EP0660887A4 - Procede et composition servant a inhiber une corrosion generalisee et la piqure de corrosion dans une tour de refrigeration. - Google Patents

Procede et composition servant a inhiber une corrosion generalisee et la piqure de corrosion dans une tour de refrigeration.

Info

Publication number
EP0660887A4
EP0660887A4 EP19920922768 EP92922768A EP0660887A4 EP 0660887 A4 EP0660887 A4 EP 0660887A4 EP 19920922768 EP19920922768 EP 19920922768 EP 92922768 A EP92922768 A EP 92922768A EP 0660887 A4 EP0660887 A4 EP 0660887A4
Authority
EP
European Patent Office
Prior art keywords
corrosion
molybdate
water
cooling tower
composition
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19920922768
Other languages
German (de)
English (en)
Other versions
EP0660887A1 (fr
Inventor
Bradley A Bucher
Jesse H Jefferies
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Gulf Coast Performance Chemical Inc
Original Assignee
Gulf Coast Performance Chemical Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gulf Coast Performance Chemical Inc filed Critical Gulf Coast Performance Chemical Inc
Publication of EP0660887A4 publication Critical patent/EP0660887A4/fr
Publication of EP0660887A1 publication Critical patent/EP0660887A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
    • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
    • C23F11/18—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 inorganic inhibitors
    • C23F11/187—Mixtures of inorganic inhibitors
    • C23F11/188—Mixtures of inorganic inhibitors containing phosphates
    • 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

