EP1090160A1 - Method for controlling the coating weight for strip-phosphating - Google Patents

Method for controlling the coating weight for strip-phosphating

Info

Publication number
EP1090160A1
EP1090160A1 EP99937820A EP99937820A EP1090160A1 EP 1090160 A1 EP1090160 A1 EP 1090160A1 EP 99937820 A EP99937820 A EP 99937820A EP 99937820 A EP99937820 A EP 99937820A EP 1090160 A1 EP1090160 A1 EP 1090160A1
Authority
EP
European Patent Office
Prior art keywords
phosphating
ions
range
phosphating solution
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP99937820A
Other languages
German (de)
French (fr)
Other versions
EP1090160B1 (en
Inventor
Jörg Riesop
Franz-Gerd Ricke
Frank Panter
Dieter Geruhn
Hubertus Peters
Manfred Wessel
Andreas Klare
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Henkel AG and Co KGaA
ThyssenKrupp Steel Europe AG
Original Assignee
Henkel AG and Co KGaA
ThyssenKrupp Stahl AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Henkel AG and Co KGaA, ThyssenKrupp Stahl AG filed Critical Henkel AG and Co KGaA
Publication of EP1090160A1 publication Critical patent/EP1090160A1/en
Application granted granted Critical
Publication of EP1090160B1 publication Critical patent/EP1090160B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • 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
    • C23C22/12—Orthophosphates containing zinc cations
    • C23C22/13—Orthophosphates containing zinc cations containing also nitrate or nitrite anions
    • 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
    • C23C22/188—Orthophosphates containing manganese cations containing also magnesium 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
    • C23C22/73—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
    • C23C22/77—Controlling or regulating of the coating process

Definitions

  • the invention relates to a method for controlling the layer weight in the phosphating of steel strip galvanized on one or both sides.
  • the layer weights can be kept reliably in the desired range from about 1 to about 2 g / m, even when the belt speed and thus the phosphating time or the change in other phosphating parameters change.
  • steel strip is galvanized on one or both sides, this is understood to mean both electrolytically galvanized and hot-dip galvanized steel strip.
  • This also includes alloy-galvanized steel strips.
  • the zinc layer contains additional alloy components such as iron, nickel and / or aluminum.
  • layer weight is common in the field of phosphating metal surfaces.
  • layer weight or more detailed “phosphate layer weight”
  • the terms "layer coating” or "area-related mass” are also used. This is understood to mean the mass of the metal phosphate layer produced on the metal surface by the phosphating, based on a unit area. It is usually given in g / m 2 . It can be determined by weighing a phosphated metal sheet with a known surface, detaching the metal phosphate layer and weighing the metal sheet again. The mass of the metal phosphate layer based on m can be calculated from the determined weight difference, taking into account the surface of the metal sheet. To remove the metal phosphate layer, for example, a 0.5 wt .-% Use chromic acid solution. The method of determining the layer weight is described in more detail in the German standard DIN 50942.
  • the layer weight represents an essential parameter for checking the phosphating result. Depending on the intended use of the phosphated metal parts, layer weights are sought in different areas.
  • the present invention is preferably concerned with sheet metal used in automotive engineering. Layer weights of above 0.8 g / m, but at most about 4 g / m, are aimed for.
  • the layer weights should preferably be below 3 g / m 2 and in particular be about 1 to about 2 g / m 2 .
  • phosphating surfaces made of iron, steel, zinc and their alloys as well as aluminum and its alloys have long been state of the art.
  • the phosphating of the surfaces mentioned serves to increase the adhesive strength of paint layers and to improve corrosion protection.
  • the phosphating is carried out by immersing the metal surfaces in the phosphating solutions or by spraying the metal surfaces with the phosphating solutions. Combined methods are also known.
  • Shaped metal parts such as automobile bodies can be phosphated, but also metal strips in high-speed conveyor systems.
  • the present invention is concerned with such a band phosphating.
  • Belt phosphating differs from partial phosphating in that, because of the high belt speeds, the phosphating, i.e. H. the growth of a closed metal phosphate layer must take place within a short period of time, for example about 2 to about 20 seconds.
  • German patent application DE-A-196 39 596 tries to provide a phosphating process which, on the one hand, solves the problem of speck formation and, on the other hand, makes it possible to also use galvanized steel strips or the non-galvanized side of one-side galvanized steel strips with the short phosphating times customary in strip systems with a to provide a closed crystalline phosphate layer.
  • "Specks” are understood to be whitish corrosion spots on the metal surface that show a crater-like appearance in microscopic images. Such specks often occur on galvanized steel surfaces if the phosphating solution has too high levels of chloride ions and / or nitrate ions.
  • this task becomes solved by a method for phosphating steel strip or steel strip galvanized on one or both sides or galvanized with alloy by spray or dip treatment for a period of time in the range from 2 to 15 seconds with an acidic, zinc and manganese-containing phosphating solution with a temperature in the range from 40 to 70 ° C, characterized in that the phosphating solution 1 to 4 g / 1 zinc ions,
  • DE-A-197 40 953 describes a method for phosphating steel strip or steel strip galvanized on one or both sides or alloy galvanized by spray or dip treatment for a period in the range from 2 to 20
  • Phosphating solution with a temperature in the range of 50 to 70 ° C, characterized in that the phosphating solution is free of nitrate ions and that it
  • free acid and total acid are generally known in the field of phosphating. They are determined by titrating the acid bath sample with 0.1 normal sodium hydroxide solution and measuring its consumption. The consumption in ml is given as a score.
