5.1 Corrosion products, in the form of particulate and dissolved metals, in the steam and water circuits of electricity generating plants are of great concern to power plant operators. Aside from indicating the extent of corrosion occurring in the plant, the presence of corrosion products has deleterious effects on plant integrity and efficiency. Deposited corrosion products provide sites at which chemicals, which are innocuous at low levels, may concentrate to corrosive levels and initiate under-deposit corrosion. Also, corrosion products in feedwater enter the steam generating components where deposition on heat transfer surfaces reduces the overall efficiency of the plant.

5.2 Most plants perform some type of corrosion product monitoring. The most common method is to sample for long time periods, up to several days, after which laboratory analysis of the collected sample gives the average corrosion product level over the collection time period. This methodology is referred to as integrated sampling. With the more frequent measurements in the on-line monitor, a time profile of corrosion product transport is obtained. Transient high corrosion product levels can be detected and measured, which cannot be accomplished with integrated sampling techniques. With this newly available data, plant operators may begin to correlate periods of high corrosion product levels with controllable plant operating events. In this way, operators may make more informed operational decisions with respect to corrosion product generation and transport.