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
  • C23F11/14—Nitrogen-containing compounds
  • C23F11/149—Heterocyclic compounds containing nitrogen as hetero atom
• • 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
  • 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
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F2303/00—Specific treatment goals
  • C02F2303/08—Corrosion inhibition

Definitions

• aqueous systems any system containing metals which contain or are contacted with aqueous fluids on a regular basis.
• Water-based fluids are typically fluids that contain at least about 50 weight percent water, the remainder being solids (suspended and/or dissolved) and/or nonaqueous fluids.
• the term aqueous fluids is intended to include not only water-based fluids, but also fluids that are predominantly non-aqueous but have sufficient water present, at least about
• Such non-aqueous fluids may be miscible or immiscible with water.
• Typical aqueous systems include, but are not limited to, open recirculating cooling systems which obtain their source of cooling by evaporation, closed loop cooling systems, boilers and similar steam generating systems, heat exchange equipment, reverse osmosis equipment, oil production systems, flash evaporators, desalinization plants, gas scrubbers, blast furnaces, paper and pulp processing equipment, steam power plants, geothermal systems, food and beverage processing equipment, sugar evaporators, mining circuits, bottle washing equipment, soil irrigation systems, closed circuit heating systems for residential and commercial use, aqueous- based refrigeration systems, down-well systems, aqueous machining fluids (e.g.
• aqueous scouring systems for use in boring, milling, reaming, broaching, drawing, turning, cutting, sewing, grinding and in thread-cutting operations, or in non-cutting shaping, spinning, drawing, or rolling operations
• aqueous scouring systems for use in boring, milling, reaming, broaching, drawing, turning, cutting, sewing, grinding and in thread-cutting operations, or in non-cutting shaping, spinning, drawing, or rolling operations
• aqueous scouring systems for use in boring, milling, reaming, broaching, drawing, turning, cutting, sewing, grinding and in thread-cutting operations, or in non-cutting shaping, spinning, drawing, or rolling operations
• water/glycol hydraulic fluids for use in boring, milling, reaming, broaching, drawing, turning, cutting, sewing, grinding and in thread-cutting operations, or in non-cutting shaping, spinning, drawing, or rolling operations
• water/glycol hydraulic fluids for use in boring, milling, reaming, bro
• the aqueous systems that may be treated using the compositions of this invention may contain dissolved oxygen, such as might be obtained from absorbing oxygen from ambient air, or they may be substantially or completely oxygen free. Further, the aqueous system may contain other dissolved gases such as carbon dioxide, hydrogen sulfide, or ammonia, or they maybe substantially or completely free of such gases.
• aqueous systems may have uniform corrosion over the entire metal surface.
• the aqueous system may also have localized corrosion, such as pitting or crevice corrosion, where the corrosion is found only in certain locations on the metal surface.
• control of localized corrosion may be the critical factor in prolonging the useful life of the metal equipment in the aqueous system.
• aqueous systems which contain high levels of aggressive anions such as chloride and sulfate are particularly prone to both generalized and localized attack. These aggressive anions may be present in the water source used for the aqueous system at levels that cause problems, or they may be concentrated to harmful levels in the aqueous system because they are part of a system that evaporates water such as an evaporative cooling system.
• oligomer we mean materials produced by the polymerization of a single monomer where the number of monomer units incorporated in the product is between 2 and about 10.
• polymer we mean materials produced by the polymerization of a single monomer without restriction on the number of monomer units incorporated into the product.
• co-oligomer we mean materials produced by the polymerization of more than one type of monomer (including 2, 3, 4, etc. different monomers) where the total number of monomer units incorporated in the product is between 2 and about 10.
• co-polymers we mean materials produced by the polymerization of more than one type of monomer (including 2, 3, 4, etc. different monomers) without restriction on the number of monomer units incorporated into the product.
• the method ofthe present invention comprises treating industrial waters with a tetrazolium salt ofthe general formula:
• R,, R 2 and R 3 can be various organic and inorganic substituents, e.g., from the group consisting of lower alkyl, aryl, aralkyl, and heterocychc substituted aryl with the proviso that neither R,, R 2 or R 3 contain more than 14 carbon atoms, and n may be 1 or 2.
• the compounds may contain positive or negative counter ions in order to balance the charges on the above structure. Chemical or electrochemical reduction of this type of compound produces tetrazolinyls and formazans that readily adsorb on metal surfaces and provide films for corrosion protection. We have also discovered that certain tetrazolium compounds given by the generalized formula:
• R,, R 2 and R 3 can be various organic and inorganic substituents, e.g., from the group consisting of lower alkyl, branched lower alkyl, aryl, substituted aryl, alkylaryl, substituted alkylaryl and heterocychc substituted aryl with the proviso that none of R,, R 2 or R 3 contain more than 14 carbon atoms, and n may be 1 or 2, synergistically combine with a wide range of compounds to provide effective general and localized corrosion protection for metals in aqueous systems. If the components chosen to be combined with the tetrazolium compounds are also scale and/or deposition inhibitors, the combinations will also provide scale and/or deposition inhibition for these aqueous systems.
• Anions and/or cations may be associated with the above structure to balance the charge depending upon the substitutions employed. If R,, R 2 and R 3 are all neutral, then the structure shown in the above formula will be positively charged and anionic species will be needed.
• the anions and/or cations utilized for balancing can be any such anions and/or cations, such as halogens, nitrates, nitrites, carbonates, bicarbonates, sulfates, phosphates, and transition metal oxygenates.
• a counter ion that is an anion with a single negative charge e.g., Cl "
• the charge associated with R,, R 2 and R 3 is not neutral, such as if the groups included sulfono, carboxyl and/or quaternary nitrogen, associated counter-ions should be present to provide a neutral charge for the tetrazolium compound.
• the tetrazolium compound could be a zinc chloride salt wherein the Zn "2 neutralizes the two carboxyl charges and the Cl " neutralizes the positive charge ofthe two ring nitrogens.
• Examples of such tetrazolium compounds that may be utilized according the this invention include Nitroblue Tetrazolium chloride (3,3'-(3,3'-Dimethoxy-4,4'-biphenylene)-bis-[2-p- nitrophenyl-5-phenyl-2H-tetrazolium chloride]), hereafter referred to as NBT, Distyryl Nitroblue Tetrazolium Chloride (2,2 ' -Di-p-nitrophenyl-5 ,5 ' -distyryl-3 ,3 ' - [3 ,3 ' -dimethoxy-4,4 ' - biphenylene] ditetrazolium chloride), hereafter referred to as DNBT, Tetranitroblue Tetrazolium chloride (3,3'-(3,3'-Dimethoxy-4,4'-biphenylene)-bis-[2,5-p-nitrophenyl-2H-tetrazolium chloride]), hereafter referred to as TNBT
• the metals in the aqueous system can be any metal for which corrosion and/ or scaling can be prevented.