  • the number of free acids means the consumption in ml of 0.1 normal sodium hydroxide solution in order to titrate 10 ml of bath solution, which has been diluted to 50 ml with deionized water, up to a pH of 4.0 .
  • the total acid score indicates consumption in ml up to a pH of 8.2.
  • Various measures are known in the prior art for adjusting the layer weight to the desired range. For example, this can be done with otherwise identical bath parameters by changing the belt speed.
  • the phosphating bath parameters must be set so that they give layer weights in the desired range at the specified belt speed.
  • the belt speeds can fluctuate considerably, for example in the range between approximately 20 and approximately 180 m / min.
  • the following are known as possibilities for regulating the layer weight: change in the temperature of the phosphating bath, change in the free acid, the total acid and / or the concentration of the layer-forming ions.
  • these changes respond very slowly, so that it takes a considerable amount of time to obtain layer weights in the desired range. It is particularly problematic to adjust the layer weight by changing the bath composition. These changes can often only be undone with a considerable time delay. At least they are associated with an additional consumption of phosphating chemicals and thus with additional costs.
  • the invention accordingly relates to a method for controlling the layer weight in the phosphating of steel strip galvanized on one or both sides with a phosphating solution which contains 1 to 6 g / 1 zinc ions and 10 to 30 g / 1 phosphate ions, characterized in that in the phosphating solution a salary 6
  • Fe (II) ions in the range from 3 to 100 mg / 1.
  • This process is based on the surprising observation that, with the process parameters remaining the same, the more iron (II) ions the phosphating bath contains, the lower the layer weight. It was observed that in the case of layer weights in the introductory range with otherwise identical phosphate parameters, the layer weight is reduced by approximately 0.1 g / m 2 if the phosphating bath is between 3 and 20 mg / 1, in particular approximately 5 to approximately 10 mg / 1 iron (II) ions are added. The longer the treatment time, the less iron (II) is sufficient.
  • the preferred procedure is to prepare a stock solution of a soluble iron (II) salt with a known iron concentration and add it to the phosphating bath if necessary.
  • the soluble iron (II) salts used are preferably salts of anions which do not have a negative effect on the phosphating result and corrosion protection. Iron (II) sulfate is particularly suitable for this.
  • the process according to the invention therefore makes it possible to counteract the increase in the layer weight by reducing the belt speed by increasing the concentration of iron (II) ions in the phosphating bath by about 3 to about 20 mg / l, depending on the treatment time, in order to reduce it of the layer weight to reach 0.1 g / m.
  • contents of iron (II) ions in the range between approximately 3 to approximately 100 mg / 1, preferably between approximately 10 and approximately 100 mg / 1 and in particular between approximately 15 and approximately 55 mg / 1 belt speeds in the range of approximately are obtained 20 to about 180 m / min and resulting phosphating times of about 2 to about 15 seconds, reliable layer weights in the range between about 1 and about 2 g / m.
  • the process according to the invention is preferably operated in such a way that the phosphating solution is supplemented with supplementary solutions which contain no iron (II).
  • the iron (II) content of the phosphating bath decreases over time as a result of drag-out or air oxidation, so that the layer weights increase over time. This effect may be desirable as long as the layer weight is in the technically preferred range. An undesirable further increase can then be counteracted by adding the appropriate amount of iron (II) ions to the phosphating bath.
  • Phosphating solutions which contain ions of one or more other divalent metals in addition to zinc ions are currently used for the phosphating of galvanized steel strips.
  • phosphating baths are currently in use which additionally contain one or more of the following cations: 1 to 5 g / 1 manganese ions, 1 to 4 g / 1 magnesium ions, 0.8 to 4.5 g / 1 nickel ions.
  • the method according to the invention can also be applied to such baths.
  • the phosphating solutions contain alkali metal and / or ammonium cations in order to adjust the value of the free acid to the desired range.
  • Phosphating baths usually also contain so-called accelerators. These are substances that react with the hydrogen generated on the metal surface during the pickling reaction. This prevents a so-called polarization of the metal surface by covering it with hydrogen.
  • the accelerators improve the uniform covering of the metal surface with finely divided phosphate crystals, which usually have a size between approximately 1 and approximately 10 ⁇ m.
  • the process according to the invention presupposes that accelerators which oxidize iron (II) to iron (III) are dispensed with.
  • Hydroxylamine is particularly suitable as an accelerator which does not have an oxidizing effect on iron (II). Accordingly, the use of a phosphating solution which additionally contains about 0.1 to about 3 g / 1 hydroxylamine in free, ionic or bound form as accelerator is preferred for the process according to the invention.
  • Hydroxylamine can be used as a free base, as a hydroxylamine-releasing compound such as hydroxylamine complexes and ketoximes or aldoximes or in the form of hydroxylammonium salts. If free hydroxylamine is added to the phosphating bath or a phosphating bath concentrate, it will largely exist 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. In the case of the phosphates, the acid salts are preferred due to the better solubility.
  • a combination of free hydroxylamine and hydroxylammonium sulfate can advantageously be used in order to take economic aspects into account on the one hand and on the other hand not to burden the phosphating baths with too much sulfate ions.
  • Hydroxylamine or its compounds are added to the phosphating solution in amounts such that the calculated concentration of the free hydroxylamine is between about 0.1 to about 3 g / 1, preferably between about 0.15 and about 1 g / 1.
