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

Definitions

• U.S. Patent 3,885,914 discloses the use of zinc/polyacrylate compositions to control the corrosion of metals by oxygen bearing waters. However, such compositions are ineffective at high pH. The inventors have surprisingly discovered that the addition of a carboxylic/sulfonic acid polymer to the compositions of the '914 patent synergistically inhibits corrosion in alkaline systems.
• U.S. Patent 4,640,793 discloses the use of zinc and carboxylic acid/sulfonic acid polymers to control the corrosion of steel in contact with aqueous systems. This reference does not, however, disclose a method of controlling corrosion at high pH.
• U.S. Patent 4,663,053 discloses a method of inhibiting the corrosion of metallic parts in contact with aqueous systems using a water soluble zinc compound in combination with a water soluble sulfonated styrene/maleic anhydride copolymer and an organophosphorus acid compound or water soluble salt thereof.
• the instant invention relates to the inhibition of corrosion in alkaline water systems in which oxygen bearing waters contact metallic surfaces.
• this invention relates to the use of compositions comprising a water-soluble, low molecular weight polycarboxylic acid, a water-soluble zinc salt and a water-soluble carboxylic acid/sulfonic acid polymer to inhibit the corrosion of metals in water systems which contain high pH, oxygen bearing waters.
• Oxygen corrosion is a serious problem in any metal-containing water system.
• the corrosion of iron and steel is a primary concern because they are extensively used in water systems. Copper and its alloys, aluminum and its alloys, and galvanized steel are also used in water systems and are subject to corrosion.
• the inventors have discovered novel corrosion inhibiting compositions which inhibit oxygen corrosion in high pH water systems containing such metals.
• compositions comprising low molecular weight, water soluble polycarboxylates, water soluble zinc salts and water soluble carboxylic/sulfonic polymers are effective corrosion inhibitors at high pH.
• Suitable carboxylic polymers include low molecular weight acrylic acid polymers, low molecular weight methacrylic acid polymers and hydrolyzed polyacrylamides. These polymers may be homo-, co-, or ter- polymers of any of the aforementioned types and may have molecular weights ranging from about 500 to about 25,000.
• Suitable water soluble zinc sources include, but are not limited to, salts such as zinc chloride, zinc acetate, zinc nitrate and zinc sulfate.
• salts such as zinc chloride, zinc acetate, zinc nitrate and zinc sulfate.
• the zinc ion may also be supplied by adding zinc to the system being treated.
• the carboxylic/sulfonic polymer is an acrylic acid/2-acrylamido-2-methylpropyl sulfonic acid-type polymer having a molecular weight of less than about 25,000, wherein the weight ratio of the carboxylic moiety to the sulfonic moiety is from about 1:20 to about 20:1.
• the addition of the carboxylic/sulfonic acid polymer to the polyacrylic acid-type polymer and the zinc source enables control of carbon steel corrosion at alkaline pH's. Polyacrylate/zinc products alone are only effective to neutral pH. Thus, the addition of the carboxylic/sulfonic polymer extends the pH range to alkaline conditions while improving corrosion control. This polymer also stabilizes zinc above pH 7.5.
• an effective amount of one of the instant compositions should be added to the aqueous system being treated.
• the term "effective amount" is that amount of an instant composition necessary to inhibit the corrosion of metallic surfaces in contact with the alkaline aqueous system being treated.
• the effective amount will range from about 1 to about 1,000 ppm of the total composition, on an active basis, based on the total weight of the aqueous system being treated.
• aqueous system as used herein, is meant to include any type of system containing water, including but not limited to, cooling water systems, boiler water systems, desalination systems, gas scrubber water systems, blast furnace water systems, reverse osmosis systems, evaporator water systems, paper manufacturing systems, mining systems and the like.
• the essential aspect of this invention is that the instant compositions are effective at controlling corrosion in alkaline systems.
