EP2179001A1

EP2179001A1 - A liquid composition suitable for use as a corrosion inhibitor and method for its preparation

Info

Publication number: EP2179001A1
Application number: EP08789784A
Authority: EP
Inventors: David Itzhak; Sharon Krumbein Rubin; Arieh Kampf; Vered Atiya Zuckerman; Mira Bergstein Freiberg
Original assignee: Bromine Compounds Ltd
Current assignee: Bromine Compounds Ltd
Priority date: 2007-08-13
Filing date: 2008-08-12
Publication date: 2010-04-28
Also published as: WO2009022332A1

Abstract

A liquid composition comprising a high-capacity aqueous carrier in which (i) a metalloid compound selected from the group consisting of antimony and germanium compounds and (ii) morpholine or derivative thereof are dissolved in the presence of (iii) unsaturated alcohol and (iv) water-soluble organic acid having reducing capacity, wherein the total concentration of said four components is not less than 5% relative to the total weight of the composition. The composition is useful as a corrosion inhibitor. Also provided is a process for preparing the composition.

Description

A liquid composition suitable for use as a corrosion inhibitor and a method for its preparation

There exists a need, in many industrial applications, to mix additives within a working fluid. It is often more convenient to pre-mix the additives in a liquid carrier, thereby supplying the additives in the form of a solution, which may be used for readily delivering the additives to the working fluid. However, the preparation of a stable, homogeneous liquid formulation in which all the necessary additives can be dissolved together completely is often encountered with considerable difficulties, in view of the fact that the solubility profiles of the individual additives may counter each other.

For example, in the oil well drilling industries, metal surfaces are brought into contact with corrosive fluids, such as concentrated aqueous solutions and specifically heavy brines. It is common to add corrosion inhibitors to the brines in order to reduce the potential damage that may be caused to the metallic equipment. One of the properties that need to be met by a corrosion inhibitor is a complete dissolution in the corrosive brine. It may therefore be sometimes beneficial to supply a corrosion inhibitor in a form of a clear, stable solution, by dissolving the corrosion inhibitor in advance in a liquid carrier which does not interfere with the contemplated use of said inhibitor.

The corrosion inhibitory properties . of antimony compounds and amines are recognized in the art. For example, US 4,522,658 describes an aqueous solution for protecting metal surfaces exposed to oxidative environments, which solution comprises the combination of an antimony compound and acetylenic alcohol, together with a quaternary ammonium compound and aromatic hydrocarbon compound.

US 5,411,670 discloses an inhibitor composition comprising antimony compound dissolved in an acidic liquid carrier.

US 5,531,937 describes the combination of alkyl-morpholine with a saturated dicarboxylic acid as a corrosion inhibitor.

Co-pending, co-assigned international patent publication WO 07/093987 describes a corrosion inhibitor that is based on the combination of an antimony compound and at least two compounds belonging to two or more of the following classes: morpholine and derivatives thereof; ascorbic acid and derivatives thereof; acetylenic alcohols; and selenium salts and oxides. Example 3 of WO 07/093987 specifically reports the results of a corrosion test which relates to a four- components mixture consisting of antimony chloride, morpholine, propargyl alcohol and isoascorbic acid.

It has now been found that it is possible to dissolve considerable quantities of an antimony or germanium compound together with morpholine or derivatives thereof in a liquid carrier, and more specifically in a high-capacity aqueous carrier, in the presence of an unsaturated alcohol and an organic acid which is preferably (iso) ascorbic acid. The resulting composition is most preferably in the form of a clear, stable aqueous solution which may be conveniently- used for handling and storing a large amount of an effective corrosion-inhibiting combination, as will be discussed in more detail below.

The term "high-capacity aqueous carrier" is used to indicate either water, an aqueous salt solution or an aqueous mixture of water and small amounts of water-miscible solvent (s), wherein the density of said aqueous carrier is less than 1.8 g/cm³, preferably less than 1.5 g/cm³ and more preferably less than 1.1 g/cm³. Under appropriate conditions, the metalloid compound and morpholine or derivative thereof, which are generally incompatible when formulated together in an aqueous environment, are dissolved in the high-capacity aqueous carrier (namely, the metalloid compound and the morpholine are contained in said carrier in the form of a solute) in the presence of an unsaturated alcohol and (iso) ascorbic acid, wherein the total concentration of said four-components combination in the resulting aqueous formulation is not less than 5% (w/w) . Water, either distilled, deionized or tap, is a particularly preferred aqueous carrier to be used according to the invention, since the resulting aqueous formulation may be employed in a variety of applications, including - but not necessarily limited to - the inhibition of corrosion in various environments. However, aqueous salt solutions, including concentrated salt solutions may also be used as carriers in order to formulate the combination indicated above, provided that the density of said salt solution is less than 1.8g/cm³. A preferred example in this regard is CaBr₂ (52% w/w) solution, which can be loaded with considerable quantities of the metalloid compound, (iso) ascorbic acid, unsaturated alcohol and morpholine or derivative thereof to afford a stable aqueous vehicle. Other salt solutions which can be used for dissolving together the four-components combination include alkali and calcium halide brines.

