GB2528112A

GB2528112A - Improvements relating to inhibition of corrosion

Info

Publication number: GB2528112A
Application number: GB1412324.4A
Authority: GB
Inventors: Richard Maxwell Barrett; David Gwyn Hooper; Shahin Partovi
Original assignee: Global Chemical Technologies Ltd
Current assignee: WCS Services Ltd
Priority date: 2014-07-10
Filing date: 2014-07-10
Publication date: 2016-01-13
Anticipated expiration: 2034-07-10
Also published as: GB201412324D0; GB2528112B

Abstract

An aqueous composition for treating aqueous systems to inhibit corrosion of metal surfaces, comprising: (i) a filming amine component comprising an alkoxylated aliphatic amine compound including a fatty organic moiety; and (ii) an oxime component. A neutralizing amine component may also be included an an aulxiliary filming amine such as a diamine. The composition may contain a hydrotope.

Description

IMPROVEMENTS RELATING TO INHIBITION OF CORROSION

TECHNICAL FIELD

This invention relates to the inhibition of corrosion. In particular, though not exclusively, this invention relates to compositions for inhibiting corrosion of metal surfaces in aqueous systems, for example in boilers and the like.

BACKGROUND

A water boiler generates steam from a structure comprising two principal parts: the furnace, which provides heat, usually by burning a fuel, and the boiler proper, a device in which the heat changes water into steam. The steam or hot fluid is then recirculated out of the boiler for use in various processes in heating applications. The boiler receives feed water, which typically consists of a varying proportion of recovered condensed water (return water) and fresh water (make up water).

Boiler internals are typically formed of metals, e.g. iron. Dissolved gasses will react with the metals in the boiler and lead to boiler corrosion. In order to protect the boiler from these contaminants, they need to be controlled.

The primary cause of corrosion in boilers is dissolved oxygen, particularly in conjunction with low pH, although excessive alkalinity can also be a factor. Corrosion can also occur in condensate return lines, caused by oxygen in steam, or carbon dioxide which leads to the production of carbonic acid.

It is known to use amines as corrosion inhibitors by adding them to boiler feed water. Such amines may be categorised broadly as: oxygen scavengers, neutralising amines and filming amines.

Oxygen scavengers are added to feed water with the aim of reducing the amount of oxygen available for corrosion. Examples of oxygen scavenger amines are hydrazine, carbohydrazine and N,N-diethylhydroxylamine (DEHA).

Examples of neutralising amines are morpholine, cyclohexylamine and diethylaminoethanol.

Neutralising amines are added to the feed water such that they can enter condensate lines with the steam and neutralise carbonic acid, thereby raising the pH. The choice of neutralising amine is influenced by its ability to neutralise carbonic acid and raise the pH and its vapour-to-liquid distribution ratio.

Filming amines are longer carbon chain amines. These molecules are added to feed water with the aim of forming a film on boiler internals, which acts as a protective coating for the metal. This helps prevent contact between the metal and the water and any dissolved gases which the water may contain, thereby protecting the metal from corrosion. Furthermore, filming amines tend to be weak bases, thereby also helping to keep the pH up. Examples of common filming amines are fatty acid amines, in particular diamines.

Formulations comprising filming amines tend to suffer from stability issues. In particular, the longer carbon chains of these amines lead to a hydrophobicity that limits their solubility in water. This in turn leads to particular difficulties in formulating concentrated compositions comprising such amines, e.g. compositions for feed water treatment.

There is a need in the art for compositions for feed water treatment which are and remain substantially homogeneous, so that the correct proportion of constituents is always fed into the boiler; any separation will result in an inconsistent boiler treatment. A satisfactory product is seen as a substantially stable solution/emulsion; in an unstable product, separation will occur which will be apparent by the formation of a white layer on the top of the product -this is the filming amine separating out of the product.

To help mitigate stability issues, prior art compositions for feed water treatment generally comprise neutralising amines and filming amines together. In particular, products which are currently available tend to have filming amine to neutralising amine weight ratios (F/N) of between about 1/5 and about 1/15. Products containing higher FIN ratios have not been formulated because they have not been found to be sufficiently stable.

However, for optimal practical use as a corrosion inhibitor for boilers, especially those with high degrees of condensate return, the ratio of filming to neutralising agents (F/N ratio) should be higher than is currently available in the industry. In particular filming amines are consumed by being absorbed onto boiler surfaces, whilst neutralising amine can recirculate with return water. Thus high amounts of prior art products must be added to supply the necessary amount of filming amine. This tends to lead to too much neutralising amine in the system, leading to undesirably high pH, which is particularly problematic where yellow metals are present.