Definitions

  • the present invention relates to a method of inhibiting corrosion in cooling tower systems and, more specifically, for lowering the pitting rate associated with tuberculation of carbon steel and other corrosion-prone materials to less than the general corrosion rate.
  • Cooling towers are widely used in the industry to cool water used in heat exchangers, refrigeration units, etc.
  • the cooling tower systems employed in such environments are of the recirculating type; that is, the water used for cooling purposes is recycled to the cooling tower for chilling via evaporation.
  • tuberculation can form on the surface of the metal which provides sites for pitting corrosion.
  • the subsequent pitting beneath the tuberculation is the most serious form of corrosion and the primary cause of corrosion-induced equipment failure in cooling systems. Specifically then, there are two types of corrosion which must be controlled.
  • G leral corrosion rate is the measure of the thickness of metal lost. It is measured in thousands of an inch of metal loss per year, referred to as mils per year (mpy). Pitting corrosion is also expressed as mils per year, but refers to depth at a specific site.
  • an untreated water system my have a general (uniform) metal loss of 0.060 inches per year (60 mpy).
  • the general corrosion rate can be reduced. In a properly treated cooling system the general corrosion rate will normally be measured at less than 5.0 mpy.
  • the pitting rate is considered to be properly controlled if it is three to five times the general corrosion rate. Both the general and pitting rates can be measured either via metal coupons, or with electrical corrosion measuring instruments.
  • Another object of the present invention is to provide a method and composition for reducing the pitting corrosion in cooling tower systems which eliminates the use of toxic, heavy metals.
  • Still a further object of the present invention is to provide a method and composition for reducing the pitting corrosion in cooling tower systems to a point less than, or equal to, the general corrosion rate.
  • a method of inhibiting the pitting corrosion rate of carbon steel in a cooling tower system comprising adding to the cooling tower water an effective amount of a corrosion inhibiting composition comprising from about 1 to about 10 part per million (ppm) of a water-soluble molybdate, calculated as molybdate, and from about 5 to about 24 ppm of a stabilized orthophosphate, calculated as phosphate, said corrosion inhibiting composition being substantially free of any added active zinc, e.g. water-soluble zinc compounds, and circulating said water in said system.
  • ppm part per million
  • compositions for use in inhibiting pitting corrosion of carbon steel in a cooling tower system comprising from about 1 to about 10 ppm of a water-soluble molybdate, calculated as molybdate, and from about 5 to about 25 ppm of a stabilized orthophosphate, calculated as phosphate, the composition being substantially free of any active zinc.
  • Fig. 1 is a graph showing a comparison of general and pitting corrosion rates usin stabilized phosphate without any molybdate.
  • Fig. 2 is a graph similar to Fig. 1 showing a comparison of general and pittin corrosion rates using stabilized phosphate and molybdate.
  • Fig. 3 is a graph showing a comparison of general and pitting corrosion rates usin stabilized phosphate and molybdate in which the molybdate has been added incrementall over time.
  • Fig. 4 is a graph showing a comparison of general and pitting corrosion rates for refinery cooling system using stabilized phosphate and molybdate.
  • Fig. 5 is a graph showing a comparison of general and pitting corrosion rates in a petrochemical cooling system using stabilized phosphate, molybdate and zinc chloride.
  • the present invention is based upon the unexpected finding that the use of a corrosion inhibiting composition containing a water-soluble molybdate and a stabilized orthophosphate results in a pitting corrosion rate which is less than, or equal to, the general corrosion rate.
  • the composition of the present invention can comprise, consist of, or consist essentially of the molybdate and the stabilized orthophosphate.
  • active zinc a corrosion inhibitor
  • Such active zinc compounds are usually inorganic, water- soluble compounds such as zinc halides.
  • a corrosion inhibiting composition which is environmentally safe since it eliminates toxic, heavy metals such as zinc.
  • the two main components used in the method and composition of the present invention are a water-soluble molybdate and a stabilized phosphate (orthophosphate).
  • the water-soluble molybdate can be virtually any molybdate, usually an inorganic molybdate, which has sufficient water solubility for the particular cooling tower water system. Alkali metal molybdates are preferred, sodium molybdate being especially preferred because of its relative high solubility.
  • the molybdate compound will be present in the compositions in an amount of from about 1 to about 10 ppm, calculated as molybdate (Mo0 -) as the active component, amounts of molybdate of from about 3 to about 6 ppm being especially desirable.
  • the second major component used in the compositions and method of the present invention is a "stabilized” phosphate.
  • stabilize refers to a condition under which orthophosphate in the water being treated will remain in solution despite a level of calcium or similar metal ions and system pH which would normally result in precipitation of generally insoluble metal (calcium) phosphate.
  • phosphate has a limited solubility in water when calcium and other alkaline earth metals are present, phosphate solubility following the equation:
  • Stabilized phosphates are achieved by incorporating in or adding to the orthophosphate-containing cooling water one or more polymeric materials which by various proposed theories prevent the precipitation of calcium or other metal phosphates. Stabilization of phosphates and polymers used therefore are disclosed in U.S. Patent No. 4,711,725, and other patents mentioned therein, all of which are hereby incorporated by reference for all purposes. In general, there are a myriad of dispersants or materials, which are generally polymeric in nature, e.g. homopolymers, copolymers, terpolymers, which will prevent precipitation or crystallization of calcium or similar metal phosphates.
  • Non-limiting examples of materials (phosphate stabilizers) used to form stabilized phosphates include polymers derived from (meth)acrylic acids and salts as well as mixtures of such polymers with other compounds and polymers, such as phosphonic acids, copolymers of (meth)acrylic acids and vinyl esters, such as hydroxyethyl methyacrylate and hydroxy proplacrylate, and copolymers of (meth)acrylic acids and salts with acrylamidl alkyl or aryl sulfonates or unsubstituted acrylamides.
  • phosphate stabilizers include any compound, polymer, whether synthetic or natural, or mixtures thereof, which can perform the function of preventing precipitation and/or crystallization of insoluble metal phosphate under conditions, e.g. pH, which would result in precipitation of such phosphates if the phosphate stabilizers were not present.
  • the phosphate stabilizers will be present in an amount ranging from about 1 to about 30 ppm.
  • the stabilized orthophosphate will be present in the method and composition of the present invention in an amount of from about 5 to about 20 ppm, calculated as phosphate (PO 4 ).
  • the orthophosphate can be any water-soluble orthophosphate and can include, without limitation, compounds such as monosodium phosphate, disodium phosphate, trisodium phosphate, phosphoric acid, etc. It will be recognized that the orthophosphates, generally the most hydrated form of phosphate, are to be distinguished from polyphosphates which can also be used in the composition and which exhibit some lower degree of hydration together with being comprised of multiple PO 4 groups.
