Atmospheric Corrosion
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Another atmospheric stimulant is hydrogen sulfide (H 2 S). Natural biological sources (such as volcanoes, moss, or damp swamp areas) and anthropogenic sources (such as pulp and paper industries, catalytic converters in
motor vehicles, sewage plants, garbage dumps, animal shelters, and geothermal plants) are responsible for the emission of H 2 S. Hydrogen sulfide can
cause the tarnishing of silver and copper by the formation of tarnish film. It
can react with OH − to form SO 2 as follows:
H S + OH
HS• + H O
HS + 2SO
HO • + SO
2
2
2
2
−
→
→
i
2
4.5.2 Nitrogen-Containing Compounds
High-temperature combustion processes such as in power plants, vehicles,
etc. produce NO and NO 2 . The combustion gas produced has a much higher
percentage of NO and NO 2 ; however, the NO is rapidly converted to NO 2
according to:
2
2
2
2
NO O
NO
+ →
•
At distances further from the emission source, the NO may also form NO 2
through the influence of ozone (O 3 ) as follows:
NO O
NO O
+ →
+
•
3
2
2
The primary nitrogen pollutant near the emission source is nitrogen dioxide
(NO 2 ). The ratio of NO 2 to NO in the atmosphere varies with time and distance from the emission source and is usually between 10 and 100. NO 2 can
be oxidized to nitric acid according to:
NO
OH
HNO
2
3
+
→
−
i
In addition, NO can be oxidized to nitric acid according to the overall reaction:
2
2
2
1
2
2
3
NO
H O
O
HNO
+
+
→
i
Because this reaction has a very low rate, the concentrations of HNO 3 and
nitrates in the immediate area of the emission source are low.
NO 2 , by absorbing solar light and the subsequent formation of ozone
through:
99
Another atmospheric stimulant is hydrogen sulfide (H 2 S). Natural biological sources (such as volcanoes, moss, or damp swamp areas) and anthropogenic sources (such as pulp and paper industries, catalytic converters in
motor vehicles, sewage plants, garbage dumps, animal shelters, and geothermal plants) are responsible for the emission of H 2 S. Hydrogen sulfide can
cause the tarnishing of silver and copper by the formation of tarnish film. It
can react with OH − to form SO 2 as follows:
H S + OH
HS• + H O
HS + 2SO
HO • + SO
2
2
2
2
−
→
→
i
2
4.5.2 Nitrogen-Containing Compounds
High-temperature combustion processes such as in power plants, vehicles,
etc. produce NO and NO 2 . The combustion gas produced has a much higher
percentage of NO and NO 2 ; however, the NO is rapidly converted to NO 2
according to:
2
2
2
2
NO O
NO
+ →
•
At distances further from the emission source, the NO may also form NO 2
through the influence of ozone (O 3 ) as follows:
NO O
NO O
+ →
+
•
3
2
2
The primary nitrogen pollutant near the emission source is nitrogen dioxide
(NO 2 ). The ratio of NO 2 to NO in the atmosphere varies with time and distance from the emission source and is usually between 10 and 100. NO 2 can
be oxidized to nitric acid according to:
NO
OH
HNO
2
3
+
→
−
i
In addition, NO can be oxidized to nitric acid according to the overall reaction:
2
2
2
1
2
2
3
NO
H O
O
HNO
+
+
→
i
Because this reaction has a very low rate, the concentrations of HNO 3 and
nitrates in the immediate area of the emission source are low.
NO 2 , by absorbing solar light and the subsequent formation of ozone
through: