Uniform corrosion theory

Rp data are meaningful for general or uniform corrosion but less so for localized corrosion, including MIC. In addition, the use of the Stem-Geary theory where the corrosion rate is inversely proportional to Rp at potentials close to is valid for conditions controlled by electron transfer, but not for the diffusion-controlled systems frequently found in MC. 

There are two implications associated with these two concepts of the mechanism of cathodic protection in respect of underprotection. If the older theory applies then it is to be expected that there will be more or less uniform corrosion over the surface. The later theory of LaQue implies that pitting... 

The theory of mixed electrodes was developed by Wagner and Traud [1] and first applied to corrosion by Stern and Geary [2]. In the following we develop the Butler-Volmer equation for a mixed electrode by taking a specific example the uniform corrosion of iron in hydrochloric acid in the absence of concentration gradients (Cj s = Ci b). Two electrode reactions take place simultaneously ... 

Electrochemical tests are often preferred to mass loss studies as a method of measuring uniform corrosion. Such tests are preferred because in theory they (1) provide a realtime measurement of the metaUic corrosion rate, (2) can provide time-corrosion rate data on a single coupon, and (3) are rapid to perform. Disadvantages of the electrochemical tests include the requirements for comparatively expensive equipment (versus mass loss tests) and higher levels of technical expertise for data analysis. Fmthermore, the data reduction requires the use of conversion-"constants," factors applied to the results of the electrical measurements to convert the data to a corrosion rate. These constants ... 

In his own paper, Frumkin also analyzed the effect of the sodium amalgam concentration on the rate of electrolysis of water, and arrived at the conclusirm that even for physically and chemically uniform surfaces, the processes of anodic metal dissolution and cathodic hydrogen evolution could occur simultaneously at the same potential. This same idea was later used by K. Wagner and W. Traud (1938) in their formulation of the theory of the mixed potential, the cornerstone of modem corrosion theory. 

In 1939 Wagner and Traud used a flat and featureless plate to portray the basic theory of corrosion for a reason such extreme simplification of the modeled system made it possible to present a statement of the basic idea of why corrosion occurs. However, real, actual corrosion, corrosion in technology, in moist environments everywhere, does not occur uniformly over the entire area of flat plates. It is nearly... 

The clear liquid yielded saltpeter upon drying. The juxtaposition of these two methods—distillation vs. precipitation —relayed Geoffroy s hope that the laws of rapports could mediate between the different chemical procedures to shape a uniform terrain of chemical theory. By going through a variety of processes that produced corrosive sublimates, Geoffrey illustrated that the same order of rapports could explain all the varieties of chemical operations in a consistent manner. The theory of the process was the same, no matter what the variations in practice were. Through the example of corrosive sublimates, Geoffroy thus presented concisely and powerfully the descriptive, predictive, and explanatory functions of his table of rapports. 

Up to now, no complete and uniform theory of anodic protection and its design principles has been developed, especially for structures of complex geometric shape. Errors made can lead to catastrophic corrosion and breakdown. However, empirical principles of its application have been developed. Anodic protection can be applied when ... 

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