions such
as nitrogen oxides from engine operating under forced modes decrease significantly
as was shown in [33]. So, mixed oxide systems applied on the aluminum alloys by
PEO are promising in the environmental technologies for both air and water media
purification [10, 11]. Also, such catalytic systems may be used for the intra-cylinder
catalysis in order to reduce toxicity of engine emissions [33].
5 Conclusions
1. The plasma electrolytic oxidizing technique for producing mixed oxide coatings
on aluminum alloys was developed. The composition of alkaline electrolytes
containing potassium permanganate as well as oxidizing current density and
regime was proposed to enrich the surface layer with manganese. It was shown
that the designed method to be the most technologically advanced for producing