WO1998009000A1 - Traitement au phosphate de zinc contenant du ruthenium - Google Patents

Traitement au phosphate de zinc contenant du ruthenium Download PDF

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Publication number
WO1998009000A1
WO1998009000A1 PCT/EP1997/004516 EP9704516W WO9809000A1 WO 1998009000 A1 WO1998009000 A1 WO 1998009000A1 EP 9704516 W EP9704516 W EP 9704516W WO 9809000 A1 WO9809000 A1 WO 9809000A1
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phosphating
phosphating solution
solution according
free
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PCT/EP1997/004516
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German (de)
English (en)
Inventor
Bernd Mayer
Jürgen Geke
Peter Kuhm
Frank Kleine-Bley
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Henkel Kommanditgesellschaft Auf Aktien
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Priority to AU44547/97A priority Critical patent/AU4454797A/en
Publication of WO1998009000A1 publication Critical patent/WO1998009000A1/fr

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    • 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
    • C23C22/34—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 fluorides or complex fluorides
    • C23C22/36—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 fluorides or complex fluorides containing also phosphates
    • C23C22/362—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 fluorides or complex fluorides containing also phosphates containing also zinc cations
    • 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
    • C23C22/12—Orthophosphates containing zinc cations
    • 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
    • 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
    • C23C22/34—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 fluorides or complex fluorides
    • C23C22/36—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 fluorides or complex fluorides containing also phosphates
    • C23C22/364—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 fluorides or complex fluorides containing also phosphates containing also manganese cations
    • 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
    • C23C22/34—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 fluorides or complex fluorides
    • C23C22/36—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 fluorides or complex fluorides containing also phosphates
    • C23C22/364—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 fluorides or complex fluorides containing also phosphates containing also manganese cations
    • C23C22/365—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 fluorides or complex fluorides containing also phosphates containing also manganese cations containing also zinc and nickel cations

