Basic Details about Corrosion and Corrosion Protection

摘要

The corrosion of metallic materials is a phenomenon in which metallic materials, subjected to environmental actions during their use, undergo surface changes due to chemical or electrochemical reactions.Corrosion is classified into two types: dry corrosion and wet corrosion. Dry corrosion occurs when a metallic material is exposed to high temperatures under moisture-less conditions and develops due mainly to interaction with one or more gases. Wet corrosion results from the ionization of metals under conditions in which moisture is present. In addition to corrosion caused by natural ionization, wet corrosion also includes corrosion induced by stray electrical currents.Further, corrosion is also classified as general corrosion or local corrosion. General corrosion denotes that a metallic material is uniformly corroded, and it occurs in cases when the environmental conditions are nearly identical over the entire surface of the metal. On the other hand, local corrosion denotes that the corrosive state is not uniform, that there is partial deep pitting corrosion or grooved corrosion, and that the cause of the corrosion is the uneven distribution of environmental factors, non-uniform material quality, or galvanic action (contact with a different metal).