  • the total phosphorus content of the phosphating bath is considered to be present in the form of phosphate ions P0 4 3 ' .
  • the known fact that the pH values of the phosphating baths in the range from about 2.0 to about 3.6, which are in the acidic region, only a very small part of the phosphate is actually in the form is ignored when calculating or determining the concentration the triple negatively charged anions are present.
  • the phosphate is present primarily as a single negatively charged dihydrogen phosphate anion, together with undisociated phosphoric acid and with smaller amounts of double negatively charged hydrogen phosphate anions.
  • a further preferred embodiment of the invention consists in using phosphating solutions which contain up to about 0.8 g / 1 fluoride in free or complex-bound form.
  • the preferred fluoride contents are in the range from 0.0 to about 0.5 g / 1, in particular in the range from about 0.1 to about 0.2 g / 1.
  • the phosphating solutions are generally prepared in the manner known to the person skilled in the art.
  • phosphate is introduced into the phosphating solutions in the form of phosphoric acid.
  • the cations are added in the form of acid-soluble compounds such as, for example, the carbonates, the oxides or the hydroxides of phosphoric acid, so that this is partially neutralized.
  • the further neutralization to the desired pH range is preferably carried out by adding sodium hydroxide or sodium carbonate.
  • Suitable sources of free fluoride anions are, for example, sodium or Potassium fluoride.
  • tetrafluoroborate or hexafluorosilicate can be used as complex fluorides.
  • phosphating solutions are preferably used which have a free acid content in the range from about 0.4 to about 4 points and a total acid content in the range from about 15 to about 45 points.
  • the terms "free acid” and “total acid” and their method of determination have already been explained above.
  • the free acid values are preferably between about 1.5 and about 3.5 and in particular between about 2.0 and about 3.0 points.
  • the total acid levels are preferably in the range of about 25 to about 35 points.
  • the temperature of the phosphating solution in the process according to the invention is preferably in the range from about 50 to about 70 ° C. and in particular between 53 and 65 ° C.
  • the steel strip galvanized on one or both sides is brought into contact with the phosphating solution for a period of time in the range from about 2 to about 30 seconds by spraying the phosphating solution onto the galvanized steel strip or by immersing the galvanized steel strip in the phosphating solution .
  • the spray treatment is technically easier to carry out and is therefore preferred. Treatment times between 3 and 15 seconds are particularly preferred.
  • the phosphating solution is rinsed off with water from the galvanized steel strip.
  • the process according to the invention assumes that iron (II) ions are not introduced into the phosphating solution in an uncontrolled manner. As already mentioned, supplementary solutions that do not contain iron (II) are therefore preferable. Furthermore, at The phosphating of steel strip, which is only galvanized on one side, prevents the non-galvanized steel side from coming into contact with the phosphating solution and iron (II) ions thereby getting into the phosphating solution through a pickling reaction. Accordingly, the process according to the invention is carried out in the case of phosphating single-sided galvanized steel strip in such a way that only the galvanized strip side is brought into contact with the phosphating solution. Appropriate technical measures such as, for example, covering the non-galvanized strip side prevent it from coming into contact with the phosphating solution.
  • the process according to the invention is preferably used to produce phosphate layers with layer weights in the range from 1 to 2 g / m 2.
  • the iron (II) ion content in the phosphating bath is adjusted so that layer weights of 1.5 ⁇ 0.3 g / m are obtained.
  • the iron (II) ion content can be checked using known analytical techniques and particularly simply by immersing corresponding commercially available measuring strips in the treatment solution.
  • the metal surface must be completely water wettable before applying the phosphating solution. This is usually the case in continuously operating conveyor systems. However, if the belt surface is oiled, this oil must be removed by a suitable cleaner before phosphating. The procedures for this are common in the art.
  • activation is usually carried out using activation agents known in the art. Solutions or suspensions are usually used which contain titanium phosphates and sodium phosphates. The activation is followed by the use of the phosphating process according to the invention, which is advantageously followed by a passivating rinse. An intermediate rinse with water usually takes place between phosphating and passivating rinsing. For a passivating rinse. treatment baths containing chromic acid widely spread.
  • the metal strips phosphated according to the invention can be provided directly with an organic coating. However, they can also be assembled in the initially unpainted state after cutting, shaping and joining to form components such as automobile bodies or household appliances. The associated forming processes are facilitated by the phosphate layer. If the corrosive stress on the finished components is low, as is the case with household appliances, for example, the devices assembled from the phosphated metal can be painted directly. For higher corrosion protection requirements, such as those made in automobile construction, it is advantageous to have a phosphating treatment again after assembling the bodies.
  • the method according to the invention for controlling the layer weight was tested in a belt system for the phosphating of galvanized steel on both sides.
  • the electrolytically galvanized metal strips were activated with an activation solution containing titanium phosphate (Fixodine R 950, Henkel KGaA, batch concentration 0.5% by weight) and phosphated under the conditions given in the table.
  • an activation solution containing titanium phosphate (Fixodine R 950, Henkel KGaA, batch concentration 0.5% by weight) and phosphated under the conditions given in the table.
  • the phosphating bath in this example had the following composition:

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  • 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)
  • Absorbent Articles And Supports Therefor (AREA)
  • Adhesive Tapes (AREA)
  • Organic Insulating Materials (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Abstract

The invention relates to a method for controlling the coating weight for the phosphating of a steel strip which is galvanised on one or both sides, with a phosphating solution containing 1 to 6 g/l zinc ions and 10 to 30 g/l phosphate ions. The method is characterised in that the quantity of Fe(II) ions in the phosphating solution is adjusted between 3 and 100 mg/l. The higher the Fe(II) content, the lower the coating weight. By modifying the Fe(II) content by 3 to 20 mg/l, it is possible to modify the coating weight by approximately 0.1 g/m2.

