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
• • 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

Definitions

• This invention relates to synergistic compositions and a method for inhibiting carbon steel corrosion in aqueous systems due to dissolved oxygen which comprises adding to said aqueous systems an effective amount of said compositions comprising a phosphorus-containing compound and borate and optionally, a copolymer, acrylic acid/2-acrylamide-­2-methyl propyl sulfonic acid (hereinafter referred to as AA/AMPS).
• AA/AMPS acrylic acid/2-acrylamide-­2-methyl propyl sulfonic acid
• oxygen in aqueous systems causes corrosion to occur.
• Other oxygen molecules combine with metal ions to form insoluble metal oxide compounds.
• the severity of attack will depend on the concentration of dissolved oxygen in the water, pH and temperature. As water temperature increases, corrosion in feed lines, heat exchanges and return lines made of iron and steel increases.
• the literature discloses numerous references for corrosion protection of aqueous systems such as polyphosphates, phosphates and zinc. For example:
• this reference discloses a method of inhibiting the formation of insoluble alluvial, metal oxide and metal hydroxide deposits in an aqueous system, comprising adding to the system at least 0.1 mg/l of a water-soluble polymer having a weight average molecular weight of less than 25,000, as determined by low angle laser light scattering, comprising an unsaturated carboxylic acid and an unsaturated sulfonic acid, or their salts, having a ratio of 1:20 to 20:1 and a phosphonate.
• This invention relates to synergistic compositions and method of inhibiting carbon steel corrosion of aqueous systems wherein said compositions comprise a phosphorus-containing compound and borate and optionally, a copolymer, AA/AMPS. Therefore, in accordance with this invention, it is found that when the compositions described herein are added to aqueous systems, the components of said compositions are effective in inhibiting carbon steel corrosion of said aqueous systems.
• a further object of the invention to describe a process wherein components of the compositions described herein produce a synergistic product that effectively inhibits corrosion of in aqueous systems.
• a still further object of the invention is to describe concentration levels wherein the phosphorus containing compound of the composition is substantially reduced such that the potential for calcium phosphate precipitation is minimized.
• Another object of the invention is to describe synergistic compositions that substantially subdue the pitting propensity of AA/AMPS.
• the synergistic compositions of the present invention are effective in inhibiting corrosion of carbon steel surfaces of aqueous system when added to said aqueous systems in amounts sufficient to maintain a concentration level ranging between 0.1 to 300 parts per million (PPM) by weight of the total aqueous content of said aqueous system.
• concentration level ranges from 1.0 to 50 ppm.
• compositions disclosed herein are improved in their corrosion inhibiting activity by the addition of zinc (calculated as Zn++), which acts as an synergist in aqueous systems.
• Zn++ zinc
• the ratio of the combined phosphorus-containing compound and borate and optionally, AA/AMPS are 1:1 to 10:1 and optionally 1:1:1 to 10:1:1, respectively.
• the zinc ion component of the corrosion inhibiting compositions of the present invention is provided by employing zinc in any convenient water soluble form, such as chloride or the sulfate salt.
• the present invention contemplates inclusion with the corrosion inhibiting compositions thereof other known additives for the treatment of aqueous systems.
• a copper corrosion inhibitor selected from the group consisting of 1,2,3-triazoles, thiols of thiazoles, oxazoles, and imidazoles as described in U.S. Pat. Nos. 2,941,953 and 2,742,369, respectively, may be employed in an amount of up to about 10% by weight.
• compositions of the present invention will actively inhibit corrosion so long as they are effectively present in the aqueous system being treated. This effective presence is dependent on the lack of any degradation or decomposition of the inhibitor compositions occassioned by pH, temperature, pressure, or other conditions. Thus, it is anticipated that the inhibitor compositions of the invention will be effective generally in a pH range of from about 7 to 9, preferrably at pH 8.
