CORROSION INHIBITOR MIXTURE
United States Patent 3655571
Aqueous acid solutions are inhibited against corrosion of metals, especially ferrous metals, by incorporation of a corrosion-inhibiting mixture composed of a combination of 1-hexyn-3-ol, 5-decyn-4,7-diol and urea.
US Patent References:
Composition for descaling ferrous metal surfaces
Cardwell et al. - October 1949 - 2485528
Corrosion inhibitors for aqueous acids
Beale et al. - January 1966 - 3231507
Corrosion inhibitor composition
Keeney et al. - May 1968 - 3382179
PROCESS OF CORROSION INHIBITION WITH 1-HEXYN-3-OL
Herman et al. - February 1969 - 3428566
Composition for descaling ferrous metal surfaces
Cardwell et al. - October 1949 - 2485528
Corrosion inhibitors for aqueous acids
Beale et al. - January 1966 - 3231507
Corrosion inhibitor composition
Keeney et al. - May 1968 - 3382179
PROCESS OF CORROSION INHIBITION WITH 1-HEXYN-3-OL
Herman et al. - February 1969 - 3428566
Inventors:
Tedeschi, Robert J. (Whitehouse Station, NJ)
Natali, Paul W. (Middletown, NJ)
Natali, Paul W. (Middletown, NJ)
Application Number:
04/789022
Publication Date:
04/11/1972
Filing Date:
12/31/1968
View Patent Images:
Export Citation:
Assignee:
Air Products and Chemicals, Inc. (Allentown, PA)
Primary Class:
Other Classes:
507/266, 252/392, 510/505, 510/501, 507/934, 134/3, 422/12, 510/267
International Classes:
C23F11/04; C23G1/06; C23G1/02; C23G1/06
Field of Search:
252/8.55L,8.55E,146,148,151,392,396 134/3,41
Other References:
Rutledge, T. F., Acetylemic Compounds, Rheinhold Book Corp., 1968.
Primary Examiner:
Rosdol, Leon D.
Assistant Examiner:
Rady, Arnold I.
Claims:
We claim
1. A metal corrosion-inhibitor mixture, for use with aqueous solutions of mineral acids, consisting essentially of:
2. The mixture of claim 1 wherein, further, the weight ratio of (a) + (b):(c) ranges from 1:5 to 5:1.
3. A corrosion-inhibited mineral acid comprising an aqueous solution of the mineral acid and from 0.01 to about 2 percent by weight of a mixture consisting essentially of:
4. The corrosion-inhibited acid of claim 3 wherein the weight ratio of (a) + (b):(c) ranges from 1:5 to 5:1.
1. A metal corrosion-inhibitor mixture, for use with aqueous solutions of mineral acids, consisting essentially of:
2. The mixture of claim 1 wherein, further, the weight ratio of (a) + (b):(c) ranges from 1:5 to 5:1.
3. A corrosion-inhibited mineral acid comprising an aqueous solution of the mineral acid and from 0.01 to about 2 percent by weight of a mixture consisting essentially of:
4. The corrosion-inhibited acid of claim 3 wherein the weight ratio of (a) + (b):(c) ranges from 1:5 to 5:1.
Description:
This invention relates to the inhibition of metal corrosion in acidic solutions and is more particularly concerned with inhibited aqueous acid solutions suitable for the treatment of metals.
Metal cleaning baths and pickling baths generally comprise aqueous solutions of inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, and are useful in the cleaning and treatment of iron, zinc, ferrous alloys, and the like.
In the use of aqueous acidic baths to treat metals, additives or inhibitors in the baths are desirable to prevent or inhibit corrosion or erosion of the metal surfaces. Similarly, in the field of oil-well acidizing, it is necessary to use inhibitors in order to prevent corrosion of the oil-well equipment by the aqueous acid solutions employed. Various other industrial operations also involve contact between an aqueous acidic solution and a metal, and an inhibitor must be used in order to minimize corrosion and/or consumption of the metal by such contact.
If no corrosion inhibitor is present when the aqueous acidic solution comes into contact with the metal, excessive metal loss, production of undesirable metal surface properties, excessive consumption or loss of acid, and like adverse results will be experienced. Many different types of inhibitors have been proposed, but there has been a continuing search for corrosion inhibitors which can be used effectively in small concentrations, and which are economical to produce, since the use of inhibitors is a necessary expense and it is economically prudent to keep this expense at a minimum while, at the same time, realizing the desired inhibition of metallic corrosion or consumption. The need is also for corrosion inhibitors which are effective at high temperatures, e.g. 200° F. and above, such as are encountered in various operations involving acidic solutions, particularly oil-well acidizing where higher and higher temperatures are encountered as the well extends further into the earth.
