The environment factor controlling the probability of a corrosion failure
According to the basic materials degradation model, the principal features underlying the environment factor consist in a long list of elements describing the chemical makeup of the environment as well as the aggravating contributors that can be part of operating conditions as schematically illustrated.
A testing program that would investigate only the nominal condition without consideration for effects such as flow, pH cells, deposits, and other galvanic effects is useless for lifetime prediction. An exact and complete environmental definition must include a description of the microenvironment actually in contact with a metallic surface. However, the circumstances producing this microenvironment are also important. Processes such as wetting and drying, build-up of deposits, and changes in flow patterns greatly influence the chemistry of a surface.