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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/78—Pretreatment of the material to be coated
• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/60—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using alkaline aqueous solutions with pH greater than 8
• • 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
  • C23G1/20—Other heavy metals

Definitions

• the invention relates to a method for preparing metal surfaces made of zinc or zinc alloys for the subsequent application of paint, lacquer and the like. By means of alkaline cleaning and passivation through chemical conversion coatings.
• FR-PS 1 411 272 it has long been known to produce a conversion coating on surfaces of zinc and zinc alloys as well as galvanized steel before the application of paint and the like.
• aqueous solutions to form conversion coatings which contain alkali, in general sodium hydroxide, cations of at least one metal other than alkali ions, preferably iron, cobalt and / or nickel, and at least one complexing agent contain.
• the amount of the complexing agent should be sufficient to keep the aforementioned cations in solution in the alkaline medium from which they would precipitate as metal hydroxide without the complexing agent.
• the most frequently used complexing agents for this are sodium gluconate and sodium glucoheptonate.
• the solutions for producing the chemical conversion coating are usually applied by spraying at a temperature between 40 and 70 ° C. for a period of about 3 to 15 seconds.
• aqueous alkaline Solutions for forming conversion coatings are associated with significant progress in terms of paint adhesion and corrosion resistance after painting, especially for strip and sheet metal.
• Industrial experience has also confirmed that it is interesting to subject the metal surface to a subsequent treatment with an aqueous, acidic solution in accordance with FR-PS 1 487 183 after the formation of a conversion coating in an alkaline medium and water rinsing.
• Such solutions contain 0.001 to 0.25% by weight of chromium (III), 0.01 to 0.06% by weight of fluoride and 0.02 to 0.1% by weight of zinc. They are used in spraying or dipping for 2 to 10 seconds at a temperature between 40 and 70 ° C. The surfaces are then dried immediately so that they can then be painted or painted.
• FR-PS 1 496 683 It is known from FR-PS 1 496 683 that an essential condition placed on the stage of alkaline degreasing is not to inhibit the formation of the conversion coating and therefore to work with silicate-free cleaning solutions. With regard to the requirements of the industry in the sense of a constant improvement in the quality of the products, however, even with a method of working in accordance with FR-PS 1 496 683, paint adhesion and corrosion protection are achieved, which are suitable for certain types of metal surfaces and in particular for hot-dip galvanized steel Acceptable limit.
• the object of the present invention is to provide a method which avoids the disadvantages of the known, in particular the aforementioned methods, and which is associated with an improvement in the adhesion of paint, paint and the like and the corrosion resistance.
• the type and amount of the alkaline-reacting cleaning agent are preferably chosen such that the pH of the solution is 11.5 to 12.5.
• the alkaline cleaning agents can be hydroxides, phosphates, carbonates and borates of alkali metals with the exception of silicate. These components are usually used in a concentration of 3 to 150 g / l, preferably 7 to 9 g / 1.
• the surfactants can in principle be anion-active, non-ionic, cation-active or amphoteric. They must be compatible in the alkaline medium and under the conditions of use of the solution. Your choice essentially depends on the pH of the cleaning and degreasing agent, the application conditions, i.e. Dip or spray application, and economic considerations. Non-ionic surfactants are preferred for solutions used in the spraying process. Their concentration should be between 0.1 and 5 g / 1, preferably about 1 g / 1. Such surfactants can be used alone or in a mixture.
• the metal ions other than alkali ions can be selected from those mentioned in French Pat. No. 1,411,272. These are in particular aluminum, antimony, Silver, cadmium, cerium, chrome, cobalt, tin, iron (II or III-valued), magnesium, manganese, molybdenum, nickel, titanium and tungsten. Cobalt, iron and nickel ions are preferred, especially nickel.
• the anion assigned to the cation for introduction should be compatible with the solution and should not have any adverse effect. For this reason, nitrate is preferably used to introduce the metal ions other than alkali ions.
• the concentration of the metal cations other than alkali ions in the solution depends on the concentration of the alkaline cleaning agent. The higher it is, the higher the concentration of cations should be.
