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
  • C23C22/06—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
  • C23C22/07—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 phosphates
  • C23C22/08—Orthophosphates
  • C23C22/10—Orthophosphates containing oxidants

Definitions

• the invention relates to a method for producing phosphate coatings on metal surfaces made of iron or steel by means of aqueous phosphating solutions containing accelerators based on magnesium phosphate.
• the process of producing phosphate coatings by means of aqueous phosphating solutions is widely used in the metalworking industry.
• the phosphate layers created with this process on the treated metal surfaces are used in particular for corrosion protection and as a lacquer primer as well as to facilitate non-cutting cold forming and sliding.
• Such phosphating processes work, for example, with phosphating solutions which have a pH between about 1.8 and 3.8 and contain zinc and phosphate ions as process-determining components.
• other cations e.g. B. ammonium, calcium, cobalt, iron, potassium, copper, sodium, magnesium and manganese may be present.
• the phosphating baths are generally oxidizing agents, e.g. B. bromate, chlorate, nitrate, nitrite, organic nitro compounds, perborate, persulfate, hydrogen peroxide are added. Oxygen-containing gas can also be used for the oxidation of iron (II) to iron (III).
• phosphating process is the so-called iron phosphating or "non-layer-forming phosphating". She usually works with phosphating solutions based on alkali phosphate, but occasionally also with levels of magnesium, calcium and barium phosphate. Such methods are comparatively simple to implement and associated with low costs. They lead to phosphate coatings of sufficient quality for many cases, especially if the objects provided with them are not exposed to high corrosive influences.
• the phosphating solutions are brought into contact with the workpiece surfaces to be treated in immersion, flooding or spraying.
• the contact time which can range from a few seconds up to approx. 15 minutes, firmly grown phosphate layers form through chemical reaction with the metal. Since residues of the phosphating solution remaining on the surface usually interfere with further processing, the water is thoroughly rinsed after the phosphating.
• non-layer-forming phosphating In a process of the so-called "non-layer-forming phosphating" it is known to apply a phosphate coating to improve the resistance of metal surfaces to corrosive attacks by treatment with solutions which predominantly contain phosphoric acid and / or a non-layer-forming phosphate (GB-PS 517 049). Alkali, ammonium and magnesium phosphate are mentioned as non-layer-forming phosphates. They are said to be advantageous because they are available cheaply and form little sludge compared to zinc, manganese, cadmium or iron phosphate.
• the solutions can also contain small amounts of nitrite, nitrate or sulfite and at most small amounts of layer-forming phosphates.
• the object of the invention is to provide a method for non-layer-forming phosphating which does not have the known, in particular the aforementioned disadvantages, and yet is inexpensive and simple to carry out and monitor.
• the object is achieved in that the method of the type mentioned according to the invention is designed in such a way that the metal surfaces are brought into contact with phosphating solutions containing 0.2 to 4 g / l of magnesium, 1 to 20 g / l of phosphate (calc as P2O5) and as an accelerator contain peroxide compound and are free of such inorganic substances that cannot be precipitated with calcium hydroxide in the neutral or alkaline range.
• phosphating solutions containing 0.2 to 4 g / l of magnesium, 1 to 20 g / l of phosphate (calc as P2O5) and as an accelerator contain peroxide compound and are free of such inorganic substances that cannot be precipitated with calcium hydroxide in the neutral or alkaline range.
• the formulation "based on magnesium phosphate" used above is intended to express that magnesium phosphate or the cation magnesium represents the predominant proportion of the phosphate component or cations present in the phosphating solution.
• Particularly suitable accelerators used in the process according to the invention are H2O2, perphosphate and percarbonate.
• the metal surfaces are brought into contact with phosphating solutions which contain H2O2 as accelerators. It is appropriate to choose the concentration such that the phosphating solution contains H2O2 in amounts of 0.02 to 0.2 g / l.
