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
  • C23G1/12—Light metals
• • 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
  • C23G1/12—Light metals
  • C23G1/125—Light metals aluminium
• • 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
  • C23F1/00—Etching metallic material by chemical means
  • C23F1/10—Etching compositions
  • C23F1/14—Aqueous compositions
  • C23F1/16—Acidic compositions
  • C23F1/20—Acidic compositions for etching aluminium or alloys thereof

Definitions

• the present invention relates to an acidic cleaning aqueous solution for an aluminum based metal and a process for cleaning the same, and more particularly, it relates to a cleaning aqueous solution which can satisfactorily remove a lubricant, an aluminum powder or the like attached on an aluminum surface at the time of molding, and a method cleaning the aluminum surface.
• a product having an aluminum surface for example, an aluminum container for a drink made of an aluminum-based metal, i.e., aluminum or an aluminum alloy, can usually be manufactured by a molding operation called drawing and ironing (hereinafter referred to as "DI").
• DI drawing and ironing
• a lubricant is applied onto a metal surface, and particularly on the inside wall of the obtained container, an aluminum powder (a smut) is deposited.
• the surface of this kind of container is usually protected by a subsequent chemical-conversion treatment or paint coating. Therefore, it is necessary that the above-mentioned lubricant or smut should be removed from the metal surface prior to this chemical-conversion treatment or the like to clean the metal surface.
• an acidic cleaning agent for suitably etching the metal surface to clean it.
• an acidic cleaning agent chromium-based and hydrofluoric acid-based cleaning agents have often been used.
• the hydrofluoric acid-based cleaning agents are excellent in that low-temperature cleaning (50°C or less) is possible.
• the above-mentioned cleaning agents are harmful substances, and therefore waste water controls are strict.
• the etching reaction of aluminum in the acidic cleaning agent comprises an anodic reaction in which aluminum becomes aluminum ions (Al 3+ ), and a cathodic reaction in which H + in the cleaning agent is reduced to 1/2 H 2 .
• the acidic cleaning agent containing the ferrics ions (Fe 3+ ) is added, the anodic reaction in which this Fe 3+ is reduced to Fe 2+ occurs simultaneously with the above-mentioned reduction of H + , so that the etching reaction of aluminum is promoted.
• the concentration of Fe 2+ which increases with the progress of the aluminum etching reaction can be inhibited and Fe 2+ can be oxidized to Fe 3+ .
• an object of the present invention is to provide an acidic cleaning aqueous solution for an aluminum-based metal which contains oxidizing metal ions as an etching promotor but contains neither harmful fluorine nor chromium ions and which can carry out acidic cleaning
• another object of the present invention is to provide a method for cleaning the aluminum-based metal.
• the acidic cleaning aqueous solution for an aluminum-based metal regarding the present invention is characterized by containing an inorganic acid in an amount necessary to become pH 2 or less, oxidizing metal ions and a chelating dispersant.
• the acidic cleaning aqueous solution for an aluminum-based metal regarding the present invention is characterized by containing an inorganic acid in an amount necessary to become pH 2 or less, oxidizing metal ions, a surfactant and a chelating dispersant.
• a method for cleaning an aluminum surface which comprises the steps of preparing an acidic cleaning aqueous solution containing at least one selected from inorganic acids in an amount necessary to become pH 2 or less, oxidizing metal ions, a chelating dispersant and a surfactant which may be used in compliance with degreasing requirement, feeding "the oxidizing metal ions and an oxidizing agent” or “the oxidizing agent” to the acidic cleaning aqueous solution, and then measuring an oxidation-reduction potential of the aqueous solution to maintain and control the concentration of the oxidizing metal ions in the aqueous solution.
• the above-mentioned acidic cleaning aqueous solution can be used as a cleaning bath for cleaning a material of the aluminum-based metal, but this cleaning bath can be obtained by diluting a concentrated aqueous solution of the above-mentioned acidic cleaning aqueous solution with a suitable amount of water to a concentration in a usable concentration range.
• examples of the inorganic acid include sulfuric acid and nitric acid will be given.
• the oxidizing metal ions include ferric ions (Fe 3+ ), metavanadic ions (VO 3 - ), cerium(IV) ions (Ce 4+ ), cobalt ions (Co 5+ ) and tin ions (Sn 4+ ). Above all, the ferric ions (Fe 3+ ) and the metavanadic ions (VO 3 - ) are preferable.
