Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
• • 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
  • C23C22/06—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 aqueous acidic solutions with pH less than 6
  • C23C22/24—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 aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds
  • C23C22/26—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 aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds containing also organic compounds
  • C23C22/28—Macromolecular 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
  • 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
  • C23C22/73—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 characterised by the process
  • C23C22/74—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 characterised by the process for obtaining burned-in conversion coatings

Definitions

• the present invention relates to a process for the production of corrosion-protective coatings on surfaces of metals other than aluminum by drying and heating a water-based coating agent which contains chromium VI and water-soluble or water-dispersible layer-forming organic polymer, and its application to the treatment of galvanized steel surfaces.
• wash primer the main components of which are polyvinyl butyral, hexavalent chromium and phosphoric acid
• the wash primer is flammable because it uses solvents such as e.g. Contains alcohols, and therefore tries to address fire hazard problems.
• solvents such as e.g. Contains alcohols, and therefore tries to address fire hazard problems.
• water-based coating agents have been developed which do not have this disadvantage.
• Japanese Patent Application No. Sho 57-45834 (1982) describes a method in which a treatment solution of water-soluble dichromate or chromic acid and water-soluble resin is applied to the steel sheet and then dried at 40 to 80 ° C. This process focuses on the solubilization of epoxy resin to produce a stable treatment solution.
• Japanese Patent Application Laid-Open No. Sho 60-228682 describes an aqueous solution of chromic acid, water-soluble acrylic resin and complex fluoride salt for the treatment of galvanized steel sheet.
• complex fluoride e.g. Sodium hexafluoroaluminate
• the layer formed should be improved both in terms of corrosion resistance and film adhesion.
• hexavalent chromium content decreases to some extent as a result of reaction with the resin, they suffer from the considerable disadvantage that a large part of hexavalent chromium is not reduced.
• hexavalent chromium can subsequently be removed from the layer, so that the usability of the correspondingly coated sheet is limited.
• the object of the invention is to provide a process for producing corrosion-protective coatings on surfaces of metals other than aluminum, which does not have the aforementioned disadvantage and leads to coatings from which practically no hexavalent chromium can be removed even in the case of long-term contact with aqueous solutions.
• the layer-forming organic polymer to be used in the present invention must be water-soluble or water-dispersible and must be capable of being cured by heating / drying. Suitable examples of such polymers are described in JP-B-58-47230 (1983) (CA 87, No. 2,7657z). Polymers based on acrylic acid or acrylate or of methacrylic acid or methacrylate or copolymers thereof are of particular importance.
• the hexavalent chromium can e.g. be introduced as anhydrous chromic acid or ammonium bichromate.
• anhydrous chromic acid or ammonium bichromate e.g. be introduced as anhydrous chromic acid or ammonium bichromate.
• the addition of smaller amounts of trivalent chromium can be advantageous.
• a preferred development of the invention consists in drying and heating a coating agent that contains the water-soluble organic compound in an amount of 0.1 to 20 g / l, preferably 0.5 to 10 g / l.
• the molar ratio of organic compound to hexavalent chromium is approximately 0.1 to 3, preferably 0.33 to 1.5.
• Another expedient embodiment of the invention provides for the coating agent applied to the metal surface to be heated at a temperature in the range from 100 to 300 °.
• the mode of action of the water-soluble organic compound to be added is not clear. This compound is presumably reduced by the hexavalent chromium in the coating agent layer to trivalent chromium, the solubility of which is lower than that of hexavalent chromium.
• the trivalent chromium in turn reacts with the oxidation product of the added water-soluble compound or the water-soluble or water-dispersible organic polymer and forms a complex compound which practically no longer releases chromium.
• Due to the weak reduction effect at room temperature the formulated coating agent can be stored stably at room temperature. The full The effect of the reduction of the hexavalent chromium only occurs during the heating / drying of the coated metal surface.
• the stability of the coating agent at room temperature can be further improved if the pH value is kept at a slightly higher value by using ammonium bichromate.
• the method according to the invention is suitable for treating a large number of metal surfaces, with the exception of surfaces made of aluminum, such as iron, steel or zinc.
• the method can be used with particular advantage for the production of corrosion-protective coatings on galvanized steel.
• Electrolytically galvanized steel sheet was degreased with an aqueous solution containing sodium phosphate and sodium silicate as the main components. After rinsing the water with an aqueous coating agent, coated that 30 g / l water-soluble acrylate resin (calc. as dry substance), 3.2 g / l Cr6+ and 1.0 g / r Cr3 be harshet contained. After drying for one minute at 180 ° C., the sheet was coated with a coating of 0.2 g / m2.
• Aqueous coating compositions of the composition as in Comparative Example 1 were added with 1.5 g / l ethylene glycol or 3 g / l diethylene glycol or 2 g / l propylene glycol.
• the test panels were treated in the same manner as in the comparative example.
• test specimens of 1 cm2 were cut out, which were immersed in 100 ml of demineralized water at 30 ° C. for seven days. The test specimens were then rinsed with demineralized water. Solution and rinse water were combined and concentrated to 50 ml. The chromium concentration was measured on the principle of atomic absorption spectrometry.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Metallurgy (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Wood Science & Technology (AREA)
• Chemical Treatment Of Metals (AREA)
• Paints Or Removers (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=18069913

Family Applications (1)

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Cited By (3)

Citations (4)

Family Cites Families (5)

• 1986
  • 1986-12-29 JP JP31581786A patent/JPS63168474A/ja active Pending
• 1987
  • 1987-12-24 EP EP87119190A patent/EP0273408A3/fr not_active Withdrawn
  • 1987-12-24 DE DE19873744033 patent/DE3744033A1/de not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (1)

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