Criteria for Selection of Technique

Eight criteria on which the choice of a technique depends are summarized in Table 8.2 for the various corrosion monitoring methods and described below. 

Some techniques provide information that is effectively instantaneous, while others are necessarily slower in this respect. 

Some techniques provide a measurement of corrosion rate, others measure total corrosion, or the remaining thickness, which is not exactly equivalent yet others provide information on the distribution of corrosion on the corrosion regime. 

Techniques that do not provide an individual measurement quickly are obviously unsuitable for situations where a fast response is required. Not all techniques that provide effectively instantaneous information are capable of a fast response, however. Where the measurement is of rate of corrosion, a fast response can be obtained, but if the measurement is of total corrosion, remaining thickness, or distribution of corrosion, the speed of response is limited by the ability of the technique to discriminate between successive readings. 

Many of the more effective techniques provide information on the behavior of a probe inserted into the plant, which does not necessarily reflect the behavior of the plant itself. The information obtained is in fact a measure of the corrosivity of the environment, from which plant behavior can be inferred. 

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