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
  • C23G1/28—Cleaning or pickling metallic material with solutions or molten salts with molten salts
• • 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
  • C23G1/063—Cleaning or pickling metallic material with solutions or molten salts with acid solutions using inhibitors organic inhibitors heterocyclic compounds
• • 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
  • C23G1/08—Iron or steel
• • 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
  • C23G1/24—Cleaning or pickling metallic material with solutions or molten salts with neutral solutions
• • 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
  • C23G1/28—Cleaning or pickling metallic material with solutions or molten salts with molten salts
  • C23G1/32—Heavy metals
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
  • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
  • C25F1/02—Pickling; Descaling
  • C25F1/12—Pickling; Descaling in melts
  • C25F1/14—Iron or steel

Definitions

• the present disclosure relates to an ionic liquid for pickling a stainless steel and a method for pickling a stainless steel by using the same, and more particularly, to an ionic liquid for pickling a stainless steel capable of rapidly removing oxide scale from the stainless steel at room temperature without using nitric acid or hydrofluoric acid and a method for pickling a stainless steel by using the same.
• oxide scale SiO 2 , (Cr,Fe) 3 O 4
• SiO 2 , (Cr,Fe) 3 O 4 oxide scale having a thickness of 100 to 300 nm, or the like is generally formed by reaction between high-temperature oxygen in a furnace and the surface of the cold-rolled steel sheet, and thus surface quality deteriorates and corrosion resistance decreases.
• a pickling process to remove such oxide scale is conducted in order to obtain a cold-rolled stainless steel sheet having high surface quality and excellent corrosion resistance.
• the pickling process is performed by using various methods, alone or in combination, such as physical descaling (brushing and shot ball blasting), electrolytic descaling (sodium sulfate, sulfuric acid, or nitric acid electrolyte), and chemical descaling (salt bath and mixed acid bath).
• a conventional pickling process is generally performed in two steps.
• a primary pickling step to remove oxide scale is conducted by immersing a stainless steel in a solution containing sodium sulfate electrolyte and applying a current thereto or by immersing the stainless steel in a salt bath containing sodium hydroxide and sodium nitrate at a high temperature of 400°C or higher, and then a secondary pickling step is performed by using nitric acid or a mixed acid containing nitric acid and hydrofluoric acid at a high temperature of 80°C or higher to obtain high surface quality and corrosion resistance by uniformly forming a passivated layer.
• nitric acid has effects on increasing the activity of hydrofluoric acid by lowering a pH in a pickling bath and maintaining an oxidation-reduction potential suitable for pickling by oxidizing ferrous cation (Fe 2+ ) dissolved on the surface of the steel sheet to ferric cation (Fe 3+ ).
• nitric acid causes various environmental problems.
• the use of a salt containing nitric acid and nitric acid generates NO x that is a substance whose emission into the atmosphere is regulated and nitrate nitrogen (NO 3 -N) is contained in waste acid and wash water.
• NO 3 -N nitrate nitrogen
• production costs are considerably increased due to additional installation of facilities to prevent environmental pollution in a pickling process and operation costs thereof because a total nitrogen contained in discharged effluent water is limited and a NO x concentration of a facility discharging to atmosphere is limited in accordance with domestic and foreign strengthened environmental regulations.
• nitric acid-free pickling method in which nitric acid is replaced with hydrochloric acid, sulfuric acid, or the like and insufficient oxidizing power is replaced by hydrogen peroxide, potassium permanganate, ferric ion (Fe 3+ ), and air injection during a pickling process.
• Patent Document 1 in which an oxidation-reduction potential of a pickling solution is maintained at 300 mV or more by using sulfuric acid, hydrofluoric acid, or iron sulfate as a pickling solution and adding hydrogen peroxide
• Patent Documents 2 and 3 in which ranges of hydrofluoric acid, iron ions, air, hydrogen peroxide, and oxidation-reduction potential (ORP) of a solution are appropriately modified, and other patent applications have been continuously filed since the 1990s.