• the concentration of cations other than alkali ions can be between 50 and 5000 mg / l, preferably between 100 and 1000 mg / l. With a concentration of the alkaline detergent of approx. 10 g / 1 and a pH of the order of 12, the preferred range of metal cations is 500 to 700 mg / 1.
• the improvement can practically not be greater than that which is usually obtained with the preferred concentration of 500 to 700 mg / l. Due to the high pH, the conditions of use and the high content of cations other than alkali ions, the solution is not entirely sludge-free, which is not harmful, however, if the amount of sludge is small, i.e. is in the order of 2 to 3% by volume, based on the entire solution.
• the complexing agents used in the cleaning and degreasing solution can be the same as those described in FR-PS 1 411 272.
• it can be condensed phosphates, dicarboxylic acids, hydroxycarboxylic acids, Act benzol carboxylic acids, hydroxy aldehydes and amines.
• the best results in terms of degreasing the metal surface and complexing the metal ions can be achieved with sodium gluconate, sodium glucoheptonate, sorbitol and sodium ethylenediaminotetraacetate.
• the concentration of complexing agent should be sufficient to stabilize the metals other than alkali ions, taking into account their concentration and the pH of the solution in the solution.
• the concentration can range between 0.1 and 30 g / l. It is preferably 0.5 to 1 g / l.
• the aqueous alkaline solution for cleaning and degreasing the metal surface can be obtained by adding a solid concentrate which contains the alkaline-reacting cleaning agent or agents, the surfactant (s), the metal ions other than alkali ions and the coplexing agent or agents.
• the solution can also be obtained if solid or liquid concentrates are used, one of which contains the alkaline detergent (s), the total amount or only part of the necessary surfactant (s) and the total amount or only part of the necessary complexing agent contains and the other of which contains the metal cations other than alkali ions, the total amount or only part of the necessary surfactant (s) and the total amount or only part of the necessary complexing agent.
• solid or liquid concentrates one of which contains the alkaline detergent (s), the total amount or only part of the necessary surfactant (s) and the total amount or only part of the necessary complexing agent contains and the other of which contains the metal cations other than alkali ions, the total amount or only part of the necessary surfactant (s) and the total amount or only part of the necessary complexing agent.
• the cleaning and degreasing solutions described above can be sprayed or dipped at a temperature in the range from 20 to 90 ° C., preferably from 45 to 65 °, for a period of from about 3 to 180 seconds, preferably from 10 to 30 seconds. be applied.
• the metal surface is then brought into contact with a solution which contains alkali, cations of at least one metal other than alkali ions and at least one complexing agent.
• a solution which contains alkali, cations of at least one metal other than alkali ions and at least one complexing agent can be, for example, a solution as described in FR-PS 1 411 272.
• the passivation solution can contain, for example, chromium III and / or chromium IV and have the nature described in French Pat. No. 1,487,183.
• a conversion coating can be created by applying a dispersion of chromic acid and / or chromium compound with colloidal silicon dioxide.
• the passivation solution applied for the passivation treatment is preferably dried.
• the metal surface treated in this way is then provided with paint, lacquer and the like.
• the method according to the invention is suitable for the surface treatment of objects which consist of zinc or zinc alloys or a coating of zinc or zinc alloys, e.g. galvanized steel. It is particularly suitable for the treatment of sheet metal or strip.
• Hot-dip galvanized steel sheets were used to carry out the tests.
• the sheets were coated with a coating of alkyd resin or acrylate resin with a thickness of approx. 30 microns. After drying, the sheets rested for 48 hours.
• Hot-dip galvanized steel sheets were treated according to the procedure in Example 1, but solutions of the following nature were used for cleaning and degreasing:
• the varnishes applied by the roller application process were of the following type: polyvinyl chloride, polyester, silicone-modified polyester, polyvinylidene and polyacrylate.

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

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Citations (6)

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• 1984
  • 1984-03-07 FR FR8403560A patent/FR2560894B1/fr not_active Expired
• 1985
  • 1985-03-02 DE DE19853507372 patent/DE3507372A1/de not_active Withdrawn
  • 1985-03-05 DE DE8585200318T patent/DE3571148D1/de not_active Expired
  • 1985-03-05 EP EP19850200318 patent/EP0154384B1/fr not_active Expired

Patent Citations (6)

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