Environmental Engineering Reference
In-Depth Information
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Introduction
Metals and alloys still constitute the most important group among engineering
materials, and the demand for metallic materials with higher strength and special
properties is on the increase with the advancement of technology. However, a
serious drawback of metallic materials (and of other materials too!) is the deterio-
ration in properties originating from their interaction with the environments in
which they are to perform. Often this leads to a premature failure of metallic
components with the allied hazards of plant shutdown and loss of economy, envi-
ronmental pollution, and risk to human lives. The annual direct loss of natural
resources, i.e., metals, due to environmental degradation is also substantial.
The environment in question may vary from a simple atmospheric exposure
at ambient temperatures to reactive gases at high temperatures, from soil to water,
from weak chemicals to strong chemicals, from liquid metals to nuclear radiation.
The nature of environmental degradation varies from environment to environ-
ment, although some features (e.g., loss of ductility, cracking) may be common
to several of them. The various types of environmental degradation of metals are
described by different terms such as corrosion, high-temperature corrosion, liquid
metal attack, hydrogen damage, and radiation damage, which again have their
narrower classifications in each group. The classification has been presented in
Fig. 1.1. It is important to understand the nature of all types of environmental
degradation of metals and alloys as vividly as possible so that preventive mea-
sures against metal loss and failures can be devised, and economy, safety, and
reliability in the use of metallic components can be ensured.
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