CA1286490C - Phosphonic acid/phosphate mixtures for controlling corrosion of metal and inhibiting calcium phosphate precipitation - Google Patents
Phosphonic acid/phosphate mixtures for controlling corrosion of metal and inhibiting calcium phosphate precipitationInfo
- Publication number
- CA1286490C CA1286490C CA000526578A CA526578A CA1286490C CA 1286490 C CA1286490 C CA 1286490C CA 000526578 A CA000526578 A CA 000526578A CA 526578 A CA526578 A CA 526578A CA 1286490 C CA1286490 C CA 1286490C
- Authority
- CA
- Canada
- Prior art keywords
- methylene phosphonic
- phosphonic acid
- mixture
- orthophosphate
- water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
- C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
- C02F5/10—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances
- C02F5/14—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances containing phosphorus
- C02F5/145—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents using organic substances containing phosphorus combined with inorganic substances
-
- 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
- C23F14/00—Inhibiting incrustation in apparatus for heating liquids for physical or chemical purposes
- C23F14/02—Inhibiting incrustation in apparatus for heating liquids for physical or chemical purposes by chemical means
Abstract
ABSTRACT OF THE DISCLOSURE
A method of controlling the corrosion of a metal surface in contact with an aqueous system while at the same time preventing the precipitation of potentially scale-forming calcium phosphate.
The water in such systems is treated with a combination of a source of orthophosphate ion and a mixture of methylene phosphonic acid derivatives of C6 diamines, or the salts thereof.
A composition for preventing the precipitation of calcium phos-phate containing a mixture of methylene phosphonic acid deriva-tives of C6 diamines or the salts thereof.
A method of controlling the corrosion of a metal surface in contact with an aqueous system while at the same time preventing the precipitation of potentially scale-forming calcium phosphate.
The water in such systems is treated with a combination of a source of orthophosphate ion and a mixture of methylene phosphonic acid derivatives of C6 diamines, or the salts thereof.
A composition for preventing the precipitation of calcium phos-phate containing a mixture of methylene phosphonic acid deriva-tives of C6 diamines or the salts thereof.
Description
BAC~GROUND OF THE INVENTION
This invention relates to a method for inhibiting the corro-sion of metal surfaces, preferably iron and iron alloys and more preferably low carbon steel, in contact with an aqueous system, S preferably a cooling water or related water-handling system, and preventing the precipitation in such systems of scale-forming calcium salts, particularly calcium phosphate.
Aqueous systems, such as cooling water and related water-handling systems, include cooling towers and associated pumps, heat exchangers, and pipelines, heating systems, gas scrubbing systems and other similar systems. Problems commonly encountered in these water handling systems include not only the electrochemical corrosion of iron and iron alloys in contact with i the circulating water but a~so the precipitation of potentially scale-forming calcium salts. These two processes are, in fact, very closely related because methods of chemical treatment in-tended to control one of these problems often aggravate the dif-ficulty caused by the other.
However, we have discovered a method and composition for treating the water in such systems that can both inhibit corro-sion and prevent the precipitation of scale-forming calcium salts. It is believed that our method and composition can be ef-fective over a wider range of water conditions than are the meth-ods of the prior art, and the objectives of the invention can be ~28~
achieved without the negative impact on the environment of some o~ the prior methods.
For many years, the most common method of controlling corro-sion in cooling water and related water-handling systems was to treat the water with hexavalent chromium salts, such as sodium chromate. At the same time, scaling due to sli~htly soluble cal-cium salts was prevented by treating the water with mineral acids, such as sulfuric acid, to keep the pH low enough to pre-vent the precipitation of the scale-forming calcium salts. Im-provements in this technology over the years included the use of zinc salts and phosphates in combination with the chromates, which could provide good corrosion control at reduced chromate concentrations. However, because of environmental concerns over the discharge of even small~amounts~of hexavalent chromium in cooling water effluents, new methods continued to be sought that would provide total corrosion inhibition without the use of hexavalent chromium.
Some of the ways that this has been achieved include the use of various combinations of zinc salts, phosphates, poly-phosphates, and organic phosphonic acid derivatives and their salts. ~owever, all of these methods in the prior art have cer-tain disadvantages, such as requiring close control of the pH to keep it within a very narrow range or using special additives or dispersants to prevent the precipitation of scale-forming salts like calcium phosphate.
~LX~6~9~3 One commonly used method of cooling water treatment is ~e-scribed by Ge qer and May in U.S. 4,305,568. In the 5~19~ d ~y patent, it is said at col. 10, beginning at line 9, that the aqueous medium must have A pH of 5.5 and above and must also con-tain calcium ion concentrations, preferably about 15 parts per million. The compositions disclosed in the Geiqer and Mav patent contain a water-soluble orthophosphate, a water-soluble polymer composed primarily of moieties derived from acrylic acid and moieties derived from an hydroxy lower alkyl acrylate.
Water-soluble organo-phosphonic acid derivatives may also be in-cluded.
In the Geiqer and May method, as practiced, relatively high concentrations of the orthophosphate are maintained in the circulating water to inhibit corrosion by passivating ferrous alloy surfaces in contact with the water, and the formation of calcium phosphate scale is inhibited by the simultaneous use of the copolymers of acrylic acid and hydroxyalkyl acrylates. The latter copolymers were reported by Godlewski in U.S. 4,029,577 to be effective antiprecipitants for calcium phosphate. As we un-derstand it, the main disadvantages of the method of Geiqer and May in practice are that it requires the use of relatively high concentrations of orthophosphate and careful control of the cal-cium concentration in the system. Such requirements complicate trouble-free control of the system.
Another type of method of corrosion control that avoids the problem of calcium phosphate deposition involves the use of what is known in the art as "all organic" corrosion inhibitors. Tech-nology of this type is described in U.S. 4,317,744 and U.S.
4,406,811. In this type of method, corrosion control is obtained by using organic phosphonic acids (or blends of phosphonic acids~
along with aromatic azoles and various water-soluble polymers (polyacrylic acid, polymethacrylic acid). No calcium phosphate precipitation can occur because no orthophosphate is present in the treatment. However, as we understand it, in practice, meth-ods of this type give limited corrosion protection and require relatively large amounts of inhibitor, and thus have limited eco-nomic feasibility.
Despite the limitations of the existing "all organic" inhib-itors, organic phosphonic acids and phosphonates have been found effective as corrosion inhibitor components when used in combina-tion with other substances. The evolution of phosphonic acid corrosion control technology began with the direct application of phosphonic acids or their water-soluble s~lts as corrosion inhib-itors, The disadvantages of this technology were twofold.
First, the phosphonic acids or phosphonates commonly available required very high feedrates to obtain acceptable corrosion inhi-bition. In addition, locali~ed corrosion, known in the art as ; "pitting", could result from insufficient passivation due to poor film formation when the phosphonic acids were used alone.
~3 , This problem was recognized by Carter (U.S. 3,837,803~ who ¦ overcame it by utilizing orthophosphate with a water-soluble organo-phosphonic acid compound selected from a wide range of phosphonic acids. However, Carter acknowledged two significant restrictions in the use of his method. First, as explained at column 3, beginning at line 4, the cooling water has to contain at least 50 ppm of calcium ion to allow the use of this method without the supplemental addition of a metal cation of the group zinc, nickel, co~alt, cadmium or chromium. The undesirable envi-ronmental impact of these heavy metal cations is significant, and, as Carter pointed out, governmental regulations often re-quire that they be avoided in effluents. In the teachings of Carter at column 3, one way of getting around the use of these metal cations, at least in systems containing more than 4 ppm of calcium, is to maintain system pH in the range of 8.5 to 9Ø
However, as pointed out by Carter at column 3, lines 34-37, this high pH can lead to the delignification of cooling tower wood and may require the supplemental feed of alkali, both of which are undesirable.
A second major drawback of the method of Carter is his statement at col. 3, lines 60-65, that it is desirable to use very tight pH controls when calcium concentrations exceed 80 ppm.