• ORP oxidation-reduction potential
• Patent Document 4 discloses a pickling method by using a pickling solution containing sulfuric acid, hydrofluoric acid, and ferric salt, periodically adding hydrogen peroxide, and adjusting a composition of a wetting agent, a polishing agent, and a corrosion inhibitor, wherein the pickling solution is automatically controlled based on Fe(III) and ORP thereby.
• CLEANOX352 as a pickling solution, has been commercialized and the most widely used worldwide. Although this method has been practically used for wire rods and hot-rolled products, manufacturing costs for products are higher than those of conventional products by 20% or more and the composition of the pickling solution and the control method are complex.
• Patent Document 5 discloses a method of increasing a pickling rate by adding copper and chlorine ions to a pickling composition.
• OCP open circuit potential
• 0.1 V oxidation-reduction potential
• copper particles may be precipitated on the surface of the steel sheet during a pickling process, thereby causing discoloration of the steel sheet.
• a pickling solution includes chlorine ions at a certain level or more, there is a risk of occurrence of pitting corrosion.
• the present disclosure has been proposed to solve the above-described problems, and provided is an ionic liquid for pickling stainless steel capable of rapidly removing oxide scale of stainless steel at room temperature without using nitric acid or hydrofluoric acid and method for pickling stainless steel by using the same.
• an ionic liquid for pickling a stainless steel may include at least one of an imidazolium cation, a betainium cation, a sulfonium cation, a piperidinium cation, a phosphonium cation, an ammonium cation, a pyridium cation, a pyrrolidinium cation, and a morpholinium cation, as a cationic functional group, and at least one of a halide anion, a sulfonate anion, an alkylsulfate anion, a phosphinate anion, a salicylate anion, a nitrate anion, a tetrafluoroborate anion, a hexafluorophosphate anion, and a bistriflimide anion, as an anionic functional group.
• the ionic liquid for pickling a stainless steel may be represented by one of the compounds (a) to (c) below.
• a method for pickling a stainless steel includes performing electrolytic pickling treatment by immersing a stainless steel in a pickling solution including an ionic liquid, wherein the ionic liquid includes at least one of an imidazolium cation, a betainium cation, a sulfonium cation, a piperidinium cation, a phosphonium cation, an ammonium cation, a pyridium cation, a pyrrolidinium cation, and a morpholinium cation, as a cationic functional group, and at least one of a halide anion, a sulfonate anion, an alkylsulfate anion, a phosphinate anion, a salicylate anion, a nitrate anion, a tetrafluoroborate anion, a hexafluor
• the ionic liquid may be represented by one of the compounds (a) to (c) below.
• the ionic liquid may be contained in the pickling solution in a concentration of 2 M or less.
• the pickling solution may be a solution prepared by adding an ionic liquid to a hydrochloric acid solution having a concentration of 1 M or less or a neutral solution including at least one of sodium chloride, potassium chloride, magnesium chloride, sodium sulfate, and potassium sulfate.
• a temperature of the pickling solution may be from 15 to 25°C.
• the electrolytic pickling treatment may be performed by applying a current density of 0.5 to 1.3 A/cm 2 while maintaining a surface potential of the stainless steel in the range of -1.5 to 1.5 V using an Ag/AgCl electrode as a reference electrode.
• a time taken to completely remove the oxide scale may be 1 minute or less.
• oxide scale of a stainless steel may be removed in an eco-friendly manner by adding an ionic liquid to a pickling solution without using nitric acid or hydrofluoric acid.
• the number of times of repeatedly applying a potential until the oxide scale of the stainless steel is completely removed in a state where the stainless steel is immersed in the pickling solution at a temperature of 15 to 25°C, rather than a high temperature of 80°C or higher, may be 5 times or less and a time taken therefor may be 1 minute or less.
• oxide scale may be removed using a low concentration of an acidic solution or neutral solution, rather than a high concentration, in a pickling solution.