The term "metalloid compound" as used herein refers to salts and oxides of antimony and germanium. Compounds that are particularly suitable for use according to the present invention are those wherein the oxidation state of the antimony is +3, namely, antimonous compounds. Especially preferred are halide salts, namely, SbX₃, wherein X is F, Cl, Br or I, and also alkali metal antimony salts (e.g., alkali metal antimony tartarate) . As to germanium, most of its compounds correspond to oxidation number +4; examples are germanium dioxide and germanium tetrachloride.

Morpholine and derivatives thereof to be used according to the present invention include unsubstituted or substituted morpholine. Preferred group is represented by the following structure of Formula I:

Wherein Ri is hydrogen or Ci-C₃ alkyl and R₂ is independently selected from the group consisting of hydrogen, C1-C3 alkyl and phenyl group and n is 0, 1, 2, 3 or 4. The Ci-C₃ alkyl and phenyl groups may be optionally substituted, e.g., with one or more hydroxy groups. Specific examples of morpholine derivatives include 2-methylmorpholine, 3-methylmorpholine, 2, 6-dimethylmorpholine, 3, 5-dimethylmorpholine, 2,2- dimethylmorpholine, 3-ethyl-3, 5, 5-trimethylmorpholine, 3,3- dimethylmorpholine, 2, 6-dimethylmorpholine 3,3,5,5- tetramethylmorpholine, 3-methyl-2-phenylmorpholine and 4- morpholineethanol . Particularly suitable morpholine derivatives which can be employed in the present invention are those of Formula (I) wherein Ri is C₁-C₃ alkyl substituted with one or more hydroxy groups, namely, the class of compounds that may be identified as A- (hydroxyalkyl) morpholines. The aforementioned A- morpholineethanol, which is also known as 4- (2-hydroxyethyl) morpholine (CAS number 622-40-2), has been found especially suitable for use according to the present invention. The morpholine derivatives to be employed according to the present invention are commercially available and may be also prepared by methods known in the art (e.g., US 3,154,544 and 4,501,889) .

The term "unsaturated alcohols" includes alcohols, and more preferably C3-C7 alcohols, which contain either a carbon- carbon double bond or a carbon-carbon triple bond. The former class, (hereinafter sometimes designated "alkenols", which term is used herein to indicate a compound that contains a carbon-carbon double bond and one or more hydroxy groups) specifically includes 2-propenol (allyl alcohol, CH₂=CHCH₂OH) , 2-methyl-2-propen-l-ol, 3-buten-l-ol , 3- buten-2-ol, , 2-buten-l-ol (crotyl alcohol, CH₃CH=CHCH₂OH) , l-penten-3-ol, 3-methyl-3-butene-2-ol, 4-penten-2-ol, 2- methyl-3-butene-l-ol, whereas the latter class (hereinafter sometimes designated "alkynols" or "acetylenic alcohols", which terms are interchangeably used herein to indicate a compound that contains a carbon-carbon triple bond and one or more hydroxy groups) preferably includes alcohols represented by the following structure of Formula II:

Wherein Ri, R₂ and R₃ are independently hydrogen or lower (C1-C3) alkyl groups. Specific examples of acetylenic alcohols to be used according to the present invention are propargyl alcohol (Ri, R₂ and R₃ in Formula II above are all hydrogen) and also 3-butynyl alcohol, 3-butyn-2-ol, 2-butyn- l-ol, l-pentyn-3-ol and 4~pentyn-2-ol . Alkenols and alkynols containing three, four or five carbon atoms are especially preferred. Straight chain primary alkenols having from 3 to 5 carbon atoms in the molecule are most preferred, such as the aforementioned allyl alcohol, CH₂=CHCH₂OH, and crotyl alcohol, CH₃CH=CHCH₂OH. Throughout the present description, the notation, C_x-C_y indicates a straight or branched alkyl chain containing between x and y carbon atoms, inclusive. The term alkenol, as used herein, also includes cycloalkenols . The alkenols operative in the present invention are commercially available and may also be prepared according to methods known in the art (e.g., US 4,400,562) .

The acids to be used according to the invention are water- soluble organic acids having reducing capacity. Organic acids which are suitable in this regard include (iso) ascorbic acid and derivatives thereof. The term " (iso) ascorbic acid" is used herein to indicate either D- Isoascorbic acid, L-Ascorbic acid, mixtures thereof and their keto-enol tautomeric forms. It is also possible to provide the acid in the form of a salt thereof, together with a mineral acid. Other possible organic acids are derivatives of (iso) ascorbic acid, such as 2-O-ethyl-L- ascorbic acid, 3-O-ethyl-L-ascorbic acid, 2, 3-di-O-methyl-L- ascorbic acid, L-dehydroascorbic acid, 2-0-α-D- glucopyranosγl-L-ascorbic acid and 5, 6-O-isopropylidene-L- ascorbic acid. Additional possible acids are 6-deoxyhex-2- enoic acid Y lactone, 3, 4-dihydroxy-5- (hydroxymethyl) -2 (5H) - furanone, 2, 3, 4-trihydroxy-2-pentenoic acid γ lactone, 2,4- dihydroxy-3-rαethyl-2-hexenoic acid Y lactone and 3-hydroxy- 4, 5-dimethyl-2 (5H) -furanone. In addition to (iso) ascorbic acid and derivatives thereof, the following vinylogous carboxylic acids may also be mentioned (compounds containing one or more hydroxyl functional groups in conjugation with one or more carbonyl functional groups through one or more carbon-carbon double bond) : hydroxy maleic acid [1115-67- 9], hydroxy fumaric acid [6153-53-3], dihydroxy maleic, acid [526-84-1] dihydroxy fumaric acid [133-38-0] 2- Hydroxy-2, 4-pentadienoic acid [50480-68-7] and 5-formyl-2- hydroxy-2, 4-pentadienoic acid [3270-98-2].