Description

"Schichtgewichtsteuerung bei Bandphosphatierung" "Coating weight control with strip phosphating"
Die Erfindung betrifft ein Verfahren zur Steuerung des Schichtgewichts bei der Phosphatierung von ein- oder beidseitig verzinktem Stahlband. Hierdurch können die Schichtgewichte auch bei Änderung der Bandgeschwindigkeit und damit der Phosphatierdauer oder bei der Änderung sonstiger Phosphatieφarameter zuverlässig im erwünschten Bereich von etwa 1 bis etwa 2 g/m gehalten werden.The invention relates to a method for controlling the layer weight in the phosphating of steel strip galvanized on one or both sides. As a result, the layer weights can be kept reliably in the desired range from about 1 to about 2 g / m, even when the belt speed and thus the phosphating time or the change in other phosphating parameters change.
Wenn im Sinne dieser Erfindung von ein- oder beidseitig verzinktem Stahlband die Rede ist, so ist hierunter sowohl elektrolytisch verzinktes als auch schmelztauchverzinktes Stahlband zu verstehen. Weiterhin werden hierunter auch legierungsverzinkte Stahlbänder verstanden. Bei diesen enthält die Zinkschicht zusätzliche Legierungsbestandteile wie beispielsweise Eisen, Nickel und/oder Aluminium.If, in the context of this invention, steel strip is galvanized on one or both sides, this is understood to mean both electrolytically galvanized and hot-dip galvanized steel strip. This also includes alloy-galvanized steel strips. The zinc layer contains additional alloy components such as iron, nickel and / or aluminum.
Der Begriff des Schichtgewichts ist auf dem Gebiet der Phosphatierung von Metalloberflächen geläufig. Anstelle von „Schichtgewicht" oder ausführlicher „Phosphatschichtgewicht" werden auch die Begriffe „Schichtauflage" oder „flächenbezogene Masse" gebraucht. Man versteht hierunter die auf eine Flächeneinheit bezogene Masse der auf der Metalloberfläche durch die Phosphatierung erzeugten Metallphosphatschicht. Sie wird üblicherweise in g/m2 angegeben. Sie kann dadurch bestimmt werden, daß man ein phosphatiertes Metallblech mit einer bekannten Oberfläche wiegt, die Metallphosphatschicht ablöst und das Metallblech erneut wiegt. Aus der ermittelten Gewichtsdifferenz kann unter Berücksichtigung der Oberfläche des Metallblechs die auf einen m bezogene Masse der Metallphosphatschicht errechnet werden. Zum Ablösen der Metallphosphatschicht kann man beispielsweise eine 0,5 Gew.-%ige Chromsäurelösung verwenden. Das Verfahren der Bestimmung des Schichtgewichts ist in der Deutschen Norm DIN 50942 näher beschrieben.The term layer weight is common in the field of phosphating metal surfaces. Instead of "layer weight" or more detailed "phosphate layer weight", the terms "layer coating" or "area-related mass" are also used. This is understood to mean the mass of the metal phosphate layer produced on the metal surface by the phosphating, based on a unit area. It is usually given in g / m 2 . It can be determined by weighing a phosphated metal sheet with a known surface, detaching the metal phosphate layer and weighing the metal sheet again. The mass of the metal phosphate layer based on m can be calculated from the determined weight difference, taking into account the surface of the metal sheet. To remove the metal phosphate layer, for example, a 0.5 wt .-% Use chromic acid solution. The method of determining the layer weight is described in more detail in the German standard DIN 50942.
Das Schichtgewicht stellt einen wesentlichen Parameter zur Kontrolle des Phosphatierergebnisses dar. Je nach Verwendungszweck der phosphatierten Metallteile werden Schichtgewichte in unterschiedlichen Bereichen angestrebt. Die vorliegende Erfindung befaßt sich vorzugsweise mit Metallblech, das im Automobilbau Verwendung findet. Hierbei werden Schichtgewichte von oberhalb 0,8 g/m , jedoch von höchstens etwa 4 g/m angestrebt. Vorzugsweise sollen die Schichtgewichte unterhalb von 3 g/m liegen und insbesondere etwa 1 bis etwa 2 g/m2 betragen.The layer weight represents an essential parameter for checking the phosphating result. Depending on the intended use of the phosphated metal parts, layer weights are sought in different areas. The present invention is preferably concerned with sheet metal used in automotive engineering. Layer weights of above 0.8 g / m, but at most about 4 g / m, are aimed for. The layer weights should preferably be below 3 g / m 2 and in particular be about 1 to about 2 g / m 2 .
