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
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
  • C23G1/22—Light metals

Definitions

• An aqueous cleaning solution for cleaning aluminum surfaces comprising from 0.5% to 15% by weight of caustic alkali, from 0.005 to 0.2% by weight of an alkalisoluble salt of a polycarboxylic acid having more than 10 carboxyl groups in the molecule, and from 0.003% to 0.1% by weight of alkaline earth metal ions; as well as the process of cleaning aluminum surfaces which comprises treating' the surfaces with the said aqueous cleaning solution at a temperature of from 50 C. to 85 C., rinsing and drying the cleaned surfaces.
• Aluminum surfaces are usually cleaned before painting, since the residues left after machining, such as grinding and polishing pastes, drawing assistants and other contaminations, must be removed.
• strongly alkaline solutions are used which, in addition to caustic alkalis and alkali metal carbonates, also contain phosphates, silicates, borates, gluconates' and possibly surface-active substances.
• An objectof the present invention is the obtaining of anaqueous cleaning solution for cleaning aluminum surfaces comprising from 0.5 to by weight of caustic alkali,-from 0.005 to 0.2% by weight of analkali-soluble salt of a polycarboxylic acid having more than 10 carboxyl groups in the molecule, and from 0.003% to 0.1% by weight of alkaline earth metal ions.
• Another object of the invention is the development of a process for cleaning aluminum surfaces, particularly prior to their being painted, which comprises the steps DESCRIPTION OF THE INVENTION
• the drawbacks of the prior art have been overcome and the above objects have been achieved by the discovery of an aqueous solution for cleaning aluminum surfaces before painting which comprises from 0.5% to 15 by weight of caustic alkali, from 0.005% to 0.2% by weight of an alkali-soluble salt of a polycarboxylic acid having more than 10 carboxyl groups in the molecule, and from 0.003% to 0.1% by weight of alkaline earth metal ions.
• the present invention provides a process for cleaning aluminum surfaces before painting which comprises treating the aluminum surfaces with an aqueous solution comprising from 0.5% to 15 by weight of caustic alkali, from 0.005% to 0.2% by weight of an alkali-soluble salt of a polycarboxylic acid having more than 10 carboxyl groups in the molecule, and from 0.003% to 0.1% by weight of alkaline earth metal ions, at a temperature of from 50 to 85 C., subsequently rinsing and'drying said cleaned surfaces.
• caustic alkalis employed are usually caustic soda or caustic potash solutions. These caustic alkali solutions may be solutions of alkali metal hydroxides such as sodium and potassium hydroxide or commercial caustic alkali solutions containing small amounts of the carbonates.
• Suitable alkali-soluble salts of polycarboxylic acids with more than 10 carboxyl groups in the molecule are, especially, salts such as the alkali metal salts of polyacrylic or polymethacrylic acid, hereinafter called polyacrylates or polymethacrylates. It has been found that relatively low molecular weight polyacrylates with a molecular weight from about 3000 also possess a good action. Such acrylates have about 30 carboxyl groups in the molecule. This is further improved, however, if polyacrylates or polymethacrylates with molecular weights up to 100,000 are used. Provided the salts are soluble in alkali solutions, however, products with a molecular weight up to 200,000 can be used.
• alkali-soluble salts of cooftreating aluminum surfaces with an aqueous solution polymers containing more than 10 carboxyl groups which can be used are those such as for example, the copolymers of ethylene and maleic acid, ethylene and acrylic or metha'crylic acid.
• polyaminopolycarboxylic acids such as poly-lower-alkyleneimine-N-carboxylic acids, for example, polyethyleneimine-N-acetic acid and polyethyleneimine-N succinic acid, are suitable.
• the corresponding acids may also be used, since the corresponding salts are formed in the alkaline solutions.
• the solutions must also contain alkaline earth metal ions, which may be added in the form of their alkali-solu ble salts.
• Suitable alkaline earth metal ions are, especially, barium, strontium'and preferably calcium.
• the addition of the alkaline earth metal ions is suitably synchronized with the amount of alkali-soluble salts of polycarboxylic acids used. That is, if relatively large amounts of the latter are used, it is expedient if a relatively large amount of alkaline earth metal ions is also present in the solutions. If, on the other hand, small amounts of polycarboxylic acid salts are used, only small amounts of alkaline earth metal ions are also needed.
• the salts of the alkalisoluble polycarboxylic acids are used in amounts from 0.005 to 0.2% by weight, while the addition of alkaline earth metal ions lies in a range from 0.003% to 0.1% by weight, preferably from 0.01% to 0.1% by weight.
• hydroxyor aminophosphonic acids with at least 2 phosphorus atoms in the molecule or their soluble salts has a favorable effect on the subsequent adhesion of the paint.
• Suitable hydroxyphosphonic acids with a least 2 phosphorus atoms in the molecule are, for example, alkali-soluble l-hydroxyalkane-1,1-diphosphonic acids such as l-hydroxyethane- 1,1-diphosphonic acid, l-hydroxypropane 1,1 diphosphonic acid, l-hydroxybutane-l,l-diphosphonic acid, or 1- hydroxyhexane-l,l-diphosphonic acids.
• Suitable aminophosphonic acids with at least 2 phosphorus atoms in the molecule are l-aminoalkanel,l-diphosphonic acids, preferably l-aminoethane-l,l-diphosphonic acid, or l-aminoaryl-1,l-diphosphonic acids, preferably a-aminobenzyl-a, a-diphosphonic acid.
• aminomethylenephosphonic acids such as aminotrimethylenephosphonic acid, ethylene diaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid or polyethyleneimino-N-methylenephosphonic acid.
• acids their soluble salts, especially the potassium and sodium salts, may also be used.
• the phosphonic acids having at least 2 phosphorus atoms in the molecule or their salts are added to the cleaning solutions in a concentration of from 0.005% to 0.2%
• sorbitol or mannitol for example, sorbitol or mannitol, and /or polyhydroxycarboxylic acids with at least two adjacent OH groups in the molecule has a favorable effect.
• Gluconic acid or heptagluconic acid is preferably used.
• polyhydroxycarboxylic acids their alkali soluble salts or their boric acid complexes such as borogluconate and boroheptonate may also be used.