The various aspects of the present invention will now be described in detail.

The present invention primarily relates to an essentially homogeneous liquid composition comprising a high-capacity aqueous carrier in which (i) a metalloid compound selected from the group consisting of antimony and germanium compounds and (ii) morpholine or derivative thereof are dissolved in the presence of (iii) unsaturated alcohol and (iv) water-soluble organic acid having reducing capacity, wherein the total concentration of said four components is not less than 5% relative to the total weight of the composition. The terms "an essentially homogeneous aqueous composition" and the like are used herein to indicate that the formation of a separate phase containing one or more of the components indicated above is not observed in the liquid composition of the present invention, namely, the liquid composition most preferably exists in the form of a clear solution during storage. However, it should be understood that a solution exhibiting a slight cloudiness, which solution is capable of regaining its clarity following shaking or warming, is also within the scope of the present invention.

The total concentration of the combination (antimony or germanium compound, morpholine or derivatives thereof, unsaturated alcohol and the acid) in the aqueous solution provided by the present invention is not less than 5% (w/w) , preferably not less than 15% (w/w) , more preferably not less than 30% (w/w) and is most preferably in the range between 40% and 60% (w/w) . It is preferred that the water content in the formulation is not less than 15% w/w, and preferably not less than 30%.

It should be noted that the pH of the aqueous composition provided by the present invention is preferably adjusted within the range of 6 and 12, and more specifically between about 7.0 and 9. 5, due to the presence of the morpholine or a derivative thereof. Notably, even in a non-acidic pH environment, the metalloid compound does not precipitate from the liquid phase and the resulting composition retains its clarity during long storage period, as may be visually confirmed even after 6 months or more.

The preferred concentrations of the individual components within the liquid composition are as follows (expressed in terms of weight percent relative to the total weight of the liquid composition) :

Metalloid compound: between 0.05 and 0.7 %, and more preferably in the range between 0.4 and 0.6 %, and most preferably in the range between 0.45 and 0.55 %.

An organic acid, and specifically, (iso) ascorbic acid: between 2.5 and 35%, and more preferably in the range between 20 and 30%.

Unsaturated alcohol: between 1 and 18%, and more preferably in the range between 7 and 18%.

Morpholine or derivative thereof: between 1.5 and 25%, and more preferably in the range between 10 and 25%.

Especially preferred composition according to the present invention is a clear aqueous solution containing about 30- 60% by weight water, 0.40-0.60 % by weight antimony halide (specifically SbCIs) , 20-30% by weight (iso) ascorbic acid, 7-18% by weight straight chain primary alkenol having from 3 to 5 carbon atoms (specifically crotyl alcohol or allyl alcohol) and 10-25% by weight morpholine or 4- (2- hydroxyalkyl) morpholine (specifically 4- (2-hydroxyethyl) morpholine) .

The liquid composition provided by the present invention may be generally prepared by either concurrently or successively introducing the components into a suitable vessel according to the quantitative proportions indicated above, while stirring the mixture for a sufficient period of time in order to obtain a clear solution. However, it has been found that the formation of a clear solution may be considerably facilitated by accomplishing the dissolution of the metalloid compound under acidic environment, wherein the addition of the metalloid compound into the vessel used for preparing the composition is carried out either concurrently with, or more preferably subsequent to, the addition of the acid into the vessel.

Thus, the present invention also relates to a process for preparing a clear aqueous composition, which comprises mixing in a vessel a high-capacity aqueous carrier, an acid, which is preferably (iso) ascorbic acid, antimony or germanium compound, unsaturated alcohol and morpholine or derivative thereof, such that the dissolution of said metalloid compound in said aqueous carrier is accomplished under acidic environment.

More specifically, the process of the present invention comprises mixing the acid, and specifically, (iso) ascorbic acid, in a high-capacity aqueous carrier to form an acidic solution, dissolving the metalloid compound in said acidic solution, introducing unsaturated alcohol into the resulting solution and subsequently adding morpholine (or derivative thereof) , to form an essentially homogeneous liquid composition .

