IMPROVED CORROSION INHIBITION OF METALS IN WATER SYSTEMS

Abstract: The inhibition of corrosion of metals in water conducting systems by organic aminoalkylenephosphonic acid deriva­ tives is improved by using in combination therewith a manganese compound capable of providing manganese ions. The said aminoalkylenephosphonic acid derivative may also contain other functional groups, eg. carboxylates, quaternary amines, hydroxyalkyl groups and the like.

Description: This invention concerns a composition having an organic aminophosphonic acid derivative and manganese ion for use in the inhibition of metal corrosion in water conducting systems. One of the main problems which occurs in hydraulic engineering is the corrosion of metals in both treated and untreated cooling water systems. The corrosion of metals such as steel, aluminum, brass and copper which are commonly found in water systems, is primarily due to dissolved oxygen and carbon dioxide. Materials which remove oxygen, such as sodium sulfite or hydrazine, are not economical and are technically inadequate. Hence Zn⁺⁺, chromates, molybdates, polyphosphates, ortho-phosphate, and organo-phosphonates are added to cooling water to form protective films on metal surfaces. Chromates are very efficient corrosion inhibitors; however, they are often environmentally undesirable due to their well known toxic effects. Zn⁺⁺ has similar environmental problems and it also has low solubility products with ortho-phosphate, hydroxide and carbonate which can form sludge and deposits responsible for promoting corrosion. Polyphosphates are not as efficient as chromates and they are unstable in a cooling water environment, thus they decompose by hydrolysis to ortho- and pyro-phosphates which often cause sludge and deposits. Ortho-phosphates are not as efficient as chromates and if they are not controlled properly they can also form sludge and deposits. Although organophosphonates provide some corrosion protection, they are not nearly as efficient as chromates. LU-A-68346 (corresponding to US-A-3837803) discloses that metal corrosion in water conducting systems can be inhibited by a synergistic mixture of an organophosphonic acid having a C-P bond or a salt thereof and an orthophosphate in the weight ratio 0.1:20 to 40:0.1. When corrosion of copper is to be inhibited, the presence of an additional copper corrosion inhibitor is required. The organophosphonic acid can be inter alia a member of a specified class of organic aminophosphonic acid derivatives in which the nitrogen and phosphorus are interconnected by a C₁-C₄ alkylene group. Four members of said class (ie. nitrilo-trimethylene phosphonic acid (ATMP), dodecylamine-dimethyl-phosphonic acid, and hexapotassium dihydrogen-dimethylene and -hexamethylene-diaminetetramethylenephosphonate) were evaluated alone and with trisodium phosphate and ATMP is shown to be clearly preferred over the other three. ATMP was significantly less active as a corrosion inhibitor than 1-hydroxymethylidene-1,1-diphosphonic acid (HEDP) both when the inhibitors were used alone and with trisodium phosphate. The water to be treated by the mixture of LU-A-68346 is required to be adjusted, if necessary, to slightly basic pH (ie. pH 7.1-9.5). If the calcium ion content is less than 50 ppm, a water soluble salt of a metallic cation may, and where said content is less than 4 ppm must, be added in an amount of 0.1 to 25 ppm. The metallic cation is specified in the disclosure and in Claims 3, 8 and 25 (US Claims 2, 7 and 22) to be zinc, nickel, cobalt, cadmium or chromium. However, Claim 30 (US Claim 27) claims a composition in which the organophosphonic acid is selected from 6 (7 in US Claim 27) specified compounds and the cation is selected from 9 specified metallic cations including manganese. Only one of said 6 (7) specified organophosphonic acids (ethylenediamine-tetra(methyl phosphonic acid) has two or more amino groups. There is no exemplification of or any other reference to water soluble manganese salts. EP-A-0096619 (corresponding to US-A-4613450) discloses that certain metal fluorophosphates inhibit metal corrosion in water conducting systems. Said fluorophosphates include those of the formulae M²PO₃F,xH₂O; M¹₂M²(PO₃F)₂,xH₂O and M²(PO₂F₂)₂,xH₂O; wherein M¹ is selected from Na, K, Rb, Cs and NH₄ and M² is selected from