• the metal can be non-ferrous metals, such as copper, aluminum, or ferrous metals, such as iron, steel, e.g. low carbon steel, and stainless steel, e.g. iron based alloys containing chromium as the main alloying element, such as steels containing between about 11 to 30% Cr, which exhibit excellent corrosion resistance to many environments.
• the present invention provides particularly beneficial results in that even when the tetrazolium compound is utilized by itself without the addition of other materials, including other anti-corrosion and/or scale prevention ingredients, low concentrations of the tetrazolium compounds can be utilized. This is especially the situation when the tetrazolium compounds are utilized in aqueous systems, in the presence of oxygen, wherein the pH ofthe system to be treated is about 6 or greater, such as cooling water systems, steam generating systems, gas scrubbing systems, and pulping and papermaking systems.
• the tetrazolium compounds of the present invention can preferably be added to the aqueous system at active treatment levels ranging from about 0.1 to about 50 parts per million, with treatment levels of from about 1 to about 25 parts per million being particularly preferred.
• the present invention is directed to methods for controlling corrosion of stainless steel in contact with an aqueous system which comprises introducing into said system at least one tetrazolium compound ofthe formula:
• R contest R 2 and R 3 are selected from the group consisting of lower alkyl, branched lower alkyl, aryl, substituted aryl, alkylaryl, substituted alkylaryl and heterocychc substituted aryl, with the proviso that neither R perpetrat R 2 , or R 3 contain more than 14 carbon atoms; and n is 1 or 2, such tetrazolium compound optionally having associated water soluble ionic species if needed to obtain a neutral charge.
• the aqueous system can include at least one other aqueous system treatment material chosen so that the material does not substantially reduce the tetrazolium compound. Such material can be added with the tetrazolium compound or separately therefrom.
• the other aqueous system treatment material is selected from the group consisting of inorganic phosphates, borates, nitrites, compounds that release a metal anion in water, 2,3- dihydroxybenzoic acid, 1,10-phenanthroline, polycarboxylates, hydrocarbyl polycarboxylates, alkyl hydroxycarboxylic acids, aminohydroxysuccinic acids, carboxyamines, polyepoxysuccinic acids, modified polyepoxysuccinic acids, monophosphonic acids, diphosphonic acids, phosphonocarboxylic acids, hydroxyphosphonocarboxylic acids, aminophosphonic acids, phosphonomethylamine oxides, polymeric amine oxides, polyetherpolyaminomethylene phosphonates, polyethe ⁇ olyamino-methylene phosphonate N-oxides, immoalkylenephosphonic acids, long chain fatty acid derivatives of sarcosine; telomeric, co-telomeric, polymeric, or copoly
• the present invention also provides beneficial results when combined with other compounds, such as compounds disclosed in U.S. Patent Application Nos. 09/136,884, filed August 19, 1998, 09/303,596, filed May 3, 1999, 09/304,181, filed May 3, 1999, and 09/309,564, filed May 12, 1999, the disclosures of which are inco ⁇ orated by reference herein.
• Examples of compounds that may be combined with the tetrazolium compounds to provide synergistically improved corrosion protection include: inorganic phosphates, such as orthophosphates or polyphosphates, borates, nitrites, and compounds that release a metal anion in water, where the metal anion is selected from the group consisting of molybdates, tungstates, vanadates, metavanadates, chromates or mixtures thereof.
• the inorganic phosphates can include orthophosphates, polyphosphates, water soluble salts thereof and mixtures thereof, such as a mixture of orthophosphoric acid and pyrophosphoric acid or the water-soluble salts thereof, such as the sodium and potassium salts thereof.
• the borates can comprise various borates, such as water-soluble borate selected from tetraborates, metaborates, and/or orthoborates, such as sodium tetraborate or a hydrate of sodium tetraborate.
• the nitrates can include nitrites such as sodium nitrite.
• Additional materials that may be combined with the tetrazolium compounds include polyacrylic acid or polymaleic acid, such as disclosed in the above-noted U.S. Application No. 09/304,181, filed May 3, 1999. Particularly preferred polyacrylic and polymaleic acids have a molecular weight of about 8,000 or below. Additional materials that may be combined with the tetrazolium compounds include polycarboxylates.
• the polycarboxylates may be simple aliphatic compounds containing between 4 and about 20 carbon atoms in the aliphatic chain which are multiply substituted with carboxyl groups (e.g., C 4 -C 15 ⁇ , ⁇ -dicarboxylates or compounds such as 1, 2, 3, 4-butanetetracarboxylic acid) or water soluble salts thereof, or may be polymeric compounds.
• the polymeric polycarboxylates may be homopolymers or copolymers (including te ⁇ olymers, tetrapolymers, etc.) of ethylenically unsaturated monomers that contain a carboxyl group.
• the polycarboxylates can comprise a copolymer obtained from the polymerization of two or more different ethylenically unsaturated monomers, each of the monomers containing one or more carboxyl groups.
• examples of such polymeric polycarboxylates include polyacrylic acid, polymaleic acid, and polymaleic anhydride, and their water soluble salts.
• the polycarboxylates may be hydrocarbyl polycarboxylates as disclosed in U.S. Patent 4,957,704, herein inco ⁇ orated by reference.
• Additional materials which may be combined with the tetrazolium compounds of the present invention include alkyl hydroxycarboxylic acids or a mixture of such alkyl hydroxycarboxylic acids having the formula:
• Y and Z are separately selected from the group of H, OH, CHO, COOH, CH 3 , CH 2 (OH), CH(OH) 2 , CH 2 (COOH), CH(OH)COOH, CH 2 (CHO) and CH(OH)CHO, so selected that the molecule has a minimum of one OH group when written in its fully hydrated form and R B4 is either H or COOH, including the various stereoisomers and chemically equivalent cyclic, dehydrated, and hydrated forms of these acids and hydro lyzable esters and acetals that form the above compounds in water or the water soluble salts of such alkyl hydroxycarboxylic acids.
• hydroxycarboxylic acids examples include tartaric acid, mesotartaric acid, citric acid, gluconic acid, glucoheptonic acid, ketomalonic acid and saccharic acid, and their water soluble salts.
• Additional materials which may be combined with tetrazolium compounds include aminohydroxysuccinic acid compounds (or mixtures of such ammohydroxysuccinic acid compounds) such as those disclosed in U.S. Patent 5,183,590, herein inco ⁇ orated by reference.