• economic feasibility may be improved by simplifying a pickling process conventionally performed in two steps into an electrolytic pickling process performed in a single step.
• An ionic liquid for pickling a stainless steel may include at least one of an imidazolium cation, a betainium cation, a sulfonium cation, a piperidinium cation, a phosphonium cation, an ammonium cation, a pyridium cation, a pyrrolidinium cation, and a morpholinium cation, as a cationic functional group, and at least one of a halide anion, a sulfonate anion, an alkylsulfate anion, a phosphinate anion, a salicylate anion, a nitrate anion, a tetrafluoroborate anion, a hexafluorophosphate anion, and a bistriflimide anion, as an anionic functional group.
• the term "stainless steel” refers to a cold-rolled stainless steel sheet manufactured by cold rolling and annealing according to a process commonly used to manufacture cold-rolled stainless steel sheets.
• the embodiment is not interpreted as being limited thereto, and the stainless steel means any stainless steel having oxide scale formed on the surface thereof within a range that may be clearly recognized by those of ordinary skill in the art.
• ionic liquid refers to a salt compound including a metal cation and a non-metal anion and present as a liquid at a temperature of 100°C or below.
• the present disclosure provides a method for removing oxide scale formed on the surface of the stainless steel by immersing the stainless steel in a pickling solution and performing an electrolytic pickling treatment.
• the pickling solution of the present disclosure refers to an acidic solution or neutral solution containing an ionic liquid.
• the present inventors have found that efficiency of pickling a stainless steel may be increased by adding an ionic liquid to a pickling solution.
• the ionic liquid according to the present disclosure may include at least one of an imidazolium cation, a betainium cation, a sulfonium cation, a piperidinium cation, a phosphonium cation, an ammonium cation, a pyridium cation, a pyrrolidinium cation, and a morpholinium cation, as a cationic functional group, and at least one of a halide anion, a sulfonate anion, an alkylsulfate anion, a phosphinate anion, a salicylate anion, a nitrate anion, a tetrafluoroborate anion, a hexafluorophosphate anion, and a bistriflimide anion, as an ani
• the ionic liquid of the present disclosure may be represented by one of the compounds (a) to (c) below.
• the compounds (a) to (c) are sequentially trihexyl(tetradecyl)phosphonium chloride, methyltrioctylammonium chloride, and 1-butyl-3-methylimidazolium chloride.
• oxide scale of a stainless steel may be removed in an eco-friendly manner by adding an ionic liquid to a pickling solution without using nitric acid or hydrofluoric acid. Also, the oxide scale of the stainless steel may be rapidly removed by immersing the pickling solution at room temperature rather than a high temperature of 80°C or higher, and the oxide scale may be sufficiently removed by using a low concentration, rather than a high concentration, of the acidic solution or neutral solution in the pickling solution. In addition, economic feasibility may be improved by simplifying a pickling process conventionally performed in two steps into an electrolytic pickling process performed in a single step.
• the ionic liquid is added to the pickling solution.
• the ionic liquid may be contained in the pickling solution in a concentration of 2 M or less.
• the pickling efficiency may be sufficiently increased in a low concentration of 0.2 M or less.
• molarity of the ionic liquid corresponds to a value calculated relative to a total volume of the pickling solution.
• oxide scale may be sufficiently removed in the case of using a low concentration of the acidic solution, rather than a high concentration, by adding the ionic liquid to the pickling solution.
• the acidic solution may be a hydrochloric acid solution having a concentration of 1 M or less.
• the molarity of the hydrochloric acid solution corresponds to a value calculated relative to a total volume of the pickling solution.
• the neutral solution according to the present disclosure is not particularly limited, as long as the neutral solution is suitable for immersing the stainless steel and the electrolytic pickling treatment and contains a water-soluble electrolyte commonly used in the electrochemical field.
• the electrolyte may include sodium chloride (NaCI), potassium chloride (KCl), magnesium chloride (MgCl 2 ), sodium sulfate (Na 2 SO 4 ), and potassium sulfate (K 2 SO 4 ).
