Atmospheric corrosion proceeds via several processes that proceed in sequence and/or parallel
across multiple classes of matter (the atmosphere, condensed aqueous solution, polymer coatings, oxide
scales, precipitated salts, and microstructurally heterogeneous metal alloys). Multiple physical and
chemical phenomena contribute to the process of corrosion, including mass-transport, electrochemical
effects, metal dissolution, grain-boundary transport, etc. For this reason, it is difficult to directly predict,
using fundamental physics or chemical principles, the corrosion rate of a metal in its environment.