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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
  • C23G1/04—Cleaning or pickling metallic material with solutions or molten salts with acid solutions using inhibitors
  • C23G1/06—Cleaning or pickling metallic material with solutions or molten salts with acid solutions using inhibitors organic inhibitors

Definitions

• This invention relates to new corrosion inhibitor compositions.
• this invention relates to corrosion resisting acid solutions useful in the cleaning of metallic surfaces.
• this invention relates to an improvement in the cleaning of metallic surfaces employing aqueous acid solutions.
• aqueous acid solutions are used to pickle iron and steel. That is, in the process of manufacturing, metal is worked at elevated temperatures and on cooling it becomes coated with a layer of oxide, generally called scale or mill scale.
• the process of removing scale and rust using dilute aqueous acid solutions is known as pickling.
• Most worked metal which is to be coated, plated or processed through a die, is first pickled. Because of its price, availability and ability to perform an efiicient job, sulfuric acid is used quite extensively in pickling, although sulfamic, phosphoric and other acids are also employed. Acid solutions are also commonly used in the cleaning of other metal surfaces such as Zinc, aluminum, brass and the like.
• the acid is free to corrode or dissolve the exposed metal surface.
• the corrosion rate of mild steel in 15%, by weight, sulfuric acid at 200 F. is over 2.5 pounds per square foot per day.
• about 2.5 pounds of 60 Baumm sulfuric acid are spent and nearly 7 cubic feet of hydrogen gas are evolved.
• pickling baths it is common for pickling baths to contain an acid corrosion inhibitor. These inhibitors must not retard the pickling efficiency of the acid, and should also reduce acid fuming and spattering into the atmosphere.
• a common deficiency in commercially available pickling bath inhibitors is the deposit of a resinous film on the surface of the metal which tends to color the same and interfere with subsequent cleaning and coating operations. Also, many of the available inhibitors are difiicult to work with by reason of their physical form and their slight solubility in the pickling bath.
• a synergistic corrosion inhibiting effect is produced by combining in a particular proportion two agents which by themselves are not particularly effective as corrosion inhibitors. These mixtures are easily handled, being liquid and soluble at ordinary temperatures, and leave the cleansed surface free of any undesirable resinous film. Also, these mixtures are particularly efiective corrosion inhibitors in sulfuric, sulfamic and phosphoric acid solutions.
• My improved corrosion inhibiting composition contains one part of dibutylthiourea and from 1 to parts by weight of a quaternary ammonium compound represented by the formula R NX wherein R is an aliphatic hydrocarbon radical having from 1 to 22 carbon atoms, said compound being further characterized by the fact that at least 1 and no more than 2 of the Rs is an aliphatic hydrocarbon radical containiug from 8 to 22 carbon atoms, and X is a halide such as chlorine or bromine.
• the preferred ratio of dibutylthiourea to quaternary ammonium compound is l to 3 parts by weight.
• Examples of long chain aliphatic hydrocarbon radicals having from 8 to 22 carbon atoms coming within the definition of R described hereinabove include octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, octadecenyl, octadecadienyl, octadecatrienyl, docosyl, eicosyl, and mixtures of the foregoing hydrocarbon radicals as contained in naturally occurring glycerides such as coconut oil, tallow, soybean oil, and the like.
• coconut oil contains a mixture comprising approximately by weight 5% octadecenyl, 5% octadecyl, 8% hexadecyl, 18% tetradecyl, 47% dodecyl, 9% decyl, and 8% octyl radicals;
• tallow contains a mixture comprising approximately by weight 45% octadecenyl, 30% octadecyl, and 25% hexadecyl radicals; soybean oil contains a mixture comprising approximately by weight 37% octadecadienyl, 26% octadecenyl, 17% octadecyl, and 20% hexadecyl radicals.
• Examples of short chain aliphatic hydrocarbon radicals coming within the definition of R as described hereinabove include methyl, ethyl, propyl, butyl, and pentyl radicals.
• Examples of preferred mixtures useful in accordance with the present invention include three parts by weight of tallowtrimcthylammonium chloride per part of dibutylthiourea; 3 parts by weight of cocotrimethylammonium chloride per part of dibutylthiourea; 3 parts by weight of dicocodimethylammonium chloride per part of dibutylthiourea; 3 parts by weight of ditallowdimethylammonium chloride per part of dibutylthiourea; and 3 parts by weight of dodecyltrimethylammonium chloride per part of dibutylthiourea.
• These mixtures can be prepared by simple mixing of the ingredients in the proper proportions.
