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
  • C23G1/125—Light metals aluminium

Definitions

• the invention relates to an aqueous acidic cleaner for aluminum containing phosphoric acid.
• cleaners that do not contain fluorine or chromium ions.
• Such cleaners contain, for example, surfactant and a combination of phosphate and sulfate ions and have a pH of at most 2, preferably 0.5 to 1.2 (CA-A-1 207 218).
• Another concept for cleaning aluminum surfaces is to use cleaning agents based on sulfuric acid and / or nitric acid which contain iron (III) ions and optionally surfactant but are free from chromium (III) ions (US Pat. No. 4,728,456 ).
• iron (III) ions form sludge and contaminate the washing system. It is often also unavoidable that the spray nozzles become blocked by the sludge when using the cleaners in the spraying process.
• the object of the invention is to provide an aqueous acidic cleaner for aluminum surfaces which does not have the disadvantages of the above-mentioned cleaners, is insensitive to the contents of active substances in the cleaner with a high cleaning action and has an excellent cleaning action.
• the object is achieved by formulating the cleaner of the type mentioned at the outset in accordance with the invention in such a way that it has a content of 3 to 50 g / l o-phosphoric acid (calculated as PO4) 0.01 to 10 g / l acceptor for aluminum ions 20 to 170 ppm iron (III) ions and 0.02 to 3 g / l H2O2 and / or NO2 having.
• the cleaner defined above contains essentially no chromium, fluoride, chloride and / or chlorine ions, i.e. ions of this type are not intentionally added to the cleaner, but at most get into the form of inevitable impurities.
• the component designated as the acceptor for aluminum in the cleaner can be selected from a group of one or more types of compounds. These include, for example, sulfuric acid, organic acids, boric acid, condensed phosphoric acids, organic phosphonic acids and phosphorous acid.
• a polybasic acid such as oxalic acid, lactic acid, glycolic acid, tartaric acid or the like is particularly recommended as the organic acid Oxicarboxylic acids, as well as citric acid.
• Suitable condensed phosphoric acids are, for example, pyrophosphoric acid (H4P2O7), tripolyphosphoric acid (H5P3O10), tetrapolyphosphoric acid (H6P4O13).
• Suitable organic phosphonic acids are, for example, the connecting groups A to C listed below, the use of a substance from the connecting group A being the most advantageous.
• R OH, COOH or -PO (OH) 2-substituted alkyl or oxyalkyl groups having 1 to 5 carbon atoms.
• a particularly suitable compound from group A is, for example, hydroxylethylidene-1,1-diphosphonic acid of the formula below
• the compounds according to B and C are aminotri (methylenephosphonic acid) of the formula N [- CH2 - (- OH) 2] 3 and ethylenediaminetetra (methylenephosphonic acid) of the formula [(HO) 2- -CH2-] 2 N- (CH2) 2-N [-CH2- - (OH) 2] 2
• One or more of the aforementioned compounds can be added to the cleaner.
• the concentration is 0.01 to 10 g / l. At less than 0.01 g / l, the effect with regard to the absorption of aluminum ions released from the aluminum surface is too low. As a result, aluminum ions can accumulate in the cleaning solution, reducing the caustic effect and the ability to remove stains on the aluminum surface. At concentrations of more than 10 g / l, an increase in the effect is not achieved, so that this concentration has to be regarded as the upper limit.
• the cleaner is formulated in such a way that the acceptor for aluminum ions has a concentration of 0.1 to 3 g / l.
• the iron (III) ions present in the cleaner serve in particular to passivate the surfaces of the Cleaning system. They are added, for example, as iron (III) sulfate or iron (III) nitrate. If the concentration of iron (III) is less than 20 ppm, its effect, the corrosion of the cleaning system and in particular of the transport elements, for example for aluminum cans, is too low. At concentrations above 170 ppm, there is practically no further increase in the corrosion-protecting effect, so that 170 ppm should be selected as the upper limit.
• An advantageous development of the invention provides for the cleaner to be designed with a concentration of iron (III) ions in the range from 50 to 170 ppm.
• the H2O2 or nitrite acting as an oxidizing agent serves, like the iron (III) ion content of the cleaner, to passivate the surfaces of the cleaning system, but also to the iron (II) ions formed by reducing the iron (III) ions oxidize. If the concentration of the oxidizing agent is below 0.02 g / l, its effect is not sufficient, whereas no additional effect can be observed at concentrations above 3 g / l.
• the content of H2O2 and / or NO2 is adjusted to a concentration of 0.1 to 1 g / l.
• Sodium nitrite in particular, should be mentioned as a suitable compound with which the nitrite can be introduced into the cleaner.
• H2O2 should be given preference, since the use of nitrite does not rule out the formation of nitrogen oxides with certainty.
• the concentration of phosphoric acid has to be in the range of 3 to 50 g / l. If the concentration is less than 3 g / l, the cleaning effect is insufficient; if the concentration is increased above 50 g / l, additional cleaning effect not achieved. According to a preferred embodiment of the invention, the phosphoric acid concentration should be in the range from 4 to 15 g / l.
• the pH of the cleaner is in the range from 0.6 to 2.
• the cleaner according to the invention is usually used at temperatures which are between normal temperature and 80 ° C., but preferably at temperatures in the range from 50 to 60 ° C.
• the application is carried out by spraying or immersion. The spraying method is preferred.
• a total of 8 cleaners were used, which had the composition listed in Table 1.
• the information regarding phosphoric acid relates to 100% phosphoric acid, if sulfuric acid has been used as an acceptor for aluminum ions, also to 100% sulfuric acid.
• the information regarding the surfactant relates to the above-mentioned surfactant groups 1 to 3.
• H2O2 was used as the oxidizing agent, which is given as 100% H2O2.
• NaNO2 was used.
• Tanks made of 3004 aluminum sheet, which had previously been deep-drawn and smoothed, and which were contaminated with lubricating oil and stains due to this pretreatment were used as test material.
• the cleaner was applied at 60 to 75 ° C by spraying for a period of 50 seconds. Subsequently, it was sprayed with tap water for 10 seconds and rinsed again with deionized water. This was followed by drying at 180 ° C.
• test materials were checked for appearance, stain removal and wettability, and the system for corrosion. The results are shown in Table 2.

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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)
• Detergent Compositions (AREA)
• Chemical Treatment Of Metals (AREA)

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• 1988
  • 1988-09-07 JP JP63223798A patent/JPH0273983A/ja active Pending
• 1989
  • 1989-08-26 EP EP89115797A patent/EP0361102A1/fr not_active Withdrawn
  • 1989-08-26 DE DE3928323A patent/DE3928323A1/de not_active Withdrawn
  • 1989-09-04 GB GB8919942A patent/GB2223238B/en not_active Expired - Lifetime
  • 1989-09-06 US US07/403,625 patent/US4980076A/en not_active Expired - Fee Related
  • 1989-09-06 CA CA000610432A patent/CA1333991C/fr not_active Expired - Fee Related
  • 1989-09-06 AU AU41072/89A patent/AU618124B2/en not_active Ceased
  • 1989-09-07 GB GB898920272A patent/GB8920272D0/en active Pending

Patent Citations (3)

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