• Another advantageous embodiment of the invention provides for the metal surfaces to be brought into contact with phosphating solutions which additionally contain activators.
• these activators must in turn be precipitated with calcium hydroxide in the neutral or alkaline range.
• the following activators with the concentrations specified in each case are particularly advantageous 0.01 - 0.2 g / l MoO3 0.01 - 0.2 g / l WO3 0.01 - 0.2 g / l VO3 0.1-2 g / l F 0.01-0.2 g / l Ni 0.01-0.2 g / l Mn 0.01 - 0.2 g / l Zn 0.1 - 1 g / l Ca and / or 0.001 - 0.02 g / l Cu Since the phosphating bath should be free of such components that cannot be precipitated with calcium hydroxide in the neutral or alkaline range, only those chemicals are suitable for the preparation and addition of the bath, through which no ions are introduced that lead to water-soluble salts.
• the application of the phosphating solution can be carried out in the usual way, e.g. B. by spraying, dipping or flooding.
• the treatment time can be 5 seconds to a few minutes.
• the layer weight of the phosphate layer produced is generally between 0.1 and 1.0 g / m2. Depending on the treatment conditions, higher layer weights can also be achieved. If a separate pH adjustment is required, it is generally done with phosphoric acid.
• the usual treatment measures can be taken before and after the phosphating stage.
• the metal surfaces can usually be subjected to a cleaning treatment to remove fat and Dirt, e.g. B. with the help of an alkaline cleaner. If necessary, pickling treatment to remove rust can follow. Between cleaning, possibly pickling, and phosphating, it is generally rinsed thoroughly with water.
• phosphating solutions to be used in the process according to the invention can be used for surfactants or emulsifiers of various types, e.g. B. contain those that are also used in metal cleaning. Of course, they must be compatible with the phosphating solution.
• the phosphate layers produced by the process described above were uniformly opaque and formed a perfect base for the subsequent powder coating.
• the rinse water in Zone 4 which has a pH of 5.3 and a conductivity of 320 ⁇ S. cm ⁇ 1 was prepared by adding as much slurry of Ca (OH) 2 in water until the mixture had a pH of 9.0.
• the conductivity of the treated rinsing water after separation of the precipitation was 110 ⁇ S. cm ⁇ 1. It could be used in zone 4 for new flushing purposes.
• the phosphate layers produced by this process were also uniformly covering and, in connection with the subsequent powder coating, provided excellent corrosion protection.
• the cleaning / phosphating solution in Zone 1 had to be prepared from time to time due to the absorption of grease, oil and other contaminants, and the used solution had to be prepared.
• the used solution (pH approx. 4.9; conductivity 2480 ⁇ S. Cm ⁇ 1) was first subjected to ultrafiltration in order to remove the organic impurities. Then there was so much slurry of Ca (OH) 2 added in water until a pH of 9.0 was reached (conductivity 140 ⁇ S. cm ⁇ 1). This measure removed not only the phosphating constituents of the solution, but also the impurities absorbed by them, so that after the precipitation had been separated off, the treated solution could be drained into the sewage system or used for rinsing purposes or to prepare a new cleaning / phosphating solution.

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• 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)
• Materials For Medical Uses (AREA)
• Glass Compositions (AREA)
• Polysaccharides And Polysaccharide Derivatives (AREA)

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• 1992
  • 1992-12-19 DE DE4243214A patent/DE4243214A1/de not_active Withdrawn
• 1993
  • 1993-11-23 AT AT93203269T patent/ATE134720T1/de not_active IP Right Cessation
  • 1993-11-23 ES ES93203269T patent/ES2085713T3/es not_active Expired - Lifetime
  • 1993-11-23 DE DE59301729T patent/DE59301729D1/de not_active Expired - Fee Related
  • 1993-11-23 EP EP93203269A patent/EP0603921B1/fr not_active Expired - Lifetime
  • 1993-12-10 CA CA002111165A patent/CA2111165A1/fr not_active Abandoned
  • 1993-12-13 US US08/166,254 patent/US5383982A/en not_active Expired - Fee Related
  • 1993-12-17 JP JP5344287A patent/JPH06228766A/ja active Pending
  • 1993-12-17 ZA ZA939466A patent/ZA939466B/xx unknown

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