• Suitable aminohydroxysuccinic acids include those selected from the group consisting of compounds ofthe generalized formulas:
• R ⁇ is H or C, to C 4 alkyl, optionally substituted with — OH, — CO 2 H, — SO 3 H, or phenyl, C 4 to C 7 cycloalkyl, or phenyl which is optionally substituted with — OH or — CO 2 H
• R ⁇ - 2 is H, C, to C 6 alkyl, optionally substituted with OH or CO 2 H (specifically including the moiety — CH(CO 2 H)CH(OH)(CO 2 H)) ;
• R ⁇ is as above, and Z c is selected from the group consisting of i) (CH 2 ) k — wherein k is an integer from 2 to 10, ii) — (CH 2 ) 2 — X ⁇ — (CH 2 ) 2 — wherein X c is — O — , — S — , — NR ⁇ -, wherein R C3 is selected from the group consisting of H, C, to C 6 alkyl, hydroxyalkyl, carboxyalkyl, acyl, — C(O)ORc 4 wherein R ⁇ is selected from the group consisting of C, to C 6 alkyl or benzyl and a residue having the general formula:
• Y is H, C, to C 6 alkyl, alkoxy, halogen, — CO 2 H, — SO 3 H, m is independently 0 or 1, and p is 1 or 2, and
• R C5 and R ⁇ are independently H or C, to C 6 alkyl
• Q is H or C, to C 6 alkyl
• s is 0, 1 or 2
• t is independently 0, 1, 2, or 3
• q is 0, 1, 2, or 3
• r is 1 or 2 or water soluble salts thereof.
• aminohydroxysuccinic acid compounds include iminodi(2- hydroxysuccinic acid), N,N'-Bis(2-hydroxysuccinyl)-l,6-hexanediamine, and N,N'-Bis(2- hydroxysuccinyl)-m-xylylenediarnine, or the water soluble salts thereof. It is preferred to utilize a mixture of orthophosphric acid or its water soluble salts with a least one aminohydroxysuccinic acid.
• Additional materials which may be combined with the tetrazolium compounds include the carboxyamine compounds which are reaction products of carboxylating agents such as epoxysuccinic acid with amines comprising a plurality of nitrogen atoms such as polyethylene polyamines as disclosed in the International Patent Application WO 96/33953, herein inco ⁇ orated by reference.
• carboxylating agents such as epoxysuccinic acid with amines comprising a plurality of nitrogen atoms
• polyethylene polyamines as disclosed in the International Patent Application WO 96/33953, herein inco ⁇ orated by reference.
• PESAs polyepoxysuccinic acids
• M ⁇ is hydrogen or a water soluble cation such as Na + , NH 4 + , or K + and R ⁇ is hydrogen, C M alkyl or C M substituted alkyl (preferably R ⁇ is hydrogen).
• R ⁇ is hydrogen, and 1 ranges from about 2 to about 10, or from about 4 to about 7.
• a corrosion inhibition process utilizing a combination of an orthophosphate, a polyepoxysuccinic acid, an acrylic acid/allyl hydroxy propyl sulfonic acid polymer, and an azole has been disclosed in U.S. Patent 5,256,332, herein inco ⁇ orated by reference.
• Preferred mixture include a mixture of orthophosphoric acid and/or its water soluble salts and polyepoxysuccinic acid.
• R D1 when present, is H, a substituted or non-substituted alkyl or aryl moiety having a carbon chain up to the length where solubility in aqueous solution is lost, or a repeat unit obtained after polymerization of an ethylenically unsaturated compound;
• R D2 and R D3 each independently are H, C, to C 4 alkyl or C, to C 4 substituted alkyl;
• Z D is O, S, NH, or NR D1 , where R D!
• Use of such compounds have been disclosed in U.S. Patents 5,871,691 and 5,489,666, herein inco ⁇ orated by reference.
• modified polyepoxysuccinic acids include derivatives according to the above formula where R DI is meta-CH 2 -C 6 H 4 -CH 2 - (m-Xylylene), Z D is -NH-, both R D2 and R D3 are H, f is 2, and M D is Na or H.
• Practical examples are typically mixtures where the individual molecules have a range of u, and are hereafter referred to as m- Xylylenediamine/PESA derivatives.
• Additional compounds that may be combined with the tetrazolium compounds include 2,3- dihydroxybenzoic acid and 1,10-phenanthroline.
• Additional compounds that may be combined with the tetrazolium compounds include monophosphonic acids having the generalized formula:
• R F is a C, to C 12 straight or branched chain alkyl residue , a C 2 to C 12 straight or branched chain alkenyl residue, a C 5 to C 12 cycloalkyl residue, a C 6 to C 10 aryl residue, or a C 7 to C 12 aralkyl residue, and where R F may additionally be singly or multiply substituted with groups independently chosen from hydroxyl, amino, or halogen; and diphosphonic acid compounds having the generalized formula:
• R ⁇ is a C, to C 12 straight or branched chain alkylene residue, a C 2 to C ]2 straight or branched chain alkenylene residue, a C 5 to C 12 cycloalkylene residue, a C 6 to C ]0 arylene residue, or a C 7 to C 12 aralkylene residue where R ⁇ may additionally be singly or multiply substituted with groups independently chosen from hydroxyl, amino, or halogen, or water soluble salts thereof.
• a preferred example of such a diphosphonic acid is 1-hydroxyethane- 1,1 -diphosphonic acid (HEDP) or water soluble salts thereof.
• Additional materials which may be combined with the tetrazolium compounds include phosphonocarboxylic acids (or mixtures of such phosphonocarboxylic acids) such as those disclosed in U.S. Patents 3,886,204, 3,886,205, 3,923,876, 3,933,427, 4,020,101 and 4,246,103, all herein inco ⁇ orated by reference.
• R H1 is H, alkyl, alkenyl, or alkinyl radical having 1 to 4 carbon atoms, an aryl, cycloalkyl, or aralkyl radical, or the radical selected from the following:
• R m is H, alkyl radical of 1 to 4 carbon atoms, or a carboxyl radical; and ⁇ is selected from the following:
• phosphonocarboxylic acid 2- phosphonobutane-l,2,4-tricarboxylic acid, or water soluble salts thereof.
• hydroxyphosphonocarboxylic acids or mixtures of such hydroxyphosphonocarboxylic compounds
• Suitable hydroxyphosphonocarboxylic acids includes those having the generalized formula:
• R E is H, a C, to C 12 straight or branched chain alkyl residue, a C 2 to C 12 straight or branched chain alkenyl residue, a C 5 to C 12 cycloalkyl residue, a C 6 to C 10 aryl residue, or a C 7 to C 12 aralkyl residue
• X E is an optional group, which when present is a C, to C, 0 straight or branched chain alkylene residue, a C 2 to C 10 straight or branched chain alkenylene residue, or a C 6 to C 10 arylene residue or water soluble salts thereof.