• the oxidizing metal ions means metal ions having a higher valence in the case that the metal has a plurality of valences.
• Examples of the feed source of the ferric ions include water-soluble ferric salts such as ferric sulfate, ferric nitrate and ferric perchlorate.
• Examples of the feed source of the metavanadic ions include sodium metavanadate, potassium metavanadate and ammonium metavanadate.
• An example of the feed source of the cerium(IV) ions is ammonium cerium (IV) sulfate.
• Examples of the feed source of the cobalt ions include cobalt(V) sulfate and ammonium cobalt(V) sulfate.
• Examples of the feed source of the tin ions include stannic sulfate and stannic nitrate.
• any compound can be used, so long as it can form a chelate with the oxidizing metal ions, can stabilize the oxidizing metal ions in the aqueous solution under a strong acid, and can improve dispersibility in the aqueous solution under the strong acid.
• a phosphonic acid compound is used.
• the preferably usable phosphonic acid compound include 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid) and ethylenediaminetetra(methylenephosphonic acid).
• the surfactant there can be used conventional surfactants of all kinds of nonionic, cationic, anionic and amphoteric systems. Above all, particularly preferable are nonionic surfactants such as ethoxylated alkylphenols, hydrocarbon derivatives, abietic acid derivatives, ethoxylated primary alcohols and modified polyethoxylated alcohols.
• bromine ion and/or polyhydric alcohol as a decomposition inhibitor for the surfactant.
• Examples of the feed source of the bromide ion include a 47% aqueous HBr solution, potassium bromide, sodium bromide, aluminum bromide and iron bromide.
• the polyhydric alcohol an alcohol having, in one molecule, at least two hydroxyl groups directly bonded to an adjacent carbon atom in a main chain is preferable, and examples of the polyhydric alcohol include divalent alcohols such as 1,2-ethanediol (ethylene glycol), 1,2-propanediol (propylene glycol), 1,2-pentanediol and 1,2-butanediol, trivalent alcohols such as 1,2,3-propanetriol (glycerin) and 1,2,4-butanetriol, and a tetravalent alcohol such as 1,2,3,4-butanetetraol.
• divalent alcohols such as 1,2-ethanediol (ethylene glycol), 1,2-propanediol (propylene glycol), 1,2-pentanediol and 1,2-butanediol
• trivalent alcohols such as 1,2,3-propanetriol (glycerin) and 1,2,4-butanetriol
• the ferric ions change into ferrous ions in accordance with Fe 3+ + e ⁇ Fe 2+ with the lapse of time, so that an oxidation-reduction potential lowers (which is also called the aging of the cleaning bath), with the result that an etching promotion effect on the aluminum surface is lost.
• the aging of the cleaning bath proceeds with time.
• the ferric ions can be fed on occasion, or an ORP control oxidising agent may be added on occasion to oxidize the ferrous ions to the ferric ions.
• examples of the ORP control oxidizing agent include hydrogen peroxide (H 2 O 2 ), persulfates (e.g., NaS 2 O 8 2- ), ozone (O 3 ), cerium compounds [e.g., ammonium cerium (IV) sulfate: (NH 4 ) 4 Ce(SO 4 ) 4 ], nitrites (e.g., NaNO 2 and KNO 2 ) and compounds capable of producing the metavanadic ions (VO 3 - ).
• these oxidizing agents are disclosed in Japanese Patent Publication No. 65436/1991. In this connection, the means an oxidation-reduction potential.
• the acidic cleaning aqueous solution of the present invention is preferably adjusted to pH 2 or less, more preferably pH 0.6 to 2 with an inorganic acid. If the pH is more than 2, the etching velocity on the aluminum surface deteriorates extremely, so that the effectiveness of the cleaning bath is Scarcely exerted. On the other hand, if the pH is less than 0.6, economy is poor, and the amount of the aqueous solution carried to a chemical step of a next step increases, which causes a chemical-conversion failure.
• the oxidizing metal ions are preferably contained in an amount of 0.05 to 4 g/l, more preferably 0.2 to 2 g/l in the acidic cleaning aqueous solution. If the content of the oxidizing metal ions is less than 0.05 g/l, the amount of the etched metal is insufficient, so that the removal of the smut tends to be insufficient. On the other hand, even if it is more than 4 g/l, no additional cleaning effect can be observed, which is uneconomical.
