TABLE OF CONTENTS There are several methods of monitoring and measuring the corrosion rate of a metal in an electrolyte. Detailed explanations of each technique are beyond the scope of the present work, so the interested reader is advised to consult one of a number of specialized corrosion texts [98,99]. Technical standards for corrosion testing include ASTM Gl for metal loss calculation, ASTM G46 for analysis of localized corrosion, and NACE TM-01 for corrosion testing.
The simplest method, which requires just the minimum of equipment with hardly any specialized instrumentation, is the weight-loss method. In this method, the test specimen is weighed after it is thoroughly dried before and after the corrosion test, and the difference in weight is calculated. This gives an indication of the extent of corrosion that the specimen has undergone. In addition, visual inspection of the test sample reveals the type of corrosion that has occurred, e.g., pitting or general corrosion. However, in practice, the formation of oxide films which give rise to weight gains impedes the accuracy of this simple technique. Nevertheless this is still the only technique that lends itself well to in vivo trails.
The second method, which is more sophisticated, is to construct a Tafel plot. This is obtained by polarizing the specimen over a range of potentials, typically 300 mV on either side of the corrosion potential. Then the resulting current is measured, the log of the current is plotted against applied potential and the linear regions are extrapolated back to the...