  • an effective corrosion inhibitor which will reduce pitting corrosion to a level equal to or below that of general corrosion can be obtained using only the molybdate compound and the stabilized phosphate as described above and provided there is no added active zinc as described hereafter, it is to be understood that other, conventional agents or additives normally employed in corrosion inhibiting compositions can be employed.
  • polyphosphates can be employed with advantage, the polyphosphates, when employed, normally being present in amounts ranging from about 1 to about 30 ppm, calculated as phosphate.
  • useful water-soluble polyphosphates include tetrapotassium pyrophosphate, sodium hexametaphosphate, sodium tripolyphosphate, tetrasodium pyrophosphate, etc.
  • polyphosphates when placed in a water solution, polyphosphates can, to some extent, convert to orthophosphates. Accordingly, it is within the scope of the present invention to form the stabilized phosphate by adding only a polyphosphate compound in an amount which will provide the required amount of orthophosphate as set out above.
  • the corrosion inhibiting composition and method of the present invention can also contain, with advantage, dispersants, such as polycarboxylic acids, e.g. polymaleic anhydride, various other homopolymers and copolymers, organic phosphonates, etc., which serve as iron sequestrants.
  • dispersants such as polycarboxylic acids, e.g. polymaleic anhydride, various other homopolymers and copolymers, organic phosphonates, etc.
  • dispersants or sequestrants will generally be present in amounts generally ranging from about 1 to about 20 ppm in the cooling tower water.
  • MCT benzotriazole
  • BZT benzotriazole
  • TTA tolyltriazole
  • copper corrosion inhibitors will generally be present in an amount of from about 1 to about 20 ppm of the cooling tower water.
  • compositions can also contain microbiocides, anti-foulants, and other such additives.
  • the corrosion inhibiting composition will be introduced into the cooling tower water in an effective amount, i.e., an amount which takes into the account parameters such as the degree of contamination of the cooling tower water, the pH, etc., which can be determined by well known methods.
  • an amount of from about 20 to about 100 ppm of the inhibitor composition is employed. It will be recognized, however, that smaller or greater amounts can be employed depending on the condition of the cooling tower water.
  • the components of the composition can be added in virtually any manner. It is convenient to add the water-soluble molybdate in conjunction with the stabilized phosphate and any other additional corrosion inhibiting additives to the cooling water as a combined mixture by conventional, well known methods. However, the individual components can be added separately if desired.
  • the present invention is buttressed on the finding that if molybdate and stabilized phosphate are used together in the substantial absence of water-soluble zinc compounds or other sources of active zinc, the pitting rate can be maintained at a level equal to or below the general corrosion rate.
  • active zinc which is generally regarded as a highly effective general corrosion inhibitor interferes with the combined action of the molybdate and the stabilized phosphate.
  • substantially free of active zinc refers to a level of zinc below which the zinc does not act to any significant extent as a corrosion inhibitor. Generally speaking, a level of zinc of 0.5 ppm or less, calculated as zinc, would be considered substantially free of active zinc. Amounts of about 0.5 ppm or greater of active zinc results in increased pitting corrosion, i.e. a pitting corrosion rate equal to or greater than the general corrosion rate. It will also be understood that substantial levels of zinc in the corrosion inhibitor can be tolerated if the zinc is in some form, e.g. chelated, which does not normally allow it to act as a corrosion inhibitor.
  • the present invention has proven to be particularly effective in preventing, or inhibiting, pitting corrosion associated with tuberculation.
  • carbon steel is the metal that is most commonly used in cooling system piping and in heat exchanger construction, pitting of carbon steel is of major interest to the industry.
  • the present invention can be used on various types of cooling tower systems, such as forced draft towers, induced draft towers, and hyperbolic towers. Tower flow may be counterflow or crossflow.
  • the method and composition find equal application to atmospheric cooling towers and natural draft towers, but find particular application in open, recirculating cooling tower systems.
  • Amounts are calculated on a per weight basis of the active agent, e.g. PO 4 ,
  • Clarified Brazos river water was concentrated to five cycles and the mAlkalinity adjusted to 100 ppm.
  • a stabilized phosphate corrosion inhibitor having the following composition:
  • Example 2 To a second sample of the Brazos River water used in Example 1 was added the corrosion inhibiting composition shown in Table 1 with the exception that the composition contained sufficient sodium molybdate to provide 6.0 ppm active molybdate (MoO 4 ). The data was obtained in the manner described in Example 1, the results being shown graphically in Fig. 2.
  • composition and method of the present invention was tested in an open, recirculating cooling tower system used in a refinery.
  • the corrosion inhibiting composition was as follows:
  • Example 5 Pitting and general corrosion measurements were made generally according to the procedure of Example 1. The results are shown graphically in Fig. 4 which plots corrosion rates over a 240 hour time period. As can be seen from Fig. 4, the same characteristic passivation curve was followed by the general corrosion rate leveling at 1.1 mpy and the pitting corrosion rate at 0.2 mpy. Data collected over a six-month period has consistently shown 0.5 mpy general and 0.1 mpy pitting corrosion rates demonstrating that the method and composition of the present invention achieved the remarkable result of maintaining the pitting corrosion rate at a level below the general corrosion rate.
  • Example 5 Example 5
  • Example 4 The procedure of Example 4 was repeated on an open, recirculating cooling tower system in a petrochemical facility.
  • the corrosion inhibiting composition employed was as shown in Table 4.
  • Fig. 5 is a graph of data accumulated over a 150-day period during which molybdate, the stabilized phosphate and, in addition, a water-soluble zinc compound were employed.
  • the pitting corrosion rate was always above the general corrosion rate. Indeed, and as is generally experienced by other workers, spiking of the pitting corrosion rate was noticeable and frequent throughout the test period.
  • a comparison of the results from Examples 4 and 5 shows that when water-soluble zinc compounds are present, and for some unexplained reason, the pitting corrosion rate remains above the general corrosion rate.
  • the cooling system water of both Examples 4 and 5 was essentially comparable and that the corrosion inhibiting compositions were essentially the same, the primary difference being that the composition used in Example 5 contained zinc chloride sufficient to provide 2 ppm calculated as zinc.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
EP92922768A 1991-04-12 1992-04-09 Procede et composition servant a inhiber une corrosion generalisee et la piqure de corrosion dans une tour de refrigeration Withdrawn EP0660887A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US685087 1984-12-21
US68508791A 1991-04-12 1991-04-12
PCT/US1992/002862 WO1992018665A1 (fr) 1991-04-12 1992-04-09 Procede et composition servant a inhiber une corrosion generalisee et la piqure de corrosion dans une tour de refrigeration

