Many methods of corrosion control were first applied in an empirical manner, often many years before the scientific principles underlying the methods were identified. Anodic protection, however, is an exception to this procedure in that an understanding of the basic mechanisms was developed in the laboratory first. These discoveries were followed by a period of pilot-scale development, which included several trial installations in chemical plants. Finally came the commercial development of the technique. This development procedure is very satisfying to the scientist and engineer.Anodic protection is a corrosion-control method with very definite limitations in that the metal-environment system must have anodic-polarization behavior characteristic of active-passive materials. The polarization curve typifying this system and its significance from practical and theoretical vie>vpoints are fully discussed in Chapters 4 and 7. For systems involving activepassive materials, anodic protection can be a successful method of controlling corrosion. The technique has been applied in a wide variety of metal-environment systems, especially during the last 18 years. While most of these applications have been successful, some have not.This chapter is a review of a wide variety of corrosion-control problems to which anodic protection has been applied. Discussion of the equipment involved is given in Chapter 3.
Sulfuric Acid ApplicationsSulfuric acid is the chemical manufactured in greatest volume worldwide. Carbon and stainless steels are the most common construction materials for equipment used in the manufacture, storage, and transportation of this commodity which is used in concentrations of 77 to 100% in the United States. Fuming sulfuric acid, or oleum, is also manufactured. Oleum is 100% sulfuric acid in which additional S03 has been dissolved. Anodic protection can be used to control these acids over a wide temperature range. 17 O. L. Riggs Jr. et al., Anodic Protection