• a preferred example of such a hydroxyphosphonocarboxylic acid is 2-hydroxy-phosphonoacetic acid, or water soluble salts thereof.
• Additional materials which may be combined with the tetrazolium compounds include aminophosphonic acids such as those disclosed in U.S. Patents 3,619,427, 3,723,347, 3,816,333, 4,029,696, 4,033,896, 4,079,006, 4,163,733, 4,307,038, 4,308,147 and 4,617,129, all herein inco ⁇ orated by reference.
• Suitable aminophosphonic acids include those having the generalized formula:
• R ⁇ is a lower alkylene having from about one to about four carbon atoms, or an amine, hydroxy, or halogen substituted lower alkylene;
• R G3 is R Q2 — PO 3 H 2 , H, OH, amino, substituted amino, or R F as previously defined;
• R ⁇ is R ⁇ or the group represented by the generalized formula:
• R ⁇ and R ⁇ are each independently chosen from H, OH, amino, substituted amino, or R F as previously defined;
• R ⁇ is R Q5 , R ⁇ , or the group R ⁇ — PO 3 H 2 with R ⁇ as previously defined;
• v is an integer from 1 to about 15;
• w is an integer from 1 through about 14 or water soluble salts thereof.
• An example of such an aminophosphonic acid is diethylenetriamine penta(methylenephosphonic acid), or water soluble salts thereof.
• Additional materials which may be combined with the tetrazolium compounds include water soluble phosphonomethyl amine oxides (or mixtures of such water soluble phosphonomethyl amine oxides) such as those disclosed in U.S. Patents 5,051 ,532, 5,096,595, and 5,167,866, all herein inco ⁇ orated by reference.
• Suitable phosphonomethyl amine oxides include those having the generalized formula:
• R A1 is selected from the group consisting of hydrocarbyl, and hydroxy-substituted, alkoxy-substituted, carboxyl-substituted and sulfonyl-substituted hydrocarbyl; and R ⁇ is selected from the group consisting of hydrocarbyl, and hydroxy-substituted, alkoxy-substituted, carboxyl- substituted and sulfonyl-substituted hydrocarbyl, — CH 2 PO 3 H 2 , and
• Hydrocarbyl includes alkyl, aryl, and alkaryl groups which do not render the amine oxide insoluble in water.
• a preferred example of such a phosphonomethylamine oxide is N,N-bis-phosphonomethylethanolamine N-oxide, hereafter referred to as EBO, or water soluble salts thereof.
• Additional materials which may be combined with the tetrazolium compounds include polymeric amine oxides as described in U.S. Patent 5,629,385, herein inco ⁇ orated by reference, polyether polyaminomethylene phosphonates and polyether polyamino methylene phosphonate N-oxides, as described in U.S. Patents 5,338,477 and 5,322,636, respectively, both herein inco ⁇ orated by reference, and iminoalkylenephosphonic acids, as described in U.S. Patent
• Additional materials which may be combined with the tetrazolium compounds include phosphorus-containing carboxylate materials (hereafter, P-carboxylates) which are telomeric, co- telomeric, polymeric or co-polymeric compounds that include at least one organic phosphorus group and multiple carboxylate groups.
• P-carboxylates phosphorus-containing carboxylate materials
• these materials may also include other substituent groups when the P-carboxylates are produced from monomers which contain substituents other than carboxylate.
• the phosphorus may be present as an end group, in which case it may be a phosphono or end-type phosphino-type moiety, or may be inco ⁇ orated into the compound as a phosphino moiety in which the phosphorus is directly bonded to two carbon atoms, a configuration sometimes referred to as a "dialkyl" phosphino moiety.
• dialkyl phosphino moiety
• X may be hydrogen or a cationic species such as an alkali metal ion, an ammonium ion, or a quaternized amine radical.
• Y may be the same as X or additionally may be a substituted or non-substituted alkyl, aryl, or alkylaryl residue, where the substitutions may or may not contain carboxylate. Y must be chosen so as to maintain adequate solubility ofthe compound in water.
• the carbon atoms shown are part ofthe carbon backbone ofthe telomer, co-telomer, polymer, or co-polymer, this backbone containing at least two carboxyl groups and optionally other phosphorus inco ⁇ orations and optionally other non-carboxyl substitutions.
• P-carboxylates having number average molecular weights under 10,000, and particularly preferred are oligomeric or polymeric P-carboxylates of low number average molecular weight, e.g., 2,000 or less, and especially 1,000 or less. It is particularly preferred that 2 or more carboxylates are substituted on a linear alkyl residue, in order of preference, in a 1,2- (adjacent) or a 1,3-substitution arrangement.
• the P-carboxylates may contain the phosphorus substitution or substitutions predominantly or exclusively as phosphono species, predominantly or exclusively as end-type phosphino species, predominantly or exclusively as dialkylphosphino species, or contain a mixture of these substitution types on an individual molecule and/or in the mixture of molecules generated by a particular preparative process.
• the various preparative processes used for P-carboxylates may also generate various inorganic phosphorus species as part ofthe synthetic process. Such mixtures of P-carboxylates and the associated inorganic phosphorus species when combined with tetrazolium compounds are considered to be within the scope of this invention.
• Non-limiting examples of the preparation of P-carboxylates suitable for use in this invention and their use as corrosion and/or scale control agents alone and in combination with other water treatment agents in aqueous systems are disclosed in U.S. patents 2,957,931, 4,046,707, 4,088,678, 4,105,551, 4,127,483, 4,159,946, 4,207,405, 4,239,648, 4,563,284,
• the processes disclosed in the art typically involve reaction of a phosphorus-containing material with one or more unsaturated monomers, at least one of which is a carboxyl monomer, to generate P- carboxylate oligomers or polymers.
• suitable carboxyl monomers include acrylic acid, maleic acid, maleic anhydride, methacrylic acid, itaconic acid, crotonic acid, vinyl acetic acid, fumaric acid, citraconic acid, mesaconic acid, acrylonitrile, methacrylonitrile, alpha-methylene glutaric acid, cyclohexenedicarboxylic acid, cis-l,2,3,6-tetrahydrophthalic anhydride, 3,6-epoxy- 1,2,3,6-tetrahydrophthalic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, bicyclo[2.2.2]-5- octene-2,3-dicarboxylic anhydride, 3-methyl-l,2,6-
• Preferred carboxyl monomers are acrylic acid, maleic acid, itaconic acid, and maleic anhydride.
• P-carboxylate materials contain a major proportion of residues that bear carboxyl groups, it may be advantageous to utilize co-oligomeric or co-polymeric P- carboxylates that contain residues that are derived from at least one carboxyl monomer and a minor proportion (under 50 percent by weight ofthe total product) of residues obtained from at least one other monomer that is not a carboxyl monomer.