The introduction of the components into the vessel may be carried out either portion-wise or continuously. Each of the consecutively added components is preferably fed to the vessel (containing the previously introduced components) under stirring, which may be carried out at room temperature or above room temperature. When water is used as the carrier, the stirring typically lasts between 5 minutes and several hours, until a clear solution is formed. As indicated above, the pH of the solution considerably varies during the preferred method of preparation provided by the invention. More specifically, the mixing of the (iso) ascorbic acid with the aqueous carrier preferably adjusts the pH of the carrier to a value below 1.5, in order to allow a rapid and effective dissolution of the metalloid compound therein. Having added the metalloid compound and subsequently the unsaturated alcohol, the pH increases to the range between 2.0 and 5.0. Finally, after the addition of the morpholine or derivative thereof, the pH of the aqueous composition is typically within the range of 6-12 and preferably in the range 7- 9.5.

Having completed the introduction of the four components into the aqueous carrier, it may be sometimes necessary to continue the stirring of the mixture for few more hours in order to arrive at a homogeneous composition. This may be the case when the aqueous carrier is a highly concentrated salt solution (such as calcium bromide brine) , or when the concentration of the water in the composition is less than about 35% (by weight) . However, in general, when there is sufficient amount of water in the aqueous carrier, namely, not less than 40-50% by weight, then a relatively rapid obtainment of a clear, stable aqueous system is possible, especially when the components are added to the aqueous carrier according to the preferred sequence described above. It is possible to slightly heat the composition during its preparation, e.g., to about 3O⁰C, in order to shorten the preparation time. The clear composition thus obtained is finally cooled to room temperature, maintaining its clarity. In addition to the four-components combination identified above, the liquid composition of the present invention may further comprise various additives that may assist in maintaining the homogeneity of the composition, e.g., stabilizers, provided, of course, that said additives do not interfere with the contemplated use of the composition.

The clear, stable homogeneous liquid composition of the present invention contains a relatively high concentration of a corrosion inhibiting combination (namely, antimony or germanium compound, morpholine or derivative thereof, unsaturated alcohol and an organic acid having reducing capacity, which is specifically isoascorbic acid) , and is therefore useful in reducing the attack of metals by- corrosive fluids. To this end, the aqueous solution provided by the present invention is added to the corrosive fluid in order to provide a corrosion-inhibiting effective amount, of said four-components combination in the corrosive fluid, which amount depends, inter alia, on the corrosive fluid to be inhibited and the composition and temperature of the metallic environment to be protected. For example-, when the corrosive fluid .is heavy brine, the aqueous solution of the present invention is added thereto such that the concentration of the four-components combination within the brine is preferably not less than 0.05%, more preferably not less than 0.1% and even more preferably in the range between 0.5 and 2.0% (w/w) .

The aqueous solution provided by the present invention may be used for conveniently delivering corrosion-inhibiting effective amounts of the four-components combination into various corrosive fluids, such as heavy brines and clear drilling fluids in order to protect various metal surfaces, including carbon steels and stainless steels, from being attacked by said corrosive fluids in a wide range of working temperatures, for example up to 200⁰C, as commonly employed in various industrial applications and especially in the oil industry. It should be noted that the aqueous composition of the present invention allows a rapid - almost instantaneous - dissolution of the corrosion-inhibiting combination in the corrosive fluid, thus clearly improving on-site working conditions .

Accordingly, another aspect of the present invention relates to a method for inhibiting the corrosion of metals in contact with a corrosive fluid, which method comprises: a) providing an aqueous solution comprising:

(i) a metalloid compound selected from the group consisting of antimony and germanium compounds;

(ii)morpholine or derivative thereof;

(iii) unsaturated alcohol; and

(iv)an organic acid having reducing capacity, which is preferably (iso) ascorbic acid; dissolved in a high-capacity aqueous carrier at a concentration of not less than 5% by weight, and b) adding to said corrosive fluid a corrosion-inhibiting effective amount of said aqueous solution.

Corrosive fluids, to which the composition of the present invention may be added in order to protect metals exposed to said fluids, include halide brines (concentrated aqueous solutions of halide salts such as NaCl, NaBr, CaCl₂, CaBr₂, ZnCl₂ and ZnBr₂ and mixtures thereof) . A specific type of corrosion that may be effectively inhibited by the composition of the present invention is halide (chloride, bromide) stress-corrosion cracking (SCC) . SCC occurs when steel or stainless steels are contacted with chloride or bromide brines at high temperatures, above about 6O⁰C, while also subjected to tensile stress. SCC can occur, for example, when hot halide brine contacts a piece of bent stainless steel, for example, welded joints in austenitic stainless steel piping. A class of steels that is particularly affected by halide (chloride/bromide) SCC includes austenitic, martensitic, ferritic and duplex stainless steels.

More specifically, it has been found that martensitic stainless steel containing chromium at about 12-14% by weight, nickel at about 3.5-4.5% by weight and molybdenum at about 0.8-1.5% by weight (this alloy is known as HP-13 Cr 110) can be protected from stress-corrosion cracking by means of adding the aqueous composition of the present invention into a corrosive halide brine that is brought into contact with said stainless steel.

Thus, the aqueous corrosion inhibitor of the present invention may be added to a corrosive fluid, and specifically, to a calcium bromide brine, which is contacted with steel exposed to an environment encouraging stress- corrosion cracking (namely, temperature higher than 60°C and acidic conditions) . Generally, the composition of the present invention should be present in a preferred amount of not less than 0.05%, and more preferably in an amount between 0.1 to 2.0% by weight of the brine to be inhibited. Of course, the effective amount of the composition to be employed may vary according to the severity of the corrosive environment and the working conditions.