While various corrosion-inhibiting agents have been proposed, all of such agents are not of equal effectiveness and of the many hundreds of agents which have been contemplated, only a few are sufficiently active to be commercially attractive. This is particularly true in the case of high-temperature operations. Some inhibitors which have been proposed are reasonably effective at low and moderate temperatures, but fail completely when high temperatures are encountered.
There has, therefore, been a continuing search for more effective inhibitors, or for ways of making a given inhibitor more effective. This search has involved the discovery of combinations of inhibitors which act together to provide an inhibitor mixture. However, many of these mixtures involve relatively expensive components so that, while they may be relatively effective in their corrosion-inhibiting activity, there are disadvantages from an economic standpoint, particularly if they have to be used in substantial quantities in order to bring about the desired corrosion-inhibiting activity. Similarly, many of these systems are ineffective at elevated temperatures. In particular, there is a need for a corrosion-inhibiting mixture comprising a plurality of components wherein relatively inexpensive compounds of poor corrosion-inhibiting action can be catalyzed or "potentiated" by the other component or components of the mixture so that the combination has a high corrosion-inhibiting activity even at elevated temperatures.
It is accordingly an object of this invention to provide a novel corrosion-inhibiting system involving a combination of agents which is highly effective from the standpoint of corrosion-inhibiting activity and which is, at the same time, commercially attractive.
It is a further object of this invention to provide a novel corrosion-inhibiting mixture comprising a combination of agents wherein one agent has a strong potentiating or catalyzing action upon the other agent so that the corrosion-inhibiting effectiveness of the combination is greater than the additive action of the components of the combination.
It is another object of the invention to provide a corrosion-inhibiting mixture of the character indicated which is effective at high temperatures .
In accordance with this invention, it has been discovered that the above and other objects can be achieved by the provision of a corrosion-inhibiting mixture comprising a combination of 1-hexyn-3-ol, 5-decyn-4,7-diol, and urea. The ratios among these components of the corrosion-inhibiting mixture may vary, but the best results are obtained with weight ratios of the two acetylenic alcohols to each other ranging between 1:10 and 10:1, preferably between 1:5 and 5:1, and most suitably between 1:2 and 2:1, and with the weight ratios of the combined acetylenic alcohols to urea ranging between 1:5 and 10:1, preferably between 1:5 and 5:1, and weight ratios between 1:2 and 2:1 being especially preferred.
The acetylenic alcohol-urea inhibitor mixture of this invention is useful, in general, in the inhibition of corrosion of metal surfaces in contact with aqueous mineral acid solutions, such as hydrochloric acid, sulfuric acid, and phosphoric acid, for example in the acidizing of oil wells, in electrolytic cleaning baths, and electrolytic refining of metals, as well as in metal cleaning and pickling baths. The use of the above-described inhibitor mixture of this invention for corrosion inhibition of metals in aqueous mineral acid solutions is advantageous in that this corrosion inhibitor mixture can be employed in such acid solutions over a wide and useful concentration range. A further advantage of this inhibitor mixture is that it may be used at elevated temperatures to provide satisfactory corrosion inhibition, even when in relatively low concentration.
The most effective amount of the corrosion-inhibiting mixture to be used in accordance with this invention can vary, depending upon local operation conditions. Thus, the temperature and other characteristics of the acid corrosive mixture may have a bearing upon the amount of inhibitor to be used. The higher the temperature and/or the higher the acid concentration, the greater is the amount of corrosion inhibitor required to give optimum results. In general, however, it has been found that a concentration of the corrosion-inhibiting mixture of the invention between 0.01 and 2 percent, preferably between 0.01 percent to 1.2 percent, by weight of the aqueous acidic solution is an effective corrosion-inhibiting concentration, although higher concentrations can be used when conditions make them desirable, with a concentration between 0.05 percent to 0.75 percent by weight being of most general use, at elevated temperatures, e.g. in the neighborhood of 200° F. The acidic solution can be dilute or concentrated and can be of any of the concentrations used in treating metals, e.g. ferrous metals, or for operations involving contact of acidic solutions with such metals, e.g. oil-well acidizing, and the like, for example 5 to 80 percent. In most operations of the character indicated, acid concentrations of 10-15 percent by weight are employed, and non-oxidizing inorganic acids are used. However, it is not intended to limit the invention to any specific use of acidic solutions or with respect to any specific metal or acid.