The present invention seeks to address one or more of these problems and to present

improvements upon the prior art.

SUMMARY OF THE INVENTION

From a first aspect, the invention resides in an aqueous composition for treating aqueous systems to inhibit corrosion of metal surfaces, the composition comprising: a filming amine component comprising an alkoxylated aliphatic amine compound including a fatty organic moiety; and an oxime component.

It has been found that the aqueous solubility of a filming amine component comprising alkoxylated aliphatic amines can be enhanced by the presence of an oxime component. This in turn facilitates homogeneity and stability of the composition and enables the incorporation of a higher concentration of alkoxylated aliphatic amines.

In addition to providing a hydrotropic benefit, i.e. enhancing solubility of the filming amine component, oximes may also provide the composition with oxygen scavenging properties.

Other oxygen scavengers, such as N,N-diethylhydroxylamine (DEHA), have not been able to provide the same hydrotropic benefit. Accordingly, the properties of the composition are unique and surprising.

In an embodiment, the composition further comprises a neutralising amine component comprising a neutralising amine. The neutralising amine component can enhance the effectiveness of the composition in neutralising carbonic acid.

The neutralising amine component may also provide a hydrotropic benefit, i.e. enhance the solubility of the filming amine component. However, it has been found that, by virtue of including the oxime component, embodiments of the invention can provide compositions with an advantageously high ratio of filming amine component to neutralising amine component (F/N). In an embodiment, the F/N ratio (w/w) of the composition is at least 1/4, for example at least 1/3, or even at least 1/2, at least 1/1.

The filming amine component comprises an alkoxylated aliphatic amine compound including a fatty organic moiety. In an embodiment, the filming amine component comprises or consists of one or more such alkoxylated aliphatic amine compounds, e.g. as described anywhere herein.

While an alkoxylated aliphatic amine compound including a fatty organic moiety may be less volatile than other available filming amines, this is outweighed by the synergy with the oxime component, which allows for enhanced stability and more effective formulation.

The aliphatic amine compound may be alkoxylated in any suitable manner. The compound may, in particular, be an ethoxylated compound and all references herein to alkoxylated may optionally be understood accordingly.

The alkoxylated aliphatic amine compound may be derived from a primary, secondary or tertiary amine. The alkoxylated aliphatic amine compound may in particular be an N-alkyl alkoxylated compound.

The alkoxylated aliphatic amine compound may comprise a single amine moiety or a plurality of amine moieties. For example, the amine compound may be derived from a diamine.

In an embodiment, the fatty organic moiety is a saturated or unsaturated hydrocarbyl moiety, in particular an aliphatic carbon chain, suitably comprising in the range of from 10 to 30 carbon atoms, for example in the range of from 12 to 24 carbon atoms or in the range of from 14 to 18 carbon atoms.

Suitable alkoxylated aliphatic amine compounds may, for example, be selected from those of formula: H-(O-R2)--N--(R2-O),z---H (A) R1 and/or (B) (RçO)H wherein R1 and R5 are independently Co to 030 hydrocarbyl radicals, R2 and R3 are independently C2 to C6 hydrocarbyl radicals, R4 is a C1 to C5 hydrocarbyl radical, x and y are integers from 0 to 50 provided 0<(x+y)<50, and p, q and z are integers from 0 to 50 provided 0<(p+q+z)<50.

Suitably, R1 and R5 may be independently C12 to C24 alkyl or alkenyl, in particular 014 to C18 alkyl or alkenyl.

In an embodiment, R2 and R3 are independently 02 to C4 alkyl diradical and R4 is a C2 to C4 alkyl diradical.

In an embodiment, x and y are integers from 1 to 25 provided 0c(x+y)c50 and p, q and z are integers from ito 25 provided 0c(p+q+z)<25.

In an embodiment, the alkoxylated aliphatic amine compound is a derivative of a saturated or unsaturated fatty acid, i.e. an alkoxylated fatty amine. Examples of fatty acids that may give rise to alkoxylated fatty amines are lauric (C12), myristic (C14), palmitic (C), stearic (C), oleic (018, unsaturated), and linoleic polyunsaturated).

In an embodiment, the alkoxylated aliphatic amine is a tallow derivative, in particular an alkoxylated tallow alkyl amine or diamine. Tallow consists chiefly of glyceryl esters of oleic, palmitic, and stearic acids (16 to 18 carbon chains).