Specifically, Carter suggests a pH between 7.1 and 7.5 when cal-cium ion exceeds this level. This is a very significant ~ 9~3 disadvantage in almost all systems, because calcium levels often vary over broader ranges than 50 to ~0 ppm. Carter requires one fnarrow pH range for calcium concentrations below 50 ppm and sug-gests a different but still narrow pH range for calcium concen-trations above 80 ppm. Also, when calcium is above 80 ppm~ the suggested restriction of pH to the 7.1 - 7.5 range is difficult to maintain on a consistent basis in most practical operating cooling water systems.
Other combinations of phosphonic acids and inorganic com-pounds are also mentioned in the prior ar~. Polyphosphates and polyacrylic acids were combined with phosphonic acids by Gaupp (U.S. 3,992,318). Polyphosphates and polymaleic anhydride or polymaleic acid were combined with phosphonic acids by Sexsmith (U.S. 4,105,581). However,`because polyphosphates revert in time to orthophosphates, it is believed that, in practice, these meth-ods also cause problems with calcium phosphate precipitation.
We have discovered a new way of overcoming the problems of, and obviating the disadvantages of the prior art. We have found that use of a certain combination of phosphonic acids (or their water-soluble salts) along with orthophosphate, preferably in low concentrations, will provide good corrosion inhibition and simul-taneously inhibit the precipitation of calcium phosphate. The present invention, moreover, is effective in both high and low pH
waters and in waters with either low or high concentrations of calcium.
SUMMARY OF THE INVENTION
The present inventior. is directed to a method for control-ling corrosion of metal surfaces in contact with an aqueous sys-tem, and simultaneously inhibiting the precipitation of calcium phosphate, comprising the step of treating the aqueous system with a source of orthophosphate ion and a mixture of (1) 1,2-diaminocyclohexanetetrakis(methylene phosphonic acid) or a salt thereof; (2) 2-methyl-1,5-pentanediaminetetrakis(methylene phosphonic acid) or a salt thereof; and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid), or a salt thereof in amounts effective to control corrosion of the metal surfaces in contact with the aqueous system and to inh;bit the precipitation of calcium phosphate.
The present invention àlso relates to a composition for con-trolling corrosion of a metal surface in contact with an aqueous system and simultaneously inhibiting the precipitation of calcium phosphate comprising a source of orthophosphate ion and a mixture of (1) 1,2-diaminocyclohexanetetrakis(methylene phosphonic acid) or a salt thereof; (2) 2-methyl-1,5-pentanediaminetetrakis (methylene phosphonic acid) or a salt thereof: and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid), or a salt thereof, in amounts effective to control corrosion of the metal surface in contact with the aqueous system and to inhibit the precipitation of calcium phosphate.
~ 28~
The present invention also relates to a composition fur pr~-venting the precipitation of calcium phosphate comprisin~ a mix-ture of (1) 1,2-diaminocyclohexanetetrakis(methylene phosphonic acid) or a salt thereof; (2) 2-methyl-1,5-pentanediaminetetrakis(methylene phosphonic acid) or a salt thereof; and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid) or a salt thereof in amounts effective to pre-vent precipitation of calcium phosphate.
Low concentrations of orthophosphate can advantageously be used in the present invention, which reduces the chance of cal-cium phosphate scale formation. In addition, the combination of phosphonic acids utilized in the present invention is effective both as a corrosion inhibitor and as an antiprecipitant for in-hibiting the precipitation of calcium phosphate and other insolu-ble calcium salts. Unlike the method of Carter as taught in U.S.
This invention relates to a method for inhibiting the corro-sion of metal surfaces, preferably iron and iron alloys and more preferably low carbon steel, in contact with an aqueous system, S preferably a cooling water or related water-handling system, and preventing the precipitation in such systems of scale-forming calcium salts, particularly calcium phosphate.
Aqueous systems, such as cooling water and related water-handling systems, include cooling towers and associated pumps, heat exchangers, and pipelines, heating systems, gas scrubbing systems and other similar systems. Problems commonly encountered in these water handling systems include not only the electrochemical corrosion of iron and iron alloys in contact with i the circulating water but a~so the precipitation of potentially scale-forming calcium salts. These two processes are, in fact, very closely related because methods of chemical treatment in-tended to control one of these problems often aggravate the dif-ficulty caused by the other.
However, we have discovered a method and composition for treating the water in such systems that can both inhibit corro-sion and prevent the precipitation of scale-forming calcium salts. It is believed that our method and composition can be ef-fective over a wider range of water conditions than are the meth-ods of the prior art, and the objectives of the invention can be ~28~
achieved without the negative impact on the environment of some o~ the prior methods.
For many years, the most common method of controlling corro-sion in cooling water and related water-handling systems was to treat the water with hexavalent chromium salts, such as sodium chromate. At the same time, scaling due to sli~htly soluble cal-cium salts was prevented by treating the water with mineral acids, such as sulfuric acid, to keep the pH low enough to pre-vent the precipitation of the scale-forming calcium salts. Im-provements in this technology over the years included the use of zinc salts and phosphates in combination with the chromates, which could provide good corrosion control at reduced chromate concentrations. However, because of environmental concerns over the discharge of even small~amounts~of hexavalent chromium in cooling water effluents, new methods continued to be sought that would provide total corrosion inhibition without the use of hexavalent chromium.
Some of the ways that this has been achieved include the use of various combinations of zinc salts, phosphates, poly-phosphates, and organic phosphonic acid derivatives and their salts. ~owever, all of these methods in the prior art have cer-tain disadvantages, such as requiring close control of the pH to keep it within a very narrow range or using special additives or dispersants to prevent the precipitation of scale-forming salts like calcium phosphate.
~LX~6~9~3 One commonly used method of cooling water treatment is ~e-scribed by Ge qer and May in U.S. 4,305,568. In the 5~19~ d ~y patent, it is said at col. 10, beginning at line 9, that the aqueous medium must have A pH of 5.5 and above and must also con-tain calcium ion concentrations, preferably about 15 parts per million. The compositions disclosed in the Geiqer and Mav patent contain a water-soluble orthophosphate, a water-soluble polymer composed primarily of moieties derived from acrylic acid and moieties derived from an hydroxy lower alkyl acrylate.
Water-soluble organo-phosphonic acid derivatives may also be in-cluded.
In the Geiqer and May method, as practiced, relatively high concentrations of the orthophosphate are maintained in the circulating water to inhibit corrosion by passivating ferrous alloy surfaces in contact with the water, and the formation of calcium phosphate scale is inhibited by the simultaneous use of the copolymers of acrylic acid and hydroxyalkyl acrylates. The latter copolymers were reported by Godlewski in U.S. 4,029,577 to be effective antiprecipitants for calcium phosphate. As we un-derstand it, the main disadvantages of the method of Geiqer and May in practice are that it requires the use of relatively high concentrations of orthophosphate and careful control of the cal-cium concentration in the system. Such requirements complicate trouble-free control of the system.
Another type of method of corrosion control that avoids the problem of calcium phosphate deposition involves the use of what is known in the art as "all organic" corrosion inhibitors. Tech-nology of this type is described in U.S. 4,317,744 and U.S.
4,406,811. In this type of method, corrosion control is obtained by using organic phosphonic acids (or blends of phosphonic acids~
along with aromatic azoles and various water-soluble polymers (polyacrylic acid, polymethacrylic acid). No calcium phosphate precipitation can occur because no orthophosphate is present in the treatment. However, as we understand it, in practice, meth-ods of this type give limited corrosion protection and require relatively large amounts of inhibitor, and thus have limited eco-nomic feasibility.
Despite the limitations of the existing "all organic" inhib-itors, organic phosphonic acids and phosphonates have been found effective as corrosion inhibitor components when used in combina-tion with other substances. The evolution of phosphonic acid corrosion control technology began with the direct application of phosphonic acids or their water-soluble s~lts as corrosion inhib-itors, The disadvantages of this technology were twofold.