Mg, Ca, Ba, Sr, Zn, Cd, Mn, Ni and Co. The preferred fluorophosphates are zinc and potassium fluorophosphates and there is no exemplification of manganese-containing fluorophosphates. Preferably, the fluorophosphates are used in association with alkylene diphosphonic acid, especially HEDP, or aminoalkylenephosphonic acid, especially sodium aminotrimethylenephosphonate (NaATMP). A general formula is given including aminoalkylenephosphonic acid derivatives having two or more amino groups but there is no exemplification of said derivatives. FR-A-2148260 (corresponding to US-A-3718603) discloses that certain substituted tertiary amine phosphonates (STAP) inhibit metal corrosion in water conducting systems. These phosphonates are derivatives of ATMP in which one methylenephosphonic acid has been replaced and contain only one amino group. They can be inter alia manganese salts but no manganese salts are exemplified and the preferred salts are those of zinc or chromium. Synergism is reported to exist between the STAP and zinc, chromate or dichromate ions. An additional copper corrosion inhibitor is desired when the water is in contact with copper or copper alloys. US-A-4033896 discloses that certain phosphonomethylaminocarboxylates (PMAC) inhibit metal corrosion in water conducting systems. These compounds contain one or two amino groups and in a preferred embodiment are derivatives of ATMP in which one methylenephosphonic acid has been replaced. They can be inter alia manganese salts but sodium, potassium and, especially, zinc or chromium salts are preferred. No manganese salts are exemplified. Reference is made to the use of the PMAC with an aminoalkylenephosphonic acid but no acid is exemplified. An additional copper corrosion inhibitor is desired when the water is in contact with copper or copper alloys. US-A-3899293 discloses that the oxidation by atmospheric oxygen of alkali metal or ammonium sulfites or bisulfites can be inhibited by the presence of a water-soluble polyphosphonate. Said sulfites and bisulfites, especially sodium sulfite, act as corrosion inhibitors in aqueous solutions by reacting with and thus reducing or eliminating the amount of dissolved oxygen which would be available to react with and corrode ferrous metal. US-A-3899293 also teaches that certain heavy metal cations such as cobalt, copper, iron, manganese and nickel are known to catalyze or accelerate the reaction between sulfite and dissolved oxygen. By stabilizing sulfite from attack by atmospheric oxygen, the more sulfite is available to react with dissolved oxygen and hence the greater the corrosion inhibition effect of the sulfite. EP-A-0118395 (corresponding to US-A-4501667) discloses that certain 2-amino-phosphonoacetic acids (APAA) inhibit metal corrosion in water conducting systems and that said action is synergistically enhanced by certain metal ions. The APAA have only one amino group and can be present as inter alia a manganous salt. The metal ion component can be inter alia manganous but there is no exemplification of either a manganous salt or a manganous ion component. Further corrosion inhibitors can be used and specified additional inhibitors include ATMP and methylamino-dimethylenephosphonic acid. Surprisingly, the compositions of the present invention provide metal corrosion protection comparable to chromates without requiring the presence of orthophosphate, ATMP or zinc. In one aspect, the present invention provides a composition useful in inhibition of metal corrosion in water conducting systems which consists essentially of at least one aminoalkylene phosphonic acid derivative in combination with a manganese compound, other than a fluorophosphate or a phosphonomethylcarboxylate, capable of providing a manganese ion in an aminoalkylene phosphonic acid derivative to manganese weight ratio of at least 2:1. The aminoalkylene phosphonic acid derivative is: (A) an organic aminophosphonic acid derivative of the formula wherein: A, B, C, D, E and F are -CH₂-PO₃H₂ or salts thereof; m and m' is each from 0-2,500; R is a -CH₂CH₂- residue or, together with two adjacent N atoms, forms a piperazine ring; (B) a mixture of pentaethylenehexamine with heavier ethylene amines (including polymers containing piperazine structures and having an average molecular weight of 275) where the mixture is then substituted