• the corrosion inhibiting compositions of the present invention are synergistic in their activity, i.e., they possess a degree of corrosion inhibiting activity which is greater than the corrosion inhibiting activity of either component alone.
• synergistic compositons disclosed herein are prepared via conventional methods.
• the manner in which the components of said compositions are added is not critical, i.e., either of the two components or optionally three compounds can be added first and formulated via conventional procedure.
• the coupon immersion test consisted of a cylindrical battery jar with a capacity of 8 liters.
• a Haake constant temperature immersion circulator (Model E-52) was used to control the solution temperature and agitate the controlled bath.
• the unit contained a 1000 watt fully adjustable stainless steel heater which permitted temperature control to ⁇ 0.01°C., and a 10 liter per minute pump with a built in pressure nozzle aGitator that ensured high temperature uniformity in the bath.
• a mercury contact thermoregulator was used as the temperature sensing element.
• the pH of the solution was controlled with Kruger and Eckels Model 440 pH Controller. This unit was capable of turning power on and off to a Dias minipump whenever the pH of the corrosive liquid environment fell below the set point.
• the peristaltic Dias pump with a pumping capacity of 20 ml. per hour, maintained the solution pH with the addition of sulfuric acid. Standard glass and sensing elements.
• the oath was continuously aerated saturated calomel electrodes were used as the through a medium porosity plastic gas dispersion tube to ensure air saturation.
• composition of the synthetic water used in the test is shown in TABLE 1 below indicating content per liter of distilled water: TABLE I Ion: Ca++ Mg++ HCO3 ⁇ Cl ⁇ SO 4 ⁇ Mg./l.: 88 24 40 70 328
• B2O3/PO4 pair The inhibitory properties of B2O3/PO4 pair was investigated in the same water as Table 1 at 50°C and pH 8 in the presence of AA/AMPS and zinc.
• the B2O3/PO4 pair is synergistic at this pH.
• the presence of AA/AMPS improves the corrosion rate while zinc acts as an antagonist.
• Table III TABLE III System Concentration, mg/L PH Corrosion Rate, mpy Control --- 8.0 45 B2O3 10 8.0 50 B2O3/PO4 5/5 8.0 4 B2O3/PO4/AA-AMPS 5/5/5 8.0 2 B2O3/PO4/AA-AMPS 5/5/5/5 8.0 13
• Any phosphorus containing compound may be used in this invention.
• Examples include polyphosphates, phosphonates, and phosphates.
• water-soluble phosphonates examples include 2-phosphono-1,2,4-tricarboxybutane, aminotri(methylene phosphonic acid), hydroxy­ethylidene diphosphonic acid, phosphonosuccinic acid, benzenephosphonic acid, 2-aminoethyl-phosphonic acid, polyaminophosphonates and the like. Additional phosphonates are identified in U.S. Patent 3,837,803, and are hereby incorporated herein by reference. The preferred phosphonates are aminotri(methylene phosphonic acid) and hydroxyethylidene diphosphonic acid.
• Any water-soluble phosphate may be used.
• Examples include orthophosphate; condensed phosphates, such as sodium hexametaphosphate; phosphate ester; organophosphate esters, such as the loweralkyl mono-, di- and trialkyl phosphates.
• the alkyl group is selected from C1-C4 and may be branched or unbranched. The alkyl group may be substituted with hydroxy, amino, halide, sulfate or sulfonate, alone or in combination; and molecularly dehydrated phospahates.
• the most preferred phosphorous-containing compound is orthophosphate.
• Any water-soluble borate compound may be used in the present invention.
• Examples include tetraborate pentaboate metaborate, boric acid and the like.
• Zinc may be added to the composition at ratios ranging from 10:1 to 1:10, thereby enhancing corrosion Inhibitant Values.
• the synergistic compositions disclosed are used at a minumum dosage of 0.1 ppm in inhibiting corrosion, preferably in a dosage of 1 to 500 ppm, and most preferably 1 to 200 ppm.

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Citations (5)

• 1989
  • 1989-10-05 EP EP89202510A patent/EP0364030A1/de not_active Withdrawn
  • 1989-10-10 AU AU42752/89A patent/AU4275289A/en not_active Abandoned
  • 1989-10-11 JP JP27056489A patent/JPH02166287A/ja active Pending

Patent Citations (5)

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