NACE Resource Center
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| Corrosion - Design |
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Temperature Influence on Corrosion Most electrochemical reactions proceed at faster rates with increasing temperature, approximating to a doubling of rate for each 10ºC rise in temperature whether the corrosion process involves dissolution leading to general attack or to a more localized form such as cracking .This statement is only valid providing the details of any part of all of the reactions involved do not change, which will usually mean that the statement is valid only over restricted range of temperature change. In general therefore lower temperatures will be beneficial, but there are exceptions. The reversal of polarity of the iron-zinc bimetallic couple with increasing temperature has already been mentioned and there are other instances of equally sharp changes in the nature or extent of corrosion as temperature is increased.It is a matter of common experience that bare steel immersed in tap water at room temperature will corrode at a relatively high rate producing the familiar orange-brown rust as a corrosion product. An identical piece of steel immersed in the same tap water but at the boiling point of the latter will develop a black, adherent, film of corrosion product called magnetite that is sufficiently protective to reduce the corrosion rate very considerably. Stress corrosion cracking of mild steels in nitrate solutions that is unlikely at 20ºC but occurs with alarming ease at 100ºC, and this largely related to the effect of temperature upon the nature of the corrosion products involved, rather than its influence upon crack tip dissolution rate and hence crack velocity. The conditions discussed here assume a single temperature or an isothermal environment but in many practical situations heat transfer occurs across the metal-solution interface and although in many such cases it is still the temperature at the interface that is critical, rather than the fact that heat transfer occurs across it, nevertheless there are circumstances in which the latter can be important. A lesson hard to learn is that corrosion usually will be lessened or prevented by avoiding unnecessarily high temperatures, especially if these are variable over a surface. Perhaps most importantly where heat transfer conditions are involved consideration should be given to the possibilities of solution concentration, especially in crevices and under scales or other thermal insulation whether present by accident or design or as the result of the service conditions. Other pages on the temperature effects on corrosion: Acid corrosivity, Atmospheric corrosion, Christ the Redeemer, Corrosion under insulation, General effects, In seawater, Natural waters |
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