Verfahren zum Phosphatieren von Oberflächen aus Eisen, Stahl, Zink und dessen Legierungen sowie Aluminium und dessen Legierungen sind seit langem Stand der Technik. Das Phosphatieren der genannten Oberflächen dient zur Erhöhung der Haftfestigkeit von Lackschichten und zur Verbesserung des Korrosionsschutzes. Die Phosphatierung erfolgt durch Eintauchen der Metalloberflächen in die Phosphatierlösungen oder durch Bespritzen der Metalloberflächen mit den Phosphatierunglösungen. Kombinierte Verfahren sind ebenfalls bekannt. Phosphatiert werden können geformte Metallteile wie beispielsweise Automobilkarossen, aber auch Metallbänder in schnellaufenden Bandanlagen. Die vorliegende Erfindung befaßt sich mit einer derartigen Bandphosphatierung. Bandphosphatierung unterscheidet sich von Teilephosphatierung dadurch, daß aufgrund der hohen Bandgeschwindigkeiten die Phosphatierung, d. h. das Aufwachsen einer geschlossenen Metallphosphatschicht, innerhalb einer kurzen Zeitspanne von beispielsweise etwa 2 bis etwa 20 Sekunden erfolgen muß.Processes for phosphating surfaces made of iron, steel, zinc and their alloys as well as aluminum and its alloys have long been state of the art. The phosphating of the surfaces mentioned serves to increase the adhesive strength of paint layers and to improve corrosion protection. The phosphating is carried out by immersing the metal surfaces in the phosphating solutions or by spraying the metal surfaces with the phosphating solutions. Combined methods are also known. Shaped metal parts such as automobile bodies can be phosphated, but also metal strips in high-speed conveyor systems. The present invention is concerned with such a band phosphating. Belt phosphating differs from partial phosphating in that, because of the high belt speeds, the phosphating, i.e. H. the growth of a closed metal phosphate layer must take place within a short period of time, for example about 2 to about 20 seconds.
Verfahren zur Phosphatierung von Metallbändern, insbesondere von elektrolytisch verzinkten oder schmelztauchverzinkten Stahlbändern, sind im Stand der Technik bekannt. Beispielsweise beschreibt die WO 91/02829 ein Verfahren zur 3Processes for phosphating metal strips, in particular electrolytically galvanized or hot-dip galvanized steel strips, are known in the prior art. For example, WO 91/02829 describes a method for 3
Phosphatierung von elektrolytisch und oder schmelztauchverzinktem Stahlband durch kurzzeitige Behandlung mit sauren Phosphatierungslösungen, die neben Zink- und Phosphationen Mangan- und Nickelkationen sowie Anionen sauerstoffhaltiger Säuren mit Beschleunigerwirkung enthalten. Unter letzterem Begriff sind insbesondere Nitrationen zu verstehen. Die DE-A-35 37 108 beschreibt ebenfalls ein Verfahren zur Phosphatierung von elektrolytisch verzinkten Stahlbändern durch Behandlung mit sauren Phosphatierungslösungen, die neben Zink-, Mangan- und Phosphationen weitere Metallkationen wie beispielsweise Nickelionen und/oder Anionen sauerstoffhaltiger Säuren mit Beschleunigerwirkung, insbesondere Nitrationen, enthalten. Die Gehalte an Zink-Kationen liegen dabei in dem verhältnismäßig tiefen Bereich von 0,1 bis 0,8 g/t.Phosphating of electrolytically and or hot-dip galvanized steel strip by brief treatment with acid phosphating solutions, which contain zinc and phosphate ions, manganese and nickel cations as well as anions of oxygen-containing acids with accelerating effect. The latter term is to be understood in particular as nitrate ions. DE-A-35 37 108 likewise describes a process for the phosphating of electrolytically galvanized steel strips by treatment with acidic phosphating solutions which, in addition to zinc, manganese and phosphate ions, contain further metal cations such as, for example, nickel ions and / or anions of oxygen-containing acids with accelerating action, in particular nitrate ions. contain. The content of zinc cations is in the relatively low range of 0.1 to 0.8 g / t.
Die deutsche Patentanmeldung DE-A-196 39 596 versucht, ein Phosphatierverfahren bereitzustellen, das einerseits das Problem der Stippenbildung löst und das es andererseits ermöglicht, auch unverzinkte Stahlbänder bzw. die unverzinkte Seite von einseitig verzinkten Stahlbändern bei den in Bandanlagen üblichen kurzen Phosphatierzeiten mit einer geschlossenen kristallinen Phosphatschicht zu versehen. Unter „Stippen" werden weißliche Korrosionspunkte auf der Metalloberfläche verstanden, die in mikroskopischen Aufnahmen ein kraterähnliches Aussehen zeigen. Derartige Stippen auf verzinkten Stahloberflächen entstehen häufig, wenn die Phosphatierlösung zu hohe Gehalte an Chloridionen und/oder Nitrationen aufweist. Gemäß dem genannten Dokument wird diese Aufgabe gelöst durch ein Verfahren zum Phosphatieren von Stahlband oder von ein- oder beidseitig verzinktem oder legierungsverzinktem Stahlband durch Spritzoder Tauchbehandlung für eine Zeitdauer im Bereich von 2 bis 15 Sekunden mit einer sauren, zink- und manganhaltigen Phosphatierlösung mit einer Temperatur im Bereich von 40 bis 70 °C, dadurch gekennzeichnet, daß die Phosphatierlösung 1 bis 4 g/1 Zinkionen,The German patent application DE-A-196 39 596 tries to provide a phosphating process which, on the one hand, solves the problem of speck formation and, on the other hand, makes it possible to also use galvanized steel strips or the non-galvanized side of one-side galvanized steel strips with the short phosphating times customary in strip systems with a to provide a closed crystalline phosphate layer. "Specks" are understood to be whitish corrosion spots on the metal surface that show a crater-like appearance in microscopic images. Such specks often occur on galvanized steel surfaces if the phosphating solution has too high levels of chloride ions and / or nitrate ions. According to the document mentioned, this task becomes solved by a method for phosphating steel strip or steel strip galvanized on one or both sides or galvanized with alloy by spray or dip treatment for a period of time in the range from 2 to 15 seconds with an acidic, zinc and manganese-containing phosphating solution with a temperature in the range from 40 to 70 ° C, characterized in that the phosphating solution 1 to 4 g / 1 zinc ions,
0,8 bis 3,5 g/1 Manganionen0.8 to 3.5 g / 1 manganese ions
10 bis 30 g/1 Phosphationen 410 to 30 g / 1 phosphate ions 4
0,1 bis 3 g/1 Hydroxylamin in freier, ionischer oder gebundener Form und nicht mehr als 1 g/1 Nitrationen enthält, einen Gehalt an freier Säure im Bereich von 0,4 bis 4 Punkten und einen Gehalt an Gesamtsäure im Bereich von 12 bis 50 Punkten aufweist.Contains 0.1 to 3 g / 1 hydroxylamine in free, ionic or bound form and not more than 1 g / 1 nitrate ion, a free acid content in the range from 0.4 to 4 points and a total acid content in the range of 12 up to 50 points.