• non-carboxyl monomers include, for example, 2-acrylamido-2-methylpropanesulfonic acid (commercially available as AMPSTM from the Lubrizol Co ⁇ oration), 2-hydroxy-3-(2- propenyloxy)propanesulfonic acid, 2-methyl-2-propene-l-sulfonic acid, allylsulfonic acid, allyloxybenzenesulfonic acid, styrenesulfonic acid, vinylsulfonic acid, allylphosphonic acid, vinylphosphonic acid, isopropenylphosphonic acid, phosphoethyl methacrylate, hydroxyalkyl and C,-C 4 alkyl esters of acrylic or methacrylic acid, acrylamides, alkyl substituted acrylamides, allyl alcohol, 2-vinyl pyridine, 4-vinyl pyridine, N-vinylpyrrolidone, N-vinylformamide, N- vinylimidazole, vinyl acetate
• phosphonic polymers having the generalized formula:
• X is H, an alkali metal atom, an alkaline earth metal atom, or an ammonium or amine residue
• Rj is a copolymer residue comprising two different residues
• z is an integer ranging from 2 to 100, and wherein, in the first residue, R J2 is -COOH, and in the second residue, R J2 is -CONHC(CH 3 ) 2 CH 2 SO 3 Xj, wherein X j is as hereinbefore defined.
• P-carboxylate materials suitable for use in this invention include
• FMC co ⁇ oration FMC co ⁇ oration
• phosphonosuccinic acid FMC co ⁇ oration
• Bricorr 288 a product of Albright and Wilson
• Bricorr 288 is described as a composition which consists essentially of up to 50% by weight of a phosphonosuccinic acid, based on the weight ofthe composition, a phosphonated dimer of alkali metal maleate, not more than a minor proportion by weight, based on the weight ofthe dimer, of higher phosphonated oligomers of maleate; and from about 0.5 to about 5% by weight of the composition of an alkali metal phosphate.
• Additional materials which may be combined with the tetrazolium compounds include long chain fatty acid derivatives of sarcosine (or mixture of such fatty acid sarcosine derivatives) or their water soluble salts.
• sarcosine or mixture of such fatty acid sarcosine derivatives
• water soluble salts An example of such a derivative is N-Lauroylsarcosine.
• the tetrazolium compounds of this invention may also be combined with water soluble alkali metal silicates, such as sodium metasilicate.
• water soluble alkali metal silicates such as sodium metasilicate.
• silicates are well known in the art as corrosion inhibitors for both ferrous metals and aluminum, both in systems where the fluid is predominantly water as well as in glycol-based aqueous systems typically used as antifreeze coolants for internal combustion engines.
• the sodium silicates may be represented generically by the formula Na 2 O «xSiO 2 «yH 2 O where x is in the range of about 1 to about 3.5. Commercial sodium silicate solutions in which the mole ratio of silica to soda is about 3.3 may be used.
• More alkaline solutions having an SiO 2 : Na ⁇ mole ratio as low as about 1:1 or less alkaline solutions having a an SiO ⁇ Na j O mole ratio up to about 3.5:1 can also be used.
• Other alkali metal silicate salts, especially potassium silicate may also be employed.
• water soluble alkali metal silicates in the practice ofthe current invention, it may be advantageous to combine the silicates with other inhibitors and/or silica stabilizers. Examples of such suitable combinations are disclosed in U.S. Patents 3,711,246, 4,085,063, 4,404,114, 5,137,657, 5,262,078, 5,578,246, and 5,589,106, all herein inco ⁇ orated by reference.
• the tetrazolium compounds of this inventions may also be combined with water soluble monofluorophosphate salts.
• the use of such salts as corrosion inhibitors for metallic surfaces has been disclosed in U.S. Patents 4,132,572 and 4,613,450, both herein inco ⁇ orated by reference.
• U.S. Patent 5,182,028, herein inco ⁇ orated by reference such salts also have utility for calcium carbonate scale control and in iron and manganese stabilization.
• a wide variety of additional aqueous system corrosion inhibitors suitable for combination with the tetrazolium materials in this invention are known in the art. Non-limiting examples of such inhibitors may be found in Corrosion Inhibitors, C.C.
• Such inhibitors include amines (e.g., mo ⁇ holine, cyclohexylamine, benzylamine), alkanolamines, ether amines, diamines, fatty amines and diamines, quaternized amines, oxyalkylated amines, alkyl pyridines; tetrazoles such as those disclosed in U.S.
• patent 5,744,069 herein inco ⁇ orated by reference; imidazoline and substituted imidazolines, amidoamines, polyamines, including polyalkylenepolyamines such as those disclosed in U.S. patent 5,275,744, herein inco ⁇ orated by reference, alkyl derivatives of benzene sulfonic acid, benzoates and substituted benzoates (e.g., p-tert-butylbenzoic acid as disclosed in U.S.
• patent 5,275,744, herein inco ⁇ orated by reference aminobenzoates, salicylates, dimer-trimer acids, petroleum oxidates, borogluconates; lignins, tannins, and the sulfonated and/or carboxylated derivatives thereof (e.g., lignosulfonates); straight chain C 5 -C,, monocarboxylates, amine salts of carboxylic acids and mercaptocarboxylic acids such as those disclosed in U.S. Patent 5,779,938, herein inco ⁇ orated by reference; amino acids, polyamino acids, and derivatives thereof such as those disclosed in U.S.
• phospho- and phosphate esters e.g., of ethoxylated alcohols
• additional agents include dispersants, copper corrosion inhibitors, aluminum corrosion inhibitors, water soluble metal salts and their chelates, scale and deposit control agents, sequestering agents, anti- foams, oxidizing and non-oxidizing biocides, non-ionic and ionic freezing point depressants, pH adjusting agents, inert and active tracers, water insoluble and soluble lubricants, surfactants, calcium hardness adjusting agents, and coloring agents.
• Dispersants are often needed to maintain system cleanliness when the aqueous system contain suspended particulate matter.
• a wide variety of polymeric and non-polymeric dispersants are known in the art which may be used in the practice of this invention.
• Preferred are a) water- soluble sulfonated polymers or copolymers obtained from the polymerization of one or more ethylenically unsaturated monomers, at least one of which contains sulfonate functionality, or the water soluble salts thereof or b) copolymers of diiosbutylene and maleic anhydride with molecular weights ⁇ 10,000 or the water soluble salts thereof.
• Additional agents that may be combined with the tetrazolium compounds of this invention include copper corrosion inhibitors, including heterocychc ring type copper inhibitors such as azole compounds.
• azoles are typically used to provide corrosion protection for copper-based alloys.
• heterocychc ring type copper inhibitors additionally provide corrosion protection for ferrous-based metals and/or aluminum, and the use of such materials for these pu ⁇ oses is considered to be within the scope of this invention.
