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
  • C23F11/10—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 using organic inhibitors

Definitions

• a composition and method for inhibiting corrosion in industrial cooling waters which contain hardness and have a pH of at least 8, which comprises a water-soluble organic phosphonate capable of inhibiting corrosion in an aqueous alkaline environment and a co- or terpolymer of acrylic acid and certain substituted acrylamides such as t-butyl acrylamide.
• phosphonate refers to organic materials containing one or more -PO3H2 groups and salts thereof.
• Phosphonates particularly useful in this invention include 1-hydroxy-1,1-ethane diphosphonic acid (HEDP), 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), amino-tris-methylenephosphonic acid (AMP), and their salts.
• HEDP 1-hydroxy-1,1-ethane diphosphonic acid
• PBTC 2-phosphonobutane-1,2,4-tricarboxylic acid
• AMP amino-tris-methylenephosphonic acid
• concentrations and dosage levels and/or ranges of polymers, phosphonates and compositions are listed as actives.
• Corrosion occurs when metals are oxidized to their respective ions and/or insoluble salts.
• corrosion of metallic iron can involve conversion to soluble iron in a 2+ or 3+ oxidation state or insoluble iron oxides and hydroxides.
• corrosion has a dual nature in that a portion of the metal surface is removed, while the formation of insoluble salts contributes to the buildup of deposits. Losses of metal cause deterioration of the structural integrity of the system. Eventually leakage between the water system and process streams can occur.
• Inhibition of metal corrosion by oxygenated waters typically involves the formation of protective barriers on the metal surface. These barriers prevent oxygen from reaching the metal surface and causing metal oxidation.
• a chemical additive In order to function as a corrosion inhibitor, a chemical additive must facilitate this process such that an oxygen-impermeable barrier is formed and maintained. This can be done by interaction with either the cathodic or anodic half-cell reaction.
• Inhibitors can interact with the anodic reaction 1 by causing the resultant Fe2+ to form an impermeable barrier, stifling further corrosion. This can be accomplished by including ingredients in the inhibitor compound which: react directly with Fe2+ causing it to precipitate; facilitate the oxidation of Fe2+ to Fe3+, compounds of which are typically less soluble; or promote the formation of insoluble Fe3+ compounds.
• Reaction (2) represents the half-cell in which oxygen is reduced during the corrosion process.
• the product of this reaction is the hydroxyl (OH ⁇ ) ion.
• OH ⁇ hydroxyl
• the pH at the surface of metals undergoing oxygen-mediated corrosion is generally much higher than that of the surrounding medium.
• Many compounds are less soluble at elevated pH's. These compounds can precipitate at corrosion cathodes and act as effective inhibitors of corrosion if their precipitated form is impervious to oxygen and is electrically nonconductive.
• Corrosion inhibitors function by creating an environment in which the corrosion process induces inhibitive reactions on the metal surface.
• the components of the composition must not precipitate under the conditions in the bulk medium.
• Inhibitors which effectively inhibit this precipitation by kinetic inhibition have been extensively described in the literature.
• An example of this art is U.S. -A- 3,880,765 which teaches the use of polymers for prevention of calcium carbonate precipitation.
• Corrosion inhibition can be achieved by a combination of the use of inhibitors and modification of the chemistry of the medium.
• U.S. -A- 4,547,540 teaches a method of corrosion inhibition relying on operation under conditions of high pH and alkalinity. This method does not rely on the use of inorganic phosphates, giving a more desirable product from an environmental impact point of view.
• the current invention describes phosphonate corrosion inhibiting compounds, containing a unique series of polymers, phosphonates and the optional use of aromatic azoles.
• the use of these polymers results in significantly improved corrosion inhibitors performance.
• copolymers of this invention as scale inhibitors is discussed in U.S. -A- 4,566,973.
• these compounds are copolymers containing t-butyl acrylamide units in conjunction with other comonomers. We have found that these compounds are effective calcium phosphonate inhibitors and that they function effectively as components in a phosphonate containing corrosion inhibitor compound.
• composition for inhibiting corrosion in industrial cooling waters which contain hardness and have a pH of at least 8 which composition comprises:
• any water-soluble phosphonate may be used that is capable of providing corrosion inhibition in alkaline systems. See U.S.-A-4,303,568 which lists a number of representative phosphonates. The disclosure is incorporated herein by reference.
• the organo-phosphonic acid compounds are those having a C-P bond, i.e.,
• R is lower alkyl having from 1 to 6 carbon atoms, e.g., methyl, ethyl, butyl, propyl, isopropyl, pentyl, isopentyl and hexyl; substituted lower alkyl of from 1 to 6 carbon atoms, e.g., hydroxyl and amino-substituted alkyls; a mononuclear aromatic (aryl) radical, e.g., phenyl, benzene, as a substituted mononuclear aromatic compound, e.g., hydroxyl, amino, lower alkyl substituted aromatic, e.g., benzyl phosphonic acid; and M is a water-soluble cation, e.g., sodium, potassium, ammonium, lithium, or hydrogen.
• aryl aryl
• M is a water-soluble cation, e.g., sodium, potassium, ammonium, lithium, or hydrogen.
