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
• • 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
  • C23F11/10—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 organic inhibitors

Definitions

• the inhibiting power I is calculated from the formula:
• alkylated and arylated derivatives of thiourea such as di-n-butyl-thiourea, diethyl-thiourea and di-o-tolyl-thiourea, are particularly well known.
• these substances are slowly soluble in water. Therefore, it is necessary to add emulsifiers to these inhibiting substances in order to distribute them uniformly in the pickling medium.
• emulsifiers for example, if a condensation product of nonyl phenol with ethylene oxide is added to dibutyl-thiourea, the inhibiting power of dibutyl-thiourea reaches 99%.
• the concentration of the salts of the metals treated increases gradually in the acid solutions.
• the non-ionic emulsifiers are generally found to be sensitive to the action of the metal salts. Consequently, the inhibitor is no longer properly emulsified in the pickling medium. Furthermore, a part of the inhibitor is removed either by the pickledarticles in the form of a cream or by settling to the bottom of the pickling bath.
• new pickling inhibiting compositions comprising (a) From about 2 to 25 parts by weight of an alkylor aryl-substituted thiourea,
• the present invention also improves the advantages generally attributed to pickling inhibitors such as a saving of metal and of the acid used; the pickling is more uniform and more bygienic.
• component (a) of the inhibiting compositions according to the present invention is an alkylor aryi-substituted thiorurea.
• alkylated derivative of thiourea with alkyl groups containing from 1 to 5 carbon atoms and more, particularly dibutyl-thiourea.
• Component (b) is a non-ionic agent consisting essentially of a condensation product of from 5 to 30 moles of ethylene oxide for each mole of a compound selected from the group consisting of a naphthol, a xylenol and a mixture of xylenols.
• the non-ionic agents preferably used are condensation products of from 8 to 25 moles of ethylene oxide for each mole of a naphthol and condensation products from 5 to 15 moles of ethylene oxide for each mole of a mixture of xylenols. These nonionic agents are not emulsifiers or possess only a very low emulsifying power.
• the inhibiting compositions may in addition, contain a suitable organic solvent, which has been indicated above as component (0).
• suitable organic solvent which has been indicated above as component (0).
• solvents are halogenated hydrocarbons, alcohols, ketones and'phenols and especially, aliphatic or alicyclic amines.
• An amount of an organic solvent sufficient to maintain the homogeneity of the mixture under normal storage conditions is used.
• the inhibiting compositions of the invention can be prepared by mixing the constituents, in suitable proportions, in any order; for 1 part of alkylor aryl-substituted thiourea are used from 0.25 to 10 parts, preferably from 1 to 5 parts of the non-ionic agent.
• compositions can, if desired, also contain surface active agents such as usually added to commercial pickling inhibitors.
• the present invention also includes the acid solutions prepared from these inhibiting compositions.
• the choice of the acid solution obviously depends on the nature of the metal to be cleaned. Use is generally made of an aqueous solution of sulfuric, hydrochloric, phosphoric or sulfamic acid, or potassium hydrogen sulfate.
• the mixture of the substituted thiourea and of the non-ionic agent is added to the acid solution in concentrations of about 0.01 to 1%, preferably 0.025 to 0.25% by Weight, referred to the concentration of the acid.
• inhibited acid solutions may be used directly or after suitable dilution for metal pickling or cleaning.
• the use of the inhibiting compositions of the invention is however not limited to picking processes, but they may also be used to protect metals against corrosion and, in general, to inhibit any corrosive effect of an acid upon a metal surface.
• a number of metal sheetscoated with oxides are pickled for a definite period of time.
• a tared metal sheet with ground surfaces is introduced at regular intervals. These operations are continued until the bath is exhausted.
• the inhibiting power is determined from the weight loss of the metal sheet with ground surfaces. This is done for different states of exhaustion of the bath and consequently for an increase in concentration of dissolved metal salts.