While the inhibitor mixture of this invention can be prepared from individual quantities of 1-hexyn-3-ol and 5-decyn-4,7-diol, a particularly advantageous source of these two chemicals is the reaction mixture obtained by the ethynylation of butyraldehyde with acetylene, using the well-known reaction wherein butyraldehyde and acetylene are reacted in the presence of a catalyst in an inert solvent medium, most commonly an ether, the reaction being carried out at various temperatures but which generally lie in the range of 0° to 50° C. This reaction, which was originally proposed by Favorskii, and has been improved upon by several other workers, is well-described in the literature, and reference is made, for example, to the book "Acetylenic Compounds" by Thomas F. Rutledge (Reinhold Book Corp., 1968), especially pages 146 to 149, and to the footnotes referred to therein. In a typical operation the aldehyde and the acetylene are reacted in an acetal or an ether as the reaction medium at substantially atmospheric pressure at a temperature of 20° to 30° C., using solid KOH as catalyst in amounts which are substantially stoichiometric (usually slightly in excess) with respect to the aldehyde, the acetylene being in excess of the stoichiometric quantity. The thus-produced mixture of 1-hexyn-3-ol and 5-decyn-4,7-diol will vary in composition somewhat, depending upon the specific reaction conditions, but the ratio of 1-hexyn-3-ol to 5-decyn-4,7-diol usually lies within the range of 5:1 to 1:4, and most commonly is about 1:1 to 2:1. The inert reaction medium is readily separated by distillation, but minor amounts of the solvent, e.g. up to 10 percent by weight or more, may be present and such presence does not interfere with the activity of the acetylenic hydroxy compounds. The mixture may also contain minor amounts of by-products produced by condensation, aldolization, or other reactions and are also unobjectionable. Such by-products may range up to 10 percent by weight but are usually less than about 5 percent by weight.
It will be understood that a reaction mixture of the character indicated is particularly attractive from a commercial standpoint since purification of the product of the ethynylation reaction is not required, yet the important benefits of the combination of 1-hexyn-3-ol with 5-decyn-4,7-diol in the mixture of this invention are realized in the critical area of corrosion inhibition, i.e. high acid concentrations and high temperatures.
The following experiments will serve to illustrate the effectiveness of the corrosion-inhibiting mixture of this invention under severe corrosion conditions encountered in practical application:
The method used to determine the inhibiting properties of the mixture of the invention employs test specimens or coupons. To prepare the coupons, they are wiped with acetone to remove any residual oils or grease, and pickled for 1 minute in 10 percent hydrochloric acid to eliminate any scale and surface film. After pickling, the coupons are dipped in sodium bicarbonate solution, rinsed well in tap water, rinsed in distilled water, and finally dried with acetone. The clean and dry specimens are then weighed to the nearest 0.1 mg. In carrying out the evaluation, hydrochloric acid of 15 percent by weight concentration is used in order to duplicate oil-well acidizing conditions. The inhibitor mixture is added to 4 oz. test bottles, 100 ml. of the acid then added to each bottle; and the mixture shaken vigorously. The bottles are suspended in a constant-temperature bath consisting of a bell jar filled with ethylene glycol and equipped with a stirrer. The temperature is regulated to maintain the samples at 200° ± 2° F. The bottles are placed in the bath one-half hour before the test coupons are added to insure temperature equilibrium. The weighed coupons, in duplicate, are then supported on glass hooks in the test bottles and the bottles are covered with watch glasses during the testing period of 16 hours. At the end of the testing period, the bottles are removed from the bath, the coupons withdrawn, rinsed with water, sodium bicarbonate solution, distilled water, and dried in acetone, then weighed to measure weight loss. Corrosion-inhibiting properties are conveniently expressed as percent inhibition, using the following formula:
When the acid concentration and temperature are such that the blank would be completely consumed by the acid in the absence of an inhibitor, the foregoing formula can be expressed as:
EXAMPLE
Using the test procedure described above, the inhibitor mixture of the invention was evaluated for its effectiveness in preventing corrosion of steel, using 1 in. × 2 in. coupons cut from a 1/16-in. sheet of a mild steel having the following typical analysis: 0.15 percent max. carbon, 0.30-0.60 percent manganese, 0.04 percent phosphorous, 0.05 percent sulfur, the balance iron. Each test sample was prepared by adding equal parts by weight of urea and a mixture comprising 1-hexyn-3-ol and 5-decyn-4,7-diol in a 2:1 weight ratio to the 15 percent hydrochloric acid, the combined mixture of the invention, i.e. the urea plus the acetylenic carbinol-glycol mixture being added in the amount of 0.5 percent by weight of the acid. Each sample was evaluated for corrosion inhibiting activity in contact with the steel coupon. At the same time, a blank test, using the same acid but without any inhibitor, was made. The following results were obtained:
% Inhibition Inhibitor 16 hrs. Hexynol + 5-decyn-4,7-diol + urea 99 + None 0
The foregoing evaluation was repeated except that the weight ratio of the carbinol-glycol mixture to the urea was 4:1. Again a percent inhibition of 99 + was recorded.