First, the phosphonic acids or phosphonates commonly available required very high feedrates to obtain acceptable corrosion inhi-bition. In addition, locali~ed corrosion, known in the art as ; "pitting", could result from insufficient passivation due to poor film formation when the phosphonic acids were used alone.
~3 , This problem was recognized by Carter (U.S. 3,837,803~ who ¦ overcame it by utilizing orthophosphate with a water-soluble organo-phosphonic acid compound selected from a wide range of phosphonic acids. However, Carter acknowledged two significant restrictions in the use of his method. First, as explained at column 3, beginning at line 4, the cooling water has to contain at least 50 ppm of calcium ion to allow the use of this method without the supplemental addition of a metal cation of the group zinc, nickel, co~alt, cadmium or chromium. The undesirable envi-ronmental impact of these heavy metal cations is significant, and, as Carter pointed out, governmental regulations often re-quire that they be avoided in effluents. In the teachings of Carter at column 3, one way of getting around the use of these metal cations, at least in systems containing more than 4 ppm of calcium, is to maintain system pH in the range of 8.5 to 9Ø
However, as pointed out by Carter at column 3, lines 34-37, this high pH can lead to the delignification of cooling tower wood and may require the supplemental feed of alkali, both of which are undesirable.
A second major drawback of the method of Carter is his statement at col. 3, lines 60-65, that it is desirable to use very tight pH controls when calcium concentrations exceed 80 ppm.
Specifically, Carter suggests a pH between 7.1 and 7.5 when cal-cium ion exceeds this level. This is a very significant ~ 9~3 disadvantage in almost all systems, because calcium levels often vary over broader ranges than 50 to ~0 ppm. Carter requires one fnarrow pH range for calcium concentrations below 50 ppm and sug-gests a different but still narrow pH range for calcium concen-trations above 80 ppm. Also, when calcium is above 80 ppm~ the suggested restriction of pH to the 7.1 - 7.5 range is difficult to maintain on a consistent basis in most practical operating cooling water systems.
Other combinations of phosphonic acids and inorganic com-pounds are also mentioned in the prior ar~. Polyphosphates and polyacrylic acids were combined with phosphonic acids by Gaupp (U.S. 3,992,318). Polyphosphates and polymaleic anhydride or polymaleic acid were combined with phosphonic acids by Sexsmith (U.S. 4,105,581). However,`because polyphosphates revert in time to orthophosphates, it is believed that, in practice, these meth-ods also cause problems with calcium phosphate precipitation.
We have discovered a new way of overcoming the problems of, and obviating the disadvantages of the prior art. We have found that use of a certain combination of phosphonic acids (or their water-soluble salts) along with orthophosphate, preferably in low concentrations, will provide good corrosion inhibition and simul-taneously inhibit the precipitation of calcium phosphate. The present invention, moreover, is effective in both high and low pH
waters and in waters with either low or high concentrations of calcium.
SUMMARY OF THE INVENTION
The present inventior. is directed to a method for control-ling corrosion of metal surfaces in contact with an aqueous sys-tem, and simultaneously inhibiting the precipitation of calcium phosphate, comprising the step of treating the aqueous system with a source of orthophosphate ion and a mixture of (1) 1,2-diaminocyclohexanetetrakis(methylene phosphonic acid) or a salt thereof; (2) 2-methyl-1,5-pentanediaminetetrakis(methylene phosphonic acid) or a salt thereof; and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid), or a salt thereof in amounts effective to control corrosion of the metal surfaces in contact with the aqueous system and to inh;bit the precipitation of calcium phosphate.
The present invention àlso relates to a composition for con-trolling corrosion of a metal surface in contact with an aqueous system and simultaneously inhibiting the precipitation of calcium phosphate comprising a source of orthophosphate ion and a mixture of (1) 1,2-diaminocyclohexanetetrakis(methylene phosphonic acid) or a salt thereof; (2) 2-methyl-1,5-pentanediaminetetrakis (methylene phosphonic acid) or a salt thereof: and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid), or a salt thereof, in amounts effective to control corrosion of the metal surface in contact with the aqueous system and to inhibit the precipitation of calcium phosphate.
~ 28~
The present invention also relates to a composition fur pr~-venting the precipitation of calcium phosphate comprisin~ a mix-ture of (1) 1,2-diaminocyclohexanetetrakis(methylene phosphonic acid) or a salt thereof; (2) 2-methyl-1,5-pentanediaminetetrakis(methylene phosphonic acid) or a salt thereof; and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid) or a salt thereof in amounts effective to pre-vent precipitation of calcium phosphate.
Low concentrations of orthophosphate can advantageously be used in the present invention, which reduces the chance of cal-cium phosphate scale formation. In addition, the combination of phosphonic acids utilized in the present invention is effective both as a corrosion inhibitor and as an antiprecipitant for in-hibiting the precipitation of calcium phosphate and other insolu-ble calcium salts. Unlike the method of Carter as taught in U.S.
3,837,803, the present invention, utilizing a source of orthophosphate ion and the mixture of methylene phosphonic acids described above, does not require close control of the pH or the supplemental addition of heavy metal cations. Unlike the method of Geiqer and May, as well as that of Carter, the present inven-tion does not require close control of the calcium concentration.
DET~ILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The metal surface may be an iron or iron alloy surface, preferably a ferrous alloy. More preferably, the metal surface is a low carbon steel surface. Preferably, the aqueous system is a cooling water system~
The organic phosphonic acids utilized in this invention may be manufactured from the corresponding diamines. These diamines all have 6 carbon atoms in their structures and include 1,2-diaminocyclohexane, 2-methyl-l,S-pentanediamine, and 1,6-hexanediamine, all of which are commercially available. The phosphonic acid derivatives are produced through the following phosphonomethylation reaction: !
~MH2 N [ CH2P (O) (OH) 2 ] 2 R + 4HCHO + 4H3PO3 ~ R \ + 4H20 2 N[CH2P(O) (H)2]2 where R represents the C6 ràdicals of the diamines listed above.
Hydrochloric acid is usually added to the reaction mixture to suppress the oxidation of phosphite to phosphate. As recited above, the phosphonic acids may be used in salt form. Preferred lS salts include the sodium, potassium~ and ammonium salts of these acids, which salts are formed by partially or completely neu-tralizing them with sodium hydroxide, potassium hydroxide, or ammonium hydroxide, respectively.
To accomplish the objectives of this invention, a mixture of the methylene phosphonic acids and/or their salts is used in com-bination with a source of orthophosphate ion to treat the water _g_ in aqueous system5. The amount of phosphonic acid mixture (100 basis) added to the water should be in the range o~ 1 to 100 parts per million (ppm), preferably from 3 to 100 ppm, more pref- ;
erably from 3 to 50 ppm, most preferably from 9-15 ppm, based on ;
the total weight of water in the system. The amount of orthophosphate compound added should be sufficient to provide 0.5 to 50 ppm orthophosphate as PO4, preferably from 1 to 9 ppm, more preferably from 3 to 5.2 ppm, based on the total weight of water in the system.
The weight ratio of the orthophosphate ion to the phosp~onic acid mixture is 1:200 to 50:1, preferably 0.1:1 to 10:1, more preferably 1:2.4 to 1:3.3.
Represen,ative sources of orthophosphate ion suitable for use in this invention inclu~e phosphoric acid (orthophosphoric acid), the sodium orthophosphates, the potassium orthophosphates, the lithiurn orthophosphates, the ammonium orthophosphates, the organic amine salts of phosphoric acid, and the organic orthophosphates set forth in U.S. Patent 3,510,436.
Exemplary lithium, sodium, potassium and ammonium orthophosphates include lithium di acid phosphate, trisodium orthophosphate, disodium orthophosphate, monosodium orthophosphate, hemisodium orthophosphate, tripotassium orthophosphate, dipotassium orthophosphate, monopotassium orthophophate, triammonium orthophosphate, diamrnoniurn orthophosphates and monoarnmonium orthophosphate.