The aqueous composition of the present invention may be also used in water-based paints and coatings.

A further aspect of the invention relates to a corrosion inhibiting composition comprising a metalloid compound selected from the group consisting of antimony and germanium compounds; morpholine or derivative thereof as represented by Formula I above; C₃-C₇ alkenol and an organic acid having reducing capacity, and specifically, (iso) ascorbic acid. The alkenol is preferably a straight chain primary alkenol having from 3 to 5 carbon atoms in the molecule, and specifically allyl alcohol, CH₂=CHCH₂OH, or crotyl alcohol, CH₃CH=CHCH₂OH, with the latter being most preferred. The preferred morpholine derivative is identified by Formula I above, wherein Ri is Ci-C₃ alkyl substituted with one or more hydroxy groups, namely, 4- (hydroxyalkyl) morpholines, such as 4- (2-hydroxyethyl) morpholine.

As illustrated in the Examples below, the composition set forth above exhibits excellent corrosion inhibiting activity. Most conveniently, the composition is dissolved in a high capacity aqueous carrier, and specifically in water, employing the preparative procedures described above, whereby a stable aqueous solution is formed, which solution may be used delivering the composition into the targeted corrosive brine. However, the present invention is not limited to the application of the corrosion inhibiting composition described above in the form of an aqueous solution. Alternatively, the four ingredients (namely, the metalloid compound, the (iso) ascorbic acid, the C₃-C₇ alkenol and the morpholine or a derivative thereof) may be successively added (in any possible order) into the corrosive brine under vigorous stirring.

Accordingly, the present invention also provides a method for inhibiting the corrosion of metals in contact with a corrosive fluid, which method comprises adding to said corrosive fluid a corrosion-inhibiting effective amount of a metalloid compound selected from the group consisting of antimony and germanium compounds; an organic acid having reducing capacity (such as (iso) ascorbic acid); 0₃-C₇ alkenol and morpholine or derivative thereof, as preferably represented by Formula I. The quantitative ratios between the components indicated above, and useful amounts thereof to be introduced within the corrosive fluid in order to obtain the desired corrosion inhibitory effect are as set forth above.

Another aspect of the present invention relates to a brine, such as the halide brine listed herein above, and specifically to calcium bromide brine, which brine includes (i) a metalloid compound selected from the group consisting of antimony and germanium compounds; (ii) morpholine or derivative thereof as represented by Formula (I) , wherein said derivative is preferably 4- (hydroxyalkyl) morpholine, such as 4- (2-hydroxyethyl) morpholine; (iii) C₃-C₇ alkenol, which is preferably a straight chain primary alkenol having from 3 to 5 carbon atoms, such as allyl alcohol, CH2=CHCH₂θH, or crotyl alcohol, CH₃CH=CHCH₂OH; and (iv) an organic acid having reducing capacity, and specifically, (iso) ascorbic acid. The brine provided by the invention comprises an effective corrosion inhibiting amount of the combination set forth above, namely, that amount which is effective in protecting metals that are in contact with the corrosive brine such that said metals preferably exhibit corrosion rate in mili inches per year of less than 50 mpy. Generally, an effective corrosion inhibiting concentration of the combination set forth above in the brine is not less than 0.1 % by weight, and preferably varies between 0.5 and 2.0% (w/w) . As described above, the brine is most conveniently prepared by pre-dissolving the four components in advance in a high- capacity aqueous carrier, which carrier is compatible with said brine, and then adding the resulting solution into the brine .

As noted above, corrosive brines, to which the compositions of the present invention may be added in order to protect metals exposed to said brines, include concentrated aqueous solutions of halide salts such as NaCl, NaBr, CaCl₂, CaBr2, ZnCl₂ and ZnBr₂ and mixtures thereof. Preferred brines have densities of not less than 11 ppg (pounds per gallon) , and more preferably of not less than about 14.2 ppg, such as 14.2 ppg CaBr2 brine (52%), and CaBr2 + ZnBr2 mixtures with a density of up to 19.2 ppg.

Examples

The results of corrosion rates reported in the following examples were determined as follows. Mild steel C-4130 corrosion coupons were rinsed in acetone, dried and weighed to the nearest 0.1 mg. One or two coupons were placed in a glass container containing 125 ml or 250 ml of the test fluid to thereby provide a volume to surface area ratio of 20 ml per sq. in. or in 200 ml of the test fluid to thereby provide a volume to surface area ratio of 45.6 ml per sq. in. The glass container holding the coupons and the test fluid was then placed into an aging cell and pressurized to 500 psi with an inert medium such as nitrogen. The cell was next placed in an oven at the desired temperature for the required test period. When not indicated otherwise, the temperature was 177⁰C (350⁰F) and the test duration was 7 days. After aging, the coupons were removed from the cell, brushed and rinsed sequentially in hot water and acetone. They were later dried, re-weighed to the nearest 0.1 mg and the weight-loss was calculated. For corrosion rate calculations the formula given below was used:

mpy = 534 W/DAT where mpy = corrosion rate in miIi inches per year W = weight loss, mg D = density of coupon, g/cm³ A = area of coupon, sq. in. T = exposure (aging) time, hr

