Carbonate tuberculation

A specific waterside problem that affects many economizers is normally one of oxygen corrosion. This affects the internal, carbon steel tube header, first-pass tubes, and primary tube bend areas because these areas first receive cold FW. This form of corrosion commonly results in red oxides, economizer pitting and tuberculation, and potentially premature tube failure. 

Under the sludge considerable orange-red tuberculation corrosion deposits may develop. In cause-and-effect fashion, the tubercles grow cause fouling, permit under-deposit corrosion to persist, and generally act as a binding agent for carbonates, silicates, and other precipitates. 

Corrosion of an iron pipe under certain conditions can also manifest itself in the formation of "pits" and "tubercules" (Fig. 7-13). The OH produced by the cathodic reaction not only may precipitate Fe(OH)2react with bicarbonate ion (alkalinity) in the water to produce carbonate ion. In the locally high pH region around the cathode, both FeCOats) and calcium carbonate may precipitate... 

Corrosion in the condensate system manifests itself in certain typical forms, depending upon the corrosive factors involved. These factors are basically oxygen, carbon dioxide, and condensed water. Attack due to dissolved oxygen is characterized by tuberculation, pitting, and build-up of iron oxide... 

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