• the mixture of dibutylthiourea and quaternary ammonium compound can be incorporated directly into the aqueous acid solution in a concentration by weight of from about 0.1 to 1.0, preferably about 0.2 to about 0.5 percent, based upon the acid concentration, and the resulting aqueous acid solution used in the conventional manner in pickling and metal cleaning processes.
• the mixture can be incorporated, at the same concentration level described, into a concentrated acid, which is then diluted before use. There is little or no adverse effect upon the corrosion inhibiting properties of the acid under these circumstances, even after a period of storage.
• Example I Test cells containing small quantities of dilute acid, both inhibited and uninhibited were prepared. The concentnation of the acid was on a weight basis, and the percent inhibitor used was based on the acid concentration. The acid solutions were pre-heated to the desired temperature and held at i2 F. Clean, weighed mild steel coupons were exposed to the acid for 6 hours. At the end of this period the coupons were washed free of acid and salts, dried, and reweighed. The corrosion rate was calculated in pound per square foot per day. Visual observations were made for discoloration and pitting of the coupons. The results of these tests are set forth in Table I.
• Slight-Evensurface and edges have a few pit marks. 4. Slight-Suriace of metal is clean and edges for the most part are pitted. 5. Very slightSuriace of 3. EdgesSnrIace metal is clean and edges have only slight indications of being pitted. 6. Excellent-No trace of pitting detected.
• Coupon color 1. BlackSelf explanatory. 2. Tint-Surface of metal is slightly discolored. 3. Light-Clean surface, no indication of discoloration While the present invention has been described and exemplified in terms of preferred embodiments, those skilled in the art will appreciate that variations can be made without departing from the spirit and scope of the invention.
• a new corrosion inhibiting composition a synergistic combination of about 1 part by weight of dibutylthiourea and from 1 to 5 parts by weight of a quaternary ammonium compound represented by the formula R NX wherein X is a halide and R is an aliphatic hydrocarbon nadical containing from 1 to 22 carbon atoms, and further characterized by the fact that said quaternary ammonium compound contains at least 1 and no more than 2 long chain aliphatic hydrocarbon radicals having from 8 to 22 carbon atoms.
• a composition substantially non-corrosive to metals comprising an aqueous solution of an acid selected from the group consisting of sulfuric, sulfamic and phosphoric acids, and from 0.1 to 1.0 weight percent, based on the acid, of a corrosion inhibiting synergistic combination of about 1 part by weight of dibutylthiourea and from 1 to 5 parts by weight of a quaternary ammonium compound having the formula R NX wherein X is a halide and R is an aliphatic hydrocarbon radical containing from 1 to 22 carbon atoms, and further characterized by the presence of at least 1 and no more than 2 aliphatic hydrocarbon radicals containing from 8 to 22 carbon atoms.
• a composition substantially non-corrosive to metals comprising an aqueous solution of an acid selected from the group consisting of sulfuric, sulfamic, and phosphoric acids, and from 0.1 to 1.0 weight percent, based on the acid, of a corrosion inhibiting synergistic combination of 1 part by weight of dibutylthiourea and 3 parts by weight of cocotrimethyiammonium chloride.
• a composition substantially non-corrosive to metals comprising an aqueous solution of an acid selected from the group consisting of sulfuric, sulfamic, and phosphoric acids, and from 0.1 to 1.0 weight percent, based on the acid of a corrosion inhibiting synergistic combination of 1 part by weight of dibutylthiourea and 3 parts by weight of tallowtrimethylammonium chloride.
• a composition substantially non-corrosive to metals comprising an aqueous solution of sulfuric acid containing from about 0.2 to about 0.5 weight percent, based on the sulfuric acid, of a corrosion inhibiting synergistic combination of 1 part by weight of dibutylthiourea and 3 parts by weight of cocotrimethylammonium chloride.
• a composition substantially noncorrosive to metals comprising an aqueous solution of sulfuric acid containing from about 0.2 to about 0.5 weight percent, based upon the sulfuric acid, of a corrosion inhibiting synergistic combination of 1 part by weight of dibutylthiourea and 3 parts by Weight of tallowtrirnethylammonium chloride.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Detergent Compositions (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

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Citations (14)

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• 0
  • FR FR1193959D patent/FR1193959A/fr not_active Expired
  • BE BE566342D patent/BE566342A/xx unknown
• 1957
  • 1957-06-05 US US663618A patent/US3047510A/en not_active Expired - Lifetime
• 1958
  • 1958-03-28 GB GB10130/58A patent/GB841925A/en not_active Expired
  • 1958-04-14 DE DEA29249A patent/DE1111899B/de active Pending

Patent Citations (14)

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