In an embodiment, the alkoxylated aliphatic amine compound has an (average) degree of alkoxylation in the range of from 1 to 15 moles of alkoxylation, in particular ethoxylation. In an embodiment, the alkoxylated aliphatic amine compound has an (average) degree of alkoxylation in the range of from 5 to 12 moles of alkoxylation, in particular ethoxylation

S

In one embodiment, the alkoxylated aliphatic amine compound is Naylamul S11TM (commercially available from Nayler Chemicals, Lancashire UK, amine value 74.5 +/-5mg KOH/g, CAS No. 61791-26-2, EC No. 500-153-8). Naylamul SluM has a structure A as defined above, where F is representative of a tallow amine derivative which typically contains a mixture of C14, and C18 unsaturated and saturated straight chain hydrocarbon substituents, R2 is ethyl and x + y is approximately 11.

In another embodiment, the alkoxylated aliphatic amine compound is Ethoduomeen 1/22 TM (N, N', N'-Polyoxyethylene (10)-N-tallow-i,3-diaminopropane commercially available from AkzoNobel, CAS 61790-85-0) and/or Ethoduomeen T/25TM (Tris(i5-hydroxyethy-N-tallowalkyl-i,3-diaminopropane commercially available as from AkzoNobel).

The filming amine component may additionally comprise one or more auxiliary filming amines.

In an embodiment, the filming amine component comprises or consists of one or more alkoxylated aliphatic amine compounds, e.g. as described anywhere herein, and one or more auxiliary filming amines, e.g. as described anywhere herein.

The auxiliary filming amine may in principle be any suitable amine that is not alkoxylated.

The auxiliary filming amine may comprise a single amine moiety or a plurality of amine moieties. For example, the amine may be a diamine.

In an embodiment, the auxiliary amine comprises a fatty organic moiety. Suitably, the fatty organic moiety may be a saturated or unsaturated hydrocarbyl moiety, in particular an aliphatic carbon chain, comprising in the range of from 10 to 30 carbon atoms, for example in the range of from 12 to 24 carbon atoms or in the range of from 14 to 18 carbon atoms.

In an embodiment, the auxiliary filming amine is a derivative of a saturated or unsaturated fatty acid, i.e. a fatty amine. Examples of fatty acids that may give rise to auxiliary fatty amines are lauric (012), myristic (C14), palmitic (016), stearic (C), oleic (018, unsaturated), and linoleic (018, polyunsaturated).

In an embodiment, the auxiliary filming amine is an oleyl diamine. In an embodiment, the auxiliary filming amine is N-oleyl-i,3-diaminopropane. Such an amine is commercially available under the name Duomeen 0 TM from AkzoNobel.

S

The oxime component comprises an oxime. In an embodiment, the oxime component comprises or consists of one or more oximes, e.g. as described anywhere herein.

Suitable oximes may, for example, be selected from those of formula: C=N-OH (C) in which R1 and R2 are the same or different and are selected from hydrogen, alkyl groups of 1 to 8 carbon atoms, in particular 1 to 3 carbon atoms, or aryl groups.

In an embodiment, the oxime is a ketoxime. In an embodiment, the oxime is methyl ethyl ketoxime (MEKO). Other examples of commercially available oximes are acetaldoxime, butyraldoxime, propionaldoxime.

Optionally one or more other additives may be added to the composition, such as for example scale inhibitors, dispersants or the like. In an embodiment, the composition comprises a polymeric dispersant. Scale inhibition may be achieved by the use phosphates and/or chelating agents which prevent the precipitation of scale onto boiler surfaces.

Organic polymers may combine with charged particles and are often used to prevent the adherence of suspended solids onto heat transfer surfaces. Further optional components include antifoaming agents and alkalinity builders.

The components of the aqueous composition, including water, may in principle be combined in any effective amount. The composition may comprise or consist of the components.

As aforesaid, the solubility of the filming amine component, in particular the alkoxylated aliphatic amine compound therein, can be enhanced by the presence of the oxime component, which facilitates homogeneity and stability of the composition and enables the incorporation of a higher concentration of alkoxylated aliphatic amines.

In an embodiment, the composition comprises in the range of from 0.1 to 25% w/w of the filming amine component, advantageously in the range of from 2 to 20 % w/w, more advantageously in the range of from 5 to 15 % w/w, or even more advantageously in the range of from 7 to 12 % w/w.