• the chelating dispersant is preferably contained in an amount of 0.05 to 5 g/l, more preferably 0.1 to 2 g/l in the acidic cleaning aqueous solution. If the content of the chelating dispersant is less than 0.05 g/l, the chelating is not sufficient, so that hydroxides of the oxidizing metal are formed, with the result that a precipitate (a sludge) is generated in the aqueous solution. In addition, on a heater portion in the precleaning step, the hydroxides of the oxidizing metal are sometimes accumulated. In the case that the cleaning method of the present invention is carried out by a spray, a spray riser and a spray nozzle are liable to be clogged. Even if it is more than 5 g/l, no additional chelating dispersion effect can be observed, which is uneconomical.
• the surfactant is preferably contained in an amount of 0.1 to 10 g/l, more preferably 0.5 to 2 g/l in the acidic cleaning aqueous solution. If the content of the surfactant is less than 0.1 g/l, cleaning properties, particularly degreasing properties, tend to deteriorate. On the other hand, even if it is more than 10 g/l, no additional cleaning effect can be observed, which is uneconomical.
• the bromide ion is preferably contained in an amount of 0.002 to 0.1 g/l in the acidic cleaning aqueous solution If the content of the bromide ion is less than 0.002 g/l, the inhibition effect of the oxidative decomposition reaction of the surfactant tends to deteriorate, and even if it is more than 0.1 g/l, no additional inhibition effect of the oxidative decomposition reaction of the surfactant can be obtained.
• the polyhydric alcohol having, in one molecule, at least two hydroxyl groups directly bonded to an adjacent carbon atom in a main chain is preferably contained in an amount of 0.1 to 5 g/l, more preferably 0.2 to 3 g/l in the acidic cleaning aqueous solution. If the content of the polyhydric alcohol having the above-mentioned structure is less than 0.1 g/l, the inhibition effect of the decomposition reaction tends to be insufficient. On the other hand, if it is more than 5 g/l, no additional cleaning effect can be obtained, which is uneconomical. In addition, since the concentration of the polyhydric alcohol is high, the load of a waste water treatment increases inconveniently.
• the acidic cleaning bath is preferably controlled to an oxidation-reduction potential (an ORP) of 0.5 to 0.8 V (vs. Ag/AgCl). If the acidic cleaning bath is less than 0.5 V, the oxidizing metal ion is insufficient, so that the amount of an etched aluminum surface is liable to be insufficient. On the other hand, if it is more than 0.8 V, economy is poor.
• the preferable oxidation-reduction potential is in the range of 0.55 to 0.7 (vs. Ag/AgCl).
• the ferrous ions are used as the oxidizing metal ions in the acidic cleaning bath
• the ferrous ions (Fe 2+ ) are accumulated in the acidic cleaning bath, if the ferric ions (Fe 3+ ) alone are fed.
• the acidic cleaning bath becomes a sludge state, and a precipitate derived from the ferrous ions is formed and a treatment operativity deteriorates.
• an article to be treated such as an aluminum can carried from the acidic cleaning bath brings the iron ions to the next step, and in consequence, a precipitate might be generated in the next step and the chemical-conversion treatment might be inversely affected.
• the oxidizing metal ions and the oxidizing agent or “the oxidizing agent” should be fed to the acidic cleaning bath to maintain and control the oxidation-reduction potential (the ORP) in the above-mentioned range, whereby the above-mentioned problems can be solved.
• a treatment temperature is preferably in the range of 35 to 80°C, more preferably 50 to 70°C. If the treatment temperature is more than 80°C, the etching is excessive, so that the aging of the cleaning bath is accelerated. On the other hand, if it is less than 35°C, the amount of the etched aluminum surface is insufficient, so that the removal of the smut tends to be insufficient.
• a acidic cleaning time is preferably in the range of 30 to 300 seconds. If the treatment time is more than 300 seconds, the etching is excessive, so that the aging of the cleaning bath is accelerated. On the other hand, if it is less than 30 seconds, the amount of the etched aluminum surface is insufficient, so that the removal of the smut tends to be insufficient. A more preferable treatment time is in the range of 45 to 120 seconds.
• the aluminum surface which has been cleaned by the acidic cleaning agent of the present invention may be washed with water and then subjected to a phosphate chemical-conversion treatment in a normal manner.