Die DE-A-197 40 953 beschreibt ein Verfahren zum Phosphatieren von Stahlband oder von ein- oder beidseitig verzinktem oder legierungsverzinktem Stahlband durch Spritz- oder Tauchbehandlung für eine Zeitdauer im Bereich von 2 bis 20DE-A-197 40 953 describes a method for phosphating steel strip or steel strip galvanized on one or both sides or alloy galvanized by spray or dip treatment for a period in the range from 2 to 20
Sekunden mit einer sauren, zink-, magnesium- und manganhaltigenSeconds with an acid, zinc, magnesium and manganese
Phosphatierlösung mit einer Temperatur im Bereich von 50 bis 70 °C, dadurch gekennzeichnet, daß die Phosphatierlösung frei ist von Nitrationen und daß siePhosphating solution with a temperature in the range of 50 to 70 ° C, characterized in that the phosphating solution is free of nitrate ions and that it
1 bis 4 g/1 Zinkionen,1 to 4 g / 1 zinc ions,
1,2 bis 4 g/1 Manganionen1.2 to 4 g / 1 manganese ions
1 bis 4 g/1 Magnesiumionen1 to 4 g / 1 magnesium ions
10 bis 30 g/1 Phosphationen10 to 30 g / 1 phosphate ions
0,1 bis 3 g/1 Hydroxylamin in freier, ionischer oder gebundener Form enthält, einen Gehalt an freier Säure im Bereich von 0,4 bis 4 Punkten und einenContains 0.1 to 3 g / 1 hydroxylamine in free, ionic or bound form, a free acid content in the range from 0.4 to 4 points and one
Gehalt an Gesamtsäure im Bereich von 15 bis zu 45 Punkten aufweist.Total acid content in the range of 15 to 45 points.
Setzt man den zink- und manganhaltigen Phosphatierlösungen zusätzlich Nickelionen zu, erhält man die sogenannten „Trikation-Phosphatierlösungen".If additional nickel ions are added to the zinc and manganese-containing phosphating solutions, the so-called "trication-phosphating solutions" are obtained.
Die Begriffe „freie Säure" und „Gesamtsäure" sind auf dem Gebiet der Phosphatierung allgemein bekannt. Sie werden bestimmt, indem man die saure Badprobe mit 0,1 -normaler Natronlauge titriert und deren Verbrauch mißt. Der Verbrauch in ml wird als Punktzahl angegeben. In dieser Schrift wird unter der Punktzahl der freien Säure der Verbrauch in ml an 0,1 -normaler Natronlauge verstanden, um 10 ml Badlösung, die mit vollentsalztem Wasser auf 50 ml verdünnt wurde, bis zu einem pH- Wert von 4,0 zu titrieren. Analog gibt die Punktzahl der Gesamtsäure den Verbrauch in ml bis zu einem pH- Wert von 8,2 an. Im Stand der Technik sind verschiedene Maßnahmen bekannt, das Schichtgewicht auf den erwünschten Bereich einzustellen. Beispielsweise kann dies bei sonst gleichen Badparametern durch Änderung der Bandgeschwindigkeit erfolgen. Üblicherweise ist jedoch eine bestimmte Bandgeschwindigkeit vorgegeben, so daß die Phosphatierbadparameter so eingestellt werden müssen, daß sie bei der vorgegebenen Bandgeschwindigkeit Schichtgewichte im gewünschten Bereich ergeben. Dabei können die Bandgeschwindigkeiten beträchtlich schwanken und beispielsweise im Bereich zwischen etwa 20 und etwa 180 m/min liegen. Als Möglichkeiten zur Regulierung des Schichtgewichts sind bisher bekannt: Veränderung der Temperatur des Phosphatierbads, Veränderung der freien Säure, der Gesamtsäure und/oder der Konzentration der schichtbildenden Ionen. Diese Veränderungen sprechen jedoch nur sehr langsam an, so daß es beträchtliche Zeit dauert, bis Schichtgewichte im erwünschten Bereich erhalten werden. Dabei ist es besonders problematisch, das Schichtgewicht durch Änderung der Badzusammensetzung einzustellen. Diese Änderungen sind häufig nur mit einer beträchtlichen Zeitverzögerung wieder rückgängig zu machen. Zumindest sind sie mit einem zusätzlichen Verbrauch von Phosphatierchemikalien und damit mit zusätzlichen Kosten verbunden.The terms "free acid" and "total acid" are generally known in the field of phosphating. They are determined by titrating the acid bath sample with 0.1 normal sodium hydroxide solution and measuring its consumption. The consumption in ml is given as a score. In this document, the number of free acids means the consumption in ml of 0.1 normal sodium hydroxide solution in order to titrate 10 ml of bath solution, which has been diluted to 50 ml with deionized water, up to a pH of 4.0 . Similarly, the total acid score indicates consumption in ml up to a pH of 8.2. Various measures are known in the prior art for adjusting the layer weight to the desired range. For example, this can be done with otherwise identical bath parameters by changing the belt speed. Usually, however, a certain belt speed is specified, so that the phosphating bath parameters must be set so that they give layer weights in the desired range at the specified belt speed. The belt speeds can fluctuate considerably, for example in the range between approximately 20 and approximately 180 m / min. The following are known as possibilities for regulating the layer weight: change in the temperature of the phosphating bath, change in the free acid, the total acid and / or the concentration of the layer-forming ions. However, these changes respond very slowly, so that it takes a considerable amount of time to obtain layer weights in the desired range. It is particularly problematic to adjust the layer weight by changing the bath composition. These changes can often only be undone with a considerable time delay. At least they are associated with an additional consumption of phosphating chemicals and thus with additional costs.