The filming amine component may itself comprise at least 10% w/w of alkoxylated aliphatic amine compound(s) including a fatty organic moiety, advantageously at least 30% w/w, more advantageously at least 50% wlw, or even at least 70% wlw or at least 90% w/w. For example, the filming amine component may comprise in the range of from 10% wlw to 90% wlw, or in the range of from 30% wlw to 70% w/w, in particular 40% w/w to 60% w/w of alkoxylated aliphatic amine compound(s) including a fatty organic moiety. The balance of the filming amine component may be made up by other or auxiliary filming amine compound(s).

In an embodiment, the composition comprises in the range of from 0.1 to 30% w/w of the neutralising amine component, advantageously in the range of from 1 to 20 % w/w, more advantageously in the range of from 2 to 10 % wlw.

As aforesaid, the invention can provide a composition with an advantageously high ratio of filming amine component to neutralising amine component (FIN). In an embodiment, the FIN ratio (w/w) of the composition is at least 1/4, for example at least 1/3, or even at least 1/2 or at least 1/1. Suitably, the F/N ratio may be at most 3/1, for example at most 2/1, in particular at most 3/2. Further envisaged concentrations of the filming amine component or neutralising amine component may be calculated from the above ranges accordingly.

In an embodiment, the composition comprises in the range of from 0.1% to 20% wlw oxime component, advantageously in the range of from 0.5 to 10% w/w, more advantageously in the range of from 1 to 7% w/w.

The balance of the composition may be made up by water and any optional additives.

Advantageously, the components of the composition may be combined to provide a suitably homogenous and advantageously stable composition. The homogeneity or stability required may vary depending on application. In an embodiment, less than 10% w/w of the filming amine component, in particular less than 5% wlw, more in particular less than 1% wlw is in un-dissolved or separated form. Advantageously, the composition may be substantially homogenous. In an embodiment, less than 10% wlw of the filming amine component, in particular less than 5% w/w, more in particular less than 1% w/w is in un-dissolved or separated after dark storage at 5 °C for at least two weeks, preferably at least four weeks.

Advantageously, the composition may be substantially homogenous after dark storage at 5 °C for at least two weeks, preferably at least four weeks.

In one particular embodiment, the composition comprises or consists of: in the range of from 7 to 12 % w/w filming amine component comprising in the range of from 30 to 70 w/w alkoxylated aliphatic amine compound(s); in the range of from 2 to 10% w/w neutralising amine component; and water.

Other embodiments and optional features will be apparent from the examples.

From a second aspect, the invention resides in a method of treating an aqueous system, in particular a steam generating system, so as to inhibit corrosion of metal surfaces, the method comprising adding to said system an effective amount of a composition according to the first aspect of the invention.

The steam generating system may, for example, be a boiler system. The system may comprise a condensate return. Suitably, the composition may be added to feed water of the system.

From a third aspect, the invention resides in the use of an oxime as a hydrotrope in an aqueous composition comprising a filming amine component.

From a fourth aspect, the invention resides in the use of an oxime in an aqueous composition comprising an emulsion of a filming amine component, for the purpose of counteracting separation of the filming amine component from the emulsion.

From a fifth aspect, the invention resides in the use of an oxime in an aqueous composition comprising a filming amine component and a neutralising amine component for the purpose of increasing the ratio of filming amine component to neutralising amine component (FIN).

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example comprising" and "comprises", mean "including but not limited to", and do not exclude other components, integers or steps.

Moreover the singular encompasses the plural unless the context otherwise requires: in particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Preferred features of each aspect of the invention may be as described in connection with any of the other aspects. Other features of the invention will become apparent from the following examples. Generally speaking the invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings). Thus features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. Moreover unless stated otherwise, any feature disclosed herein may be replaced by an alternative feature serving the same or a similar purpose.

Where upper and lower limits are quoted for a property then a range of values defined by a combination of any of the upper limits with any of the lower limits may also be implied.

In this specification, references to parameters are -unless stated otherwise -to properties measured under ambient conditions, i.e. at atmospheric pressure and at a temperature of about 20°C.

Specific embodiments of the present invention will now be further described with reference to the following non-limiting examples.

EXAM PLES

Ten compositions were prepared and evaluated for homogeneity and stability. The compositions were made up of the following, together with water: Filming Amine I (FAI): N-oleyl-1,3-diarninopropane (Duomeen 0) Filming Amine 2 (FA2): N-alkyl tallow amine ethoxylate (Naylamul Si 1) Neutralising Amine I (NA 1): monoethanolamine, Neutra/ising Amine 2 (NA2): cyclohexylamine, Neutralising Amine 3 (NA3): diethylam inoethanol, Dispersant (D): acrylic acid / 2-acrylamido-2-methylpropanesulfonic acid copolymer DEHA: N,N-diethylhydroxylamine MEKO: 2-butanone oxime The details of each composition are shown in Table 1.