Definitions

  • the invention relates to processes for phosphating metal surfaces with aqueous, acidic phosphating solutions which contain zinc and phosphate ions and ruthenium ions, and to their use as pretreatment of the metal surfaces for subsequent painting, in particular electro-dip painting or powder painting.
  • the method is applicable for the treatment of surfaces made of steel, galvanized or alloy galvanized steel, aluminum, aluminized or alloy aluminized steel.
  • the phosphating of metals pursues the goal of producing firmly adhered metal phosphate layers that already improve the corrosion resistance and in conjunction with paints and other organic coatings contribute to a significant increase in paint adhesion and resistance to infiltration when exposed to corrosion.
  • Such phosphating processes have long been known.
  • the low-zinc phosphating processes are particularly suitable, in which the phosphating solutions have comparatively low zinc ion contents of e.g. B. 0.5 to 2 g / l.
  • An important parameter in these low-zinc phosphating baths is the weight ratio of phosphate ions to zinc ions, which is usually in the range> 8 and can take values up to 30.
  • DE-A-39 20 296 describes a phosphating process which dispenses with nickel and uses magnesium ions in addition to zinc and manganese ions.
  • the phosphating baths described here contain, in addition to 0.2 to 10 g / l nitrate ions, further oxidizing agents which act as accelerators, selected from nitrite, chlorate or an organic oxidizing agent.
  • EP-A-60 716 discloses low-zinc phosphating baths which contain zinc and manganese as essential cations and which can contain nickel as an optional component.
  • the necessary accelerator is preferably selected from nitrite, m-nitrobenzenesulfonate or hydrogen peroxide.
  • EP-A-228 151 also describes phosphating baths which contain zinc and manganese as essential cations.
  • the phosphating accelerator is selected from nitrite, nitrate, hydrogen peroxide, m-nitrobenzenesulfonate, m-nitrobenzoate or p-nitrophenol.
  • the nitrate content is specified at 5 to about 15 g / l and an optional nickel content between 0.4 and 4 g / l.
  • EP-A-321 059 teaches zinc phosphating baths which, in addition to 0.1 to 2.0 g / l zinc and an accelerator, also 0.01 to 20 g / l tungsten in the form of a soluble tungsten compound, preferably alkali metal or ammonium tungstate or silicotungstate, alkaline earth metal silicotungstate or boro- or silicotungstic acid.
  • the accelerator is selected from nitrite, m-nitrobenzenesulfonate or hydrogen peroxide.
  • Optional components include nickel in amounts of 0.1 - 4 g / l and nitrate in amounts of 0.1 - 15 g / l.
  • DE-C-27 39 006 describes a phosphating process for surfaces made of zinc or zinc alloys which is free of nitrate and ammonium ions.
  • a phosphating process for surfaces made of zinc or zinc alloys which is free of nitrate and ammonium ions.
  • an essential content of zinc in amounts between 0.1 and 5 g / l, 1 to 10 parts by weight of nickel and / or cobalt are required per part by weight of zinc.
  • Hydrogen peroxide is used as an accelerator. From the point of view of workplace hygiene and environmental protection, cobalt is not an alternative to nickel.
  • DE-A-40 13 483 discloses phosphating processes with which similarly good corrosion protection properties can be achieved as with the trication processes. These processes do without nickel and instead use copper in low concentrations, 0.001 to 0.03 g / l. Oxygen and / or other oxidizing agents with the same effect are used to oxidize the divalent iron formed in the pickling reaction of steel surfaces to the trivalent stage. Nitrite, chlorate, bromate, peroxy compounds and organic nitro compounds, such as nitrobenzenesulfonate, are specified as such.
  • WO93 / 20259 modifies this process by adding hydroxylamine, its salts or complexes in an amount of 0.5 to 5 g / l hydroxylamine as a modifying agent for the morphology of the phosphate crystals formed.
  • EP-A-315 059 specifies, as a special effect of the use of hydroxylamine in phosphating baths, the fact that the phosphate crystals are still formed in steel in a desired columnar or bulbous form when the zinc concentration in the phosphating bath corresponds to that for low-zinc Procedure exceeds the usual range. This makes it possible to operate the phosphating baths with zinc concentrations up to 2 g / l and with weight ratios of phosphate to zinc down to 3.7. No further statements are made about advantageous cation combinations of these phosphating baths, but nickel is used in all patent examples.
  • German patent application 195 00 927.4 describes the use of lithium in nickel-free zinc phosphating baths.
  • the object of the invention is to provide phosphating baths which are free of nickel or the similarly questionable cobalt, which is of concern for environmental and workplace hygiene reasons, but which have a corrosion protection effect comparable to that of the trication and phosphating processes.
  • Ruthenium is preferably used as an acid-soluble salt, in particular as a hydroxide, chloride, carbonate, nitrate or sulfate. Since phosphating baths are solutions, all metals, including those listed below as optional, are present as ions. Ru is preferably trivalent and is preferably used in amounts of 0.005 to 0.1 g / l.
  • the phosphating baths according to the invention can contain further divalent metal ions, the positive effect of which on the corrosion protection of zinc phosphate layers is known in the prior art. It is therefore preferred that the phosphating solution according to the invention additionally contains one or more of the following cations:
  • the presence of manganese is particularly preferred.
  • the possibility of the presence of divalent iron depends on the accelerator system described below.
  • the presence of iron (II) in the concentration range mentioned requires an accelerator which has no oxidizing effect on these ions. Hydroxylamine is an example of this.
  • the phosphating baths are preferably, but not necessarily, free of nickel and cobalt. This means that these elements or ions are not deliberately added to the phosphating baths. In practice, however, it cannot be ruled out that such constituents may reach the phosphating baths in traces via the material to be treated. In particular, it cannot be ruled out that when phosphating steel coated with zinc-nickel alloys, nickel ions are introduced into the phosphating solution. However, the expectation of the phosphating baths according to the invention is that under technical conditions the nickel concentration in the baths is below 0.01 g / l, in particular below 0.0001 g / l.