These tests show the positive action of the combination of hexynol, 5-decyn-4,7-diol, and urea in accordance with this invention, in inhibiting metal corrosion of commercial steel in an acid solution of high concentration at an elevated temperature only slightly below the boiling point of water, over a prolonged period of time. The results shown in the foregoing test data are obtained when an ethynylation reaction mixture comprising 1-hexyn-3-ol and 5-decyn-4,7-diol of the type described above is employed in combination with the urea. When the urea is directly added to the acetylenic carbinol-glycol mixture, it is advantageous first to dissolve it in a small amount of water, e.g. a 25 percent aqueous solution, and then add the solution to the acetylenic alcohols.
It will be apparent that various changes and modifications may be made in the operations described in the foregoing without departing from the scope of the invention as defined in the appended claims. It is intended, therefore, that all matter contained in the above description of the invention shall be interpreted as illustrative only and not as limitative.
Metal cleaning baths and pickling baths generally comprise aqueous solutions of inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, and are useful in the cleaning and treatment of iron, zinc, ferrous alloys, and the like.
In the use of aqueous acidic baths to treat metals, additives or inhibitors in the baths are desirable to prevent or inhibit corrosion or erosion of the metal surfaces. Similarly, in the field of oil-well acidizing, it is necessary to use inhibitors in order to prevent corrosion of the oil-well equipment by the aqueous acid solutions employed. Various other industrial operations also involve contact between an aqueous acidic solution and a metal, and an inhibitor must be used in order to minimize corrosion and/or consumption of the metal by such contact.
If no corrosion inhibitor is present when the aqueous acidic solution comes into contact with the metal, excessive metal loss, production of undesirable metal surface properties, excessive consumption or loss of acid, and like adverse results will be experienced. Many different types of inhibitors have been proposed, but there has been a continuing search for corrosion inhibitors which can be used effectively in small concentrations, and which are economical to produce, since the use of inhibitors is a necessary expense and it is economically prudent to keep this expense at a minimum while, at the same time, realizing the desired inhibition of metallic corrosion or consumption. The need is also for corrosion inhibitors which are effective at high temperatures, e.g. 200° F. and above, such as are encountered in various operations involving acidic solutions, particularly oil-well acidizing where higher and higher temperatures are encountered as the well extends further into the earth.
While various corrosion-inhibiting agents have been proposed, all of such agents are not of equal effectiveness and of the many hundreds of agents which have been contemplated, only a few are sufficiently active to be commercially attractive. This is particularly true in the case of high-temperature operations. Some inhibitors which have been proposed are reasonably effective at low and moderate temperatures, but fail completely when high temperatures are encountered.
There has, therefore, been a continuing search for more effective inhibitors, or for ways of making a given inhibitor more effective. This search has involved the discovery of combinations of inhibitors which act together to provide an inhibitor mixture. However, many of these mixtures involve relatively expensive components so that, while they may be relatively effective in their corrosion-inhibiting activity, there are disadvantages from an economic standpoint, particularly if they have to be used in substantial quantities in order to bring about the desired corrosion-inhibiting activity. Similarly, many of these systems are ineffective at elevated temperatures. In particular, there is a need for a corrosion-inhibiting mixture comprising a plurality of components wherein relatively inexpensive compounds of poor corrosion-inhibiting action can be catalyzed or "potentiated" by the other component or components of the mixture so that the combination has a high corrosion-inhibiting activity even at elevated temperatures.
It is accordingly an object of this invention to provide a novel corrosion-inhibiting system involving a combination of agents which is highly effective from the standpoint of corrosion-inhibiting activity and which is, at the same time, commercially attractive.