~8~9~3 The methylene phosphonic acid mixture and the source of orthophosphate ion can be added separately and individually to the water system to be treated, but it is preferable to mix all of these materials prior to addition to the water. If necessary, the combined mixture can be diluted with water and/or stabilized by the additional of adjuvants to keep the mixture from separating prior to its addition to the water system to be treated. Other compatible water treatment components, such as biocides, antifoulants, and dispersants, can also be added to the mixture.
In a preferred embodiment of the invention, the methylene phosphonic acid mixture produced as described above is analyzed for both total phosphonic acids and total inorganic phosphate.
Then phosphoric acid is addèd to the mixture until the concentra-tion of orthophosphate as P04 reaches the desired ratio to the total weight of methylene phosphonic acids in the mixture. This mixture can then be diluted with water to any convenient use con-centration. The mixture can also be formulated with other types of water treatment compounds.
To disclose the nature of this inverltion even more clearly, the following illustrative examples will be given. It is under-stoocl, however, that the invention is not to be limited to the specific conditions or details set forth in these represen~ative examples.
In determining the corrosion inhibition provided by the com-positions and methods of our invention one of the techniques used was the Spinning Disk Test Method, a testing procedure that is widely employed, with many variations, in evaluating the effec-tiveness of corrosion inhibitors for cooling water treatment. In the Spinning Disk Test Method, a plastic disk is attached to the end of a plastic stirrer shaft. Metal test coupons are mounted vertically on this disk, usually two coupons per test. The shaft is fastened vertically in a stirrer motor chuck, and the disk and attached coupons ar-e immersed in water contained in a 4-liter plastic cylindrical tank, which is surrounded by a constant tem-perature bath.
The water volume in the cylindrical tank is maintained at a level that will keep the di'sk and coupons covered when the stirrer is started and the disk is rotated. The rotation speed of the disk is controlled at 100 rpm so that erosion and velocity effects are kept equal in all tests. The water is automatically replenished from a reservoir, with the addition being controlled with a timer and solenoid valve, at the rate of 60 milliliters of water added every 30 minutes, Excess water overflows through a special outlet to a drain. The cylindrical tank is kept covered except for the hole for the stirrer shaft to minimize evaporation losses.
The composition of the water is cGntrolled to simulate the water conditions in typical cooling water and other water-handling systems. The inhibitor being tested is added to this water in an appropriate concentration. For control pur-poses, tests are run in water with the same composition to which no inhibitor has been added.
The metal coupons are cleaned and weighed on an analytical balance before and after exposure to the water. As a rule, the exposure time is at least five days (120 hours). The corrosion rate is calculated from the loss in weight of the coupons, the exposed area of the coupons, the density of the metal, and the time of exposure. The rate is expressed as mils (of thickness) lost per year (mpy). The percent inhibition o~ corrosion obtained with a given concentration of an inhibitor is calculated from the corrosion rate with this concentration of inhibitor added to the water compared to the corrosion rate in the same water containing no inhibitor, using the following formula:
% Corrosion Inhibition =
(mpy Corrosion w/o Inhibitor - mpy Corrosion with Inhibitor) x 100 _ __________ _____________________________________________________ (mpy Corrosion w/o Inhibitor) Another method we used in evaluating corrosion inhibition efficacy involved treating the water in a Continuous Circulation Test Loop with the corrosion inhibitors to be checked. The Test Loop system consists of a 100-gallon reservoir, a circulation pump, a flow control valve, a rotameter, pipelines in which cor-rosion test coupons are mounted, and instruments for controlling the temperature and pH and monitoring other system variables such as the dissolved oxygen level. The water is pumped from the res-ervoir at a controlled rate through the pipeline containing the test coupons and then back to the reservoir. The corrosion rate in this system is determined by the weight loss of the test cou- j pons, and the calculation of the percent corrosion inhibition is done in the same way as described for the Spinning Disk Test Method.
A l-liter, 3-neck glas~ reaction flask was fitted with an agitator, a reflux condenser, and a thermometer and placed in a cooling water bath to which ice could be added as needed to con-trol the temperature of the contents of the flask. To this flask were charged 234.3 9 of 70% phosphorous acid. To the acid were added, slowly to avoid overheating, 57.5 9 o~ a mixture of diamines composed of approximately equimolar amounts of 1l6-diaminocyclohexane, 2 methyl-1,5-pentanediamine, and 1-6-hexanediamine. The temperature was controlled during the re-action to keep it below 70C, and the mixture was stirred contin-uously. After the diamines were added, 98.6 9 of concentrated (37.5%) hydrochloric acid were added to the reaction flask, and the mixture was heated to 90-95C.
Next, 174.3 9 of a 37% formaldehyde solution were added slowly to the reaction mixture over a period of 1-3/4 hours. The mixture was stirred and maintained at 90-95C for an additional 2 hours. The mixture was allowed to cool to 25C be~ore being ana-lyzed for its total phosphonic acid content and orthophosphate content. The reaction yielded 560 9 of solution containing 35.8%
by weight of C6 diamine tetrakis(methylene phosphonic acid) mix-ture, based on an average molecular weight of 492, and 0.15%
orthophosphate as P04. This solution was used as the source of the phosphonic acids in the tests described in the following e~-amples.
A combination of ortho~hosphate with the phosphonic acids prepared as described in Example 1 was tested as a corrosion in-hibitor using the Spinning Disk Test Method previously described.
The source of the orthophosphate ions was phosphoric acid, which was blended with the phosphonic acids prior to addition to the water. The synthetic cooliny water ion concentrations, test con-ditions, and results of this evaluation are shown in Table 1.
The concentrations of phosphonic acids and orthophosphate are expressed as the amounts of active ingredients present in the water. The results show that very low concentrations of a corro-sion inhibitor prepared according to our invention provide excel-lent corrosion protection to mild steel in a high calcium, high pH water with a composition typical of a large number of practi~
,cal operating cooling water systems. A concentration of the cor-rosion inhibitor equivalent to 14.6 mg/L (ppm) of the diamine ,phosphonic acids and 4.6 mg/L orthophosphate as PO4, provided 96.2% corrosion inhibition, and a concentration equivalent to 9.7 mg/L of the phosphonic acids and 3.0 mg/L PO4 provided over 93% corrosion inhibition.
_________ _________~______ I
ION CONCENTRATIO~ :
Calcium as Ca ~+ 80 mg/L (pp~) Magneslum aB M8 60 mg/L
Bicarbonate lon as HC03 125 mg/L
Chloride ion a~ Cl 300 mg/L
Sulfate as S04 300 mg/L
TEST CONDI~IONS:
p~ 8.0 Temporature 40 C
Rota~ional Speed ~ 100 rpm Duratlon of Test 144 hours Test coupons: c-1010 low carbon steel TEST RESULTS:
Phosphonlc Acids ~ Corrosion Rate mg/L mg/L mpy O (Control) 0 49.7 14.6 4.6 1.9 9.7 3.0 3.2 4,9 1.5 7.6 _______________________________________________________________________ To demonstrate the effectiveness of the corrosion inhibitors of our invention in a low calcium, low pH system, a composition containing the phosphonic acids and phosphate was tested in the Continuous Circulation Test Loop described previously. In the ~3649~
Test Loop, an automatic controller keeps the pH at a fixed value throughout the period of the test. The composition tested again used the phosphonic acids prepared as described in Example l to which was added phosphoric acid as the orthophosphate source.
The synthetic cooling water ion concentratiOnS, test conditions, and results of this evaluation are shown in Table ~. These results clearly demonstrate that excellent inhibition of corro-sion can be obtained in this rather corrosive water with a rela-tively low concentration of a corrosion inhibitor prepared according to our invention. The corrosion rate of mild steei was reduced from 63 mpy to 2.8 mpy, which is equivalent to 95.6% cor-rosion inhibition.
