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
  • C23C22/18—Orthophosphates containing manganese cations
  • C23C22/182—Orthophosphates containing manganese cations containing also zinc cations
  • C23C22/184—Orthophosphates containing manganese cations containing also zinc cations containing also nickel cations

Definitions

• the present invention relates to a method for phosphating metal surfaces, in particular a method for producing manganese and nickel-containing zinc phosphate layers on steel, zinc and / or their alloys. These nickel and manganese-containing zinc phosphate layers are applied by spraying, splash-dipping and dipping with aqueous solutions.
• Zinc phosphating baths can contain, for example, monozinc phosphate, free phosphoric acid, zinc nitrate and oxidizing agents as main components.
• the pH of such solutions is usually in the range between 2.8 and 3.4.
• the process consists essentially of two reactions: the pickling reaction and the formation of a zinc phosphate layer on the surface to be phosphated.
• manganese-modified zinc phosphate coatings are known as a basis of liability for modern coatings.
• the use of manganese ions in addition to zinc and nickel ions in Low-zinc phosphating processes have been shown to improve corrosion protection, especially when using surface-coated sheet metal.
• the incorporation of manganese into the zinc phosphate coatings leads to smaller and more compact crystals with increased stability to alkali.
• the working range of phosphating baths is increased; Aluminum can also be phosphated in combination with steel and galvanized steel to form a layer, whereby the generally achieved quality standard is guaranteed.
• the object of the present invention was to provide a phosphating process which is free of both nitrite and chlorate and which, in particular, does not cause so-called “specks”. This means, on the one hand, growths of zinc salts, which are called “white staining” in English and are caused by the cleaning solution. On the other hand, during the phosphating process, crater-shaped openings are created, which are known in English as "nubbing".
• the commonly used systems contain chlorate, bromate, nitrate, nitrite, peroxide and / or organic accelerators Nitro compounds such as 3-nitrobenzenesulfonate.
• 3-nitrobenzenesulfonate has hitherto generally been used together with chlorate and / or nitrite accelerators according to the prior art.
• the 3-nitrobenzenesulfonic acid / chlorate system usually used produces the abovementioned specks in the presence of nitrate on electrolytically galvanized steel, so that it is usually necessary to work without nitrates.
• the above-mentioned object is achieved by a chlorate- and nitrite-free process for the production of nickel and manganese-containing zinc phosphate layers on steel, zinc and / or their alloys by spraying, spray-immersion and / or immersion with an aqueous solution 0.3 to 1.5 g / l zinc (II), 0.01 to 2.0 g / 1 manganese (II), 0.01 to 0.8 g / l iron (II), 0.3 to 2.0 g / l nickel (II), 10.0 to 20.0 g / l phosphate ions, 2.0 to 10.0 g / l nitrate ions and 0.1 to 2.0 g / 1 of an organic oxidizing agent, wherein the aqueous solution has a free acid content of 0.5 to 1.8 points and a total acid content of 15 to 35 points and Na+ is present in the amount necessary to adjust the free acid.
• a low-zinc process which has a defined iron (II) content.
• iron (II) is oxidized to iron (II) and removed from the system as iron phosphate sludge.
• the desired iron (II) value can be added to the sludge elimination system by adding hydrogen peroxide and / or potassium permanganate Iron (II) can be adjusted to iron (II).
• the advantage of the process according to the invention is, in particular, that if the above limits for iron (II) are observed and if a single accelerator, namely an organic oxidizing agent, is used, no nitrous gases are formed.
• a single accelerator namely an organic oxidizing agent
• the iron (II) concentration is determined continuously and / or discontinuously.
• Such analytical determinations are known to the person skilled in the art.
• an excessively high iron (II) concentration can be changed so that iron (III) is formed.
• the precise control of the iron (II) content is an extremely essential point of the present invention.
• the present invention is therefore a zinc phosphating process which can be used in particular in the low zinc range. With the help of this process, phosphate layers are created which contain cations and iron as well as nickel and manganese.
• the organic oxidizing agent to be used is selected according to the invention in such a way that it does not contribute or makes little contribution to the oxidation of iron (II) to iron (II). This is mainly used to depolarize the nascent hydrogen.
• the chlorate- and nitrite-free process for producing zinc phosphate layers on steel, zinc and / or their alloys is modified by dipping, spray-dipping and / or dipping with an aqueous solution in such a way that an aqueous solution is obtained 0.8 to 1.0 g / l zinc (II), 0.8 to 1.0 g / l manganese (II), 0.2 to 0.4 g / l iron (II), 0.5 to 0.7 g / l nickel (II), 12.0 to 16.0 g / l phosphate ions, 3.0 to 6.0 g / l nitrate ions and 0.3 to 0.8 g / l of an organic oxidizing agent starts.