Table I

Composition 1 2 3 4 5 6 7 8 9 10 FAi(%w/w) 5 5 5 5 5 5 5 5 i i FA2(%w/w) 5 5 5 5 1 i 1 1 1 1 NA1(%w/w) 3 3 12 12 12 12 3 3 9 9 NA2(%w/w) 2 2 18 18 18 18 2 2 6 6 NA3 (% w/w) 2.5 2.5 2.5 2.5 MEKO (% w/w) 5 3.6 3.6 5 1 DEHA(%w/w) 5 3.6 3.6 5 1 D(%wlw) 10 iO iD iO 5 5 DlWater(%w/w) 77.5 77.5 81.5 81.5 Soft water (% w/w) 46.4 46.4 50.4 50.4 77 77 Samples were made in a glass jar using a magnetic stirrer. Sample preparation was conducted at room temperature with components being added in the following order and the mixture being stirred after each addition: 1 filming amine 2 neutralising amine 3 DEHA or MEKO (can be added before neutralising amine) 4 water 5 dispersant After the final addition, the mixture was stirred for at least 15 minutes. A lid was put on the jar and the samples were placed in the fridge for at least two weeks. Following this time the samples were inspected visually for signs of separation. Keeping the samples in the fridge at 500 accelerates any separation and is therefore indicative of the sample stability The results observed following initial mixing and after 2 and 4 weeks of storage respectively are summarised in Table 2.

Composition Initial 2 weeks 4 weeks 1 Homogeneous Homogeneous Homogeneous emulsion emulsion 2 Homogeneous Emulsion, some Emulsion, some separation visible separation visible 3 Homogeneous Emulsion, some n/a separation visible 4 Homogeneous Emulsion, some n/a separation visible Homogeneous Reasonably clear Reasonably clear liquid, some liquid, some separation visible separation visible 6 Homogeneous Reasonably clear Liquid still liquid, some reasonably clear separation visible liquid but cloudier than after 2 weeks, some separation visible 7 Homogeneous Separation yielding n/a opaque emulsion B Homogeneous Very significant n/a phase separation 9 Homogeneous Reasonably clear Reasonably clear liquid, some liquid but cloudier separation visible than after 2 weeks, some separation visible Homogeneous Reasonably clear Emulsion with liquid, separation separation visible visible Table 2 clearly shows that the best result is obtained from composition 1 which contains MEKO rather than DEHA in combination with 5% FA1 and a ratio of filming to neutralising amines of 10:7.5. The ratio of FA2 to FA1 is 1:1.

Reducing the FA1 content to 1% (samples 7 and 8) results in samples that are unstable.

At ratios of filming to neutralising amines of 1:3 (samples 3 and 4), it is hard to see any improvement in stability in the samples containing MEKO rather than DEHA after two weeks.

However visual examination of compositions containing ratios of filming to neutralising amines of 1:5 (samples 5 and 6) after 4 weeks does indicate that the sample containing MEKO at 3.6% shows better stability.

At ratios of filming to neutralising amines of 1:7.5 (samples 9 and 10), there appears to be a slight improvement in stability in the samples containing MEKO rather than DEHA after two weeks; this improvement in stability is more evident after four weeks. This stability is apparent although the level of MEKO is only 1%. In this case the ratio of the FA2 to FA1 is 1:1.

The data indicate that the oxime MEKO enhances the stability of filming and neutralising amines in aqueous solution more than DEHA, particularly where alkoxylated filming amine is present at levels ?1 %. The best ratio of FA2 to FA1 was found to be 1:1. The ratio of filming to neutralising amines will vary depending upon the application.

We have shown that we can produce stable products using the combination of MEKO and alkoxylated tallow amines and such products can contain varying F/N ratios. Making the samples in either Dl water or softened water with a polymer does not seem to have any effect.