Example 1

Distilled water (500 g) is placed in a vessel equipped with a stirrer. Solid d-isoascorbic acid (245 g) is added to the vessel and the resulting mixture is stirred for twenty minutes, to form an acidic solution (pH~l) . Antimony trichloride (5 g) is then added under vigorous stirring for ten minutes. Propargyl alcohol (100 g; approximately 1.05 ml) is gradually poured into the vessel and the vigorous stirring is allowed to continue for additional ten minutes until a homogeneous mixture is obtained, with a pH value in the range between 2 and 4. Morpholine (150 g; approximately 150 ml) is then slowly added to the acidic solution, which is gently stirred to give a clear solution; the dissolution of morpholine in the solution is exothermic. The color of the solution is green-amber and its pH is alkaline.

Examples 2-8

Table 1 lists the compositions and the properties of additional aqueous solutions prepared according to the procedure of Example 1. The components are indicated in the column headed "composition" according to the order by which they were added to form the composition.

In addition, the table also reports the results of corrosion tests which were performed according to the general procedure described above. The tested corrosive fluid was ZnBr₂/CaBr₂ brine with density of 18.2 ppg (2.184 g/cc) . The composition of the invention was added into the tested brine at a concentration of 2% by weight (such that the concentration of the corrosion-inhibiting ingredients was about 1% relative to the total weight of the brine) . Table 1

Example 10 (comparative)

The purpose of this example is to point out the role of the high-capacity aqueous carrier in preparing the aqueous solutions of the present invention. An attempt was made to dissolve the combination of antimony chloride, morpholine, isoascorbic acid and unsaturated alcohol in an aqueous carrier which is a heavy brine (ZnBr2) with a density of

2.65 g/cm³. The data are shown in Table 2 below [the components are indicated in the middle column according to the order by which they were added to form the composition) .

Table 2

Examples 11-12 (comparative)

Table 3 summarizes the preparation and properties of corrosion-inhibiting combinations, which cannot be formulated into stable aqueous solutions (the components are indicated in the middle column according to the order by which they were added to form the composition) .

Table 3

Example 13

The aqueous composition according to Example 2 was evaluated in order to determine whether it is capable of preventing, or significantly retarding, the formation of stress- corrosion cracks in specimens of steel exposed to potentially problematic environments. To this end, the stress-corrosion cracking resistance of C-rings made of HP- 13CrIlO steel was tested as follows: The composition to be tested was added to calcium bromide 52% brine. The C-rings were placed in the calcium bromide brine at temperature of 146°C for one month under nitrogen atmosphere. In addition, CO2 was introduced at different pressures into the pressure vessel, in order to generate acidic environment therein. Following the one-month period, the specimens were visually observed in order to evaluate the formation of stress- corrosion cracks. The parameters of the series of experiments performed and the results obtained are tabulated in the following table.

Table 4

It is apparent that the aqueous composition provided by the present invention effectively prevents the formation of stress-corrosion cracks in steel exposed to an environment which generates stress-corrosion cracking. It is noted that the desired inhibition of stress-corrosion cracking is achieved using a relatively low amount of the composition in the corrosive brine (e.g., in calcium bromide) .

Examples 14 -19

Table 5 lists compositions and properties of additional aqueous solutions prepared according to the procedure of Example 1, using various unsaturated alcohols. The components are indicated in the column headed "composition" according to the order by which they were added to form the composition. The aqueous compositions prepared were tested for their corrosion inhibiting properties. To this end, the aqueous composition was added to ZnBr₂/CaBr₂ brine having density of 18.2 ppg (2.184 g/cc) , at a concentration of 2 wt%, such that the concentration of the corrosion inhibiting components was about 1 wt% relative to the total weight of the brine. Mild steel C-4130 specimens were exposed for seven days to the brine under the conditions indicated hereinbefore .

Table

Examples 20-22

The following examples illustrate additional compositions according to the present invention, with 4- (2-hγdroxyethyl) morpholine being used in combination with antimony halide, D-isoascorbic acid and a straight chain primary alkenol (crotyl alcohol or allyl alcohol) . An illustrative preparative procedure is as follows:

Add 375 grams of distilled water to a vessel equipped with a stirrer. Add 245 grams of solid D-isoascorbic acid to the distilled water while stirring. Continue stirring for 60 minutes. At the end of this period, there is an acidic solution with a pH below 1. Add 5 grams of solid antimony trichloride to the acidic solution while stirring. Stir vigorously for 60 minutes. Add 150 grams (approximately 177 ml) of liquid crotyl alcohol to the solution while stirring. Stir vigorously for 10 minutes. Slowly add 225 grams (approximately 208 ml) of liquid 4- (2-hydroxyethyl) morpholine while stirring. Stir vigorously for 8 hours. At the end of this period, a clear solution is obtained, with a characteristic yellowish to amber color. The pH of the composition is approximately 7. Table 6 presents the composition and properties of the solution prepared above, together with two additional solutions. The components are indicated in the column headed "composition" according to the order by which they were added to form the solution. The aqueous solutions prepared were also tested for their corrosion inhibiting properties. To this end, the tested solution was added to ZnBr2/CaBr2 brine at a concentration of 2 wt% (such that the concentration of the corrosion-inhibiting ingredients was about 1%) . Mild steel C-4130 specimens were exposed for seven days to the brine under the conditions set forth hereinbefore .