Daher besteht ein Bedarf nach einem Verfahren, das Schichtgewicht insbesondere bei einer Änderung der Bandgeschwindigkeit möglichst rasch, reversibel und mit möglichst geringem Chemikalienverbrauch auf den erwünschten Bereich einzustellen.There is therefore a need for a method for adjusting the layer weight to the desired range as quickly, reversibly and with as little chemical consumption as possible, in particular when the belt speed changes.
Die Erfindung betrifft demnach ein Verfahren zur Steuerung des Schichtgewichts bei der Phosphatierung von ein- oder beidseitig verzinktem Stahlband mit einer Phosphatierlösung, die 1 bis 6 g/1 Zinkionen und 10 bis 30 g/1 Phosphationen enthält, dadurch gekennzeichnet, daß man in der Phosphatierlösung einen Gehalt 6The invention accordingly relates to a method for controlling the layer weight in the phosphating of steel strip galvanized on one or both sides with a phosphating solution which contains 1 to 6 g / 1 zinc ions and 10 to 30 g / 1 phosphate ions, characterized in that in the phosphating solution a salary 6
an Fe(II)-Ionen im Bereich von 3 bis 100 mg/1 einstellt.of Fe (II) ions in the range from 3 to 100 mg / 1.
Diesem Verfahren liegt die überraschende Beobachtung zugrunde, daß bei sonst gleichen Verfahrensparametern das Schichtgewicht um so geringer ist, je mehr Eisen(II)-Ionen das Phosphatierbad enthält. Dabei wurde beobachtet, daß bei Schichtgewichten im einleitend genannten Bereich bei sonst gleichen Phosphatieφarametern eine Absenkung des Schichtgewichts um etwa 0,1 g/m2 eintritt, wenn man dem Phosphatierbad zwischen 3 und 20 mg/1, insbesondere etwa 5 bis etwa 10 mg/1 Eisen(II)-Ionen zusetzt. Dabei genügt umso weniger Eisen(II), je länger die Behandlungszeit ist. Vorzugsweise verfährt man hierbei so, daß man eine Stammlösung eines löslichen Eisen(II)-Salzes mit bekannter Eisenkonzentration herstellt und diese bei Bedarf dem Phosphatierbad zugibt. Als lösliche Eisen(II)- Salze setzt man vorzugsweise Salze von Anionen ein, die sich nicht negativ auf Phosphatierergebnis und Korrosionsschutz auswirken. Hierfür ist Eisen(II)-Sulfat besonders geeignet.This process is based on the surprising observation that, with the process parameters remaining the same, the more iron (II) ions the phosphating bath contains, the lower the layer weight. It was observed that in the case of layer weights in the introductory range with otherwise identical phosphate parameters, the layer weight is reduced by approximately 0.1 g / m 2 if the phosphating bath is between 3 and 20 mg / 1, in particular approximately 5 to approximately 10 mg / 1 iron (II) ions are added. The longer the treatment time, the less iron (II) is sufficient. The preferred procedure is to prepare a stock solution of a soluble iron (II) salt with a known iron concentration and add it to the phosphating bath if necessary. The soluble iron (II) salts used are preferably salts of anions which do not have a negative effect on the phosphating result and corrosion protection. Iron (II) sulfate is particularly suitable for this.
Das erfindungsgemäße Verfahren ermöglicht es demnach, der Steigerung des Schichtgewichts bei Verringerung der Bandgeschwindigkeit dadurch entgegen zu wirken, daß man die Konzentration an Eisen(II)-Ionen im Phosphatierbad je nach Behandlungszeit um etwa 3 bis etwa 20 mg/1 erhöht, um eine Absenkung des Schichtgewichts um 0,1 g/m zu erreichen. Bei Gehalten an Eisen(II)-Ionen im Bereich zwischen etwa 3 bis etwa 100 mg/1, bevorzugt zwischen etwa 10 und etwa 100 mg/1 und insbesondere zwischen etwa 15 und etwa 55 mg/1 erhält man bei Bandgeschwindigkeiten im Bereich von etwa 20 bis etwa 180 m/min und hieraus resultierenden Phosphatierzeiten von etwa 2 bis etwa 15 Sekunden zuverlässig Schichtgewichte im Bereich zwischen etwa 1 und etwa 2 g/m .The process according to the invention therefore makes it possible to counteract the increase in the layer weight by reducing the belt speed by increasing the concentration of iron (II) ions in the phosphating bath by about 3 to about 20 mg / l, depending on the treatment time, in order to reduce it of the layer weight to reach 0.1 g / m. With contents of iron (II) ions in the range between approximately 3 to approximately 100 mg / 1, preferably between approximately 10 and approximately 100 mg / 1 and in particular between approximately 15 and approximately 55 mg / 1, belt speeds in the range of approximately are obtained 20 to about 180 m / min and resulting phosphating times of about 2 to about 15 seconds, reliable layer weights in the range between about 1 and about 2 g / m.