• the instant compositions are effective when the pH of the aqueous system being treated is greater than 7.0, preferably from about 7.0 to about 10.0, more preferably from about 7.0 to about 9.0, and most preferably about 7.0 to about 8.5.
• Component (A) of the instant compositions may be any water-soluble polycarboxylate selected from the group consisting of polymers prepared from acrylic acid, methacrylic acid, vinyl acetic acid, allyl acetic acid, fumaric acid, maleic acid or anhydride, itaconic acid, ⁇ -halo acrylic acid and ⁇ -carboxyethylacrylate.
• component A is selected from the group consisting of water soluble homopolymers of acrylic acid, water soluble homopolymers of methacrylic acid, water soluble copolymers of acrylic acid and methacrylic acid and water soluble hydrolyzed polyacrylamides, wherein the molecular weight is less than about 25,000, preferably about 1,000 to about 10,000, and salts of these polymers.
• any zinc ion source may be used as component B.
• the zinc ion may be added by utilizing a water-soluble zinc salt, such as zinc chloride, zinc acetate, zinc nitrate or zinc sulfate.
• the zinc ion may be added by supplying zinc to the aqueous system being treated.
• any unsaturated carboxylic acid or salt thereof may be used as (i).
• examples include, but are not limited to, acrylic acid, methacrylic acid, ⁇ -halo acrylic acid, maleic acid, itaconic acid, vinyl acetic acid, allyl acetic acid, fumaric acid, ⁇ -carboxyethyl acrylate, their salts and admixtures thereof.
• the most preferred carboxylic monomers are acrylic acid, methacrylic and their salts.
• Any unsaturated sulfonic acid or salt thereof may be used as (ii) in component C.
• Examples include, but are not limited to, 2-acrylamido-2-methylpropyl sulfonic acid, 2-methacrylamido-2-methylpropyl sulfonic acid, styrene sulfonic acid, vinyl sulfonic acid, sulfo alkyl acrylate or methacrylate, allyl sulfonic acid, methallyl sulfonic acid, 3-methacrylamido-2-hydroxy propyl sulfonic acid acrylate, their salts and mixtures thereof.
• the most preferred sulfonic monomers are 2-acrylamido-2-­methylpropylsulfonic acid, 2-methacrylamido-­2-methylpropylsulfonic acid and their salts.
• nonionic monomers such as acrylamide, methacrylamide and acrylonitrile
• copolymers are preferred.
• These polymers are prepared using an (i):(ii) monomer weight ratio of about 1:20 to about 20:1, preferably about 1:10 to about 10:1, and most preferably about 1:4 to about 4:1.
• the preferred polymers for component C are water soluble polymers having an intrinsic viscosity of 0.05 to 2.5 dl/g, prepared from:
• component C is 20 to 80%, by weight, acrylic acid or its salt and 80 to 20%, by weight, 2-acrylamido-2-methylpropylsulfonic acid, or its salt, wherein the intrinsic viscosity is about 0.05 to about 0.5 dl/g.
• compositions An additional advantage of the instant compositions is that the component C polymer stabilizes the aqueous system being treated against zinc deposition, especially at pH's above 7.5.
• components A, B, and C are critical to the instant method in that compositions comprising these components effectively control corrosion of metallic surfaces in contact with aqueous systems having alkaline pH's.
• azole compounds are tolyltriazole and mercapto­benzotriazole.
• the components of the instant invention may be added to the aqueous system being treated by any technique known in the art of water treatment.
• the components may be added as a mixture or separately. However, if added separately, the zinc source should be added last to prevent deposition of zinc salts in highly alkaline waters.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Anti-Oxidant Or Stabilizer Compositions (AREA)

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Citations (4)

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• 1988
  • 1988-09-26 NZ NZ226331A patent/NZ226331A/en unknown
  • 1988-09-29 AT AT88202136T patent/ATE78064T1/de not_active IP Right Cessation
  • 1988-09-29 ES ES88202136T patent/ES2042717T3/es not_active Expired - Lifetime
  • 1988-09-29 DE DE8888202136T patent/DE3872646T2/de not_active Expired - Lifetime
  • 1988-09-29 EP EP88202136A patent/EP0311192B1/de not_active Expired - Lifetime
  • 1988-10-04 AU AU23368/88A patent/AU619764B2/en not_active Ceased
  • 1988-10-05 JP JP63250018A patent/JPH01165780A/ja active Pending

Patent Citations (4)

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