• Example 1 An acid pickling bath containing sulfuric acid (200 g. of H SO per liter) is used at a temperature of 85 C. A mixture of 20 part of dibutyl-thiourea, 20 parts of nonyl phenol condensed with 30 moles of ethylene oxide and 60 parts of trichlorethylene is used as inhibiting composition. This mixture is added to the acid bath in a concentration of 1 g. per1000 g. of 100% sulfuric acid. The inhibiting power is determined and the following values are found:
• the example shows the inhibiting action of dibutylthiourea in the presence of a known non-ionic emulsifier.
• the inhibition is almost perfect at the start of pickling but a decrease of the action during pickling is observed.
• Example 3 mixture of 15 parts of dibutyl-thiourea, 70 part of betanaphthol condensed with 11 moles of ethylene oxide and 15 parts of cyclohexylamine is used as inhibiting composition. 1.33 g. of this mixture is added per 1000g. of 100% sulfuric acid. The inhibiting power is determined and the following values are found:
• This example shows the inhibiting action of dibutylthiourea in the presence of a non-ionic agent according to the invention.
• the perfect inhibition at the start of pickling is almost fully maintained during pickling.
• Example 4 An acid pickling bath is used which contains sulfuric acid (200 g. of H 80 per liter) at a temperature of 85 C. A mixture of 15 parts of dibutyl-thiourea, 70 parts of a mixture'of xylenols condensed with 10 moles'of ethylene oxide and 15 parts of cyclohexylamine is used as inhibiting composition. 1.33 g. of this mixture is added per 1000 g. of 100% sulfuric acid. The inhibiting power is determined and the following values are found:
• Example 6 An acid pickling bath containing phosphoric acid (150 g. of phosphoric acid per liter) is used at a temperature of 80 C. A mixture of 15 parts of dibutyl-thiourea,.70
• Example 7 A pickling bath containing potassium hydrogen sulfate (200 g. of KHSO per liter) is used at a temperature of C. A mixture of 15 parts of dibutyl-thiourea, 70
• Example 8 A descaling bath containing sulfarnic acid g. of NH SO H per liter) is used at a temperature of 65 C. A mixture of 15 parts of dibutyl-thiourea, 70 parts of betanaphthol condensed with 11 moles of ethylene oxide and 15 parts of cyclohexylamine is used as inhibiting composition.v '10 g. of this mixture is added per 1000 g. of 99% solid sulfamic acid. I
• the inhibiting power determined according to the usual method is 99.6%.
• a substantially non-emulsifying non-ionic surfaceactive agent consisting of a condensation product of from 5 to 30 moles of ethylene oxide per mole ofa compound selected from the group consisting of betanaphthol and xylenol, the proportion of (a) to (b) being about 2 to 25 parts by weight
• An inhibiting composition for metal pickling consisting essentially of (a) dibutyl-thiourea and (b) 'a substantially non-emulsifying non-ionic surface active agent consisting of a condensation product of from '5 to 30 moles of ethylene oxide per mole of beta-naphthol, the
• proportion of (a) to (b) being-about 2 to 25 parts by Weight of (a) per about 5 to 75 parts by weight of (b);
• An aqueous acid pickling solution normally corroi g l i 5 sive towards metal surfaces, containing dispersed therein about 0.01 to 1% by Weight, based on the weight of the acid of an inhibiting composition according to claim 2.
• An aqueous acid pickling solution normally corrosive towards metal surfaces, containing dispersed therein about 0.01 to 1% by Weight, based on the weight of th acid of an inhibiting composition according to claim 3.
• a process for pickling a metal selected from the group consisting of iron and steel which comprises immersing the metal in an acid bath containing dispersed therein about 0.01 to 1% by weight, based on the weight of the acid of an inhibiting composition as defined in claim 1.
• a process for pickling a metal selected from the group consisting of iron and steel which comprises immersing the metal in an acid bath containing dispersed therein about 0.01 to 1% by weight, based on the weight References Cited by the Examiner UNITED STATES PATENTS 1,734,949 11/29 Vignos 252-149 1,970,578 8/34 Schoeller et a1. 25289 2,799,659 7/57 Mayhew et a1 252148 XR 2,823,184 2/58 Plump et a1. 252149 2,947,703 8/60 Larsonneur 252149 JULIUS GREENWALD, Primary Examiner.

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

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• 1960
  • 1960-06-13 GB GB20756/60A patent/GB923865A/en not_active Expired
• 1961
  • 1961-05-19 LU LU40163D patent/LU40163A1/xx unknown
  • 1961-05-29 US US113138A patent/US3188292A/en not_active Expired - Lifetime
  • 1961-06-06 FR FR864045A patent/FR1291340A/fr not_active Expired
  • 1961-06-08 CH CH668661A patent/CH393872A/fr unknown
  • 1961-06-09 DE DEU8093A patent/DE1281777B/de active Pending

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