• R1 is an alkylene having from 1 to 12 carbon atoms or a substituted alkylene having from 1 to 12 carbon atoms, e.g., hydroxyl, amino substituted alkylenes, and M is as earlier defined above.
• R2 is a lower alkylene having from 1 to 4 carbon atoms, or an amine or hydroxy substituted lower alkylene
• R3 is [R2-PO3M2] H, OH, amino, substituted amino, an alkyl having from 1 to 6 carbon atoms, a substituted alkyl of from 1 to 6 carbon atoms (e.g., OH, NH2 substituted) a mononuclear aromatic radical and a substituted mononuclear aromatic radical (e.g., OH, NH2 substituted)
• R4 is R3 or the group represented by the formula where R5 and R6 are each hydrogen, lower alkyl of from 1 to 6 carbon atoms, a substituted lower alkyl (e.g., OH, NH2 substituted), hydrogen, hydroxyl, amino group, substituted amino group, a mononuclear aromatic radical, and a substituted mononuclear aromatic radical
• Preferred phosphonates are the two compounds:
• additives such as tolytriazole may be utilized.
• Tolytriazole is effective in the reduction of copper substrate corrosion.
• the copolymers suitable herein are random polymers containing polymerized units of an acrylic acid and substituted acrylamide, represented by the following structural formula I: where m and n are numbers in the range of 0.1 to 700, with m being in the range of 10 to 700 and n is in the range of 0.1 to 350, subject to molecular weight limitations; R and R1 are selected from hydrogen and methyl; X is hydrogen, alkali metal, alkaline earth metal, or ammonium, particularly hydrogen, sodium, potassium, calcium, ammonium, and magnesium; and R2 and R3 are hydrogen, alkyl and substituted alkyl groups each containing a total of 1 to 8 carbon atoms, provided that both R2 and R3 are not hydrogen although either R2 or R3 can be hydrogen.
• structural formula I where m and n are numbers in the range of 0.1 to 700, with m being in the range of 10 to 700 and n is in the range of 0.1 to 350, subject to molecular weight limitations; R and R1 are selected from hydrogen and
• R2 and R3 groups include alkyl, aryl, and keto groups, however, in a preferred embodiment, R2 and R3 are selected from alkyl groups of 1 to 8 carbon atoms and substituted alkyl groups of 1 to 8 carbon atoms containing a keto substituent group. Specific examples of R2 and R3 include t-butyl, isopropyl, isobutyl, methyl, 2-(2,4,4-trimethylpentyl) and 2-(2-methyl-4-oxopentyl).
• Suitable acrylic acids for purposes herein are generally defined as monounsaturated monocarboxylic acids containing 3 or 4 carbon atoms. Specific examples of such acids include acrylic and methacrylic acids, with acrylic acid being preferred.
• Substituted acrylamides referred to herein are generally defined to include the class of acrylamides substituted on the nitrogen atom with alkyl groups each containing 1 to 8 carbon atoms.
• comonomers can be used with an acrylic acid and a substituted acrylamide provided that such additional comonomers do not deleteriously affect the desired properties.
• additional comonomers include acrylate and methacrylate esters, acrylamide and methacrylamide, acrylonitrile, vinyl esters.
• the acrylic acid units in the copolymer can be in the acid form or in a neutralized form where the hydrogen of the carboxyl group is replaced with an alkali metal, alkaline earth metal, or an ammonium cation, depending on the neutralizing medium.
• the copolymers can be neutralized with a strong alkali, such as sodium hydroxide, in which instance, the hydrogen or the carboxyl group of the acrylic acid units will be replaced with sodium.
• a strong alkali such as sodium hydroxide
• the hydrogen or the carboxyl group of the acrylic acid units will be replaced with sodium.
• an amine neutralizing agent the hydrogen will be replaced with an ammonium group
• Useful copolymers include copolymers that are unneutralized, partially neutralized, and completely neutralized.
• the copolymer is preferably formed in a high yield ranging from 50% to 99% by weight of the comonomers.
• polymers of the type described above may be modified by incorporating into their structure up to 30% by weight of a termonomer which contains; a non-ionic or anionic polar group from the group selected perferably consisting of amido, lower alkyl ester, and maleic acid salt groups.
• Examples of preferred monomers that may be polymerized to form terpolymers are acrylamide, methyl, or ethyl acrylate, maleic anhydride.
• Other polar monomers that may be used are, for example, vinyl acetate, acrylonitrile, the various vinyl ketones, and vinyl esters.
• Illustrative of these monomers are the compounds: vinyl pyrrolidone, methyl vinyl ether, methacrylonitrile, allyl alcohol, methyl methacrylate, beta-diethylaminoethyl methacrylate, vinyl trimethylacetate, methyl isobutyrate, cyclohexyl methacrylate, vinyl laurate, vinyl stearate, N-vinyl imides, N-vinyl lactams, diethylene glycol dimethacrylate, diallylmaleate, allyl methacrylate, diallyl phthalate, and diallyl adipate.
• the polymers formed may have weight average molecular weight in the range of 1,000 to 50,000 and preferably 2,000 to 30,000, as determined of known gel permeation chromatography using polystyrene of known molecular weight as a reference material.