  • fluoride-containing baths are therefore advantageous if the surfaces to be phosphated are at least partially made of aluminum or contain aluminum. In these cases, it is favorable not to use fluoride bound to the complex, but only free fluoride, preferably in concentrations in the range from 0.5 to 1.0 g / l.
  • the phosphating baths For the phosphating of zinc surfaces, it is not absolutely necessary that the phosphating baths contain so-called accelerators.
  • the Phosphating solution contains one or more accelerators.
  • accelerators are known in the prior art as components of zinc phosphating baths. These are understood to mean substances which chemically bind the hydrogen generated by the acid pickling on the metal surface by reducing them themselves.
  • Oxidizing accelerators also have the effect of oxidizing released iron (II) ions to the trivalent stage by pickling on steel surfaces, so that they can precipitate out as iron (III) phosphate.
  • the phosphating baths according to the invention can contain one or more of the following components as accelerators:
  • nitrate ions in amounts of up to 10 g / l can be present as co-accelerators, which can have a particularly favorable effect on the phosphating of steel surfaces.
  • the phosphating solution contain as little nitrate as possible.
  • Nitrate concentrations of 0.5 g / l should preferably not be exceeded, since at higher nitrate concentrations there is a risk of so-called "speck formation". This means white, crater-like defects in the phosphate layer.
  • nitrite as an accelerator leads to technically satisfactory results, especially on steel surfaces. For reasons of occupational safety (risk of developing nitrous gases), however, it is advisable to avoid nitrite as an accelerator. For the phosphating of galvanized surfaces, this is also advisable for technical reasons because Nitrate can form nitrate, which, as explained above, can lead to the problem of speck formation
  • Hydrogen peroxide is preferred for reasons of environmental friendliness, and hydroxylamine is particularly preferred as an accelerator for technical reasons of simplified formulation options for replenishing solutions. However, the use of these two accelerators together is not advisable, since hydroxylamine is decomposed by hydrogen peroxide. Hydrogen peroxide is used in free or bound form Accelerator on, concentrations of 0.005 to 0.02 g / l hydrogen peroxide are particularly preferred. The hydrogen peroxide can be added to the phosphating solution as such. However, it is also possible to use hydrogen peroxide in bound form as compounds which provide hydrogen peroxide in the phosphating bath by hydrolysis reactions.
  • Examples such compounds are persalts such as perborates, perphosphates, percarbonates, peroxosulfates or peroxodisulfates.
  • Other sources of hydrogen peroxide are ionic peroxides such as alkali metal peroxtde into consideration
  • Hydroxylamine can be used as a free base, as a hydroxylamine complex or in the form of hydroxyammonium salts. If free hydroxylamine is added to the phosphating bath or a phosphating bath concentrate, it will largely be present as a hydroxylammonium cation due to the acidic nature of these solutions. When used as a hydroxylammonium Salt, the sulfates and the phosphates are particularly suitable.
  • the acid salts are preferably hydroxylamine or its compounds are added to the phosphating bath in amounts such that the calculated concentration of the free hydroxylamine is between 0.1 and 10 g / l, preferably between 0.2 and 6 g / l and in particular between 0.3 and 2 g / l.
  • hydroxylamine in bound form are aldoximes or ketoximes which can split off hydroxylamine in acidic solution
  • the phosphating baths contain hydroxylamine as the only accelerator, at most together with a maximum of 0.5 g / l nitrate. Accordingly, in a preferred embodiment, phosphating baths are used which do not contain any of the other known accelerators such as nitrite, Oxoa ⁇ ions of halogens, peroxides or nitrobenzenesulfonate contain As a positive side effect, hydroxylamine concentrations above about 1.5 g / l reduce the risk of rust formation in insufficiently flooded areas of the components to be phosphated
  • the accelerator hydroxylamine can be slowly inactivated even if no metal parts to be phosphated are introduced into the phosphating bath. It has surprisingly been found that the inactivation of the hydroxylamm can be significantly slowed down if the phosphating bath is additionally added one or more a phatic hydroxy or aminocarboxylic acids with 2 to 6 carbon atoms in a total amount of 0.01 to 1.5 g / l are added.
  • the carboxylic acids are preferably selected from glycine, lactic acid, gluconic acid, tartronic acid, malic acid, tartaric acid and citric acid, citric acid, lactic acid and glycine are particularly preferred
  • reducing sugars as accelerators is known from US Pat. No. 5,378,292. Within the scope of the present invention, they can be used in amounts between about 0.01 and about 10 g / l, preferably in amounts between about 0.5 and about 2. 5 g / l are used. Examples of such sugars are galactose, mannose and in particular glucose (dextrose).
  • phosphating baths that contain manganese (II) in addition to zinc and ruthenium.
  • the manganese content of the phosphating bath should be between 0.1 and 4 g / l, since with lower manganese contents there is no longer a positive influence on the corrosion behavior of the phosphate layers and with higher manganese contents there is no further positive effect. Contents of between 0.3 and 2 g / l and in particular between 0.5 and 1.5 g / l are preferred.
  • the zinc content of the phosphating bath is preferably set to values between 0.45 and 1.5 g / l as a result of the pickling removal
  • the current zinc content of the working bath rises to up to 3 g / l.
  • the zinc and manganese ions enter the phosphating baths is basically irrelevant. It is particularly advisable to use the oxides and / or the carbonates as the zinc and / or manganese source.
  • iron (II) contents can build up in the phosphating baths, which are significantly higher than the contents containing baths containing oxidizing agents. In this sense, iron (II) concentrations of up to 50 ppm are normal, although values of up to 500 ppm can also occur briefly in the production process. Such iron (II) concentrations are not detrimental to the phosphating process according to the invention.
