|MadSci Network: Chemistry|
some research: http://www.onepetro.org/mslib/servlet/onepetropreview? id=NACE-08332&soc=NACE&speAppNameCookie=ONEPETRO
The requirements for corrosion to take place in aqueous conditions are:
Interrupting, inhibiting, removing etc. any one of the seven requirements will prevent [or at least considerably slow because in actual conditions several mechanisms may be operating simultaneously] corrosion.
So-called uniform corrosion is rarely uniform unless conditions are carefully controlled in procedures such as electropolishing or control of anode dissolution in electroplating, There are two common examples of uniform corrosion. The first is when there are cathode and anode areas and the anode area is physically large. Since corrosion occurs over the entire anode area it will appear uniform, but careful examination usually shows increased corrosion rate closer to the cathode. The second common example is that of an ostensibly pure metal that corrodes all over when immersed in water. Since corrosion appears somewhat uniform over the surface the cathode and anode sites must be miniscule and evenly distributed over the material. These sites can be crystal imperfections, atoms or domains of alloying elements, even machining or casting imperfections. Microscopic or electron microscopic examination of such corrosion usually reveals pitting and sometimes even shows cathodic sites of impurites in the pitted areas. "Uniform" corrosion is sensitive to slight liquid motion or stirring, temperature and chemical concentration variations and physicak interfaces.
Try the links in the MadSci Library for more information on Chemistry.