• Treatment solutions which contain 0.05% to 10% by weight of caustic alkali, 0.01% to 0.2% by weight of alkali-soluble polyacrylates or polymethacrylates, 0.01% to 0.2% by weight of hydroxyethane-1,1-diphosphonic acids and/or aminotrimethylenephosphonic acids or their salts, 0.01% to 0.2% by weight of gluconic acids and/or heptagluconic acid or their salts or the corresponding boric acid complexes, and 0.01 to 0.1% by weight of calcium ions have proved specially favorable in regard to subsequent paint adhesion, little attack on the aluminum surfaces, good cleaning action and prevention of hardening of the coatings.
• the treatment solutions maystill contain the usual constituents of cleaning agents, especially alkali metal compounds such as ortho and polymeric-phosphates, carbonates, borates, silicates, and, if desired, surfaceactive compounds.
• alkali metal compounds such as ortho and polymeric-phosphates, carbonates, borates, silicates, and, if desired, surfaceactive compounds.
• the treatment solutions may be used in dipping processes, flooding processes and spray processes.
• the most favorable treatment temperature lies between 50 and 85 C. At lower temperatures the cleaning efifect is generally not suflicient to attain the desired effect in technically convenient times. At higher temperatures, error easily occur through drying of the surface before the rinsing step.
• the strongly alkaline cleaning solutions used may be produced either directly from the components or by dissolving the corresponding compounded solid or liquid cleaning agents.
• the aluminum surfaces are rinsed with water and then dried in a known way.
• the last rinsing is suitably carried out wtih water containing very little salt or completely demineralized.
• the aluminum surfaces are satisfactorily cleaned of all adhering contaminations by the process of the invention, and the adhesion of paint is substantially better in the method according to the invention than when the treatment has been only with the previously known aluminum cleaning agents.
• the process has proved specially advantageous in the cleaning of aluminum spray cans and satisfactory adherence of the paint is guaranteed in such cases even on later deforming of the tube blanks.
• a further advantage of the method of the invention is the very small removal of surface material caused by the treatment solutions in spite of their high alkalinity. It is frequently less than 10% and in the most favorable case is less than 5% of the corrosion caused when corresponding aluminum cleaning and pickling solutions are used without the additives according to the invention.
• Surfaces of pure alumi-. num and aluminum wrought alloys may be treated with the cleaning solutions according to the invention.
• troublesome incrustation may occur in spite of the little attack on the material which make good adhesion of paint impossible. 1
• the adhering tenacity of the coating was examined by a modified grid sectioning test according to DIN 53,151, whereby, instead of the grid sectioning, 'a scoring of exactly 5.5 mm. was carried out with the Erichsen apparatus (DIN 53,156) and after a quick tearing off of an adhesive strip pasted on the section, the pieces of paint remaining on the surface of the metal are estimated.
• the quality of the painting was denoted by the grid sectioning characteristic values (DIN 53,151) Gt 0-4:
• Gt 3 about 35% of the-pieces
• Gt 4 more than.65% of the pieces peeled off.
• the cleaning was effected with difierently constituted cleaning solutions and at dilferent temperatures and times of treatment, which are given below in each case.
• the respective additions to the basic cleaning solutions are given under a-h for 1) and ad for 2) and the grid 5 section characteristic values are given under Gt.
• a process for cleaning aluminum surfaces, particularly prior to their being painted which consists essentially of the steps of treating aluminum surfaces with an aqueous solution consisting essentially of from 0.5% to 15% by weight of caustic alkali, from 0.005% to 0.2% by weight of a caustic alkali-soluble salt of a polycarboxylic acid having more than 10 carboxyl groups in the molecule selected from the group consisting of polyacrylates, polymethacrylates and mixtures thereof, having a molecular weight of from 3,000 to 200,000, polyethyleneimine-N-acetic acid and polyethyleneimine-N-succinic acid, and from 0.003% to 0.1% by weight of alkaline 7 earth metal ions selected from the group consisting of barium, calcium and strontium, in the form of their caustic alkali-soluble salts, at a temperature of from 50 C. to 85 C., subsequently rinsing the cleaned aluminum surfaces and recovering said cleaned aluminum surfaces.
• an aqueous solution consisting essentially of from 0.5% to
• aqueous solution has a further content of from 0.005% to 0.2% by weight of a caustic alkali-soluble salt of a phosphonic acid having at least 2 phosphonic acid groups in the molecule selected from the group consisting of hydroxyphosphonic acids, aminophosphonic acids and aminomethyl enephosphonic acids.
• caustic alkali is selected from the group consisting of caustic soda and caustic potash.
• alkali-soluble salt of a polycarboxylic acid is selected from the group consisting of polyacrylates, polymethacrylates and mixtures thereof, having a molecular weight of from 3,000 to 200,000.
• aqueous solution has a further content of from 0.005 to 0.3% by weight of a caustic alkali-soluble hexanehexols, gluconates, heptogluconates, boric acid complexes of said gluconates and heptogluconates, and mixtures thereof.
• aqueous solution has a further content of from 0.005% to 0.3% by weight of a caustic alkali-soluble hexanehexols, gluconates, heptogluconates, boric acid complexes of said gluconates and heptogluconates, and mixtures thereof.
• a process for cleaning aluminum surfaces, particularly prior to their being painted which consists essentially of the steps of treating aluminum surfaces with an aqueous cleaning solution for cleaning aluminum surfaces consisting essentially of from 0.5% to 10% by weight of caustic alkali, from 0.01% to 0.2% by weight of a caustic alkali-soluble salt of a polycarboxylic acid having a molecular weight of from 3,000 to 200,000 selected from the group consisting of polyacrylates and polymethacrylates, from 0.01% to 0.2% by weight of a phosphonic acid selected from the group consisting of 1- hydroxyethane-1,1-diphosphonic acid, aminotrimethylenephosphonic acid, and caustic alkali-soluble salts thereof, from 0.01% to 0.2% by weight of a compound selected from the group consisting of gluconic acid, boric acid complexes with gluconic acid, heptagluconic acid, boric acid complexes with heptagluconic acid and caustic alkalisoluble salts thereof, and from