on its amine hydrogens such that 10 mole percent are replaced by 2-hydroxy-3-(trimethylammonium chloride) propyl groups, and the remaining amine hydrogens substantially completely phosphonomethylated, or a salt thereof; (C) a mixture of ethylenediamine having 25 mole percent of its amine hydrogens substituted by 2-hydroxypropylsulfonic acid which has been phosphonomethylated, or salts thereof; (D) a reaction product of: 1) a mixture of pentaethylenehexamine with heavier ethylene amines (including polymers containing piperazine structures and having an average molecular weight of 275), and 2) ethylene dichloride; the reaction product then substituted on its amine hydrogens with 25 mole percent of 2-hydroxy-3-(trimethylammonium chloride) propyl groups, and the remaining amine hydrogens substantially completely phosphonomethylated, or a salt thereof; or (E) hydroxyethylethylenediaminetri(methylenephosphonic acid), or a salt thereof. In a second aspect, the invention provides a method of inhibiting metal corrosion in a water conducting system, having a metal component and oxygen (O₂) present in the water, which comprises adding to the water therein a composition, consisting essentially of at least one said aminoalkylene phosphonic acid derivative in an amount of 1 to 300 ppm acid or equivalent and a manganese compound, other than a fluorophosphate or phosphonomethylcarboxylate, in an amount providing 0.1 to 30 ppm manganese, the weight ratio of aminoalkylene phosphonic acid derivative to manganese being at least 2:1. In a third aspect, the present invention provides a method of inhibiting metal corrosion in a water conducting system, having a metal component and oxygen (O₂) present in the water, which consists essentially of adding to the water therein at least one said aminoalkylene phosphonic acid derivative in an amount of 1 to 300 ppm acid or equivalent and a manganese compound, other than a fluorophosphate or a phosphonomethylcarboxylate, in an amount providing 0.1 to 30 ppm manganese. In a further aspect, the present invention provides a method of inhibiting metal corrosion in a water conducting system, having a metal component containing copper alloy and oxygen (O₂) present in the water, which comprises adding to the water therein a composition comprising at least one said aminoalkylene phosphonic acid derivative in an amount of 1 to 300 ppm acid or equivalent and a manganese compound, other than a fluorophosphate or a phosphonomethylcarboxylate, in an amount providing 0.1 to 30 ppm manganese and wherein no additional copper corrosion inhibitor is added to the water conducting system. In another aspect, the present invention provides a method of inhibiting metal corrosion in a water conducting system, having a metal component containing copper alloy and oxygen (O₂) present in the water, which comprises adding to the water therein at least one said aminoalkylene phosphonic acid derivative in an amount of 1 to 300 ppm acid or equivalent and a manganese compound, other than a fluorophosphate or a phosphonomethylcarboxylate, in an amount providing 0.1 to 30 ppm manganese and wherein no additional copper corrosion inhibitor is added to the water conducting system. The said aminoalkylene phosphonic acid derivatives tested alone (without manganese) in hard or deionized water do not provide the level of protection that the instant composition does. The corrosion protection of metals by the said aminoalkylene phosphonic acid derivatives is surprisingly enhanced by the addition of a manganese compound to provide a source of manganese ion. The said aminoalkylene phosphonic acid derivatives can be prepared by a number of known synthetic techniques. Of particular importance is the reaction of compounds containing reactive amine hydrogens with a carbonyl compound (aldehyde or ketone) and phosphorous acid or derivative thereof. Detailed procedures can be found in US-A-3,288,846. Some specific, but non-limiting, examples of the said aminoalkylene phosphonic acid derivatives useful in the present invention are diethylenetriaminepenta(methylenephosphonic acid) (DETA-PMP), hydroxyethylethylenediaminetri(methylenephosphonic acid) (HEEDA-TMP), pentaethylenehexamineocta(methylenephosphonic acid), and phosphonomethylated polyethylene polyamines having molecular weights up to 100,000 or more, which