  • Phosphating solutions which additionally contain 20 to 800 mg / l, preferably 50 to 600 mg / l tungsten in the form of water-soluble tungstates, silicotungstates and / or borotungstates can be used in the phosphating processes according to the invention.
  • the anions mentioned can be used in the form of their acids and / or their water-soluble salts, preferably ammonium salts.
  • the weight ratio of phosphate ions to zinc ions in the phosphating baths can vary within wide limits, provided it is in the range between 3.7 and 30. A weight ratio between 10 and 20 is particularly preferred.
  • the concentration of the phosphate ions the total phosphorus content of the phosphating bath is considered to be present in the form of phosphate ions PO ⁇ " . Accordingly, the known fact is disregarded when calculating the quantitative ratio that the pH values of the phosphating baths, which are usually in the Range from about 3 to about 3.6, only a very small fraction of the phosphate is actually in the form of the triple negatively charged anions. At these pH values it is rather to be expected that the phosphate is primarily as a single negatively charged Dihydrogen phosphate anion is present, together with smaller amounts of undisociated phosphoric acid and double negatively charged hydrogen phosphate anions.
  • Phosphating baths are usually sold in the form of aqueous concentrates which are adjusted to the application concentrations on site by adding water. For reasons of stability, these concentrates can contain an excess of free phosphoric acid, so that when diluted to a bath concentration, the value of the free acid is initially too high or the pH is too low. By adding alkalis such as ammonia or sodium or potassium hydroxide or carbonate, the value of the free acid is reduced to the desired range. Furthermore, it is known that the free acid content during use of the phosphating baths can increase over time due to the consumption of the layer-forming cations and, if appropriate, through decomposition reactions of the accelerator.
  • Low-zinc phosphate baths generally require additions of alkali metal or ammonium ions in order to be able to adjust the free acid to the desired value range at the desired weight ratio PO ⁇ " : Zn> 8.
  • Analogous considerations can be made also about the proportions of alkali metal and / or ammonium ions to other bath components, for example phosphate ions.
  • Phosphating baths according to the invention are suitable for phosphating surfaces made of steel, galvanized or alloy-galvanized steel, aluminum, aluminized or alloy-aluminized steel.
  • aluminum includes the technically customary aluminum alloys such as AIMgO, 5Si1, 4. The materials mentioned can - as is becoming increasingly common in automotive engineering - also coexist.
  • the invention also encompasses a method for phosphating metal surfaces made of steel, galvanized or alloy-galvanized steel and / or aluminum, in which the metal surfaces are sprayed or immersed for a time between 3 seconds and 8 minutes with a phosphating solution according to one or more of the Claims 1 to 9 in contact.
  • the process is suitable for use in immersion, spray or spray / immersion processes. It can be used in particular in automobile construction, where treatment times between 1 and 8 minutes, in particular 2 to 5 minutes, are common. However, it can also be used for strip phosphating in the steel mill, with treatment times between 3 and 12 seconds. When used in tape phosphating processes, it is advisable to set the bath concentrations in the upper half of the ranges preferred according to the invention.
  • the zinc content in the range from 1.5 to 2.5 g / l, the ruthenium content in the range from 0.05 to 0.2 g / l, the manganese content in the range from 1.5 to 3 g / l and the content of free acid are in the range of 1.5 to 2.5 points.
  • a particularly suitable substrate for strip phosphating is galvanized steel, in particular electrolytically galvanized steel.
  • the suitable bath temperatures are between 30 and 70 ° C., regardless of the field of application, the temperature range between 45 and 60 ° C. being preferred.
  • the phosphating process according to the invention is intended in particular for treating the metal surfaces mentioned before painting, for example before cathodic electrocoating, as is customary in automobile construction. It is also suitable as a pretreatment before a powder coating, such as is used for household appliances.
  • the phosphating process is to be seen as a sub-step of the technically usual pretreatment chain.In this chain, the steps of cleaning / degreasing, intermediate spooling and activation are usually preceded by the phosphating process, with activation usually with titanium phosphate-containing activating agents
  • the phosphating according to the invention can, after an intermediate rinse, possibly be followed by a passivating aftertreatment.
  • chromic acid-containing treatment baths are widespread to be replaced by chrome-free treatment baths
  • an intermediate rinse is usually carried out with deionized water
  • the phosphating processes and comparative processes according to the invention were checked on steel sheets (St 1405, CRS), on hot-dip galvanized (HDG) and on both sides electrolytically galvanized steel sheets (ZE), as are used in automobile construction.
  • the following process used in body production was carried out in the immersion process:
  • Phosphating with phosphating baths (bath temperature 50 - 55 ° C) according to Table 1.
  • the phosphating baths contained sodium ions to adjust the free acid as well as Fe (II) in the range of 100 ppm and 0.5 g / l nitrate ions.
  • Hydroxylamine was used as the sulfate.
  • Demineralized water was used for all baths. The pH of the baths was 3.0 to 3.1, the free acid content 2.5 points and the total acid content 23 points.
  • the free acid score is understood to mean the consumption in ml of 0.1 normal sodium hydroxide solution in order to titrate 10 ml of bath solution up to a pH of 3.6. Similarly, the total acid score indicates consumption in ml up to a pH of 8.2.
  • the phosphated test panels were coated with a cathodic dip coating from BASF (FT 85-7042). For example 8, a full structure (VW Candy white) was applied. The corrosion protection was tested with a VDA alternating climate test (1008 hours). Table 2 contains the paint infiltration at the scratch (half the scratch width) as well as information on the layer weight and the size of the phosphate crystals, which were taken from scanning electron microscope images. Ruthenium was detected in the phosphate layers by elemental analysis.