_____________________________ ~________________________________________ ION CONCENTRATIO ~ :
Calcium as Ca +~10 mg/L (ppm) Magne~lum as Mg 60 mg/L
8icarbonste lon as HC03125 mg/L
Chloride lon as Cl 300 mg/L
Sulfate as S04 300 mg/L
TEST CONDITIONS:
p~l 7.0 Temperature 40 C
Water velocl~y (over coupons) 3.6 ft/sec Duratlon of Test 143 hours Test coupons: c-1010 low carbon steel TEST RESULTS:
Phosphonlc aclds P04 Corroslon Rate mg/L mg/L mpy O (Control) 0 63.0 32.5 11.5 2.8 __________________________________________________________________.____ EX~MPLE 4 The effectiveness of the combination of phosphonic acids of our invention in preventing the precipitation of calcium phos-phate was demonstrated by an antiprecipitation test. The combi-nation of phosphonic acids prepared as described in Example 1, designated Composition A, was used for these tests. For compari-son, similar tests were run with two other in~ividual phosphonic acids that are widely used in the treatment of cooling water.
These are aminotris(methylene phosphonic acid), commonly called AMP, and l-hydroxyethylidene-l,l-diphosphonic acid, commonly called HEDP. Calcium phosphate precipitation inhibition was mea- , sured by adding a calcium chloride solution and a disodium hydro- j gen phosphate solution in amounts that provided 160 mg/L calcium ion as Ca and approximately 10 mg/L phosphate ion as P04. The appropriate amount of phosphonic acid inhibitor was added, and the solution pH was adjusted to 8.5. The treated sample was capped and placed in an oven at 50C for 24 hours. After removal from the oven, a portion of the supernatant liquid from each bot-tle was taken, filtered through a 0.45 micrometer pore size fil-ter to remove any precipitated calcium phosphate, and analyzed for orthophosphate. As a "Blank", a sample was prepared in the same way except that the pH was not adjusted to the alkaline side but kept on the acid side so that no precipitation would occur.
The percent inhibition of precipitation was calculated from the amount of phosphate.added (~lank) and the difference between the amount of phosphate in solution in samples without inhibitor (Control) compared to those with inhibitor, using the following formula:
% Inhibition = (mg/L PO~ with Inhibitor - mg/L P04 in Control) x 100 (mg/L P04 in Blank - mg/L P04 in Control) The results of these antiprecipitation tests, which are shown in Table 3, clearly demonstrate that the combination of phosphonic acids of the present invention provides significantly greater inhibition of the formation of insoluble calcium phos-phate than do AMP or HEDP. Inhibitor concentrations in Table 3 show the amount of active ingredient present~
_______________________________________________________________________ Test No. Inhlbltor Concn. PO ln soln. Inhibitlon mg/L mg/L %
1 Control (no lnhlbitor) -- 1.1 __ Blank -- 9.7 --Compositlon A 3.0 8.3 83.7 " 5.0 8.3 83.7 2 Control -- 1.7 --Blank -- 9.5 --HEDP 3.0 5.7 51.3 " 5.0 6.1 60.3 3 Control -- 0.9 --Blank -- 9.8 --AMP 3,0 7.0 68.5 " 5.0 6.2 59.6 _____________________________________.~_______________________________._ To demonstrate the effectiveness of the corrosion inhibitors 'of our invention in preventing deposit formation a~ well as con-trolling corrosion, a composition containing the phosphonic acids and phosphate was tested in the Continuous Circulation Tes~ Loop described previously. A high calcium, high pH water was used, because this is the type of water in which deposits are more likely to form. The composition tested again used the phosphonic acids prepared as described in Example 1 to which was added phos- j phoric acid as the orthophosphate ion source. The pH was auto-matically controlled during the test cycle to keep it on the ¦alkaline, deposit-forming side. The synthetic cooling water ion concentrations, test conditions, and the results of this test are shown in Table 4. The amount of corrosion inhibitor added to the water provided 12.5 mg/L of the phosphonic acids and 5.2 mg/L of P04. In addition to checking the corrosion inhibition in this test, we also checked the heating elements in the Test Loop sys-tem for deposition of calcium phosphate or other deposits. No measurable deposits were formed, even though, as mentioned previ-ously, the water had a relatively high concentration of calcium salts and high pH. Therefore the results of this test show that not only did this composition provide good corrosion protection (96.2% inhibition), it also prevented the formation of scale on heated surfaces in what is usually a deposit-forming water.
~364~
i _______________________________________________________________________ ION CONCENTRATIO~ :
Calcium aB Ca 80 m~/L (ppm) Magnesium as M8~ 60 mg/L
Blcarbonate ion as HCO 125 ~g/L
Chloride ion as Cl 3 300 mgtL
Sulfate as S04 300 m~/L
TEST CONDITIONS:
pH 8.3 Temperature 40 Water veloclty (past coupons) 3.6 ft/sec Duration of Test 143 hours Test coupons:c-1010 low carbon steel TEST RESULTS:
Corrosion Rate mpy Control (no lnhlbitor) 49.7 Wlth corroslon lnhlbltor 1.9 No measurable deposlts on heating elements.
______________________________________________________________________.
DET~ILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The metal surface may be an iron or iron alloy surface, preferably a ferrous alloy. More preferably, the metal surface is a low carbon steel surface. Preferably, the aqueous system is a cooling water system~
The organic phosphonic acids utilized in this invention may be manufactured from the corresponding diamines. These diamines all have 6 carbon atoms in their structures and include 1,2-diaminocyclohexane, 2-methyl-l,S-pentanediamine, and 1,6-hexanediamine, all of which are commercially available. The phosphonic acid derivatives are produced through the following phosphonomethylation reaction: !
~MH2 N [ CH2P (O) (OH) 2 ] 2 R + 4HCHO + 4H3PO3 ~ R \ + 4H20 2 N[CH2P(O) (H)2]2 where R represents the C6 ràdicals of the diamines listed above.
Hydrochloric acid is usually added to the reaction mixture to suppress the oxidation of phosphite to phosphate. As recited above, the phosphonic acids may be used in salt form. Preferred lS salts include the sodium, potassium~ and ammonium salts of these acids, which salts are formed by partially or completely neu-tralizing them with sodium hydroxide, potassium hydroxide, or ammonium hydroxide, respectively.
To accomplish the objectives of this invention, a mixture of the methylene phosphonic acids and/or their salts is used in com-bination with a source of orthophosphate ion to treat the water _g_ in aqueous system5. The amount of phosphonic acid mixture (100 basis) added to the water should be in the range o~ 1 to 100 parts per million (ppm), preferably from 3 to 100 ppm, more pref- ;
erably from 3 to 50 ppm, most preferably from 9-15 ppm, based on ;
the total weight of water in the system. The amount of orthophosphate compound added should be sufficient to provide 0.5 to 50 ppm orthophosphate as PO4, preferably from 1 to 9 ppm, more preferably from 3 to 5.2 ppm, based on the total weight of water in the system.
The weight ratio of the orthophosphate ion to the phosp~onic acid mixture is 1:200 to 50:1, preferably 0.1:1 to 10:1, more preferably 1:2.4 to 1:3.3.
Represen,ative sources of orthophosphate ion suitable for use in this invention inclu~e phosphoric acid (orthophosphoric acid), the sodium orthophosphates, the potassium orthophosphates, the lithiurn orthophosphates, the ammonium orthophosphates, the organic amine salts of phosphoric acid, and the organic orthophosphates set forth in U.S. Patent 3,510,436.
Exemplary lithium, sodium, potassium and ammonium orthophosphates include lithium di acid phosphate, trisodium orthophosphate, disodium orthophosphate, monosodium orthophosphate, hemisodium orthophosphate, tripotassium orthophosphate, dipotassium orthophosphate, monopotassium orthophophate, triammonium orthophosphate, diamrnoniurn orthophosphates and monoarnmonium orthophosphate.
~8~9~3 The methylene phosphonic acid mixture and the source of orthophosphate ion can be added separately and individually to the water system to be treated, but it is preferable to mix all of these materials prior to addition to the water. If necessary, the combined mixture can be diluted with water and/or stabilized by the additional of adjuvants to keep the mixture from separating prior to its addition to the water system to be treated. Other compatible water treatment components, such as biocides, antifoulants, and dispersants, can also be added to the mixture.