• Suitable azole compounds include triazoles, tetrazoles, pyrazoles, imidazoles, isoxazoles, oxazoles, isothiazoles, and thiazoles, all optionally substituted with alkyl, aryl, aralkyl, alkylol, and alkenyl radicals, including those disclosed in U.S. Patents 2,618,608, 2,742,369, and 2,941,953 and summarized in U.S.
• Suitable azoles and related heterocylic ring compounds include benzotriazole, tolyltriazole, alkyl or alkoxy substituted benzotriazoles wherein the substitution occurs on the 4 or 5 position of the benzene ring, 2-mercaptobenzothiazole, 2-mercaptobenzotriazole, 1,2,3- triazole, 4-phenyl-l,2,3-triazole, 1,2-napthotriazole, 4-nitrobenzotriazole, pyrazole, 6- nitroindazole, 4-benzylpyrazole, 4,5-dimethylpyrazole, 3-allylpyrazole, imidazole, adenine, guanine, benzimidazole, 5-methyl benzimidazole, 2-phenyl imidazole, 2-benzyl imidazole, 4- allylimidazole, 4-(betahydroxy efhyl)-imidazole,
• Suitable azoles include mixed compositions such as a tolyltriazole composition which includes at least 65% ofthe 5-methylbenzotriazole isomer by weight as disclosed in U.S. Patent 5,503,775, herein inco ⁇ orated by reference.
• halogen-tolerant azoles which give improved corrosion performance, no objectionable odor, and reduced biocide consumption when halogen-based oxidizing biocides (e.g., chlorine) are used in the aqueous system.
• halogen-based oxidizing biocides e.g., chlorine
• Non-limiting examples of such halogen-tolerant azoles are disclosed in U.S. Patents 5,772,919, 5,863,463 and 5,863,464, herein inco ⁇ orated by reference, and include chloro- tolyltriazole, bromotolyltriazole, mono-halo-benzotriazole, di-halo-benzotriazole, and mixtures of mono-halo and di-halo-benzotriazoles.
• Preferred azoles are tolyltriazole, benzotriazole and halogen-tolerant azoles, especially chloro-tolyltri azole.
• Additional agents that may be combined with the tetrazolium compounds of this invention include aluminum corrosion inhibitors.
• Preferred are water soluble nitrate salts, particularly sodium nitrate, and the combination of nitrate salts with alkali metal silicates.
• Additional agents that may be combined with the tetrazolium compounds of this invention include water-soluble metal salts of metals chosen from the group zinc, manganese, aluminum, tin, nickel, yttrium, and the rare earth metals (atomic numbers 57 to 71) and/or organic metal chelates of such metals, where the organic chelant is chosen to impart a desired level of water solubility ofthe metal ion. As is known in the art, such metal salts and chelates may be utilized to provide additional corrosion protection.
• zinc ions as a corrosion inhibitor is well known in the art, especially in combination with other water treatment agents such as phosphates, phosphonates, P-carboxylates, carboxylates and hydroxycarboxylates.
• Preferred sources of zinc ions are the sulfate, chloride, acetate, or nitrate zinc salts and the zincate ion obtained by dissolving zinc oxide in base. Particularly preferred are the sulfate and chloride salts and the zincate ion.
• Additional agents that may be combined with the tetrazolium compounds of this invention include scale and deposit control agents. Although many of the previously described combinations of this invention provide both corrosion and scale and/or deposit control
• Additional agents that may be combined with the tetrazolium compounds of this invention include sequestering agents. Such agents are needed to prevent metallic (e.g., iron, copper) or alkaline earth ions from fouling the aqueous system or from interfering with the proper functioning of corrosion inhibitors or other agents in the system. Such sequestering agents are known in the art and in some cases may be selected to be effective on a specific ion. Non-limiting examples of suitable sequestering agents include ethylenediaminetetra(acetic acid) nitrolotriacetic acid, and N,N-di(2-hydroxyethyl)glycine or water soluble salts thereof.
• anti-foams include silicones (e.g., polydimethylsiloxanes), distearylsebacamides, distearyladipamide and related products derived from ethylene oxide or propylene oxide condensations, and fatty alcohols, such as capryl alcohols and their ethylene oxide condensates.
• silicones e.g., polydimethylsiloxanes
• distearylsebacamides distearyladipamide and related products derived from ethylene oxide or propylene oxide condensations
• fatty alcohols such as capryl alcohols and their ethylene oxide condensates.
• Additional agents that may be combined with the tetrazolium compounds of this invention include biocides.
• biocides may be necessary to control microbiological growth in both the aqueous system and in the feed sources for the compositions of this invention.
• Both oxidizing and non-oxidizing biocidal agents may be utilized for these pu ⁇ oses.
• Suitable oxidizing biocides include at least one of chorine, hypochlorite, bromine, hypobromite, chlorine and/or bromine donor compounds (e.g., bromochlorohydantoin), peracetic acid, inorganic peroxides and peroxide generators, chlorine dioxide, and ozone.
• Suitable non-oxidizing biocides include at least one of amines, quaternary ammonium compounds (e.g., N-alkyl dimethylbenzylammonium chloride), 2-bromo-2-nitropropane-l,3-diol, ⁇ -bromonitrostyrene, dodecylguanidine hydrochloride, 2,2- dibromo-3-nitrilopropionamide, gluteraldhyde, chlorophenols, sulphur-containing compounds such as sulphones, methylene bis thiocyanates and carbamates, isothiazolones, brominated propionamides, triazines (e.g.,
• a preferred non-oxidizing biocide is a mixture of (a) 2-bromo-2-nitropropane-l,3-diol (BNPD) and (b) a mixture of about 75% 5-chloro-2-methyl-4-isothiazolin-3-one and about 25% 2-mefhyl-4- isothiazolin-3-one, the weight ratio said BNPD (a) to said mixture (b) being about 16:1 to about
• Additional agents that may be combined with the tetrazolium compounds of this invention include freezing point depressants. Such agents are needed for aqueous systems such as refrigeration, dehumidification, and internal combustion engine coolant systems.
• the depressants may be ionic or non-ionic in nature.
• suitable ionic agents include calcium chloride, sodium chloride, lithium bromide, and lithium chloride.
• suitable non-ionic agents are water-soluble alcohols such as ethylene glycol, propylene glycol, ethanol, glycerol, isopropanol, methanol, and mixtures thereof.
• Additional agents that may be combined with the tetrazolium compounds of this invention include pH adjusting agents.
• suitable agents include sodium hydroxide, potassium hydroxide, lithium hydroxide, hydrochloric acid, sulfuric acid, nitric acid, carbon dioxide, ammonia, organic acids such as oxalic acid, alkali metal carbonates, and alkali metal bicarbonates.