• the concentration of the neutral solution is not particularly limited, as long as the electrolytic pickling treatment is performed using the neutral solution.
• the neutral solution according to an embodiment may be a 1 M to 2 M sodium chloride solution.
• oxide scale may be rapidly removed by immersing the stainless steel in the pickling solution at a temperature of 15 to 25°C, rather than a high temperature of 80°C or higher.
• the number of times of repeatedly applying a potential until the oxide scale of the stainless steel is completely removed may be 5 times or less and a time taken therefor may be 1 minute or less.
• the electrolytic pickling treatment according to the present disclosure is a process of removing oxide scale formed on the surface of the stainless steel by performing electrolytic pickling treatment after immersing the stainless steel in a pickling solution prepared by adding an ionic liquid to an acidic solution or neutral solution.
• the electrolytic pickling treatment may be performed by applying a current density of 0.5 to 1.3 A/cm 2 while maintaining a surface potential of the stainless steel at -1.5 to 1.5 V using an Ag/AgCl electrode as a reference electrode.
• the electrolytic pickling treatment may be performed by AC electrolysis or DC electrolysis in which a currents is applied, or by a constant voltage method in which a voltage is applied.
• STS 304 type steel containing 18 wt% of Cr and 8 wt% of Ni was cold-rolled and annealed using a process commonly used to manufacture cold-rolled stainless steel sheets.
• the STS 304 type steel was used in the examples of the present disclosure, any other stainless steel having a different compositions and including oxide scale formed on the surface thereof may also be pickled according to the pickling method of the present disclosure.
• the stainless steel was immersed in the pickling solution shown in Table 1 below at a temperature of 15 to 25°C, and then electrolytic pickling treatment was performed.
• the electrolytic pickling treatment was performed by repeatedly applying a potential several times at a scan speed of 0.5 V/s until the oxide scale is completely removed in a state where the surface potential of the stainless steel was maintained in the range of -1.5 to 1.5 V using an Ag/AgCl electrode as a reference electrode.
• the removal of the oxide scale was observed by using an optical microscope and an electron microscope.
• the compositions (acidic solution or neutral solution, ionic liquid) of the pickling solution are listed in the order of molarity (M) and compounds of compositions.
• the molarity is a value calculated relative to a total volume of the pickling solution.
• the current density (A/cm 2 ) of Table 1 means a current density applied to the stainless steel, and the number of repetition means the number of repeatedly applying a potential until the oxide scale is completely removed.
• the time (sec) of Table 1 means a time taken until the oxide scale is completely removed.
• oxide scale of the stainless steel may be removed in an eco-friendly manner by adding the ionic liquid to the pickling solution without using nitric acid or hydrofluoric acid according to the present disclosure. Also, it was confirmed that the oxide scale of the stainless steel may be completely removed at a high speed within 1 minute by repeatedly applying a potential 5 times or less by immersing the stainless steel in the pickling solution at room temperature, rather than at a high temperature of 80°C or higher according to the present disclosure. Also, it was confirmed that oxide scale may be removed by using a low concentration of the acidic solution or neutral solution, rather than a high concentration, in the pickling solution according to the present disclosure.
• an ionic liquid for pickling a stainless steel and a method for pickling the stainless steel using the same may be provided with improved economic feasibility.

Landscapes

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

Applications Claiming Priority (2)

Publications (2)

Family

ID=75981320

Family Applications (1)

Country Status (5)

Family Cites Families (14)

• 2019
  • 2019-11-21 KR KR1020190150288A patent/KR102300834B1/ko active IP Right Grant
• 2020
  • 2020-10-16 CN CN202080086975.4A patent/CN114829682A/zh active Pending
  • 2020-10-16 EP EP20889474.1A patent/EP4056737A4/fr active Pending
  • 2020-10-16 WO PCT/KR2020/014199 patent/WO2021101076A1/fr unknown
  • 2020-10-16 US US17/777,907 patent/US20230059039A1/en active Pending

Also Published As

Similar Documents

Legal Events