Table 6

* The mixture was stirred for six hours following the addition of the morpholine derivative. Example 23-24

The compositions of Examples 20-21 were evaluated in order to determine whether they are capable of preventing, or significantly retarding, the formation of stress-corrosion cracks in specimens of steel exposed to potentially- problematic environments. To this end, the stress-corrosion cracking resistance of C-rings made of HP-13CrllO steel was tested as follows: The composition to be tested was added to calcium bromide 52% brine. The C-rings were placed in the calcium bromide brine at temperature of 146°C for one month under nitrogen atmosphere. In addition, CO₂ was introduced at different pressures into the pressure vessel, in order to generate acidic environment therein. Following the one-month period, the specimens were visually observed in order to evaluate the formation of stress-corrosion cracks. The parameters of the series of experiments performed and the results obtained are tabulated in the following table.

Table 7

Claims

1) A liquid composition comprising a high-capacity aqueous carrier in which (i) a metalloid compound selected from the group consisting of antimony and germanium compounds and (ii) morpholine or derivative thereof are dissolved in the presence of (iii) unsaturated alcohol and (iv) water- soluble organic acid having reducing capacity, wherein the total concentration of said four components is not less than 5% relative to the total weight of the composition.

2) A composition according to claim 1, wherein the composition is in the form of a clear solution.

3) A composition according to claim 2, wherein the total concentration of the four components in the ' aqueous composition is not less than 30% by weight and the water content of the composition is not less than 30% by weight.

4) A composition according to claim 1, wherein the metalloid compound is antimony halide.

5) A composition according to claim 1, wherein the morpholine and derivative thereof are represented by the structure of Formula I:

wherein Ri is hydrogen or C₁-C₃ alkyl and R₂ is independently selected from the group consisting of hydrogen, Ci-C₃ alkyl and phenyl group and n is 0, 1, 2, 3 or 4, said Ci-C₃ alkyl and phenyl groups being optionally substituted.

6) A composition according to claim 5, wherein in Formula (I) Ri is hydrogen or Ci-C₃ alkyl substituted with one or more hydroxy groups and R₂ is hydrogen.

7) A composition according to claim 1, wherein the unsaturated alcohol comprises alkenol or alkynol having from 3 to 7 carbon atoms, or a mixture thereof.

8) A composition according to claim 7, wherein the unsaturated alcohol is a straight chain primary alkenol having from 3 to 5 carbon atoms .

9) A composition according to claim 8, wherein the alkenol is allyl alcohol (CH₂=CHCH₂OH) , crotyl alcohol (CH₃CH=CHCH₂OH) or a mixture thereof.

10) A composition according to any one of claims 1-9, wherein the water-soluble organic acid having reducing capacity is (iso) ascorbic acid.

11) A composition according to claim 3, which is a clear solution comprising water and

(i) a metalloid compound which is antimony compound;

(ii) morpholine or derivative thereof as represented by the structure of Formula I :

(i: wherein R₁ is hydrogen or Ci-C₃ alkyl and R₂ is independently selected from the group consisting of hydrogen, Ci-C₃ alkyl and phenyl group and n is 0, 1, 2, 3 or 4, said C_x-C₃ alkyl and phenyl groups being optionally substituted;

(iii) unsaturated alcohol selected from the group consisting of alkenols having from 3 to 7 carbon atoms, alkynols having from 3 to 7 carbon atoms, and mixtures thereof; and

(iv) (iso) ascorbic acid.

12) A composition according to claim 11, wherein the morpholine of Formula I is selected from the group consisting of morpholine and 4- (2-hydroxyalkyl) morpholines, and the unsaturated alcohol comprises a straight chain primary alkenol having from 3 to 5 carbon atoms .

13) A composition according to claim 12, which is a clear solution containing about 30-60% by weight water; (i) 0.40- 0.60 % by weight antimony halide; (ii) 10-25% by weight morpholine or 4- (2-hydroxyalkyl) morpholine; (iii) 7-18% by weight straight chain primary alkenol having from 3 to 5 carbon atoms and (iii) 20-30% by weight (iso) ascorbic acid.

14) A composition according to claim 13, wherein the antimony halide is SbCl₃, the morpholine derivative is 4- (2- hydroxyethyl) morpholine and the alkenol is selected from group consisting of allyl alcohol (CH₂=CHCH₂OH) , crotyl alcohol (CH₃CH=CHCH₂OH) and a mixture thereof.

15) A process for preparing a clear aqueous composition, which comprises mixing in a vessel a high-capacity aqueous carrier, water-soluble organic acid having reducing capacity, a metalloid compound which is antimony or germanium compound, unsaturated alcohol and morpholine or derivative thereof, such that the dissolution of said metalloid compound in said aqueous carrier is accomplished under acidic environment.

