Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/02—Well-drilling compositions
  • C09K8/04—Aqueous well-drilling compositions
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/54—Compositions for in situ inhibition of corrosion in boreholes or wells
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids

Definitions

• corrosive fluids such as concentrated aqueous solutions and specifically heavy brines.
• 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.
• US 5,411,670 discloses an inhibitor composition comprising antimony compound dissolved in an acidic liquid carrier.
• 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.
• 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/cm 3 , preferably less than 1.5 g/cm 3 and more preferably less than 1.1 g/cm 3 .
• 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) .
• 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/cm 3 .
• a preferred example in this regard is CaBr 2 (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.
• metal compound 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.
• halide salts namely, SbX 3 , wherein X is F, Cl, Br or I, and also alkali metal antimony salts (e.g., alkali metal antimony tartarate) .
• 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:
• Ri is hydrogen or Ci-C 3 alkyl and R 2 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-C 3 alkyl and phenyl groups may be optionally substituted, e.g., with one or more hydroxy groups.
• 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 C 1 -C 3 alkyl substituted with one or more hydroxy groups, namely, the class of compounds that may be identified as A- (hydroxyalkyl) morpholines.
• 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) .
• unsaturated alcohols includes alcohols, and more preferably C3-C7 alcohols, which contain either a carbon- carbon double bond or a carbon-carbon triple bond.
• Ri, R 2 and R 3 are independently hydrogen or lower (C1-C3) alkyl groups.
• acetylenic alcohols to be used according to the present invention are propargyl alcohol (Ri, R 2 and R 3 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.
• C x -C y indicates a straight or branched alkyl chain containing between x and y carbon atoms, inclusive.
• 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.
• 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- ⁇ -D- glucopyranos ⁇ l-L-ascorbic acid and 5, 6-O-isopropylidene-L- ascorbic acid.
• 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- ⁇ -D- glucopyranos ⁇ l-L-ascorbic acid and 5, 6-O-isopropylidene-L- ascorbic acid.
• 6-deoxyhex-2- enoic acid Y lactone 3, 4-dihydroxy-5- (hydroxymethyl) -2 (5H) - furanone, 2, 3, 4-trihydroxy-2-pentenoic acid ⁇ lactone, 2,4- dihydroxy-3-r ⁇ ethyl-2-hexenoic acid Y lactone and 3-hydroxy- 4, 5-dimethyl-2 (5H) -furanone.
• 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 present invention primarily relates to an essentially homogeneous liquid composition
• 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.
• 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.
• 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%.
• 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.
• 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%.
• 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) .
• SbCIs antimony halide
• iso ascorbic acid
• straight chain primary alkenol having from 3 to 5 carbon atoms specifically crotyl alcohol or allyl alcohol
• straight chain primary alkenol having from 3 to 5 carbon atoms
• 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.
• 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.
• 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.
• 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.
• 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.
• the stirring typically lasts between 5 minutes and several hours, until a clear solution is formed.
• 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.
• the pH of the aqueous composition is typically within the range of 6-12 and preferably in the range 7- 9.5.
• 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) .
• a highly concentrated salt solution such as calcium bromide brine
• concentration of the water in the composition is less than about 35% (by weight) .
• water in the aqueous carrier namely, not less than 40-50% by weight
• 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.
• 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.
• 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
• 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.
• 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 200 0 C, 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 .
• 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:
• a metalloid compound selected from the group consisting of antimony and germanium compounds
• 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, CaCl 2 , CaBr 2 , ZnCl 2 and ZnBr 2 and mixtures thereof) .
• halide brines concentrated aqueous solutions of halide salts such as NaCl, NaBr, CaCl 2 , CaBr 2 , ZnCl 2 and ZnBr 2 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 6O 0 C, 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.
• 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.
• 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) .
• 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.
• 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
• 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; C 3 -C 7 alkenol and an organic acid having reducing capacity, and specifically, (iso) ascorbic acid.
• the preferred morpholine derivative is identified by Formula I above, wherein Ri is Ci-C 3 alkyl substituted with one or more hydroxy groups, namely, 4- (hydroxyalkyl) morpholines, such as 4- (2-hydroxyethyl) morpholine.
• the composition set forth above exhibits excellent corrosion inhibiting activity.
• 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.
• the present invention is not limited to the application of the corrosion inhibiting composition described above in the form of an aqueous solution.
• the four ingredients namely, the metalloid compound, the (iso) ascorbic acid, the C 3 -C 7 alkenol and the morpholine or a derivative thereof
• 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); 0 3 -C 7 alkenol and morpholine or derivative thereof, as preferably represented by Formula I.
• a metalloid compound selected from the group consisting of antimony and germanium compounds
• morpholine or derivative thereof as represented by Formula (I) wherein said derivative is preferably 4- (hydroxyalkyl
• 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.
• 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) .
• 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 .
• 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, CaCl 2 , CaBr2, ZnCl 2 and ZnBr 2 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.
• the temperature was 177 0 C (350 0 F) and the test duration was 7 days.
• 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.
• the formula given below was used:
• 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.
• 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.
• the table also reports the results of corrosion tests which were performed according to the general procedure described above.
• the tested corrosive fluid was ZnBr 2 /CaBr 2 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) .
• 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
• 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) .
• 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.
• 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.
• 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) .
• 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 ZnBr 2 /CaBr 2 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 .
• compositions according to the present invention with 4- (2-h ⁇ droxyethyl) 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:
• 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.
• 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, CO 2 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.

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