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
  • C23C22/05—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
  • 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
• • 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
  • C23C22/82—After-treatment
  • C23C22/83—Chemical after-treatment

Definitions

• the object of the invention is to provide a method by means of which the corrosion resistance and the adhesion of a lacquer applied in a later phase to steel sheets which are provided with a zinc / aluminum alloy can be improved without thereby having to accept a complex method to have to.
• the object is achieved by the method of the type mentioned in the introduction according to the invention is designed in such a way that the metal surface in process step b) is brought into contact with a solution which additionally contains silica.
• the metal ions contained in the alkaline solution according to stage a) are usually used as inorganic salts, for example nitrates, sulfates, carbonates, chlorides and the like. the like. However, other compounds are also suitable as long as they are soluble in the alkaline medium.
• the concentration of the metal ions is generally 0.01 to 10 g / l, preferably 0.05 to 5 g / 1. These metal ions must be bound by a sufficient amount of complexing agent to ensure that they are and remain in the dissolved state. The amount of complexing agent is therefore about 0.1 to 20 g / l.
• the complexing agents can be inorganic or organic in nature.
• Suitable inorganic complexing agents are, for example, condensed phosphates, ammonia or amine compounds.
• Suitable organic complexing agents are, for example, dicarboxylic acids, in particular malonic acid, fumaric acid, amino acids, such as glycine, hydroxycarboxylic acids, such as citric acid, gluconic acid and lactic acid, polyhydroxyaliphatic compounds, such as sorbitol or 1,2-ethanediol, phenylcarboxylic acids, such as salicylic acid and phthalic acid, aminocarboxylic acids, such as ethylenedic acid, Polyamino acids such as diethanolamine methane phosphonate, lignin sulfonate and the like.
• Particularly preferred complexing agents are hexahydroxyheptanoic acid, sodium gluconate and sodium ethylenediaminetetraacetate.
• the treatment solution according to stage a) is applied at a temperature between room temperature and the boiling point of the solution in spraying or dipping for a time sufficient to selectively dissolve aluminum out of the alloy layer.
• Treatment at a temperature of 50 to 80 ° C. for a period of 4 to 10 seconds with a continuously operating belt system is particularly expedient. If necessary, shorter treatment times can also be used, in which case solutions of higher concentration and higher temperature should be used.
• the treatment solution according to process stage b) is obtained in the simplest way by dissolving chromic acid and incorporating colloidal silica.
• the layer formed with this solution should - after Drying on - have a layer weight of 10 to 400 mg / m 2 .
• the purpose pursued by the invention is only incompletely achieved, with higher layer weights there is a risk that the paint adhesion will decrease.
• Preferred refinements of the invention envisage using a treatment solution in process stage b) which additionally contains chromium III ions and / or phosphate ions.
• the chromium III ion content is created in the simplest manner by adding a reducing agent, such as starch, oxalic acid, tannin or alcohol, to the aqueous solution of chromate in certain amounts.
• the metal surfaces in process step b) into contact with a solution in which the weight ratio of SiO 2 : chromium VI is in the range from 0.6 to 15.
• the weight ratio chromium III: chromium VI should be 0.2 to 1. If the solution contains phosphate, it is recommended to set the weight ratio of P0 4 : Chrom-VI to a value in the range of 0.6 to 3.
• the method according to the invention is intended for the treatment of steel sheets provided with zinc / aluminum alloys, in which the aluminum content in the alloy layer is generally 1 to 70% by weight.
• the adhesion to organic coatings mediated by the layer formed is particularly high if an epoxy lacquer is applied in step d).
• at least the base lacquer should be an epoxy lacquer.
• Steel sheets of the nature mentioned in the test example were at 57 to 63 ° C. for 10 seconds with an alkaline solution containing 0.17 g / l Fe (III) and 0.24 g / 1 Ni ions (each introduced as nitrate) as well as 1.7 g / 1 sodium hexahydroxy heptonate and 22 g / l sodium hydroxide and had a pH of 13.6, treated by spraying, rinsed with water and with an aqueous solution containing provided by roll order. It was then dried. The layer weight was 190 mg / m 2 .
• the solution for producing the chromate coating used in comparative experiment la of table 2 had the same nature as the aforementioned solution.
• test sheets which were again the same, were pretreated with an alkaline solution at 55 to 60 ° C. and for 6 seconds in spraying, the 0.17 g / 1 Fe (III) -, 0.24 g / 1 Co ions (in each case as nitrate introduced), 1.7 g / 1 Contained sodium hexahydroxy heptonate and 22 g / 1 sodium hydroxide.
• the pH of the solution was 13.6. Then it was rinsed with water and a solution was applied by roller application contained and had a pH of 1.5. After drying, the layer weight was 280 mg / m2.
• the chromium-containing solution used in Table 2 in Comparative Example 2 had the same nature as the last-mentioned solution.
• the sheets treated as in Examples 1 and 2 above were subjected to two different coatings.
• it was a two-layer coating system with a Epoxy as a base paint was applied with a layer thickness of 5 / um and then baked at 190 ° C.
• a polyester paint which was applied with a layer thickness of 13 / um and baked at 200 ° C was used.
• the other painting consisted of a single-layer paint structure, for which a polyester top coat had been used. There were carried out the deposition with a layer thickness of 14 / um, and the baking at 210 ° C.
• a device from Du Pont was used to carry out the impact test. It works with a beater bar with a diameter of 12.7 mm, which is loaded with 1 kg and hits the painted sheet metal surface from a height of 50 cm. The paint adhesion is again determined using adhesive tape, as stated above.
• the evaluation is as follows.
• a cut was made with a knife to determine corrosion resistance and paint infiltration down to the metal surface.
• Such scored sheets and sheets deformed in accordance with the bending test were subjected to the salt spray test, which works with a 5% saline solution, for 500 hours (with a single-layer paint structure) or for 1000 hours (with a two-layer paint structure) in accordance with JIS-Z-2371. The evaluation takes place at the interfaces, on the edges and at the bending point.
• the treated sheets were exposed to the weather for a period of 3 years.
• the evaluation was carried out according to the following standards:

Landscapes

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

Applications Claiming Priority (2)

Publications (3)

Family

ID=15662426

Family Applications (1)

Country Status (6)

Cited By (3)

Families Citing this family (7)

Family Cites Families (10)

• 1985
  • 1985-07-19 JP JP15801685A patent/JPS6220880A/ja active Granted
• 1986
  • 1986-07-11 AU AU60084/86A patent/AU6008486A/en not_active Abandoned
  • 1986-07-15 GB GB8617211A patent/GB2178065B/en not_active Expired
  • 1986-07-17 DE DE19863624101 patent/DE3624101A1/de not_active Withdrawn
  • 1986-07-17 DE DE8686109842T patent/DE3679866D1/de not_active Expired - Lifetime
  • 1986-07-17 EP EP19860109842 patent/EP0209143B1/fr not_active Expired - Lifetime
  • 1986-07-18 BR BR8603404A patent/BR8603404A/pt unknown

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