Publications (2)

Publication Number Publication Date
EP0660887A4 true EP0660887A4 (fr) 1994-08-19
EP0660887A1 EP0660887A1 (fr) 1995-07-05

Family

ID=24750727

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92922768A Withdrawn EP0660887A1 (fr) 1991-04-12 1992-04-09 Procede et composition servant a inhiber une corrosion generalisee et la piqure de corrosion dans une tour de refrigeration

Country Status (7)

Country Link
EP (1) EP0660887A1 (fr)
KR (1) KR970001009B1 (fr)
AU (1) AU660027B2 (fr)
CA (1) CA2107791C (fr)
GB (1) GB2271107B (fr)
RO (1) RO109562B1 (fr)
WO (1) WO1992018665A1 (fr)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2272431B (en) * 1992-08-17 1997-04-09 Grace W R & Co Inhibition of corrosion in aqueous systems
US5602888A (en) * 1993-10-29 1997-02-11 General Electric Company Radiation-induced palladium doping of metals to protect against stress corrosion cracking
US5773096A (en) * 1993-10-29 1998-06-30 General Electric Company Method of catalyst preparation by high-temperature hydrothermal incorporation of noble metals onto surfaces and matrices
US5600692A (en) * 1993-10-29 1997-02-04 General Electric Company Method for improving tenacity and loading of palladium on palladium-doped metal surfaces
US5600691A (en) * 1993-10-29 1997-02-04 General Electric Company Noble metal doping or coating of crack interior for stress corrosion cracking protection of metals
US5608766A (en) * 1993-10-29 1997-03-04 General Electric Company Co-deposition of palladium during oxide film growth in high-temperature water to mitigate stress corrosion cracking
US5818893A (en) * 1993-10-29 1998-10-06 General Electric Company In-situ palladium doping or coating of stainless steel surfaces
US5625656A (en) * 1993-10-29 1997-04-29 General Electric Company Method for monitoring noble metal distribution in reactor circuit during plant application
TW253058B (en) * 1994-03-10 1995-08-01 Gen Electric Method of doping or coating metal surfaces with metallic elements to improve oxide film insulating characteristics
KR102093142B1 (ko) 2017-12-08 2020-05-27 (주) 시온텍 냉각수 정화장치