• the acid numbers of the copolymers formed may range from 310 to 740, corresponding to a weight fraction of from 40% to 95 % by weight of monomer units having COOH groups.
• the preferred polymers have more than 50% by weight of free carboxyl groups and an acid number in the range from 390 to 700.
• Preferred species are described in Table A below as Polymer Composition Nos. 1-12.
• Polymer Composition Nos. 1-4 are unneutralized copolymers of acrylic acid and t-butylacrylamide (t-BAm).
• Polymer Composition No. 5, Polymer Composition No. 6, and Polymer Composition Nos. 7-12 are terpolymers which respectively contain the additional mer units of ethyl acrylate (EA), acrylamide (Am), and methacrylic acid (MAA).
• EA ethyl acrylate
• Am acrylamide
• MAA methacrylic acid
• the copolymers composed of acrylic acid and t-butyl acrylamide contains between 50 to 90% by weight of acrylic acid and from 50 - 10% by weight of t-butyl acrylamide.
• the acrylic acid is present in a weight percent amount ranging between 70-90 with the t-butyl acrylamide being present at between 30 - 10.
• the acrylic acid is present in a weight percent amount ranging between 80-90 with the t-butyl acrylamide being present at between 20-10.
• the terpolymers are within the following weight percent composition ranges:
• the aqueous system is dosed based on active ingredients to provide thereto on a weight basis from between 5-50ppm, preferably 8 to 40ppm and most preferably 15-30ppm of Compositions 1 and 2 previously described.
• compositions When the compositions are first added it is beneficial if they are dosed on the high side to control the corrosion and to begin forming protective films. After a week or so the dosages can be diminished until an optimum maintenance dosage is established.
• the systems treated are industrial recirculating and once through cooling waters that either due to their natural make-up or by pH adjustment have a pH of at least 8.
• the pH of the systems are within the range of 8-9.5 and are most often within the range of 8.5-9.2.
• These systems are characterized as containing at least 10 ppm of calcium ion and are considered to be corrosive to ferrous metals as well as non-ferrous with which they come in contact.
• the mixture was cooled in an ice-bath and then basified by slow addition of approximately 22 grams of aqueous sodium hydroxide (50 wt%) to the vigorously stirred solution. During the addition of base, the solution's temperature was maintained below (130°F) 55°C. The pH was adjusted to 13 with 4.7 grams of a 50 weight percent of a sodium tolyltriazole solution. Finally, sufficient softened water to produce 100 grams of product were added. The cooling bath was removed and the solution stirred until ambient temperature was reached.
• aqueous sodium hydroxide 50 wt%
• distilled water 400 ml was added to the jacketed-beakers maintained at 60 ⁇ 2°C.
• the stock solutions were added to attain 360 pm Ca2+, 10 ppm inhibitor, 5.6 ppm Dequest and 8 ppm PBS-AM in the final 500ml test volume.
• the pH was adjusted to 9.2 using aqueous sodium hydroxide.
• test samples The pH of the test samples was manually adjusted at 15 minute intervals during the first hour and at 1 hour intervals, subsequently. A 4 hour test duration was sufficient for these precipitation reactions to stabilize. Finally, a portion of each test solution was passed through cellulose acetate/nitrate Millipore filter (type HA, 0.45 ⁇ m). Both filtered and unfiltered aliquots were spectrophotometrically analyzed for total phosphate content. To study particle size effects, an additional sample was passed through a 0.10 ⁇ m Millipore filter (type VC). The % inhibition was determined by a following formula:
• the calcium phosphonate "inhibition" process involves minimizing particle growth. Maintaining scale particles at an extremely small size and mass may ultimately prove to be a pivotal factor in determining polymer performance.
• filters with mean pore sizes of 0.10 and 0.45 ⁇ m differences in polymer performance were readily observed.
• Versa TL-4 the low molecular weight copolymer of sulfonated styrene and maleic acid
• Polymer Composition Nos. 1 and 5 exhibited very good inhibition (0.45 ⁇ m filter), but performance decreased rapidly when the filter pore size was reduced to 0.10 ⁇ m.
• Polymer Composition No. 11 exhibited the best overall performance in both bench-top and PCT tests.
• the pilot cooling tower test is a dynamic test which simulates many features present in an industrial recirculating cooling water system.
• the general test method is described in the article "Small-Scale Short-Term Methods of Evaluating Cooling Water Treatments...Are They Worthwhile?", by D. T. Reed and R. Nass, Minutes of the 36th Annual Meeting of the INTERNATIONAL WATER CONFERENCE, Pittsburgh, Pennsylvania, November 4-6, 1975.
• Tolytriazole is explained inhackh's Chemical Dictionary, Fourth Edition, page 91 (CF. benzotriazole) and is employed as a corrosion inhibitor for copper and copper alloy surfaces in contact with water when it is used it is applied to the system at a dosage ranging between 1-20ppm by weight.

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• 1986
  • 1986-12-30 EP EP86118127A patent/EP0238728B1/fr not_active Expired - Lifetime
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• 1987
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