Basic Principles of Corrosion of Food Metal Packaging

Abstract

The corrosion of metal packs is of major importance for health reasons and with reference to the possible reduction of shelf-life values. Basically, main failures of metal packages can be excessive metal amounts in food products, hydrogen swelling, perforation, lacquer blistering or delaminating, and modification of sensorial properties. Therefore, the possibility of minimising corrosion phenomena is of great concern depending on the exact knowledge of chemical and physical factors and causes. This chapter examines the thermodynamic and kinetic aspects of the corrosion mechanisms of tinplate, tin-free steel (TFS) and aluminium with a brief introduction to corrosion theory. In detail, a description of main anodic, cathodic and galvanic coupling prevailing reactions is provided in this chapter with particular reference to preserved foods and possible consequences (aggressiveness). The following factors with some correlation with corrosive phenomena are considered: chemistry of the metallic material, food formulation, packaging process, properties of the organic coating, and shape and capacity of the container. In particular, the role of oxygen is discussed. In addition, the description of the corrosion morphology is shown along with some practical examples with reference to failures such as detinning and pitting.