In a preferred embodiment of the invention, the methylene phosphonic acid mixture produced as described above is analyzed for both total phosphonic acids and total inorganic phosphate.
Then phosphoric acid is addèd to the mixture until the concentra-tion of orthophosphate as P04 reaches the desired ratio to the total weight of methylene phosphonic acids in the mixture. This mixture can then be diluted with water to any convenient use con-centration. The mixture can also be formulated with other types of water treatment compounds.
To disclose the nature of this inverltion even more clearly, the following illustrative examples will be given. It is under-stoocl, however, that the invention is not to be limited to the specific conditions or details set forth in these represen~ative examples.
In determining the corrosion inhibition provided by the com-positions and methods of our invention one of the techniques used was the Spinning Disk Test Method, a testing procedure that is widely employed, with many variations, in evaluating the effec-tiveness of corrosion inhibitors for cooling water treatment. In the Spinning Disk Test Method, a plastic disk is attached to the end of a plastic stirrer shaft. Metal test coupons are mounted vertically on this disk, usually two coupons per test. The shaft is fastened vertically in a stirrer motor chuck, and the disk and attached coupons ar-e immersed in water contained in a 4-liter plastic cylindrical tank, which is surrounded by a constant tem-perature bath.
The water volume in the cylindrical tank is maintained at a level that will keep the di'sk and coupons covered when the stirrer is started and the disk is rotated. The rotation speed of the disk is controlled at 100 rpm so that erosion and velocity effects are kept equal in all tests. The water is automatically replenished from a reservoir, with the addition being controlled with a timer and solenoid valve, at the rate of 60 milliliters of water added every 30 minutes, Excess water overflows through a special outlet to a drain. The cylindrical tank is kept covered except for the hole for the stirrer shaft to minimize evaporation losses.
The composition of the water is cGntrolled to simulate the water conditions in typical cooling water and other water-handling systems. The inhibitor being tested is added to this water in an appropriate concentration. For control pur-poses, tests are run in water with the same composition to which no inhibitor has been added.
The metal coupons are cleaned and weighed on an analytical balance before and after exposure to the water. As a rule, the exposure time is at least five days (120 hours). The corrosion rate is calculated from the loss in weight of the coupons, the exposed area of the coupons, the density of the metal, and the time of exposure. The rate is expressed as mils (of thickness) lost per year (mpy). The percent inhibition o~ corrosion obtained with a given concentration of an inhibitor is calculated from the corrosion rate with this concentration of inhibitor added to the water compared to the corrosion rate in the same water containing no inhibitor, using the following formula:
% Corrosion Inhibition =
(mpy Corrosion w/o Inhibitor - mpy Corrosion with Inhibitor) x 100 _ __________ _____________________________________________________ (mpy Corrosion w/o Inhibitor) Another method we used in evaluating corrosion inhibition efficacy involved treating the water in a Continuous Circulation Test Loop with the corrosion inhibitors to be checked. The Test Loop system consists of a 100-gallon reservoir, a circulation pump, a flow control valve, a rotameter, pipelines in which cor-rosion test coupons are mounted, and instruments for controlling the temperature and pH and monitoring other system variables such as the dissolved oxygen level. The water is pumped from the res-ervoir at a controlled rate through the pipeline containing the test coupons and then back to the reservoir. The corrosion rate in this system is determined by the weight loss of the test cou- j pons, and the calculation of the percent corrosion inhibition is done in the same way as described for the Spinning Disk Test Method.
A l-liter, 3-neck glas~ reaction flask was fitted with an agitator, a reflux condenser, and a thermometer and placed in a cooling water bath to which ice could be added as needed to con-trol the temperature of the contents of the flask. To this flask were charged 234.3 9 of 70% phosphorous acid. To the acid were added, slowly to avoid overheating, 57.5 9 o~ a mixture of diamines composed of approximately equimolar amounts of 1l6-diaminocyclohexane, 2 methyl-1,5-pentanediamine, and 1-6-hexanediamine. The temperature was controlled during the re-action to keep it below 70C, and the mixture was stirred contin-uously. After the diamines were added, 98.6 9 of concentrated (37.5%) hydrochloric acid were added to the reaction flask, and the mixture was heated to 90-95C.
Next, 174.3 9 of a 37% formaldehyde solution were added slowly to the reaction mixture over a period of 1-3/4 hours. The mixture was stirred and maintained at 90-95C for an additional 2 hours. The mixture was allowed to cool to 25C be~ore being ana-lyzed for its total phosphonic acid content and orthophosphate content. The reaction yielded 560 9 of solution containing 35.8%
by weight of C6 diamine tetrakis(methylene phosphonic acid) mix-ture, based on an average molecular weight of 492, and 0.15%
orthophosphate as P04. This solution was used as the source of the phosphonic acids in the tests described in the following e~-amples.
A combination of ortho~hosphate with the phosphonic acids prepared as described in Example 1 was tested as a corrosion in-hibitor using the Spinning Disk Test Method previously described.
The source of the orthophosphate ions was phosphoric acid, which was blended with the phosphonic acids prior to addition to the water. The synthetic cooliny water ion concentrations, test con-ditions, and results of this evaluation are shown in Table 1.
The concentrations of phosphonic acids and orthophosphate are expressed as the amounts of active ingredients present in the water. The results show that very low concentrations of a corro-sion inhibitor prepared according to our invention provide excel-lent corrosion protection to mild steel in a high calcium, high pH water with a composition typical of a large number of practi~
,cal operating cooling water systems. A concentration of the cor-rosion inhibitor equivalent to 14.6 mg/L (ppm) of the diamine ,phosphonic acids and 4.6 mg/L orthophosphate as PO4, provided 96.2% corrosion inhibition, and a concentration equivalent to 9.7 mg/L of the phosphonic acids and 3.0 mg/L PO4 provided over 93% corrosion inhibition.
_________ _________~______ I
ION CONCENTRATIO~ :
Calcium as Ca ~+ 80 mg/L (pp~) Magneslum aB M8 60 mg/L
Bicarbonate lon as HC03 125 mg/L
Chloride ion a~ Cl 300 mg/L
Sulfate as S04 300 mg/L
TEST CONDI~IONS:
p~ 8.0 Temporature 40 C
Rota~ional Speed ~ 100 rpm Duratlon of Test 144 hours Test coupons: c-1010 low carbon steel TEST RESULTS:
Phosphonlc Acids ~ Corrosion Rate mg/L mg/L mpy O (Control) 0 49.7 14.6 4.6 1.9 9.7 3.0 3.2 4,9 1.5 7.6 _______________________________________________________________________ To demonstrate the effectiveness of the corrosion inhibitors of our invention in a low calcium, low pH system, a composition containing the phosphonic acids and phosphate was tested in the Continuous Circulation Test Loop described previously. In the ~3649~
Test Loop, an automatic controller keeps the pH at a fixed value throughout the period of the test. The composition tested again used the phosphonic acids prepared as described in Example l to which was added phosphoric acid as the orthophosphate source.
The synthetic cooling water ion concentratiOnS, test conditions, and results of this evaluation are shown in Table ~. These results clearly demonstrate that excellent inhibition of corro-sion can be obtained in this rather corrosive water with a rela-tively low concentration of a corrosion inhibitor prepared according to our invention. The corrosion rate of mild steei was reduced from 63 mpy to 2.8 mpy, which is equivalent to 95.6% cor-rosion inhibition.
