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Corrosion Monitoring TechniquesCorrosion monitoring is the practice of measuring the corrosivity of process stream conditions by the use of "probes" which are inserted into the process stream and which are continuously exposed to the process stream condition. Corrosion monitoring "probes" can be mechanical, electrical, or electrochemical devices. These probes are an essential element of all corrosion monitoring systems. The nature of the sensors depends on the various individual techniques used for monitoring but often a corrosion sensor can be viewed as an instrumented coupon. In older systems, electronic sensor leads were usually employed for these purposes and to relay the sensor signals to a signal-processing unit. Advances in microelectronics are facilitating sensor signal conditioning and processing by microchips, which can essentially be considered to be integral to the sensor units. Some corrosion measurement techniques can be used on-line, constantly exposed to the process stream, while others provide off-line measurement, such as that determined in a laboratory analysis. Some techniques give a direct measure of metal loss or corrosion rate, while others are used to infer that a corrosive environment may exist. Real-time corrosion measurements refer to highly sensitive measurements, with a signal response taking place essentially instantaneously as the corrosion rate changes. Numerous real-time corrosion monitoring programs in diverse branches of industry have revealed that the severity of corrosion damage is rarely uniform with time. Complementary data from other relevant sources such as process parameter logging and inspection reports can be acquired together with the data from corrosion sensors, for use as input to the management information system. (reference)
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