16) A process according to claim 15, which comprises mixing (iso) ascorbic acid in the aqueous carrier to form an acidic aqueous carrier, dissolving the metalloid compound in said carrier, introducing unsaturated alcohol into the resulting solution and subsequently adding morpholine or derivative thereof, to form an essentially homogeneous liquid composition with a pH in the range between 6 to 12.

17) A process according to claim 16, wherein the metalloid compound is antimony halide, the unsaturated alcohol is selected from the group consisting of alkenols and alkynols having from 3 to 7 carbon atoms and the morpholine or derivative thereof is represented by Formula I

wherein Ri is hydrogen or Ci-C₃ alkyl and R₂ is independently selected from the group consisting of hydrogen, Ci-C₃ alkyl and phenyl group and n is 0, 1, 2, 3 or 4, said Ci-C₃ alkyl and phenyl groups being optionally substituted.

18) A process according to claim 17, wherein the alkenol is straight chain primary alkenol containing from 3 to 5 carbon atoms and the morpholine of Formula I is selected from the group consisting of morpholine, 4- (2-hydroxyethyl) morpholine and mixtures thereof. 19) A method for inhibiting the corrosion of metals in contact with a corrosive fluid, which method comprises: a) providing a solution comprising:

(i) a metalloid compound selected from the group consisting of antimony and germanium compounds; (ii)morpholine or derivative thereof; (iii) unsaturated alcohol; and

(iv) water-soluble organic acid having reducing capacity; wherein said components are dissolved in a high-capacity aqueous carrier at a concentration of not less than 5% by weight, and b) adding to said corrosive fluid a corrosion-inhibiting effective amount of said solution.

20) A method according to claim 19, wherein the corrosion to be inhibited is stress-corrosion cracking and the corrosive brine is calcium bromide brine.

21) A corrosion inhibiting composition comprising:

(ii) morpholine or derivative thereof as represented by the structure of Formula I:

wherein R₁ is hydrogen or Ci-C₃ alkyl and R₂ is independently selected from the group consisting of hydrogen, Ci-C₃ alkyl and phenyl group and n is 0, 1, 2, 3 or 4, said Ci-C₃ alkyl and phenyl groups being optionally substituted; (iii) C₃-C₇ alkenol; and (iv) water-soluble organic acid having reducing capacity.

22) A corrosion inhibiting composition according to claim 21, wherein the alkenol is a straight chain primary alkenol having from 3 to 5 carbon atoms .

23) A composition according to claim 22, wherein the alkenol is selected from the group consisting of allyl alcohol (CH₂=CHCH₂OH), crotyl alcohol (CH₃CH=CHCH₂OH) and a mixture thereof.

24) A corrosion inhibiting composition according to claim 21, wherein the morpholine derivative is 4- (hydroxyalkyl) morpholine .

25) A composition according to claim 21, wherein the antimony compound is SbCl₃, the morpholine derivative is 4- (2-hydroxyethyl) morpholine, the alkenol is selected from group consisting of allyl alcohol (CH₂=CHCH₂OH) , crotyl alcohol (CH₃CH=CHCH₂OH) and a mixture thereof and the water- soluble organic acid is (iso) ascorbic acid.

26) A method for inhibiting the corrosion of metals in contact with a corrosive fluid, which method comprises adding to said corrosive fluid a corrosion-inhibiting effective amount of a metalloid compound selected from the group consisting of antimony and germanium compounds; water- soluble organic acid having reducing capacity; C₃-C₇ alkenol; and morpholine or a derivative thereof as represented by the structure of Formula I: wherein Ri is hydrogen or Ci-C₃ alkyl and R₂ is independently selected from the group consisting of hydrogen, Ci-C₃ alkyl and phenyl group and n is 0, 1, 2, 3 or 4, said Ci-C₃ alkyl and phenyl groups being optionally substituted.

27) A method according to claim 26, wherein the alkenol is a straight chain primary alkenol having from 3 to 5 carbon atoms and the morpholine derivative is 4- (hydroxyalkyl) morpholine .

28) A method according to claim 27, wherein the alkenol is selected from the group consisting of allyl alcohol (CH₂=CHCH₂OH), crotyl alcohol (CH₃CH=CHCH₂OH) or a mixture thereof and the morpholine is 4- (2-hydroxyethyl) morpholine.

29) A method according to claim 26, wherein the antimony halide is SbCl₃, the morpholine derivative is 4- (2- hydroxyethyl) morpholine, the alkenol is selected from group consisting of allyl alcohol (CH₂=CHCHaOH) , crotyl alcohol (CH₃CH=CHCH₂OH) and a mixture thereof and the water-soluble organic acid is (iso) ascorbic acid.

30) A method according to any one of claims 26-29, wherein the corrosion to be inhibited is stress-corrosion cracking.

31) A method according to claim 30, wherein the corrosive fluid is calcium bromide brine. 32) Halide brine, which comprises one or more of the following salts: NaCl, NaBr, CaCl₂, CaBr₂, ZnCl₂ and ZnBr₂, and further comprises a corrosion-inhibiting effective amount of the composition according to any one of claims 21 to 25.

33) Halide brine according to claim 32, which comprises CaBr2.