- Industrial Water Engineering, Inc.
- CHEMICAL WATER TREATMENT
- toll free 1-800-543-6519
an 
Company
- GSA # GS-10F-7884A (1/31/2007)
- DOD Cage # 0MV90
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Alkalinity is present in boiler feedwater, usually in the form of bicarbonate or HCO3. Bicarbonate enters the boiler and is converted to carbon dioxide and hydroxide ion with the following reaction.
The hydroxide ion stays in the boiler and is used in the reaction of magnesium with silica, calcium with phosphate, or others. The carbon dioxide carries with the steam and as the steam starts to condense to water forms the corrosive carbonic acid. The reaction is:
The carbonic acid will cause corrosion in the steam and condensate system. To prevent this, a volatile base is added to neutralize the carbonic acid. The amine is added to maintain an alkaline pH in the steam and condensate systems. Commonly used neutralizing amines are:
All neutralizing amines raise pH. Most small systems are maintained at pH 8.4 to 8.8, while large utility systems are maintained at 8.8 to 9.2 pH. If the pH is above 9.2, copper will corrode. If pH is below 8.4, iron corrosion is accelerated. In a condensate system, steam will start to condense immediately downstream or close to the boiler. At the far reaches of the system, steam is still condensing to water. Different amines will condense with the steam at different locations. Morpholine will condense nearest to the boiler, DEAE will condense next, and cyclohexylamine will be the last to condense. By blending neutralizing amines, protection of the entire steam condensate system is possible. SL-5055 and SL-5050 are blends of morpholine, cyclohexylamine, and DEAE. SL-5035 is DEAE.
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