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 corrosion restraining compositions and more particularly it relates to liquid compositions for restraining the corrosion of ferrous metals in acid pickling baths.
• Ferrous metals such as steel, which are subjected to working at elevated temperatures during the course of manufacture become coated with a layer of oxide impurity, often referred to as mill scale.
• a layer of oxide impurity often referred to as mill scale.
• acid pickling an operation referred to as acid pickling.
• the acid commonly used for this purpose is sulphuric acid, although other acids such as hydrochloric acid, phosphoric acid and sulphamic acid may be used.
• a particularly valuable corrosion-restraining composition for acid pickling baths may be obtained from a mixture of di-n-butylthiourea, an amine/alkylene oxide condensate and a propylene glycol solvent.
• a corrosion restraining composition which comprises a mixture of 1 part by weight of di-n-butylthiourea and from 2 to 5 part-s by weight of an amine/alkylene oxide condensate as hereinafter defined incorporated with a propylene glycol solvent as hereinafter defined, the weight of the said solvent being from 1 to 4 times the weight of the said mixture.
• the amine/alkylene oxide condensates used in the corrosion restraining compositions of our invention are the condensates of 1 mol. of an aliphatic primary amine containing from 8 to 18 carbon atoms or of 1 mol. of a mixture of such amines with from 3 to 20 mols. of an alkylene oxide.
• the condensates are thus essentially tertiary amines having an aliphatic hydrocarbon radical of from 8 to 18 carbon atoms as one of the N-substituents and having as the remaining N-substituents two polyalkanoxy radicals, or are mixtures of such amines.
• the aliphatic primary amines from which the condensates are derived may have saturated or unsaturated hydrocarbon radicals which include, for example, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, octadecenyl, octadecadienyl and octadecatrienyl.
• Such aliphatic primary amines and mixtures of such amines may be derived, for example, from naturally occurring fatty glycerides such as coconut oil, soyabean oil and tallow, which contain mixtures of such saturated and unsaturated hydrocarbon radicals.
• the alkylene oxide from which the amine/alkylene oxide condensates are derived may be ethylene oxide or propylene oxide, but is preferably ethylene oxide.
• the amine/alkylene oxide condensates contain a substantial proportion of compounds which may be represented by the following formulaice in which R represents a saturated or unsaturated hydrocarbon radical of from 8 to 18 carbon atoms, n represents one of the integers 2 and 3, and p and q independently represent zero or a positive integer although the condensates are not restricted solely to compounds of this formula.
• the condensates are obtained by methods al' ready well known in themselves. Depending on the molecular size of the hydrocarbon radical of the amine and the number of mols. of alkylene oxide used in the prep aration, the condensates may or may not be soluble in water. We prefer that the condensates are soluble in water, but the invention is not limited to water-soluble condensates.
• a propylene glycol solvent we mean a monopropylene glycol, a dipropylene glycol, a tripropylene glycol or mixtures of two or more of these glycols. Particularly suitable are mixtures of a major proportion by weight of a dipropylene glycol with a minor proportion by weight of a monopropylene glycol.
• the corrosion restraining compositions of our invention are obtained from mixtures of 1 part by weight of di-n-butyl thiourea with from 2 to 5 parts by weight of the amine/alkylene oxide condensate. Particularly valuable are those compositions in which about 3 parts of amine/alkylene oxide condensate are used for each part of di-n-butylthiourea.
• the mixture is incorporated with from 1 to 4 times its weight of the propylene glycol solvent. Within these limits the proportion of the solvent to the mixture is not critical, and the formulation may be varied depending on the particular circumstances in which the corrosion restraining composition is to be used.
• the corrosion restraining compositions of our invention may be prepared by simple mixing of the components optionally followed by heating, for example, to 50 C. to ensure complete solution.
• compositions of our invention have the further advantage that they remain fluid and pourable down to quite low temperatures. This is particularly important since in some of the acid pickling plants in which corrosion restraining compositions are used it is not always possible to store them in heated conditions in cold weather.
• the compositions of our invention remain fluid and pourable at temperatures substantially below that of the freezing point of water, for example down to temperatures of 12 C. (10 F.).
• Our compositions also have the advantage that they induce foaming in acid-pickling baths, and so reduce acid spray.
• Example 1 A mixture of 10 parts of di-nbutylthiourea and 30 parts of the condensation product of a cocoarnine with 15 mols. of ethylene oxide was dissolved in 70 parts of dipropylene glycol.
• Example 2 A 40 cm. length of bright annealed mild steel strip, 6 mm. wide and 0.3 mm. thick, was immersed in 20% w./w. aqueous sulphuric acid containing 0.05% W./w. of the composition of Example 1 for 15 minutes at 95 C. and was found to have lost 0.0178 gram in weight. A similar mild steel strip treated under the same conditions with 20% w./w. aqueous sulphuric acid omitting the composition of Example 1 was found to have lost 1.7740 grams in weight.
• a corrosion restraining composition which consists essentially of a mixture of 1 part by weight of di-n-butylthiourea and from 2 to parts by weight of an amine/alkylene oxide condensate incorporated with a propylene glycol solvent selected from the class consisting of monopropylene glycol, dipropylene glycol, tripropylene glycol and mixtures of said glycols, the weight of said solvent being from 1 to 4 times the weight of the said mixture, and said amine/alkylene oxide condensate having the formula:
• R represents a radical selected from the class consisting of saturated and unsaturated hydrocarbon radicals containing from 8 to 18 carbon atoms, and the sum of p and q represents a number selected from 0 to 20.
• R represents a radical selected from the class consisting of saturated and unsaturated hydrocarbon radicals containing from 8 to 18 carbon atoms, and the sum of p and q represents a number selected from 0 to 20.
• a liquid corrosion restraining composition which consists essentially of a mixture of 10 parts of di-n-butylthiourea and 30 parts of the condensation product of 1 molecular proportion of a cocoamine with 15 molecular proportions of ethylene oxide dissolved in parts of dipropylene glycol.
• An acid pickling bath consisting of an aqueous pickling acid containing a corrosion restraining composition which comprises a mixture of 1 part by weight of di-nbutylthiourea and from 2 to 5 parts by weight of an amine/alkylene oxide condensate incorporated with a propylene glycol solvent selected from the class consisting of monopropylene glycol, dipropylene glycol, tripropylene glycol and mixtures of said glycols, the Weight of the said solvent being from 1 to 4 times the weight of the said mixture, said amine/alkylene oxide condensate having the following formula:
• R represents a radical selected from the class consisting of saturated and unsaturated hydrocarbon radicals containing from 8 to 18 carbon atoms, and the sum of p and q represents a number selected from 0 to 20.
• An acid pickling bath as claimed in claim 5 which contains between 0.03% and 0.5% of the corrosion restraining composition calculated on the weight of acid.
• An acid pickling bath as claimed in claim 5 in which the aqueous acid is 5% to 25% sulphuric acid.

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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)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Detergent Compositions (AREA)

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Citations (2)

• 1963
  • 1963-08-22 GB GB33303/63A patent/GB1010753A/en not_active Expired
• 1964
  • 1964-07-27 US US385450A patent/US3277011A/en not_active Expired - Lifetime
  • 1964-08-04 DK DK385564A patent/DK128660B/da unknown
  • 1964-08-11 NL NL6409242A patent/NL6409242A/xx unknown
  • 1964-08-14 BE BE651880A patent/BE651880A/xx unknown
  • 1964-08-21 DE DE19641521790 patent/DE1521790B2/de not_active Withdrawn
  • 1964-08-21 SE SE10135/64A patent/SE315782B/xx unknown

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