It is a further object of this invention to provide a novel corrosion-inhibiting mixture comprising a combination of agents wherein one agent has a strong potentiating or catalyzing action upon the other agent so that the corrosion-inhibiting effectiveness of the combination is greater than the additive action of the components of the combination.
It is another object of the invention to provide a corrosion-inhibiting mixture of the character indicated which is effective at high temperatures .
In accordance with this invention, it has been discovered that the above and other objects can be achieved by the provision of a corrosion-inhibiting mixture comprising a combination of 1-hexyn-3-ol, 5-decyn-4,7-diol, and urea. The ratios among these components of the corrosion-inhibiting mixture may vary, but the best results are obtained with weight ratios of the two acetylenic alcohols to each other ranging between 1:10 and 10:1, preferably between 1:5 and 5:1, and most suitably between 1:2 and 2:1, and with the weight ratios of the combined acetylenic alcohols to urea ranging between 1:5 and 10:1, preferably between 1:5 and 5:1, and weight ratios between 1:2 and 2:1 being especially preferred.
The acetylenic alcohol-urea inhibitor mixture of this invention is useful, in general, in the inhibition of corrosion of metal surfaces in contact with aqueous mineral acid solutions, such as hydrochloric acid, sulfuric acid, and phosphoric acid, for example in the acidizing of oil wells, in electrolytic cleaning baths, and electrolytic refining of metals, as well as in metal cleaning and pickling baths. The use of the above-described inhibitor mixture of this invention for corrosion inhibition of metals in aqueous mineral acid solutions is advantageous in that this corrosion inhibitor mixture can be employed in such acid solutions over a wide and useful concentration range. A further advantage of this inhibitor mixture is that it may be used at elevated temperatures to provide satisfactory corrosion inhibition, even when in relatively low concentration.
The most effective amount of the corrosion-inhibiting mixture to be used in accordance with this invention can vary, depending upon local operation conditions. Thus, the temperature and other characteristics of the acid corrosive mixture may have a bearing upon the amount of inhibitor to be used. The higher the temperature and/or the higher the acid concentration, the greater is the amount of corrosion inhibitor required to give optimum results. In general, however, it has been found that a concentration of the corrosion-inhibiting mixture of the invention between 0.01 and 2 percent, preferably between 0.01 percent to 1.2 percent, by weight of the aqueous acidic solution is an effective corrosion-inhibiting concentration, although higher concentrations can be used when conditions make them desirable, with a concentration between 0.05 percent to 0.75 percent by weight being of most general use, at elevated temperatures, e.g. in the neighborhood of 200° F. The acidic solution can be dilute or concentrated and can be of any of the concentrations used in treating metals, e.g. ferrous metals, or for operations involving contact of acidic solutions with such metals, e.g. oil-well acidizing, and the like, for example 5 to 80 percent. In most operations of the character indicated, acid concentrations of 10-15 percent by weight are employed, and non-oxidizing inorganic acids are used. However, it is not intended to limit the invention to any specific use of acidic solutions or with respect to any specific metal or acid.
While the inhibitor mixture of this invention can be prepared from individual quantities of 1-hexyn-3-ol and 5-decyn-4,7-diol, a particularly advantageous source of these two chemicals is the reaction mixture obtained by the ethynylation of butyraldehyde with acetylene, using the well-known reaction wherein butyraldehyde and acetylene are reacted in the presence of a catalyst in an inert solvent medium, most commonly an ether, the reaction being carried out at various temperatures but which generally lie in the range of 0° to 50° C. This reaction, which was originally proposed by Favorskii, and has been improved upon by several other workers, is well-described in the literature, and reference is made, for example, to the book "Acetylenic Compounds" by Thomas F. Rutledge (Reinhold Book Corp., 1968), especially pages 146 to 149, and to the footnotes referred to therein. In a typical operation the aldehyde and the acetylene are reacted in an acetal or an ether as the reaction medium at substantially atmospheric pressure at a temperature of 20° to 30° C., using solid KOH as catalyst in amounts which are substantially stoichiometric (usually slightly in excess) with respect to the aldehyde, the acetylene being in excess of the stoichiometric quantity. The thus-produced mixture of 1-hexyn-3-ol and 5-decyn-4,7-diol will vary in composition somewhat, depending upon the specific reaction conditions, but the ratio of 1-hexyn-3-ol to 5-decyn-4,7-diol usually lies within the range of 5:1 to 1:4, and most commonly is about 1:1 to 2:1. The inert reaction medium is readily separated by distillation, but minor amounts of the solvent, e.g. up to 10 percent by weight or more, may be present and such presence does not interfere with the activity of the acetylenic hydroxy compounds. The mixture may also contain minor amounts of by-products produced by condensation, aldolization, or other reactions and are also unobjectionable. Such by-products may range up to 10 percent by weight but are usually less than about 5 percent by weight.