may contain piperazine rings in the chain. Additional examples of the said aminoalkylene phosphonic acid derivatives are disclosed in "New Metal Ion Control Agents Based on Dicyclopentadiene Derivatives" , US-A-4,500,470; "New Compounds Containing Quaternary Ammonium and Methylenephosphonic Acid Groups", US-A-4,459,241; "Polymeric Alkylene-phosphonic Acid Piperazine Derivatives", US-A-4,489,203; and "New Metal Ion control compounds based on Norbornane", US-A-4,500,469. The said aminoalkylene phosphonic acid derivatives containing other functional groups in addition to a methylenephosphonic acid group (US-A-3,288,846) as a nitrogen substituent can be prepared by the following methods. Hydroxyalkyl groups can be substituted for a hydrogen of an amine by reacting the amine with an alkylene oxide in aqueous medium, e.g. propylene oxide (1,2-epoxypropane), as described in US-A-3,398,198. The 2-hydroxypropylsulfonic acid group may be substituted for an amine hydrogen by reacting the amine in aqueous solution with 3-chloro-2-hydroxy-1-propanesulfonic acid in the presence of caustic (NaOH). The hydroxypropylsodiumsulfonate group is the nitrogen substituent. If the acid is desired, acidification with a strong acid, e.g. HCl is sufficient to convert the sodium salt to the acid. This reaction is taught in US-A-3,091,522. The hydroxypropyltrimethylammonium chloride group may be substituted for an amine hydrogen by reacting the amine with an aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride prior to the reaction to make the phosphonic acid derivative. For the purpose of the present invention, effective aminoalkylene phosphonic acid derivatives described herein and salts thereof are considered equivalent. The salts referred to are the acid addition salts of those bases which will form a salt with at least one acid group of the aminoalkylene phosphonic acid derivative. Suitable bases include, for example, the alkali metal and alkaline earth metal hydroxides, carbonates, and bicarbonates such as sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium carbonate, sodium bicarbonate, and magnesium carbonate, ammonia, primary, secondary and tertiary amines. These salts may be prepared by treating the aminoalkylene phosphonic acid derivative having at least one acid group with an appropriate base. The preferred quantity of the aminoalkylene phosphonic acid derivatives to inhibit corrosion of either copper- or iron-containing metal alloys in water conducting systems is from 2 to 50 ppm acid or equivalent. The operable amounts usually are from 1 to 300 ppm. The addition of manganese compounds to the aminoalkylene phosphonic acid derivatives in such water conducting systems has an unexpected enhancement of inhibiting corrosion. The manganese compound usually is employed in an amount to provide from 0.1 to 30 ppm manganese by weight in the aqueous solution. Preferred amounts provide from 0.2 to 10 ppm. Representative of suitable manganese compounds which may be employed as a source of manganese ion are MnO, MnO₂, MnCl₂·4H₂O, KMnO₄, and Mn(CH₃COO)₂·4H₂O. The manganese compound can be added simultaneously with the aminoalkylene phosphonic acid derivative or may be added separately to the water. Alternatively, the manganese can be complexed by the aminoalkylene phosphonic acid derivative prior to adding to the water. While zinc compounds have been used in conjunction with the aminoalkylene phosphonic acid derivatives in the art, the use of manganese compounds together with the aminoalkylene phosphonic acid derivatives provides unexpectedly superior results. Some comparisons are shown in Table II. The following examples are representative of the invention. EXAMPLE 1 This example demonstrates the enhanced corrosion inhibition of 1018 carbon steel provided by manganese with a commercially available aqueous solution of DETA-PMP. Tanks of 8 liter capacity were filled with tap water having the following characteristics: WATER CHARACTERISTICS Conductivity (µmhos/cm) 750 Alkalinity (ppm as CaCO₃) 120 Total Hardness (ppm as CaCO₃) 178 Ca Hardness (ppm as CaCO₃) 136 Fe (ppm) 0.28 SO₄ = (ppm) 85 Cl⁻ (ppm) 126 pH 7.4 Air was sparged at 10 SCFH (280 l/h) through a glass tube which was situated at one end of the tank and extended to the bottom of the tank. The air sparge was used to recirculate the water, oxygenate