Filming amines

Condensate systems can be chemically treated to reduce metal corrosion. Treatment chemicals include neutralising amines, filming amines, and oxygen scavenger-metal passivators. 

Fig. 7. Test specimens illustrate the nonwettable surface produced by a filming amine (381) compared with an untreated surface (380).

Inject a filming amine to provide a protective barrier that will prevent cyanide from contacting the iron sulfide layer. 

Filming amines In such situations, one approach is to use the filming type of amine, of which octadecylamine is the most common example. This, and related substances, forms a barrier on the internal surfaces of the feed system offering some protection against corrosive attack. 

Filming amines are of a wax-like consistency and require dispersion before introduction to the system. Particular care is needed when starting the dosage in case agglomerates formed from the amine, and debris (crud), cause blockage. 

An advantage of filming amines over neutralising amines is their relative independence of the concentration of corrosive substances. About l-2mg/kg of filming amine are usually adequate. This non-stoichiometric... 

Gunking This may occur when beginning the use of filming amines in condensate systems or polymeric sludge dispersants in FW systems. Here the new program may dislodge old corrosion debris or salt deposits and cause them to redeposit elsewhere (usually ultimately in the boiler section). 

However, most smaller boiler plants do not do this rather, control usually takes place by curing the effect of corrosion by the use of various neutralizing and/or filming amines rather than by curing the cause. 

Filming amines generally produce a much worse fouling condition than neutralizing amines so where fdmers are required, the typical prac-... 

Condensate treatments include neutralizing amines such as morpholine and filming amines such as octadecylamine (ODA). 

Under these conditions, because the neutralizing amine has no effect on oxygen ingress, it is common to supplement the neutralizing amine blend with a filming amine. Thefilmer may be applied separately (usually to a steam header) or blended with the neutralizers and added to the FW, or sometimes directly to the boiler. Care should be exercised when filmers are employed in previously corroded systems because it is very likely that old corrosion debris will be transported away to cause severe blockages in steam traps and valves. 

Octadecylamine (filming amine) 3 ppm maximum in steam, and excluding the use of such steam in milk and milk products. 

The use of filming amines, which have very low DRs that limit their spread through all regions of the steam lines. 

Some commonly used filming amines are better at promoting dropwise condensation, whereas others, notably octadecylamine (stearylamine), are better at reducing friction and improving the drop runoff rate. 

Figure 11.2 Surface activity on the waterside of a condensate line, showing filmwise condensation of water on an unprotected area (a) and dropwise condensation on an area protected by a closely packed arrangement of filming amine molecules (b).

Functional Properties and Mode of Action of Filming Amines... 

Filming amines are steam-volatile and in the steam-condensate system will condense and migrate to the metal-water interface to form a nonwettable film with polar groups adsorbed to the metal surface. 

Filming amine programs are often selected because the feed rate of actives generally is significantly lower than that required for neu-... 

When the filming amine condenses, the hydrophilic polar radical of the molecule (the head) adsorbs onto the metal surface and the hydrophobic, long chain (the tail) is directed at a 90° angle of inclination away from the metal surface. Provided the feed rate is adequate, the critical concentration is eventually reached and a continuous monomolecular surface film is formed. At this stage, the physical size of the interstices between the polar groups is smaller than the molecules of water, carbon dioxide, or oxygen, and these molecules are thus physically prevented from reaching the metal surface. 

A number of filming amines are available for boiler water treatment. These include ... 

NOTE In simple filming amine formulations ODA is the most widely employed ingredient. Formulations are typically available as 100% concentrated flakes, 2 to 5% strength aqueous solutions, or 5 to 10% strength emulsions. Solid ODA should be stored without exposure to air because it gradually reacts with carbon dioxide to form ODA carbonate, which is white and crumbly in composition. 

The smallest cooling systems may simply be treated with filming amines in the form of slowly dissolving waxy blocks that are suspended in baskets, whereas larger or more difficult systems employ feed and control systems to dispense liquid products containing diamine acetates in an alcohol-water solvent system. 

Most commonly, filming amines are aspirated into the steam line from a steel dilution tank to increase the potential for complete coverage of the post-boiler section, although steam distillation with... 

Both anodic and general inhibitors are nonpassivating and are suitable for use with hydrochloric acid-based cleaners. Other inhibitor groups include filming amines such as polymethylimine and diamines, the rosin-amine ketones, and also some of the imidazoline surfactants. The imidazolines provide increased protection at levels up to their critical miscelle concentration (CMC), above which there is a leveling off as a thick, adherent diffusion barrier is formed. 

Obrecht, Malvern F. PhD. Steam and Condensate Return Line Corrosion. How to Employ Filming Amines for Its Control. Heating, Piping Air Conditioning, USA, October 1964. 

---