Copper patinas formed in the atmosphere. lll. A semi-quantitative assessment of rates and constraints in the Greater New York City Metropolitan Area.

Almost all metals and alloys corrode in use. The limits to their use are therefore provided not by the tendency to corrode but by the rates at which the corrosion occurs. Information concerning corrosion rates has traditionally been gathered by field experience rather than by an understanding of the processes involved, a situation which makes difficult any corrosion prediction for new environments or new materials. Because of copper's ability to interact with a variety of atmospheric species and to retain the signatures of those interactions in a stable patina layer, copper is a particularly appropriate material for a study of the rates of corrosion processes. The rate of formation of copper patinas in a specific geographical location is dependent upon the atmospheric concentrations of corrosive species, their degree of interaction with the copper surface, and the mechanisms and rates of the processes that govern interaction.