the water, and aid in evaporation. Water level in the tank was automatically controlled by a gravity feed system and heat was added to the water by electric immersion heaters. The water temperature was measured by a platinum RTD (resistance temperature detector) and controlled at 125°F (51.7°C) by an "on/off" controller which provided power to the immersion heaters. The pH of the water was adjusted to pH 8.0 by addition of caustic (50%) and was automatically maintained at 8.0 by a controller which fed HCl to the tank in response to an increase in pH. The DETA-PMP (100 ppm) was added to each of Tanks 1 and 2. Manganese (5ppm) as MnCl₂·4H₂O was added to Tank 1 only. The pH of each tank was initially adjusted to 8.0 using NaOH. Carbon steel (1018) electrodes which had been cleaned with 1:1 HCl and sanded with 320 grade sandpaper to remove all surface oxides were attached to three electrode corrosion probes and immersed in the tanks. The corrosion rates were monitored using a potentiostatic corrosion rate instrument. Unless otherwise noted, the experiments were conducted for a period of five days at which time the concentration of salts in the baths was approximately four times that in the feed water. At the end of this time the average corrosion rates from all runs were found to be 0.5 mpy (mils per year metal lost) (0.013 mm/y) for Tank 1 and 2.45 mpy (0.062 mm/y) for Tank 2. Comparative Examples A, B, and C were conducted without manganese, without the aminophosphonic acid derivative and with no additives, respectively, under the same conditions of temperature, pH and using the same water and metal as used in Example 1. All were evaluated over a five day period. Results are shown in Table I in which all examples of the invention are shown by numbers and the comparative examples are shown by letters. EXAMPLES 2 AND 3 Experiments were conducted in the manner of Example 1, using different sources of manganese with the same aminophosphonic acid derivative. Results are shown in Table I. In the case of using MnO, or other insoluble sources of manganese, it is added to a solution of the phosphonic acid derivative in which the compound will dissolve and then added to the water system. EXAMPLE 4 An experiment using DETA-PMP and manganese ion as MnCl₂·4H₂O and a no-treatment control was performed to determine the effects on Admiralty brass (Brass CDA-443) corrosion rates. These were conducted according to the procedure in Example 1 except that the test was run for 9 days and Admiralty brass electrodes were used. The average corrosion rates for these tests are also shown in Table I. Examples D and E are for comparison with Example 4 using Admiralty brass. EXAMPLE 5 Ethyleneamine E-100 (E-100-MP) was substantially completely phosphonomethylated and used in experiments conducted as described in Example 1. Results are shown in Table I. EXAMPLE 6 An experiment was conducted in the manner of Example 5 except that deionized water was employed in place of tap water. A comparision without manganese (Example F) was also run. Results are shown in Table I. EXAMPLE 7 Ethyleneamine E-100 having 10 mole percent of the amine hydrogens substituted by 2-hydroxy-3-(trimethylammonium chloride)propyl groups and substantially all the rest by methylenephosphonic acid groups (E-100-QMP) was tested under the same conditions as described in Example 1. Tanks 3 (this example) and 4 (Example G) were loaded with 100 ppm of active product and Tank 3 contained additionally 5 ppm manganese as MnCl₂·4H₂O. At the end of 5 days the average corrosion rates on 1018 carbon steel electrodes were 0.75 mpy (0.019 mm/y) for Tank 3 and 1.7 mpy (0.043 mm/y) for Tank 4. EXAMPLE 8 Ethylenediamine having 25 mole percent of its amine hydrogens substituted by 2-hydroxypropylsulfonic acid groups and substantially all its remaining amine hydrogens substituted by methylenephosphonic acid groups (EDA-HPS-MP) was tested according to the method in Example 1, at 150 ppm of active material alone and with 7.5 ppm of manganese as MnCl₂·4H₂O. After 5 days the average corrosion rates for carbon steel 1018 were 1.5 mpy (0.038 mm/y) without manganese (Example H) and 0.7 mpy (0.018 mm/y) with manganese (this example). EXAMPLE 9 A polyalkylene polyamine of ∼100,000 molecular weight, having 25 mole percent of its amine hydrogens substituted by 