_____________________________ ~________________________________________ ION CONCENTRATIO ~ :
Calcium as Ca +~10 mg/L (ppm) Magne~lum as Mg 60 mg/L
8icarbonste lon as HC03125 mg/L
Chloride lon as Cl 300 mg/L
Sulfate as S04 300 mg/L
TEST CONDITIONS:
p~l 7.0 Temperature 40 C
Water velocl~y (over coupons) 3.6 ft/sec Duratlon of Test 143 hours Test coupons: c-1010 low carbon steel TEST RESULTS:
Phosphonlc aclds P04 Corroslon Rate mg/L mg/L mpy O (Control) 0 63.0 32.5 11.5 2.8 __________________________________________________________________.____ EX~MPLE 4 The effectiveness of the combination of phosphonic acids of our invention in preventing the precipitation of calcium phos-phate was demonstrated by an antiprecipitation test. The combi-nation of phosphonic acids prepared as described in Example 1, designated Composition A, was used for these tests. For compari-son, similar tests were run with two other in~ividual phosphonic acids that are widely used in the treatment of cooling water.
These are aminotris(methylene phosphonic acid), commonly called AMP, and l-hydroxyethylidene-l,l-diphosphonic acid, commonly called HEDP. Calcium phosphate precipitation inhibition was mea- , sured by adding a calcium chloride solution and a disodium hydro- j gen phosphate solution in amounts that provided 160 mg/L calcium ion as Ca and approximately 10 mg/L phosphate ion as P04. The appropriate amount of phosphonic acid inhibitor was added, and the solution pH was adjusted to 8.5. The treated sample was capped and placed in an oven at 50C for 24 hours. After removal from the oven, a portion of the supernatant liquid from each bot-tle was taken, filtered through a 0.45 micrometer pore size fil-ter to remove any precipitated calcium phosphate, and analyzed for orthophosphate. As a "Blank", a sample was prepared in the same way except that the pH was not adjusted to the alkaline side but kept on the acid side so that no precipitation would occur.
The percent inhibition of precipitation was calculated from the amount of phosphate.added (~lank) and the difference between the amount of phosphate in solution in samples without inhibitor (Control) compared to those with inhibitor, using the following formula:
% Inhibition = (mg/L PO~ with Inhibitor - mg/L P04 in Control) x 100 (mg/L P04 in Blank - mg/L P04 in Control) The results of these antiprecipitation tests, which are shown in Table 3, clearly demonstrate that the combination of phosphonic acids of the present invention provides significantly greater inhibition of the formation of insoluble calcium phos-phate than do AMP or HEDP. Inhibitor concentrations in Table 3 show the amount of active ingredient present~
_______________________________________________________________________ Test No. Inhlbltor Concn. PO ln soln. Inhibitlon mg/L mg/L %
1 Control (no lnhlbitor) -- 1.1 __ Blank -- 9.7 --Compositlon A 3.0 8.3 83.7 " 5.0 8.3 83.7 2 Control -- 1.7 --Blank -- 9.5 --HEDP 3.0 5.7 51.3 " 5.0 6.1 60.3 3 Control -- 0.9 --Blank -- 9.8 --AMP 3,0 7.0 68.5 " 5.0 6.2 59.6 _____________________________________.~_______________________________._ To demonstrate the effectiveness of the corrosion inhibitors 'of our invention in preventing deposit formation a~ well as con-trolling corrosion, a composition containing the phosphonic acids and phosphate was tested in the Continuous Circulation Tes~ Loop described previously. A high calcium, high pH water was used, because this is the type of water in which deposits are more likely to form. The composition tested again used the phosphonic acids prepared as described in Example 1 to which was added phos- j phoric acid as the orthophosphate ion source. The pH was auto-matically controlled during the test cycle to keep it on the ¦alkaline, deposit-forming side. The synthetic cooling water ion concentrations, test conditions, and the results of this test are shown in Table 4. The amount of corrosion inhibitor added to the water provided 12.5 mg/L of the phosphonic acids and 5.2 mg/L of P04. In addition to checking the corrosion inhibition in this test, we also checked the heating elements in the Test Loop sys-tem for deposition of calcium phosphate or other deposits. No measurable deposits were formed, even though, as mentioned previ-ously, the water had a relatively high concentration of calcium salts and high pH. Therefore the results of this test show that not only did this composition provide good corrosion protection (96.2% inhibition), it also prevented the formation of scale on heated surfaces in what is usually a deposit-forming water.
~364~
i _______________________________________________________________________ ION CONCENTRATIO~ :
Calcium aB Ca 80 m~/L (ppm) Magnesium as M8~ 60 mg/L
Blcarbonate ion as HCO 125 ~g/L
Chloride ion as Cl 3 300 mgtL
Sulfate as S04 300 m~/L
TEST CONDITIONS:
pH 8.3 Temperature 40 Water veloclty (past coupons) 3.6 ft/sec Duration of Test 143 hours Test coupons:c-1010 low carbon steel TEST RESULTS:
Corrosion Rate mpy Control (no lnhlbitor) 49.7 Wlth corroslon lnhlbltor 1.9 No measurable deposlts on heating elements.
______________________________________________________________________.
Claims (16)
1. A method for controlling corrosion of a metal surface in contact with an aqueous system and simultaneously inhibiting the precipitation of calcium phosphate comprising the step of treating the aqueous system with a source of orthophosphate ion and a mixture of (1) 1,2-diaminocyclohexanetetrakis(methylene phosphonic acid) or a salt thereof; (2) 2-methyl-1,5-pen-tanediaminetetrakis(methylene phosphonic acid) or a salt thereof;
and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid) or a salt thereof in amounts effective to control corrosion of metal surfaces exposed to aqueous systems and to inhibit the precipita-tion of calcium phosphate.
and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid) or a salt thereof in amounts effective to control corrosion of metal surfaces exposed to aqueous systems and to inhibit the precipita-tion of calcium phosphate.
2. The method of claim 1 wherein component (1), component (2), and component (3) each comprises 20 to 40 weight percent of the total weight of the mixture of methylene phosphonic acids.
3. The method of claim 1 wherein the weight ratio of the orthophosphate ion to the methylene phosphonic acid mixture is from about 1:200 to 50:1.
4. The method of claim 3 wherein the weight ratio of the orthophosphate ion to the methylene phosphonic acid mixture is 0.1:1 to 10:1.
5. The method of claim 1 wherein the source of ortho-phosphate ion is added to the water in an amount that provides a concentration of 0.5 to 50 parts of orthophosphate as PO4 per million parts of water.
6. The method of claim 1 wherein the methylene phosphonic acid mixture is added to the water in an amount that provides a concentration of 1 to 100 parts of the mixture per million parts of water.
7. The method of claim 1 wherein the source of ortho-phosphate ion is orthophosphoric acid.
8. The method of claim 1 wherein the source of ortho-phosphate ion is sodium orthophosphate.
9. The method of claim 1 wherein the source of ortho-phosphate ion is potassium orthophosphate.
10. The method of claim 1 wherein the aqueous system treated is a cooling water system.
11. A composition for controlling corrosion of a metal sur-face in contact with an aqueous system and simultaneously inhib-iting the precipitation of calcium phosphate comprising a source of orthophosphate ion and a mixture of (1) 1,2-diaminocyclohexanetetrakis(methylene phosphonic acid) or a salt thereof; (2) 2-methyl-1,5-pentanediaminetetrakis(methylene phosphonic acid) or a salt thereof; and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid) or a salt thereof in amounts effective to control corrosion of the metal surfaces in contact with the aqueous system and to inhibit the precipitation of calcium phosphate.
12. The composition of claim 11, wherein component (1), component (2), and component (3) each comprises 20 to 40 weight percent of the total weight of the mixture of methylene phosphonic acids.
13. The composition of claim 12, wherein the weight ratio of the orthophosphate ion to the methylene phosphonic acid mixture is from about 1:200 to 50:1.
14. The composition of claim 13 wherein the weight ratio of the orthophosphate ion to the methylene phosphonic acid mixture is 0.1:1 to 10:1.
15. A composition for preventing the precipitation of calcium phosphate comprising a mixture of (1) 1,2-diaminocyclohexanetetrakis(methylenephosphonic acid) or a salt thereof; (2) 2-methyl-1,5-pentanediaminetetrakis(methylene phosphonic acid) or a salt thereof; and (3) 1,6-hexanediaminetetrakis(methylene phosphonic acid) or a salt thereof in amounts effective to prevent precipitation of calcium phosphate.
