The selection of materials of construction for heat exchangers is in many instances influenced by the design of the equipment. Less often the properties of the required material dictate the type of design that can be used. The need for economy in material on the one hand, and for efficient heat transfer on the other, requires that when metals are used the heat exchange takes place across relatively thin sections, and this in turn means that the selected material must have sufficient corrosion resistance to operate for a reasonable time without perforation.

The fact that in almost every case heat interchange implies fluid flow means that the metal may also be exposed to erosion-corrosion or impingement, which increases the severity of any corrosive effect that may be present. On the other hand, there are cases where the corrosivity is too severe or the temperature too high for metals to be suitable. For highly corrosive conditions it may be necessary to use a brittle material such as glass or carbon, and the need to minimize exposure to stress is an important factor in determining the design. For high-temperature applications, refractory material may be required and the brittleness of refractories is a factor in the design of, for example, recuperators.

In the space available it will not be practicable to deal with materials for all the various types of interchangers. Moreover, there is some mention of materials in the chapters on special exchangers, and the elastic properties of heat exchanger materials are discussed in detail in Section 522 and #%SECTION_5.4.8_%#. Therefore, the present survey will be concerned mainly with shell-and-tube exchangers and air coolers. The available materials will be considered first, after which the various modes of deterioration that heat exchangers may suffer in service will be reviewed.