Landscapes

• 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)
• Detergent Compositions (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=3605990

Family Applications (1)

Country Status (12)

Cited By (17)

Families Citing this family (9)

• 1968
  • 1968-09-02 AT AT849868A patent/AT292408B/de not_active IP Right Cessation
• 1969
  • 1969-07-23 US US844184A patent/US3687858A/en not_active Expired - Lifetime
  • 1969-07-25 DE DE1937841A patent/DE1937841C3/de not_active Expired
  • 1969-07-30 SE SE10697/69*A patent/SE350987B/xx unknown
  • 1969-07-30 NL NL6911636.A patent/NL167206C/xx not_active IP Right Cessation
  • 1969-08-29 BE BE738235D patent/BE738235A/xx unknown
  • 1969-08-29 GB GB1226314D patent/GB1226314A/en not_active Expired
  • 1969-09-01 ES ES371103A patent/ES371103A1/es not_active Expired
  • 1969-09-01 CH CH1322369A patent/CH527279A/de not_active IP Right Cessation
  • 1969-09-02 FR FR6929916A patent/FR2017213A1/fr not_active Withdrawn
  • 1969-09-02 TR TR16674A patent/TR16674A/xx unknown
  • 1969-09-02 JP JP44069637A patent/JPS4820012B1/ja active Pending

Also Published As

Similar Documents