Atmospheric corrosion environmental effect

Environmental Effects on Metallic Corrosion Products Formed in Short-Term Atmospheric Exposures... 

Atmospheric corrosion of zinc is roughly proportional to the time of wetness in a particular location, a point emphasized by Mikhailovskii et al. (1986) for areas of the former Soviet Union, provided the nature and quantity of environmental pollution do not change a high relative humidity, which can cause condensation, increases corrosion. Rain obviously increases time of wetness, but it can have an indirect beneficial effect by removing corrosive materials. In practice, time of wetness is often taken as the time when relative humidity (RH) exceeds 80% and the temperature is above 0°C. Thin layers of solutions (except acids) are more corrosive than bulk solutions (Mansfield and Tsai, 1979). The general consensus is that the significance of atmospheric humidity in the corrosion of zinc is related to the conditions that may cause condensation of moisture on the metal surface and to the frequency and duration of the moisture contact. 

Cramer, S. D., Carter, J. P., Linstrom, P. J., and Flinn, D. R. (1987). Environmental effects in the atmospheric corrosion of zinc. Symposium on the Degradation of Metals in the Atmosphere, ASTM STP 965. American Society for Testing and Materials, Philadelphia, pp. 229-247. 

Goodwin, F. E. (1991). The effect of environmental acidification on atmospheric corrosion of zinc. 16th Int. Galv. Conf., EGGA, London, pp. GHl/l-12. 

Goodwin, F. E The Effect of Environmental Acidification on Atmospheric Corrosion of Zinc," 16th International Galvanizing Conference, European General Galvanizers Association, London, 1991, pp. GHl/1-12. 

Corrosion is the degradation of a material s properties or mass over time due to environmental effects. It is the natural tendency of a material s compositional elements to return to their most thermodynamically stable state. For most metallic materials, this means the formation of oxides or sulfides, or other basic metallic compounds generally considered to be ores. Fortunately, the rate at which most of these processes progress is slow enough to provide useful building materials. Only inert atmospheres and vacuums can be considered free of corrosion for most metallic materials. 

There are obvious reasons why scientists interest in atmospheric corrosion has become even more widespread during the past decades and why atmospheric corrosion has become a tmly interdisciplinary field of science. Environmental effects on outdoor constmctions— not least those that are part of our cultural and historical... 

S. D. Cramer, S. A. Matthes, B. S. Covino Jr., S. J. Bullard, and G. R. Holcomb, Environmental factors affecting the atmospheric corrosion of copper, ASTM Special Techn. Publ. 1421 245 (2002). I. Odnevall Wallinder, P. Verbiest, W. He, and C. Leygraf, Effects of exposiue direction and inclination of the runoff rates of zinc and copper roofs, Corros. Sci. 42 1471 (2000). 

The deleterious effect of sulfur dioxide and sulfites in domestic water is increased corrosivity owing to the lowered pH. However, oxidation of sulfite to sulfate in aqueous solutions uses dissolved oxygen, and lliis may retard corrosion. While llte oxichition of sulfite and sulfiirous acid to sulfate and sulfuric acid in the atmosphere is an environmental concern, this reaction is too... 

Ethene and propene are produced as bulk feedstocks for the chemical (polymer) industry and therefore their purities are important parameters. In particular, H2S and COS are compounds which may not only cause corrosion problems in processing equipment, but also may have detrimental effects on the catalysts in use. Eurthermore, air pollution regulations issued by, among others, the US Environmental Protection Agency (EPA) require that most of the sulfur gases should be removed in order to minimize Sulfur emissions into the atmosphere. Therefore, these compounds have to be determined to the ppb level. 

The results obtained with this equipment show that the corrosion rate in the rig is about four times that encountered in an industrial UK atmosphere. This acceleration, however, is not achieved by accentuating any of the environmental factors, but rather by holding them near to the worst natural conditions for as long as possible. The procedure used ensures that the rust film is completely dried for short periods, thus simulating the conditions that bring out the beneficial effects of protective rust films on the steels under study. 

Testing may also consist of environmental testing, to consider effects such as temperature and humidity changes and a corrosive atmosphere. 

P(2) Testing shall consist of loading the connection, either statically or dynamically, to determine its mechanical properties and/or behaviour. Alternatively the effects of environmental loads, such as temperature cycling or a corrosive atmosphere, may be used to determine the durability of the connection. 

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