In this chapter, we discuss the most frequent problems of corrosion resulting from the application of detergents and disinfectants in the operational complexity and environmental conditions of a food industry. One should be familiar with the elements of electrochemistry, metallography, chemistry of metals, chemistry of the components of formulations, the confi guration of plants, and electromagnetism induced by motors and electrical conductors in order to succeed in identifying the causes and kinetics of corrosion.
The intensity of corrosion is expressed as the weight change per unit of surface (e.g., g/m 2 /year) and as the corrosion rate considered as penetration of the corrosive process into the metallic mass per unit of time (mm/year). Stainless steel (AISI 304, 316) and aluminium represent the most common reference materials in the food industry. Acids, caustics, chloride, and biofi lm provide potentially corrosive environments, while oxidants (oxygen donors) affect the kinetics of corrosion in progress.
Corrosion is costly not only because of its sheer destruction of expensive equipment but also because of the possible contamination of fi nished foods by causing product instabilities (off -fl avors and fragrance changes, appearance modifi cation, shorter shelf -life) and health dangers. Therefore, it is always necessary to strike a balance between the cost of anticorrosion measures and their effi cacy as illustrated in Figure 17.1 .
Each industry defi nes its own degree of safety by a point (P) that gives the most profi table compromise. Equipment planning, materials selection, and periodic inspection (maintenance) enable corrosion to be prevented or kept under control. The types of corrosion, the resistance of materials to corrosion, and the corrosion potential of the various chemicals are exhaustively described in the literature (see, for example Refs [1 -7] ).
17.1 Calculation and Monitoring of Corrosion
The measurement of weight is the simplest method to obtain quantitative evidence of corrosion, but it only has a practical meaning if it refers to generalized