• compositions of this invention are used in aqueous systems that involve moving contact between a surface and a metal (e.g., such as encountered in systems containing pumping equipment or in applications involving metal machining or forming), it may be desirable to employ a lubricant to improve the performance of the machining operation or to decrease wear ofthe contacting and or metal surface.
• a lubricant may be water soluble or water insoluble.
• Suitable water insoluble organic lubricants such as naturally occurring or synthetic oils include those disclosed in U.S. 5,716,917, herein inco ⁇ orated by reference.
• Suitable water soluble lubricants include those disclosed in U.S.
• surfactants may be anionic, cationic, amphoteric or non-ionic in nature and are well known in the art.
• agents may be added to the compositions of this invention for a variety of functions (e.g., as emulsifiers, dispersants, hydrotroping agents, anti-foaming agents, lubricants, corrosion inhibitors). The process of selecting appropriate surfactants for accomplishing a given pu ⁇ ose is well known to those skilled in the art.
• Additional agents that may be combined with the tetrazolium compounds of this invention include calcium hardness adjusting agents. It is well known in the art that the efficacy of many aqueous system corrosion inhibitors, particularly those commonly used to treat open recirculating cooling system, is dependent upon the presence of a certain minimum level of dissolved calcium in the water. Although the efficacy ofthe compositions of this invention is somewhat independent of dissolved calcium, it may be advantageous in the practice of this invention to increase the dissolved calcium concentration in the system.
• suitable calcium hardness adjusting agents include the bicarbonate, carbonate, chloride, sulfate, and acetate salts of calcium as well as calcium hydroxide and calcium oxide.
• Additional agents that may be combined with the tetrazolium compounds of this invention include coloring agents.
• Non-limiting examples of the use of such agents include improving product appearance, aiding in product identification, and serving as additives on which automatic feed control systems which utilize colorimetric methods can be controlled.
• Non-limiting examples of such agents include water soluble dyes.
• the tetrazolium compounds combine synergistically with a wide range of known scale and/or co ⁇ osion inhibitors to provide greatly increased performance for both generalized corrosion and pitting. The combinations are effective over a range of calcium hardness and pH, including low hardness waters.
• a reduction of one order of magnitude or more in the corrosion rate occurs when employing the combination compared to the treatment without using a tetrazolium compound, even when keeping total active treatment levels constant.
• the tetrazolium compounds of this invention are known to be reducible species. While the mechanistic details have not been studied in depth and are not fully understood, it is believed that one important element of the corrosion inhibiting effect of the novel compositions of this invention is the reduction of the soluble tetrazolium compound to a relatively insoluble and protective film at the surface ofthe corroding metal.
• the reduction may be a multi-step process, and the protective film may contain several ofthe intermediate reduction products.
• intermediate reduction products may not be part ofthe protective film, but may be still capable of further reduction to form a corrosion-inhibiting film.
• Such corrosion-inhibiting intermediate reduction products ofthe tetrazolium compounds are also considered to be within the scope of this invention.
• the protective action ofthe tetrazolium compound works in concert with the protective action of the additional water treatment agent to provide effective aqueous system corrosion control.
• the additional water treatment agent also provides protection against water formed scales and deposits, and for these cases, the combinations of this invention are effective for the control of both corrosion and scaling/deposition.
• the additional water treatment agent may impart other desirable properties to the composition (e.g., the ability to disperse particulate matter).
• certain water treatment agents e.g., oxygen scavengers
• water treatment agents that substantially reduce tetrazolium compounds in aqueous solution under the particular conditions of use are not suitable for use with this invention.
• the conditions of use include such considerations as the relative proportions of tetrazolium compound and the tetrazolium-reducing water treatment agent (e.g., the use of an amount of a reducing water treatment agent that did not substantially reduce the amount of tetrazolium compound present would still fall within the scope of this invention).
• the conditions of use also would include the absolute concentrations of both tetrazolium compounds and other species, temperature, time, the presence or absence of additional oxidizing and/or reducing agents or other compounds that might alter the interaction between the tetrazolium compound and the tetrazolium-reducing water treatment agent, the presence or absence of catalytic surfaces (e.g., metal surfaces), and the like.
• One skilled in the art may readily determine if a particular agent substantially reduces the tetrazolium compound under the conditions of use. Because the reduction products of the tetrazolium compounds are generally highly colored while the parent materials are not, simple methods of making this determination include visual inspection and colorimetry.
• the aqueous system does not contain materials therein that affect the corrosion inhibition of the tetrazolium compounds so that the tetrazolium compound does not inhibit corrosion. Therefore, the tetrazolium compounds should not be substantially reduced by the materials so that the tetrazolium compound cannot inhibit corrosion. Moreover, any materials that negate the corrosion inhibition and/or scaling prevention of the terazolium compounds and/or additional materials should preferably not be included in the aqueous system, or should preferably be included in amounts that would not permit the tetrazolium compounds from achieving their intended corrosion inhibition and/or scaling prevention.
• a combination of a tetrazolium compound and an aqueous system treatment material is added to the aqueous system in need of treatment, with from about 10 to 1000 parts per million of said combination being particularly preferred.
• the weight ratio ofthe other aqueous system treatment material to tetrazolium compound is preferably from about 100: 1 to 1 :20, with a weight ratio of from about 20:1 to 1:1 particularly preferred.
• the pH ofthe aqueous system in which the compositions of this invention may be applied ranges from about 5 to about 12.
• the pH is preferably in the range from about 6 to about 10.
• the components of this invention may be dosed into the aqueous system at an effective concentration by a slug feed or by blending with the aqueous fluid as the system is being filled.
• compositions of this invention may be fed to the system on a continuous basis, on an intermittent basis, or using a combination ofthe two (e.g., utilizing a continuous low level feed supplemented by slug feeds as needed).
• a combination ofthe two e.g., utilizing a continuous low level feed supplemented by slug feeds as needed.
• Timing and rate of treatment feed may be controlled by a variety of methods known in the art.
• One suitable method is to utilize metering pumps or other feed system devices which may be variously configured to feed continuously at a fixed rate, on a time schedule, on signals generated by other system components such as makeup or blowdown pumps, or on signals generated by an analog or computer-based feed control system.
• suitable feed systems have been disclosed in U.S. Patents 4,648,043, 4,659,459, 4,897,797, 5,056,036, 5,092,739 and 5,695,092.
• the feed control systems may utilize signals corresponding to the concentration of one or more ofthe treatment components, to the concentration of one or more inert or active tracer materials added to the treatment, to the value of one or more measures of system performance (e.g., values obtained from corrosion rate meters, scaling monitors, heat transfer monitoring devices, analytical devices that detect the amount corrosion product in the water such as total or dissolved iron or other metal constituent, and the like), to the value of one or more ofthe physical characteristics ofthe system (e.g., temperature, flow rate, conductivity), to the value of one or more chemical characteristics of the system (e.g., pH, calcium hardness, redox potential, alkalinity) or to combinations of these signals to feed and maintain levels of treatment adequate for effective performance in a particular aqueous system.
