The service life of a material must be defined with reference to the environment in which it is exposed. Therefore, in assessing the atmospheric corrosion of metals, knowledge of the service environment is essential. In the broadest sense, the environmental factors which influence atmospheric corrosion may be divided into the following five categories: Weathering, Biological, Mechanical, Incompatibility, and Use. The effects of these different categories of environmental factors are not independent, and substantial interaction may occur between them. The impacts of biological, incompatibility, and use factors on atmospheric corrosion tend to be specific to each application. Similarly, mechanical factors tend to be of major importance only for certain types of applications. The effects of weathering factors on atmospheric corrosion are, however, ubiquitous and are, therefore, more amenable to a broad overview.