It will be understood that a reaction mixture of the character indicated is particularly attractive from a commercial standpoint since purification of the product of the ethynylation reaction is not required, yet the important benefits of the combination of 1-hexyn-3-ol with 5-decyn-4,7-diol in the mixture of this invention are realized in the critical area of corrosion inhibition, i.e. high acid concentrations and high temperatures.
The following experiments will serve to illustrate the effectiveness of the corrosion-inhibiting mixture of this invention under severe corrosion conditions encountered in practical application:
The method used to determine the inhibiting properties of the mixture of the invention employs test specimens or coupons. To prepare the coupons, they are wiped with acetone to remove any residual oils or grease, and pickled for 1 minute in 10 percent hydrochloric acid to eliminate any scale and surface film. After pickling, the coupons are dipped in sodium bicarbonate solution, rinsed well in tap water, rinsed in distilled water, and finally dried with acetone. The clean and dry specimens are then weighed to the nearest 0.1 mg. In carrying out the evaluation, hydrochloric acid of 15 percent by weight concentration is used in order to duplicate oil-well acidizing conditions. The inhibitor mixture is added to 4 oz. test bottles, 100 ml. of the acid then added to each bottle; and the mixture shaken vigorously. The bottles are suspended in a constant-temperature bath consisting of a bell jar filled with ethylene glycol and equipped with a stirrer. The temperature is regulated to maintain the samples at 200° ± 2° F. The bottles are placed in the bath one-half hour before the test coupons are added to insure temperature equilibrium. The weighed coupons, in duplicate, are then supported on glass hooks in the test bottles and the bottles are covered with watch glasses during the testing period of 16 hours. At the end of the testing period, the bottles are removed from the bath, the coupons withdrawn, rinsed with water, sodium bicarbonate solution, distilled water, and dried in acetone, then weighed to measure weight loss. Corrosion-inhibiting properties are conveniently expressed as percent inhibition, using the following formula:
When the acid concentration and temperature are such that the blank would be completely consumed by the acid in the absence of an inhibitor, the foregoing formula can be expressed as:
EXAMPLE
Using the test procedure described above, the inhibitor mixture of the invention was evaluated for its effectiveness in preventing corrosion of steel, using 1 in. × 2 in. coupons cut from a 1/16-in. sheet of a mild steel having the following typical analysis: 0.15 percent max. carbon, 0.30-0.60 percent manganese, 0.04 percent phosphorous, 0.05 percent sulfur, the balance iron. Each test sample was prepared by adding equal parts by weight of urea and a mixture comprising 1-hexyn-3-ol and 5-decyn-4,7-diol in a 2:1 weight ratio to the 15 percent hydrochloric acid, the combined mixture of the invention, i.e. the urea plus the acetylenic carbinol-glycol mixture being added in the amount of 0.5 percent by weight of the acid. Each sample was evaluated for corrosion inhibiting activity in contact with the steel coupon. At the same time, a blank test, using the same acid but without any inhibitor, was made. The following results were obtained:
% Inhibition Inhibitor 16 hrs. Hexynol + 5-decyn-4,7-diol + urea 99 + None 0
The foregoing evaluation was repeated except that the weight ratio of the carbinol-glycol mixture to the urea was 4:1. Again a percent inhibition of 99 + was recorded.
These tests show the positive action of the combination of hexynol, 5-decyn-4,7-diol, and urea in accordance with this invention, in inhibiting metal corrosion of commercial steel in an acid solution of high concentration at an elevated temperature only slightly below the boiling point of water, over a prolonged period of time. The results shown in the foregoing test data are obtained when an ethynylation reaction mixture comprising 1-hexyn-3-ol and 5-decyn-4,7-diol of the type described above is employed in combination with the urea. When the urea is directly added to the acetylenic carbinol-glycol mixture, it is advantageous first to dissolve it in a small amount of water, e.g. a 25 percent aqueous solution, and then add the solution to the acetylenic alcohols.
It will be apparent that various changes and modifications may be made in the operations described in the foregoing without departing from the scope of the invention as defined in the appended claims. It is intended, therefore, that all matter contained in the above description of the invention shall be interpreted as illustrative only and not as limitative.