Filming Amine (Aliphatic Amine) Test Kits

Methyl Orange Method

This three minute CHEMetrics procedure uses the industry standard methyl orange chemistry and features a unique extraction technique. The extraction eliminates several steps required in other procedures and increases the sensitivity of the test. The filming amine compound reacts with methyl orange to form a yellow-coloured complex that is extracted into an immiscible organic solvent. Results are expressed in ppm (mg/l) Octadecylamine (ODA).

The filming amine test kit K-1001 can be used in conjunction with the CHEMetrics Comparator Light Source (CLS), an independent light source for use in low-light conditions.

Reference:
ASTM D 2327-80, Mono- and Dioctadecylamines in Water.

Technical Data Sheet

Rose Bengal Method

Rose Bengal is a widely accepted method for measuring filming amines but most commercially available test kits have one key drawback. Rose Bengal dye adheres to glass and labware to the point of staining. Typically, it is necessary to clean glass cuvettes with solvents to prevent measurement bias, and dedicated labware may be required.

With the CHEMetrics self-filling reagent ampoule technology, the dye is packaged in the single-use ampoule. No cuvettes are required since the ampoule is used to make the measurement. The ampoules contain a premeasured dose of reagent for a single test. After the addition of acidifier solution to the sample simply snap the ampoule in the sample and wait 2 minutes for colour to develop to obtain your results. Our convenient corrosion inhibitor test kits eliminate staining problems and associated solvent cleaning and disposal costs, saving you time and reducing complexity.

The CHEMetrics Rose Bengal test kits are applicable primarily for the analysis of boiler water. When buffered under acidic conditions (pH 2.3 – 3.3), the sample forms a magenta complex with rose bengal (4,5,6,7-tetrachloro-2′,4′,5′,7′-tetraiodofluorescein disodium salt) in direct proportion to the concentration of filming amines such as Octadecylamine (ODA) or Oleylamine (OLA).

Reference:
K Stiller, T Wittig, M Urschey. ‘The Analysis of Film-Forming Amines – Methods, Possibilities, Limits and Recommendations’, 2010

Technical Data Sheet

Which Method to Choose?

Most commercially available Film Forming Amine Products (FFAPs) on the market contain a proprietary mixture of chemicals, including complex FFAs and neutralising amines, which vary by supplier and formulation. Complex FFAs tend to perform better than simpler FFAs such as ODA, and hence are more commonly used. However, complex FFAs may not react with test kit reagents the same sensitivity as simple FFAs and so dosing levels are less easily measured.

CHEMetrics offers two very different chemistries for measuring FFAPs, the Methyl Orange method, and the Rose Bengal method. The test chemistries will react with long-chain aliphatic amines or compounds having a long-chain amine group in the molecule. They will also measure secondary and tertiary amines, and to a lesser extent ethoxylated soy amines, with decreased sensitivity and accuracy. Which method works best in each case will depend on the exact blend of FFAs being analysed and on the presence of potentially intefering compounds in the test sample. Please see the technical data sheets above for more information. CHEMetrics encourages customers to try both methods against standard solutions of the FFAP being used to determine which provides the best results.

Applications

Film forming amines (FFAs) are water treatment chemicals commonly used in high pressure boilers, cooling systems, and heat recovery steam generators (HRSGs) to prevent corrosion of metal surfaces. They are applied to different components of the steam cycle including the boiler feedwater, generator, and condensate return lines.

Filming amines are fed continuously into boiler feedwater to protect metal surfaces from corrosion caused by dissolved oxygen and carbon dioxide in condensate water. The filming amine forms a thin hydrophobic film on metal surfaces and system piping that repels the potentially corrosive water, thereby acting as a corrosion inhibitor. The amount of corrosive condensate forming on those metal surfaces as well as the amount of dissolved gasses reaching the metal surfaces is thus minimised.

FFAs offer protection from corrosion, reduced corrosion product transport, prevention of scale and deposit build-up, formation of smooth heat transfer surfaces, and corrosion protection of equipment during shutdown or layups. FFAPs can be used alongside or replace conventional corrosion inhibitor treatment regimes. FFAs are frequently dosed in conjunction with neutralising amines such as cyclohexylamine, morpholine (both aromatic amines) or diethylaminoethanol (tertiary alkanolamine) which are used to raise the pH to prevent acid corrosion; and also oxygen scavengers.

Correctly measuring the amount of FFA in your system is critical for optimum system performance. Underdosing a system can leave it vulnerable to corrosion such as pitting. Overdosing can lead to the creation of micelles, or ‘gunk balls’ as they are commonly known. These can lead to clogged pipes and reduced efficiency. Frequent and consistent filming amine analysis is a best practice to ensure dosing is at the correct levels. Please see the Film Forming Amines & Applications in the Power Plant Industry article for more information.

What are Film Forming Amines?

Amines are derivatives of ammonia (NH₃) where one or more hydrogen atoms is replaced by a carbon-based molecule. An amine is characteristed by the presence of one or more amine groups (-NH₂). Amines are basic, like ammonia, but are a weaker base than metal hydroxides, and react readily with acidic substances in solution. Amines are generally categorised in structural terms into aliphatic amines and aromatic amines depending on the type of carbon molecule the amine group is attached to. Aromatic amines (containing an aromatic carbon (benzene) ring, i.e. an aryl group) and very long chain aliphatic amines tend to be insoluble in water.

Aliphatic amines contain carbon chains, which can be very long, normally saturated with single covalent bonds. e.g. alkyl amines based on alkanes, such as propane or butane etc. Long chain aliphatic amines are typically insoluble and hydrophobic because of the carbon chain molecular structure, and the hydrophobic properties tend to push the amine to the surface or edge of the water where the amine head bonds with any metal surfaces present, forming a protective, water repellent (hydrophobic), monomolecular film or complex. This is why aliphatic amines, particularly those with 10 to 18 carbon atoms in the chain, and one or several primary and/or secondary amine groups, are ideal candidates for corrosion inhibitors in boiler feedwater. For this reason, they are commonly referred to as filming amines, film forming amines (FFAs), film forming amine product (FFAP), film forming product (FFP) or film forming substances (FFS). These terms are a description of their characteristics and intended usage. Some manufacturers choose to classify the FFAs in their products as fatty amines, which are aliphatic amines prepared or derived from fatty acids; or as polyamines, a structural term describing aliphatic amines with more than one amine group.

Oleyl Propylenediamine (OLDA) with the chemical formula CH₃(CH₂)₇CH=CH(CH₂)₈NH(CH₂)₃NH₂, also known as (Z)-N-9-octadecenylpropane-1,3-diamine, is a commonly used FFA. It is a a diamine, with two amine groups, and also has multiple uses in chemical manufacturing. Oleylamine (OLA) with the formula CH₃(CH₂)₇CH=CH(CH₂)₇CH₂NH₂, also known as (Z)-N-9-octadec-9-enylamine, contains a single carbon double bond and a single amine group. For instance, Kurita's Cetamine product series includes FFAPs containing OLDA (e.g. Cetamine V219) and OLA (e.g. Cetamine V217).

Octadecylamine (ODA) with the formula CH₃(CH₂)₁₆CH₂NH₂, also known as 1-aminooctadecane, was a commonly used FFA in boiler systems historically. ODA is a straight carbon chain with a single amine group and has a number of disadvantages compared to other more complex filming amines, such as its viscosity and tendency to form gum/gunk if overfed or when reacting with corroded iron.