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  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
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Abstract

L'invention concerne une solution de phosphatation aqueuse acide contenant entre 0,2 et 3 g/l d'ions de zinc, entre 3 et 50 g/l d'ions de phosphate, calculés sous forme de PO4. La solution contient en outre entre 0,002 à 0,2 g/l d'ions de ruthénium, ainsi que de préférence des ions de manganèse et un ou plusieurs accélérateurs, notamment de l'amine d'hydroxy.
PCT/EP1997/004516 1996-08-28 1997-08-19 Traitement au phosphate de zinc contenant du ruthenium WO1998009000A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU44547/97A AU4454797A (en) 1996-08-28 1997-08-19 Ruthenium-containing zinc phosphate treatment

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE1996134732 DE19634732A1 (de) 1996-08-28 1996-08-28 Rutheniumhaltige Zinkphosphatierung
DE19634732.7 1996-08-28

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Publication Number Publication Date
WO1998009000A1 true WO1998009000A1 (fr) 1998-03-05

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PCT/EP1997/004516 WO1998009000A1 (fr) 1996-08-28 1997-08-19 Traitement au phosphate de zinc contenant du ruthenium

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DE (1) DE19634732A1 (fr)
WO (1) WO1998009000A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10006338C2 (de) * 2000-02-12 2003-12-04 Chemetall Gmbh Verfahren zur Beschichtung von Metalloberflächen, wässeriges Konzentrat hierzu und Verwendung der beschichteten Metallteile

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1888189A (en) * 1929-12-18 1932-11-15 Parker Rust Proof Co Coated metal article and method of and composition for producing said article
FR1092299A (fr) * 1953-03-27 1955-04-20 Parker Ste Continentale Revêtements noirs pour métaux et leur procédé d'obtention
EP0158177A2 (fr) * 1984-03-23 1985-10-16 Hitachi, Ltd. Procédé d'inhibition de la corrosion de zirconium ou de ses alliages
EP0315059A1 (fr) * 1987-10-30 1989-05-10 HENKEL CORPORATION (a Delaware corp.) Procédé et composition pour former un revêtement au phosphate de zinc
DE4013483A1 (de) * 1990-04-27 1991-10-31 Metallgesellschaft Ag Verfahren zur phosphatierung von metalloberflaechen

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1888189A (en) * 1929-12-18 1932-11-15 Parker Rust Proof Co Coated metal article and method of and composition for producing said article
FR1092299A (fr) * 1953-03-27 1955-04-20 Parker Ste Continentale Revêtements noirs pour métaux et leur procédé d'obtention
EP0158177A2 (fr) * 1984-03-23 1985-10-16 Hitachi, Ltd. Procédé d'inhibition de la corrosion de zirconium ou de ses alliages
EP0315059A1 (fr) * 1987-10-30 1989-05-10 HENKEL CORPORATION (a Delaware corp.) Procédé et composition pour former un revêtement au phosphate de zinc
DE4013483A1 (de) * 1990-04-27 1991-10-31 Metallgesellschaft Ag Verfahren zur phosphatierung von metalloberflaechen

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DE19634732A1 (de) 1998-03-05
AU4454797A (en) 1998-03-19

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