Filming Amines

Filming amines represent an effective and economical approach to condensate system corrosion control. Protection by filming amines is through the formation of an adherent, nonwettable organic film on metal surfaces preventing contact between the metal surface and corrosive condensate. The treatment level, typically 1-3 ppm of the pure amine, is not dependent on carbon dioxide or oxygen concentration.

The chemicals historically used for this pur. are high molecular weight amines or amine salts which contain straight carbon chains of 10 to 18 atoms and include the following:

• octadecylamine - CH₃(CH₂)₁₆CH₂NH
• hexadecylamine - CH₃(CH₂)₁₄CH₂NH₂
• dioctadecylamine - (CH₃(CH₂)₁₆CH₂)₂NH

The acetate salts of these amines, or the pure compound in combination with an emulsifier, are often used to ease preparation of feed solutions or dispersions. 

The amines by themselves are not soluble in water and they are usually incompatible with other boiler water treatment chemicals, the exceptions being volatile oxygen scavengers as previously discussed. Amines are dispersed in condensate-quality water kept in a separate tank and fed to the system through separate chemical feed pumps and lines.

In more recent times, advances have been made in filming amine chemistries to improve their performance. One of the more common filmers of this type is ethoxylated soya amine. Its chemistry versus that of octadecylamine is shown below.

 

octadecylamine		ethoxylated soya amine

Soya amine shows several advantages over octadecylamine in that it is more water soluble due to the double bond in its hydrocarbon chain. This will lead to less of a sludging tendency of the film. Additionally, the ethoxyl groups bound to the nitrogen portion of the molecule provide two additional sites for bonding to the metal surface of the afterboiler lines, yielding a more durable film. 

The octadecylamine containing filmers, are distributed from Water Services Ltd under the name of WSB SFA (Food approved), while the ESA containing are distributed under the WSB ESA.

All formulations include mixture of neutralizing and filming amines.

• WSB SFA
• WSB ESA

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