78
Fundamentals of Corrosion
degradation as a result of the action of ozone, oxygen, and sunlight. These
three weathering agents can greatly affect the properties and appearance
of a large number of synthetic materials. Surface cracking, discoloration of
colored stock, and serious loss of tensile strength are the result of this attack.
Elastomeric materials may also suffer loss of elongation and other rubberlike properties.
4.1 Atmospheric Types
Because corrosion rates are affected by local conditions, atmospheres are
generally divided into the following categories:
Rural
•
Industrial
•
Marine
•
Additional subdivisions such as urban, arctic, and tropical (wet or dry) can
also be included. However, of main concern are the three major categories.
For all practical purposes, the more rural the area, with little or no heavy manufacturing operations, the less will be the problem of atmospheric corrosion.
In industrial atmospheres, all types of contamination by sulfur in the
form of sulfur dioxide or hydrogen sulfide are important. The burning of
fossil fuels generates a large amount of sulfur dioxide, which is converted
to sulfuric and sulfurous acid in the presence of moisture. Combustion of
these fossil fuels and hazardous waste products should produce only carbon dioxide, water vapor, and inert gas as combustion products. This is seldom the case. Depending on the impurities contained in the fossil fuel, the
chemical composition of the hazardous waste materials incinerated, and the
combustion conditions encountered, a multitude of other compounds may
be formed.
In addition to the most common contaminants previously mentioned, pollutants such as hydrogen chloride, chlorine, hydrogen fluoride, and hydrogen bromide are produced as combustion products from the burning of
chemical waste. When organophosphorous compounds are incinerated, corrosive phosphorus compounds are produced. Chlorides are also a product of
municipal incinerators.
Road traffic and energy production lead to the formation of NO x , which
may be oxidized to ΗΝΟ 3 . This reaction has a very low rate; therefore, in the
vicinity of the emission, the contents of HNO 3 and nitrates are very low. The
antipollution regulations that have been enacted do not prevent the escape
into the atmosphere of quantities of these materials sufficiently to prevent
Fundamentals of Corrosion
degradation as a result of the action of ozone, oxygen, and sunlight. These
three weathering agents can greatly affect the properties and appearance
of a large number of synthetic materials. Surface cracking, discoloration of
colored stock, and serious loss of tensile strength are the result of this attack.
Elastomeric materials may also suffer loss of elongation and other rubberlike properties.
4.1 Atmospheric Types
Because corrosion rates are affected by local conditions, atmospheres are
generally divided into the following categories:
Rural
•
Industrial
•
Marine
•
Additional subdivisions such as urban, arctic, and tropical (wet or dry) can
also be included. However, of main concern are the three major categories.
For all practical purposes, the more rural the area, with little or no heavy manufacturing operations, the less will be the problem of atmospheric corrosion.
In industrial atmospheres, all types of contamination by sulfur in the
form of sulfur dioxide or hydrogen sulfide are important. The burning of
fossil fuels generates a large amount of sulfur dioxide, which is converted
to sulfuric and sulfurous acid in the presence of moisture. Combustion of
these fossil fuels and hazardous waste products should produce only carbon dioxide, water vapor, and inert gas as combustion products. This is seldom the case. Depending on the impurities contained in the fossil fuel, the
chemical composition of the hazardous waste materials incinerated, and the
combustion conditions encountered, a multitude of other compounds may
be formed.
In addition to the most common contaminants previously mentioned, pollutants such as hydrogen chloride, chlorine, hydrogen fluoride, and hydrogen bromide are produced as combustion products from the burning of
chemical waste. When organophosphorous compounds are incinerated, corrosive phosphorus compounds are produced. Chlorides are also a product of
municipal incinerators.
Road traffic and energy production lead to the formation of NO x , which
may be oxidized to ΗΝΟ 3 . This reaction has a very low rate; therefore, in the
vicinity of the emission, the contents of HNO 3 and nitrates are very low. The
antipollution regulations that have been enacted do not prevent the escape
into the atmosphere of quantities of these materials sufficiently to prevent