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4176059A (en) * 1978-06-08 1979-11-27 Quatic Chemicals Limited Anti-corrosion composition for use in aqueous systems
US4409121A (en) * 1980-07-21 1983-10-11 Uop Inc. Corrosion inhibitors
US4440721A (en) * 1981-10-26 1984-04-03 Basf Wyandotte Corporation Aqueous liquids containing metal cavitation-erosion corrosion inhibitors
US4711725A (en) * 1985-06-26 1987-12-08 Rohm And Haas Co. Method of stabilizing aqueous systems
US4798683A (en) * 1988-04-21 1989-01-17 Calgon Corporation Method for controlling corrosion using molybdate compositions
EP0329560A1 (fr) * 1988-02-18 1989-08-23 Gaz De France Inhibiteurs de corrosion des aciers et compositions aqueuses d'halogénure de métal alcalin les contenant
US4867944A (en) * 1988-01-13 1989-09-19 Gulf Coast Performance Chemical, Inc. Method of preventing corrosion by contaminated cooling tower waters
EP0339716A1 (fr) * 1988-04-21 1989-11-02 Calgon Corporation Procédé et composition pour contrôler la corrosion dans l'eau douce ou dure
US5002697A (en) * 1988-03-15 1991-03-26 Nalco Chemical Company Molybdate-containing corrosion inhibitors

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4176059A (en) * 1978-06-08 1979-11-27 Quatic Chemicals Limited Anti-corrosion composition for use in aqueous systems
US4409121A (en) * 1980-07-21 1983-10-11 Uop Inc. Corrosion inhibitors
US4440721A (en) * 1981-10-26 1984-04-03 Basf Wyandotte Corporation Aqueous liquids containing metal cavitation-erosion corrosion inhibitors
US4711725A (en) * 1985-06-26 1987-12-08 Rohm And Haas Co. Method of stabilizing aqueous systems
US4867944A (en) * 1988-01-13 1989-09-19 Gulf Coast Performance Chemical, Inc. Method of preventing corrosion by contaminated cooling tower waters
EP0329560A1 (fr) * 1988-02-18 1989-08-23 Gaz De France Inhibiteurs de corrosion des aciers et compositions aqueuses d'halogénure de métal alcalin les contenant
US5002697A (en) * 1988-03-15 1991-03-26 Nalco Chemical Company Molybdate-containing corrosion inhibitors
US4798683A (en) * 1988-04-21 1989-01-17 Calgon Corporation Method for controlling corrosion using molybdate compositions
EP0339716A1 (fr) * 1988-04-21 1989-11-02 Calgon Corporation Procédé et composition pour contrôler la corrosion dans l'eau douce ou dure

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
BATROFF, ANN. UNIV. FERRARA, vol. 5, no. 7, 1980, pages 1103 - 1110 *
CHEMICAL ABSTRACTS, vol. 92, no. 22, 2 June 1980, Columbus, Ohio, US; abstract no. 184400j, CHOMITZ: "agent for preventing corrosion of iron" page 200; *
CHEMICAL ABSTRACTS, vol. 94, no. 10, 9 March 1981, Columbus, Ohio, US; abstract no. 69499c, BATROFF: "inhibition of pitting corrosion by heteropolyacids" page 245; *
See also references of WO9218665A1 *

Also Published As

Publication number Publication date
GB2271107A (en) 1994-04-06
GB2271107B (en) 1995-02-22
CA2107791C (fr) 2002-03-12
KR970001009B1 (ko) 1997-01-25
EP0660887A1 (fr) 1995-07-05
WO1992018665A1 (fr) 1992-10-29
GB9320754D0 (en) 1994-01-26
AU1879492A (en) 1992-11-17
RO109562B1 (ro) 1995-03-30
AU660027B2 (en) 1995-06-08
CA2107791A1 (fr) 1992-10-13

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