• the free acid content as well as the total acid content corresponds to the above as does the amount of sodium.
• 3-nitrobenzenesulfonic acid is used as the organic oxidizing agent.
• a preferred embodiment of the present invention consists in limiting the upper limit of the concentration of iron (II) in the aqueous solution to less than or equal to 0.3 g / l.
• Atmospheric oxygen is primarily used for this. In principle, however, other oxidizing agents, such as hydrogen peroxide, oxygen and / or potassium permanganate, can also be used.
• the sodium salt of 3-nitrobenzenesulfonic acid is used as the preferred organic oxidizing agent.
• the iron (II) content in the bath solution was determined using oxidizing agents such as hydrogen peroxide, potassium and / or sodium permanganate, ozone, oxygen, and / or atmospheric oxygen, which was continuous or were added batchwise in the amounts required to adjust the iron (II) concentration, below the values given in Table 1.
• oxidizing agents such as hydrogen peroxide, potassium and / or sodium permanganate, ozone, oxygen, and / or atmospheric oxygen
• Steel sheets of quality St. 1405 treated according to application type B show the following layer composition: 52% hopeit (including Zn2Mn (PO4) 2 x 4 H2O) 48% phosphophyllite.
• Corrosion tests in an alternating climate according to VW standard P 1210 were carried out with the test sheet using the application types (B) spray-immersion and (C) immersion with a test time of 30/60 days: (The standard KET primer FT 85 7042, Manufacturer BASF Paints and Varnishes, related) Application type B 30 days 60 days CRS 1) Z 2) ZE 3) CRS Z.
• blistering that occurs in paints is defined by specifying the degree of blistering.
• the degree of bubbles according to this standard is a measure of the formation of bubbles on a coating according to the frequency of the bubbles per unit area and the size of the bubbles.
• the degree of bubbles is indicated by a code letter and a code number for the frequency of the bubbles per unit area as well as a code letter and a code number for the size of the bubbles.
• the code letter and the code m0 mean no bubbles, while m5 defines a certain frequency of bubbles per unit area according to the degree of bubbles according to DIN 53 209.
• the size of the bubbles is given the code letter g and the code number in the range from 0 to 5.
• Code letter and code number g0 has the meaning - no bubbles - while g5 is shown according to the size of the bubbles according to the degree of bubbles in DIN 53 209.
• the degree of blistering is determined, the image of which is most similar to the appearance of the coating.
• the salt spray test according to this standard is used to determine the behavior of paints, coatings and similar coatings when exposed to sprayed sodium chloride solution. If the coating has weak points, pores or injuries, the coating preferably infiltrates from there. This leads to a reduction in adhesion or to loss of adhesion and corrosion of the metallic surface.
• the salt spray test is used so that such errors can be recognized and the infiltration can be determined.
• the VW standard P-VW 1210 is an alternating test that consists of a combination of different standardized test methods.
• a test cycle is maintained which consists of 4 h salt spray test according to DIN 50 021, 4 h rest at room temperature and 16 h condensation constant climate according to DIN 50 017.
• test bone is bombarded with a defined amount of steel shot with a certain grain size distribution. After the test period has expired, a key figure is assigned to the degree of corrosion.
• the key figure 1 denotes an invisible corrosion, while with a key figure 10 practically the entire surface is corroded.

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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)
• Inorganic Compounds Of Heavy Metals (AREA)
• Cosmetics (AREA)

Applications Claiming Priority (3)

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• 1989
  • 1989-04-21 DE DE3913089A patent/DE3913089A1/de not_active Withdrawn
• 1990
  • 1990-04-14 EP EP19900906149 patent/EP0469011B1/de not_active Expired - Lifetime
  • 1990-04-14 CA CA002053244A patent/CA2053244A1/en not_active Abandoned
  • 1990-04-14 US US07/768,692 patent/US5312492A/en not_active Expired - Fee Related
  • 1990-04-14 AT AT90906149T patent/ATE116693T1/de active
  • 1990-04-14 BR BR909007301A patent/BR9007301A/pt not_active Application Discontinuation
  • 1990-04-14 DE DE59008202T patent/DE59008202D1/de not_active Expired - Fee Related
  • 1990-04-14 WO PCT/EP1990/000592 patent/WO1990012901A1/de active IP Right Grant
  • 1990-04-14 JP JP2505950A patent/JPH04504881A/ja active Pending
  • 1990-04-14 ES ES90906149T patent/ES2066200T3/es not_active Expired - Lifetime

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