• measures of system performance e.g., values obtained from corrosion rate meters, scaling monitors, heat transfer monitoring devices, analytical devices that detect the amount corrosion product in the water such as total or dissolved iron or other metal constituent, and the like
• the physical characteristics ofthe system e
• controlled release also referred to as gradual release or time release
• the material or materials to be fed are impregnated or are otherwise inco ⁇ orated into a controlled release system matrix.
• Suitable controlled release delivery systems include those in which the matrix is exposed to the fluid in the aqueous system or to a fluid stream being fed to the aqueous system and the treatment components are gradually released into the system by the action of various processes (e.g., diffusion, dissolution, osmotic pressure differences) and which may further be designed to vary the release rate in response to aqueous fluid characteristics such as temperature, flow rate, pH, water hardness, conductivity, and the like.
• concentrations may be determined by continuous, semi-continuous, or batch type analytical techniques including spectroscopic methods (UN, visible emission, visible abso ⁇ tion, IR, Raman, fluorescence, phosphorescence, etc.), electrochemical methods (including pH, ORP, and ion selective electrode measurements), chromatographic methods (GC, LC), methods that rely on antibody binding or release, chemical based analytical/colorimetric methods such as those commercially available from the Hach Company, and the like.
• a suitable spectrophotometric method is described in U.S. 5,242,602, herein inco ⁇ orated by reference.
• a suitable method for regulating the in-system concentration of a water treatment agent is disclosed in U.S. 5,411,889.
• U.S. 5,855,791, herein inco ⁇ orated by reference discloses suitable methods for determining the feed rates of corrosion and fouling inhibitors based on certain performance monitors and system characteristics.
• the tracer compounds that may optionally be employed may be compounds that serve no particular treatment function, referred to as inert tracers, or may be water treatment compounds that are also readily monitored, such treatment compounds being referred to as active tracers.
• Suitable tracers include soluble lithium salts such as lithium chloride, transition metals such as described in U.S. 4,966,711, herein inco ⁇ orated by reference, and fluorescent inert tracers such as described in U.S. 4,783,314, herein inco ⁇ orated by reference.
• Suitable fluorescent inert tracers include the mono-, di-, and trisulfonated naphthalenes (e.g., water soluble salts of naphthalene sulfonic acid or of naphthalene disulfonic acid).
• Suitable active tracers include fluorescently tagged polymers such as described in U.S. 5,171,450, herein inco ⁇ orated by reference, and polymers containing a photo-inert, latently detectable moiety which will absorb light when contacted with a photoactivator, as described in U.S. 5,654,198, herein inco ⁇ orated by reference, azole-based copper corrosion inhibitors such as tolyltriazole, and water soluble molybdate and tungstate salts.
• PBTC 2-phosphono- butane-l,2,4-tricarboxylic acid
• the tetrazolium compound can significantly reduce the total treatment dosage needed to effectively limit corrosion in the aqueous system.
• Many of the combinations of the tetrazolium compounds are with materials that are primarily or exclusively utilized as scale and/or deposition inhibitors. However, the combinations are effective for both scaling/deposition and corrosion control.
• Test Methods and Conditions The corrosion inhibition activity ofthe treatments in the present invention were evaluated using the Beaker Corrosion Test Apparatus (BCTA).
• the BCTA consists of a 2 liter beaker equipped with an air/CO2 sparge, 1010 low carbon steel (LCS) coupon(s), a 1010 LCS electrochemical probe, and a magnetic stir bar.
• the test solution volume was 1.9 liters. Air/CO 2 sparging is continuous during the test.
• the reference electrode and counter electrode used in making the electrochemical corrosion measurements are constructed of Hastelloy C22.
• the beaker is immersed in a water bath for temperature control.
• Electrochemical corrosion data were obtained periodically on the probe during the test using a polarization resistance technique. All tests were conducted at 120°F, using a 400 RPM stir rate. Unless otherwise noted, the test duration was 18 hours. Two values are reported for each test; EC(avg), the average value ofthe electrochemically measured corrosion rate during the test, and EC(18 hour), the value of the corrosion rate at the end ofthe test. The latter value is thought to be more indicative ofthe longer term corrosion rate expected.
• test water contains 100 mg/1 Ca (as CaCO 3 ), 50 mg/1 Mg (as CaCO 3 ), 100 mg/1 chloride, and 100 mg/1 sulfate. Using this water, tests were conducted at pHs of 8.6, 7.6, and 6.8. The corresponding "M" alkalinities at these pHs were 110, 32, and 4 mg/1 (all as CaCO 3 ).
• Example #1 BCTA results for tests conducted at pH 8.6 are shown in Table 1.
• the tetrazolium compound utilized for these tests was ⁇ BT.
• Belcor 575 is hydroxyphosphonoacetic sold by FMC.
• Bricorr 288 is a mixture of phosphonosuccinic acid, the phosphonated dimer of maleic acid, phosphoric acid, and a minor proportion by weight of higher phosphonated oligomers of maleic acid sold by Albright and Wilson.
• Dequest 2060 is diethylenetriamine penta(methylenephosphonic acid) sold by Monsanto.
• Bayhibit AM is 2-phosphonobutane- 1 ,2,4- tricarboxylic acid sold by Bayer.
• Goodrite K-752 is a polyacrylate sold by B. F. Goodrich.
• Max maximum depth
• Avg average depth
• Min minimum depth
• the hardness and pH of waters in aqueous systems can vary widely. It is greatly advantageous to have inhibitor formulations which can function effectively over a wide hardness range and pH range while inhibiting both corrosion and deposition. It is of further advantage in certain systems that must use uncycled water which typically has low calcium ( ⁇ 100 mg/1 Ca as CaCO 3 ) and is relatively neutral pH (6.5-7.5) that the inhibitors used need not rely on alkaline pH, high hardness conditions to function effectively, as is the case with many of the treatments currently in use. Examples of such systems are closed loop cooling systems once through cooling systems, hot water heating systems, and the like.
• Table 8 shows results from a water containing 15 mg/1 Ca as CaCO 3 , 7.6 mg/1 Mg as CaCO 3 , 71 mg/1 Cl, 48 mg/1 SO 4 , with 5 mg/1 active AA/AHPSE at pH 7.0. A significant decrease in corrosion rate is observed when 5 mg/1 NBT is added.
• Table 10 shows the results from a pH 8.6 test water that contains 360 mg/1 Ca as CaCO 3 ,

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