Claims

CLAIMS1. An aqueous composition for treating aqueous systems to inhibit corrosion of metal surfaces, the composition comprising: (i) a filming amine component comprising an alkoxylated aliphatic amine compound including a fatty organic moiety; and (U) an oxime component.
2. The composition of claim 1 further comprising a neutralising amine component comprising a neutralising amine, and wherein the ratio of filming amine component to neutralising amine component (F/N) is at least at least 1/2 wlw.
3. The composition of claim 1 or claim 2, wherein the filming amine component comprises or consists of one or more said alkoxylated aliphatic amine compounds including a fatty organic moiety.
4. The composition of any preceding claim wherein the fatty organic moiety is a saturated or unsaturated hydrocarbyl moiety comprising in the range of from 10 to 30 carbon atoms.
5. The composition of any preceding claim, wherein the alkoxylated aliphatic amine compound is selected from those of formula: H-(O-R2)---N-(R2-O)j---H (A) R1 and/or (B) (R3O)rH wherein R1 and R5 are independently C10 to C30 hydrocarbyl radicals, R2 and R3 are independently C2 to C5 hydrocarbyl radicals, R4 is a C1 to C6 hydrocarbyl radical, x and y are integers from 0 to 50 provided 0<(x+y)<50, and p, q and z are integers from 0 to 50 provided 0<(p+q+z)<50.
6. The composition of claim 5 wherein, R1 and R5 are independently 012 to 024 alkyl or alkenyl, R2 and R3 are independently C2to C4alkyl diradical and R4 is a 02 to 04 alkyl diradical, x and y are integers from ito 25 provided 0c(x+y)<50, and p, q and z are integers from ito 25 provided 0<(p+q+z)<25.
7. The composition of any preceding claim, wherein the alkoxylated aliphatic amine compound is a derivative of a saturated or unsaturated fatty acid.
8. The composition of any preceding claim, wherein the alkoxylated aliphatic amine is an alkoxylated tallow alkyl amine or diamine.
9. The composition of claim 8, wherein the alkoxylated aliphatic amine or diamine has an (average) degree of alkoxylation in the range of from i to iS moles of alkoxylation.
iO. The composition of any preceding claim, wherein the filming amine component additionally comprises one or more auxiliary filming amines.
ii. The composition of claim iD, wherein the auxiliary filming amine is a diamine.
12. The composition of claim 10 or claim ii, wherein the auxiliary amine comprises a fatty organic moiety.
i 3. The composition of claim i2 wherein the fatty organic moiety of the auxiliary amine is a saturated or unsaturated hydrocarbyl moiety comprising in the range of from 10 to carbon atoms.
i4. The composition of any one of claims 10 to i3 wherein the auxiliary filming amine is N-oleyl-l,3-diaminopropane iS. The composition of any preceding claim, wherein the oxime component comprises an oxime selected from those of formula:NN-OH (C)in which R1 and R2 are the same or different and are selected from hydrogen, alkyl groups of 1 to 8 carbon atoms or aryl groups.16. The composition of claim 15 wherein the oxime component comprises a ketoxime.17. The composition of claim 15 wherein the oxime component comprises methyl ethyl ketoxime (MEKO).18. The composition of any preceding claim comprising a polymeric dispersant.19. The composition of any preceding claim comprising in the range of from 2 to 20 % of the filming amine component.20. The composition of claim 19 comprising in the range of from 5 to 15 % wlw of the filming amine component.21. The composition of any preceding claim wherein the filming amine component comprises at least 10% w/w of said alkoxylated aliphatic amine compound(s) including a fatty organic moiety.22. The composition of claim 21 wherein the filming amine component comprises in the range of from 30 % to 70% w/w of said alkoxylated aliphatic amine compound(s) including a fatty organic moiety.23. The composition of claim 2 or any claim dependent on claim 2, comprising in the range of from 1 to 20 % w/w of the neutralising amine component.24. The composition of any preceding claim comprising in the range of from 0.5% to 10% w/w oxime component.25. The composition of any preceding claim wherein less than 10% wlw of the filming amine component is in un-dissolved or separated form.26. The composition of any preceding claim, wherein less than 10% wlw of the filming amine component is in un-dissolved or separated after dark storage at 5 °C for at least two weeks, preferably at least four weeks.27. A method of treating an aqueous system, in particular a steam generating system, so as to inhibit corrosion of metal surfaces, the method comprising adding to said system an effective amount of a composition according to any preceding claim.28. The method of claim 27 wherein the steam generating system comprises a boiler system and wherein the composition is added to feed water of the system.29. Use of an oxime as a hydrotrope in an aqueous composition comprising a filming amine component.30. Use of an oxime in an aqueous composition comprising an emulsion of a filming amine component, for the purpose of counteracting separation of the filming amine component from the emulsion.31. Use of an oxime in an aqueous composition comprising a filming amine component and a neutralising amine component for the purpose of increasing the weight ratio of filming amine component to neutralising amine component (F/N).