2-hydroxy-3-(trimethylammonium chloride)propyl groups and substantially all its remaining amine hydrogens substituted by methylenephosphonic acid groups (PAPA-QMP), was tested according to the method in Example 1. The tests were performed with 94 ppm of this phosphonic acid derivative alone (Example I) and with 5 ppm manganese as MnCl₂·4H₂O (this example). The average corrosion rates for carbon steel at the end of the tests were 2.5 mpy (0.064 mm/y) without Mn and 0.3 mpy (0.008 mm/y) with Mn. EXAMPLE 10 Tests using the substantially completely phosphonomethylated ethyleneamine E-100 product described in Example 5 were performed in combination with KMnO₄ according to the procedure of Example 1. The phosphonomethylated ethyleneamine E-100 product was added at a concentration of 100 ppm with 5 ppm of manganese as KMnO₄. The final average corrosion rate on 1018 carbon steel electrodes was 0.58 mpy (0.015 mm/y). The following additional comparative examples (J and K), using a non-amine based phosphonic acid, show that the use of manganese ion provides no significant improvement with these derivatives (See Table I). EXAMPLES J AND K (BOTH COMPARATIVE) Tests using 1-hydroxyethylidene-1,1 diphosphonic acid (HEDP) and manganese ion as MnCl₂·4H₂O were performed according to the procedure described in Example 1. The experiments were conducted with 100 ppm of active HEDP in both Tanks 1 (K) and 2 (J). Tank 2 contained, in addition, 5 ppm manganese as MnCl₂·4H₂O. The average corrosion rates for carbon steel electrodes were 7.8 mpy (0.20 mm/y) for Tank 1 and 8.2 mpy (0.21 mm/y) for Tank 2. Example No. Organo-Phosphonic Acid Deriv. Amt. (ppm) Mn Source Mn⁺⁺ (ppm) Corrosion (mpy) mm/y 1 DETA-PMP 100 MnCl₂ 5.0 0.50 0.013 A DETA-PMP 100 -- -- 2.45 0.062 B -- -- MnCl₂ 5.0 10.00 0.254 C Control (no additives) -- 10.00 0.254 2 DETA-PMP 150 MnCl₂ 7.5 0.36 0.009 3 DETA-PMP 150 MnO 7.5 0.39 0.010 4 DETA-PMP 200 MnCl₂ 10.0 0.25 0.006 D DETA-PMP 200 -- -- 8.00 0.203 E DETA-PMP -- -- -- 0.61 0.016 5 E-100-MP 87 MnCl₂ 5.0 0.44 0.011 6 E-100-MP 142 MnCl₂ 5.0 0.77 0.020 F E-100-MP 142 -- -- 6.25 0.159 7 E-100-QMP 100 MnCl₂ 5.0 0.75 0.019 G E-100-QMP 100 -- -- 1.70 0.043 8 EDA-HPS-MP 150 MnCl₂ 7.5 0.70 0.018 H EDA-HPS-MP 150 -- -- 1.50 0.038 9 PAPA-QMP 94 MnCl₂ 5.0 0.30 0.008 I PAPA-QMP 94 -- -- 2.50 0.064 10 E-100-MP 100 KMnO₄ 5.0 0.58 0.015 J HEDP 100 MnCl₂ 5.0 8.20 0.208 K HEDP 100 -- -- 7.80 0.198 Table II shows results employing some of the phosphonic acid derivatives of the present invention together with Mn⁺⁺ as compared to the same derivatives employed with Zn⁺⁺. Examples of the invention are numbered, while the comparative examples are indicated by letters in the same manner as in Table I. EXAMPLES 11-14 AND L-P Experiments were run in the manner of Example 1 employing Mn⁺⁺ ion in combination with various phosphonomethylated organic amines (Examples 5 and 11-14) and for comparison the same compounds were used in combination with the Zn⁺⁺ ion (Examples L-P) as generically disclosed in the prior art. These compounds are the E-100-MP of Example 5, the DETA-PMP of Example 4, Poly AEP-MP, described in the footnote to Table II, the PAPA-QMP of Example 9 and HEEDA-TMP. The manganese and zinc ions were compared on an equal molar basis (9 X 10⁻⁵ moles/liter). Example No. Organo-Phosphonic Acid Deriv. Amt (ppm) Mn⁺⁺ Source Ion ppm Zn⁺⁺ Source Ion ppm Corrosion (mpy) mm/y C Control -- -- -- -- -- 10.00 0.254 5 E-100-MP 87 MnCl₂ 5.0 -- -- 0.44 0.011 L E-100-MP 87 -- -- ZnCl₂ 6.2 1.37 0.035 11 DETA-PMP 100 MnCl₂ 5.0 -- -- 0.60 0.015 M DETA-PMP 100 -- -- ZnCl₂ 6.0 1.40 0.036 12 Poly AEP -MP 100 MnCl₂ 5.0 -- -- 0.20 0.005 N Poly AEP -MP 100 -- -- ZnCl₂ 6.0 0.45 0.011 13 PAPA-QMP 100 MnCl₂ 5.0 -- -- 0.66 0.017 0 PAPA-QMP 100 -- -- ZnCl₂ 6.0 2.10 0.053 14 HEEDA-TMP 100 MnCl₂ 5.0 -- -- 0.53 0.013 P HEEDA-TMP 100 -- -- ZnCl₂ 6.0 0.73 0.019 The aminoalkylene phosphonic acid derivatives and manganese ion employed according to the invention are also operable in the presence of other additives commonly used in the water of cooling systems, providing, of course, there is no adverse effect as a result of the use of such combinations. Some representative additives are dispersants such as polyacrylates, polymethacrylates, polymaleic anhydride, acrylate/methacrylate and acrylate/acrylamide copolymers; biocides such as 