• the chelating dispersant can particularly be used, whereby a chelate can be formed in the acidic aqueous solution with the aid of the oxidizing metal ion and a chelate dispersant, and the dispersibility of the oxidizing metal ion in the acidic aqueous solution can be improved, whereby the generation of a precipitate (a sludge) of hydroxides of the oxidizing metal ion can be prevented.
• a precipitate a sludge
• Containers without a lid which were obtained by subjecting an aluminum plate of a 3004 alloy to a DI process and on which a lubricant and a smut were deposited.
• Acidic cleaning aqueous solutions were used which were constituted of addition amounts described in items of Example and Comparative Examples shown in Table 1 given below.
• the above-mentioned containers were spray-treated at 70 to 75°C for 60 seconds with the respective cleaning agents, next spray-washed with tap water for 15 seconds and successively with deionized water for 5 seconds, and then dried at 95°C.
• a whiteness of each dried container was visually judged.
• each container is shaken three times to drain water, and the container is allowed to stand upright. After 30 seconds, a water wet area (%) on the outside surface of the container is measured.
• a transparent adhesive tape is stuck on the inside surface of the dried container, and this tape is peeled therefrom and then stuck on a white mount. Next, a whiteness of the stuck tape is compared with that of the other white mount portion.
• the dirt-free sample in which the smut has been completely removed is estimated to be good, and the evaluation is ranked on the basis of the following five steps in accordance with the degree of the dirt.
• the cleaning agent used in the evaluation of the cleaning properties is diluted 20 times with water, and then heated (60°C for 1 day) by an electric heater. Afterwards, a stuck sludge state on the electric heater is evaluated on the basis of the following three steps.
• Example 14 in Table 1, two kinds of chelating dispersants were used. Table 2 Result of Evaluation Sludge Preventing Properties (%) Cleaning Properties Appearance Water Wetness(%) Desmutting Properties Example 1 3 ⁇ 80 4 2 3 ⁇ 80 4 3 3 o 100 5 4 3 o 100 5 5 3 o 100 5 6 3 o 100 5 7 3 o 100 5 8 3 ⁇ 100 4 9 3 ⁇ 100 4 10 3 o 100 5 11 3 ⁇ 100 5 12 3 o 100 5 13 3 o 100 5 14 3 o 100 5 15 3 ⁇ 100 4 16 3 o 100 5 Comparative Example 1 1 ⁇ 0 1 2 1 o 100 5 3 2 ⁇ 100 4 4 1 ⁇ 80 3
• Example 3 The same procedure as in Example 3 was repeated except that 0.04 g/l of bromide ion was added to the cleaning agent of Example 3. The results were the same as in Example 3, and all the evaluation items were good.
• Containers without a lid which were obtained by subjecting an aluminum plate of a 3004 alloy to a DI process and on which a lubricant and a smut were deposited.
• the above-mentioned containers were spray-treated at 70°C for 60 seconds with the respective cleaning agents, next spray-washed with tap water for 15 seconds and successively with deionized water for 5 seconds, and then dried at 95°C.
• Oxidizing efficiency (a/b) ⁇ 100 (%) wherein a is an amount of hydrogen peroxide theoretically required in oxidizing the ferrous ions (Fe 2+ ) to ferric ions (Fe 3+ ), and b is an amount of actually required hydrogen peroxide.
• a lubricant and a smut stuck on the aluminum surface can be removed therefrom without using harmful chromium ions and fluoride ions which bring about environmental pollution and pollute an operational environment.
• cleaning can be carried out so that a chemical-conversion treatment and a coating operation can be carried out in order.
• the present invention can be applied to a cleaning aqueous solution and a cleaning method for removing a lubricant and an aluminum powder (a smut) stuck on a metal surface, in manufacturing an aluminum container for a drink made of an aluminum-based metal, i.e., aluminum or an aluminum alloy by a molding operation called drawing and ironing (hereinafter referred to as "DI").
• DI drawing and ironing

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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)
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• 1995
  • 1995-06-12 EP EP95921156A patent/EP0789094A4/fr not_active Withdrawn
  • 1995-06-12 WO PCT/JP1995/001171 patent/WO1996012832A1/fr active IP Right Grant
  • 1995-06-12 KR KR1019970702506A patent/KR100231390B1/ko not_active IP Right Cessation
  • 1995-06-12 CN CN95196828A patent/CN1063236C/zh not_active Expired - Fee Related

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