16. The composition of claim 15 wherein component (1), component (2), and component (3) each comprises 20 to 40 weight percent of the total weight of the mixture of methylene phosphonic acids.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US853,612 | 1986-04-08 | ||
| US06/853,612 US4671934A (en) | 1986-04-18 | 1986-04-18 | Aminophosphonic acid/phosphate mixtures for controlling corrosion of metal and inhibiting calcium phosphate precipitation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1286490C true CA1286490C (en) | 1991-07-23 |
Family
ID=25316508
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000526578A Expired - Fee Related CA1286490C (en) | 1986-04-08 | 1986-12-31 | Phosphonic acid/phosphate mixtures for controlling corrosion of metal and inhibiting calcium phosphate precipitation |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US4671934A (en) |
| EP (1) | EP0242229B1 (en) |
| JP (1) | JP2592822B2 (en) |
| AU (1) | AU588192B2 (en) |
| CA (1) | CA1286490C (en) |
| DE (1) | DE3760624D1 (en) |
| ES (1) | ES2012482B3 (en) |
| MX (1) | MX164115B (en) |
| ZA (1) | ZA87242B (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4759852A (en) * | 1987-10-15 | 1988-07-26 | Nalco Chemical Company | Use of sulfamic acid to inhibit phosphonate decomposition by chlorine-bromine mixtures |
| US5061797A (en) * | 1988-03-29 | 1991-10-29 | Buckman Laboratories International, Inc. | 1-methyl-3,5,7-triaza-1-azoniatricyclodecane compounds |
| US5245031A (en) * | 1988-03-29 | 1993-09-14 | Buckman Laboratories International, Inc. | 1-methyl-3,5,7-triaza-1-azoniatricyclodecane compounds, a method for preparing these compounds, their use in the control of microorganisms in aqueous systems, and their use in the inhibition of corrosion |
| US5019343A (en) * | 1989-12-15 | 1991-05-28 | W. R. Grace & Co.-Conn. | Control of corrosion in aqueous systems using certain phosphonomethyl amines |
| US5962603A (en) * | 1996-07-23 | 1999-10-05 | Georgia-Pacific Resins, Inc. | Intumescent composition and method |
| US5864003A (en) * | 1996-07-23 | 1999-01-26 | Georgia-Pacific Resins, Inc. | Thermosetting phenolic resin composition |
| US6228914B1 (en) | 1998-01-02 | 2001-05-08 | Graftech Inc. | Intumescent composition and method |
| DE50211920D1 (en) * | 2002-07-02 | 2008-04-30 | Mueller Martini Holding Ag | Means for transporting a stack formed in a gathering machine standing upright from one another, lying on a support stack |
| US7087703B2 (en) * | 2004-07-26 | 2006-08-08 | Georgia-Pacific Resins, Inc. | Phenolic resin compositions containing etherified hardeners |
| JP7188190B2 (en) * | 2019-02-28 | 2022-12-13 | 栗田工業株式会社 | Water-based anti-corrosion method and water-based system |
Family Cites Families (22)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1201334A (en) * | 1966-10-12 | 1970-08-05 | Albright & Wilson Mfg Ltd | Corrosion inhibition |
| US3738806A (en) * | 1968-01-26 | 1973-06-12 | Monsanto Co | Process for the prevention of corrosion |
| DE1767454C2 (en) * | 1968-05-11 | 1983-01-27 | Henkel KGaA, 4000 Düsseldorf | Process for corrosion and stone formation protection in warm and hot water systems |
| US3714066A (en) * | 1970-04-13 | 1973-01-30 | Monsanto Co | Methods of inhibiting corrosion with ethane diphosphonate compositions |
| US3816333A (en) * | 1971-07-07 | 1974-06-11 | Monsanto Co | Methods of inhibiting corrosion with condensed polyalkylenepolyamine derivatives |
| US3837803A (en) * | 1972-07-11 | 1974-09-24 | Betz Laboratories | Orthophosphate corrosion inhibitors and their use |
| US3992318A (en) * | 1973-10-09 | 1976-11-16 | Drew Chemical Corporation | Corrosion inhibitor |
| CA1051188A (en) * | 1974-12-03 | 1979-03-27 | Chih M. Hwa | Composition and method of inhibiting corrosion |
| US4029577A (en) * | 1975-11-17 | 1977-06-14 | Betz Laboratories, Inc. | Polymers for use in water treatment |
| SE435456B (en) * | 1976-01-07 | 1984-10-01 | Calgon Corp | COMPOSITION AND PROCEDURE TO CONTROL THE BUILDING OF THE FLAVOR IN GAS WASHER |
| US4105581A (en) * | 1977-02-18 | 1978-08-08 | Drew Chemical Corporation | Corrosion inhibitor |
| US4217216A (en) * | 1977-04-01 | 1980-08-12 | The Mogul Corporation | Corrosion inhibiting compositions |
| US4222779A (en) * | 1979-06-04 | 1980-09-16 | Dart Industries Inc. | Non-chromate conversion coatings |
| US4317744A (en) * | 1979-04-25 | 1982-03-02 | Drew Chemical Corporation | Corrosion inhibitor |
| US4303568A (en) * | 1979-12-10 | 1981-12-01 | Betz Laboratories, Inc. | Corrosion inhibition treatments and method |
| US4406811A (en) * | 1980-01-16 | 1983-09-27 | Nalco Chemical Company | Composition and method for controlling corrosion in aqueous systems |
| DE3032226A1 (en) * | 1980-08-27 | 1982-04-01 | Henkel KGaA, 4000 Düsseldorf | METHOD AND MEANS FOR PASSIVATING IRON AND STEEL SURFACES |
| US4497713A (en) * | 1982-04-01 | 1985-02-05 | Betz Laboratories | Method of inhibiting corrosion and deposition in aqueous systems |
| US4551262A (en) * | 1983-10-05 | 1985-11-05 | Samakaev Rafail K | Composition for preventing deposition of inorganic salts |
| DE3506932A1 (en) * | 1985-02-27 | 1986-08-28 | Messer Griesheim Gmbh, 6000 Frankfurt | DEVICE FOR GENERATING A DRY COLD GAS FLOW |
| US4650591A (en) * | 1985-08-29 | 1987-03-17 | Calgon Corporation | Acrylic acid/2-acrylamido-2-methylpropylsulfonic acid/2-acrylamido-2-methylpropyl phosphonic acid polymers as scale and corrosion inhibitors |
| AU612603B2 (en) * | 1986-11-13 | 1991-07-18 | B.F. Goodrich Company, The | Calcium phosphonate scale inhibition |
-
1986
- 1986-04-18 US US06/853,612 patent/US4671934A/en not_active Expired - Lifetime
- 1986-12-31 CA CA000526578A patent/CA1286490C/en not_active Expired - Fee Related
-
1987
- 1987-01-14 ZA ZA87242A patent/ZA87242B/en unknown
- 1987-02-10 MX MX5192A patent/MX164115B/en unknown
- 1987-02-20 JP JP62037682A patent/JP2592822B2/en not_active Expired - Fee Related
- 1987-04-06 AU AU71113/87A patent/AU588192B2/en not_active Ceased
- 1987-04-16 EP EP87303423A patent/EP0242229B1/en not_active Expired
- 1987-04-16 DE DE8787303423T patent/DE3760624D1/en not_active Expired
- 1987-04-16 ES ES87303423T patent/ES2012482B3/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0242229B1 (en) | 1989-09-27 |
| AU588192B2 (en) | 1989-09-07 |
| AU7111387A (en) | 1987-10-22 |
| ZA87242B (en) | 1987-09-30 |
| EP0242229A1 (en) | 1987-10-21 |
| US4671934A (en) | 1987-06-09 |
| MX164115B (en) | 1992-07-17 |
| JP2592822B2 (en) | 1997-03-19 |
| JPS62256973A (en) | 1987-11-09 |
| ES2012482B3 (en) | 1990-04-01 |
| DE3760624D1 (en) | 1989-11-02 |
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