2,2-dibromo-2-nitrilopropionamide, bis(tributyltin)oxide, chlorine, chlorine dioxide and bromine chloride; and antifoam agents. Other ion control agents including phosphate esters, phosphonates and sulfonates and corrosion inhibitors such as zinc, polyphosphates, and tolyltriazole may also be present, providing, as before indicated, there is no adverse effect. EXAMPLE 15 An industrial open recirculation cooling system was operated in accordance with the present invention in which DETA-PMP was maintained at a concentration within the range of 3 to 10 ppm and the manganese ion maintained at a concentration within the range of 0.2 to 1.0 ppm. The cooling system water also had been chlorinated to prevent the growth of slime and algae. It also contained a commercially available polyacrylic acid-based dispersant, a non-oxidizing biocide and an antifoam agent (added as needed). The corrosion rates of carbon steel and Admiralty brass were measured using both potentiostatic techniques and corrosion coupons. The maximum corrosion rates for carbon steel were less than 1.5 mpy (0.04 mm/y) and for Admiralty brass were less than 0.1 mpy (0.003 mm/y) as determined by both methods.

Claims: A composition useful in inhibition of metal corrosion in water conducting systems which consists essentially of at least one aminoalkylene phosphonic acid derivative which is: (A) an organic aminophosphonic acid derivative of the formula wherein: A, B, C, D, E and F are -CH₂-PO₃H₂ or salts thereof; m and m' is each from 0-2,500; R is a -CH₂CH₂- residue or, together with two adjacent N atoms, forms a piperazine ring; (B) a mixture of pentaethylenehexamine with heavier ethylene amines (including polymers containing piperazine structures and having an average molecular weight of 275) where the mixture is then substituted on its amine hydrogens such that 10 mole percent are replaced by 2-hydroxy-3-(trimethylammonium chloride) propyl groups, and the remaining amine hydrogens substantially completely phosphonomethylated, or a salt thereof; (C) a mixture of ethylenediamine having 25 mole percent of its amine hydrogens substituted by 2-hydroxypropylsulfonic acid which has been phosphonomethylated, or salts thereof; (D) a reaction product of: 1) a mixture of pentaethylenehexamine with heavier ethylene amines (including polymers containing piperazine structures and having an average molecular weight of 275), and 2) ethylene dichloride; the reaction product then substituted on its amine hydrogens with 25 mole percent of 2-hydroxy-3-(trimethyl ammonium chloride) propyl groups, and the remaining amine hydrogens substantially completely phosphonomethylated, or a salt thereof; or (E) hydroxyethylethylenediaminetri(methylenephosphonic acid), or a salt thereof; in combination with a manganese compound, other than a fluorophosphate or a phosphonomethylcarboxylate, capable of providing a manganese ion to provide a weight ratio of aminoalkylene phosphonic acid derivative to manganese of at least 2:1. A composition as claimed in Claim 1, wherein said derivative is diethylenetriaminepenta(methylenephosphonic acid) or a salt thereof. A composition as claimed in Claim 1, wherein said derivative is of type (A) and the precursor amine is the reaction product of aminoethylpiperazine and ethylene dichloride in the mole ratio of 1 to 0.56, respectively. A composition as claimed in Claim 1, wherein said derivative is of type (A) and the component is a mixture of pentaethylenehexamine with heavier ethylene amines (including polymers containing piperazine structures and having an average molecular weight of 275) which has been substantially completely phosphonomethylated, or a salt thereof. A composition as claimed in any one of the preceding claims, wherein the manganese ion is in a chelated form. A method of inhibiting metal corrosion in a water conducting system, having a metal component and oxygen (O₂) present in the water, which comprises adding to the water therein a composition, consisting essentially of at least one aminoalkylene phosphonic acid derivative in an amount of 1 to 300 ppm acid or equivalent and a manganese compound in an amount providing 0.1 to 30 ppm manganese, as claimed in any one of the preceding claims. A method as claimed in Claim 6, wherein said derivative is present in an amount of 2 to 50 ppm acid or equivalent and said manganese compound is present in an amount providing 0.2 to 10 ppm manganese. A method as claimed in Claim 6 or Claim 7, wherein the metal component is an iron or copper-containing metal alloy. A method as claimed in Claim 6 or Claim 7, wherein the metal component is a copper alloy. A method as claimed in Claim 9, wherein the copper alloy is a brass. A method as claimed in Claim 10, wherein the brass is Admiralty brass. A method as claimed in any one of Claims 8 to 11, wherein no additional copper corrosion inhibitor is added to the water conducting system. A method of inhibiting metal corrosion in a water conducting system, having a metal component and oxygen (O₂) present in the water, which consists essentially of adding to the water therein at least one aminoalkylene phosphonic acid derivative in an amount of 1 to 300 ppm acid or equivalent and a manganese compound in an amount providing 0.1 to 30 ppm manganese each as defined in any one of Claims 1 to 5. A method as claimed in Claim 13, wherein said derivative is present in an amount of 2 to 50 ppm acid or equivalent and said manganese compound is present in an amount providing 0.2 to 10 ppm manganese. A method as claimed in Claim 13 or Claim 14, wherein said manganese compound is added simultaneously with the said derivative. A method as claimed in Claims 13 or Claim 14, wherein said manganese compound is complexed by said derivative prior to adding to the water. A method as claimed in any one of Claims 13 to 16, wherein the metal component is an iron or copper-containing metal alloy. A method as claimed in any one of Claims 13 to 16, wherein the metal component is a copper alloy. A method as claimed in Claim 18, wherein the copper alloy is a brass. A method as claimed in Claim 19, wherein the brass is Admiralty brass. A method of inhibiting metal corrosion in a water conducting system, having a metal component containing copper alloy and oxygen (O₂) present in the water, which comprises adding to the water therein a composition comprising at least one aminoalkylene phosphonic acid derivative in an amount of 1 to 300 ppm acid or equivalent and a manganese compound in an amount providing 0.1 to 30 ppm manganese each as defined in any one of Claims 1 to 5 and wherein no additional copper corrosion inhibitor is added to the water conducting system. A method as claimed in Claim 21, wherein said derivative is present in an amount of 2 to 50 ppm acid or equivalent and said manganese compound is present in an amount providing 0.2 to 10 ppm manganese. A method as claimed in Claim 21 or Claim 22, wherein the copper alloy is a brass. A method as claimed in Claim 23, wherein the brass is Admiralty brass. A method of inhibiting metal corrosion in a water conducting system, having a metal component containing copper alloy and oxygen (O₂) present in the water, which comprises adding to the water therein at least one aminoalkylene phosphonic acid derivative in an amount of 1 to 300 ppm acid or equivalent and a manganese compound in an amount providing 0.1 to 30 ppm manganese each as defined in any one of Claims 1 to 5 and wherein no additional copper corrosion inhibitor is added to the water conducting system. A method as claimed in Claim 25, wherein said derivative is present in an amount of 2 to 50 ppm acid or equivalent and said manganese compound is present in an amount providing 0.2 to 10 ppm manganese. A method as claimed in Claim 25 or Claim 26, wherein said manganese compound is added simultaneously with the said derivative. A method as claimed in Claim 25 or Claim 26, wherein said manganese compound is complexed by said derivative prior to adding to the water. A method as claimed in any one of Claims 25 to 28, wherein the copper alloy is a brass. A method as claimed in Claim 29, wherein the brass is Admiralty brass. The use of a composition as claimed in any one of Claims 1 to 5, to inhibit corrosion of a metal component of a water conducting system. A use as claimed in Claim 31, wherein the metal component is a copper alloy. A use as claimed in Claim 32, wherein the copper alloy is a brass. A use as claimed in Claim 33, wherein the brass is Admiralty brass.

Inventors: GRIERSON, JEFFREY GORDON, JONES, CAROL ANN, SPEARS, WILLIAM DOYCE
Applicants: THE DOW CHEMICAL COMPANY
Application year: 1985
Main classification: C23F11
IPC codes: C23F11