Soll bei einer erneuten Änderung von Verfahrensparametern, beispielsweise einer Erhöhung der Bandgeschwindigkeit und damit verbunden einer Verkürzung der Phosphatierzeit, einem zu niedrig . werdenden Schichtgewicht entgegengewirkt werden, muß die entsprechende Menge an Eisen(II)-Ionen aus dem Phosphatierbad entfernt werden. Um das Schichtgewicht um etwa 0,1 g/m2 anzuheben, müssen je nach Behandlungszeit zwischen etwa 3 und etwa 20 mg/1, insbesondere etwa 5 bis etwa 10 mg/1 Eisen(II)-Ionen dem Phosphatierbad entzogen werden. Dies kann am einfachsten dadurch erfolgen, daß man dem Phosphatierbad die errechnete Menge eines Oxidationsmittels zugibt, um die erwünschte Menge an Eisen(II)-Ionen zu Eisen(III)-Ionen zu oxidieren. Diese fallen als Eisen(III)-Phosphat aus, so daß ihr Einfluß auf das Schichtgewicht verschwindet.If the process parameters are changed again, for example an increase in the belt speed and associated reduction in the phosphating time, one should be too low. counteracted layer weight the corresponding amount of iron (II) ions must be removed from the phosphating bath. In order to raise the layer weight by about 0.1 g / m 2 , depending on the treatment time, between about 3 and about 20 mg / 1, in particular about 5 to about 10 mg / 1, of iron (II) ions must be removed from the phosphating bath. The easiest way to do this is to add the calculated amount of an oxidizing agent to the phosphating bath in order to oxidize the desired amount of iron (II) ions to iron (III) ions. These precipitate out as iron (III) phosphate, so that their influence on the layer weight disappears.
Vorzugsweise betreibt man das erfindungsgemäße Verfahren so, daß man die Phosphatierlösung mit Ergänzungslösungen ergänzt, die kein Eisen(II) enthalten. Dies hat zur Folge, daß sich infolge Ausschleppung oder Luftoxidation der Eisen(II)-Gehalt des Phosphatierbads mit der Zeit erniedrigt, so daß sich die Schichtgewichte mit der Zeit erhöhen. Dieser Effekt kann erwünscht sein, solange das Schichtgewicht im technisch bevorzugten Bereich liegt. Einer unerwünschten weiteren Erhöhung kann dann dadurch entgegengewirkt werden, daß man dem Phosphatierbad die entsprechende Menge an Eisen(II)-Ionen zugibt.The process according to the invention is preferably operated in such a way that the phosphating solution is supplemented with supplementary solutions which contain no iron (II). As a result, the iron (II) content of the phosphating bath decreases over time as a result of drag-out or air oxidation, so that the layer weights increase over time. This effect may be desirable as long as the layer weight is in the technically preferred range. An undesirable further increase can then be counteracted by adding the appropriate amount of iron (II) ions to the phosphating bath.
Derzeit sind für die Phosphatierung von verzinkten Stahlbändern Phosphatierlösungen gebräuchlich, die außer Zinkionen zusätzlich Ionen von einem oder mehreren anderen zweiwertigen Metallen enthalten. Insbesondere sind derzeit Phosphatierbäder gebräuchlich, die zusätzlich eines oder mehrere der folgenden Kationen enthalten: 1 bis 5 g/1 Manganionen, 1 bis 4 g/1 Magnesiumionen, 0,8 bis 4,5 g/1 Nickelionen. Auch auf solche Bäder ist das erfindungsgemäße Verfahren anwendbar.Phosphating solutions which contain ions of one or more other divalent metals in addition to zinc ions are currently used for the phosphating of galvanized steel strips. In particular, phosphating baths are currently in use which additionally contain one or more of the following cations: 1 to 5 g / 1 manganese ions, 1 to 4 g / 1 magnesium ions, 0.8 to 4.5 g / 1 nickel ions. The method according to the invention can also be applied to such baths.
Außer den genannten schichtbildenden Kationen enthalten die Phosphatierlösungen Alkalimetall- und/oder Ammonium-Kationen, um den Wert der freien Säure auf den erwünschten Bereich einzustellen. Üblicherweise enthalten Phosphatierbäder zusätzlich sogenannte Beschleuniger. Dies sind Substanzen, die mit dem bei der Beizreaktion an der Metalloberfläche entstehenden Wasserstoff reagieren. Sie verhindern dadurch eine sogenannte Polarisation der Metalloberfläche durch Belegung mit Wasserstoff. Die Beschleuniger verbessern hierdurch die gleichmäßige Belegung der Metalloberfläche mit feinteiligen Phosphatkristallen, die üblicherweise eine Größe zwischen etwa 1 und etwa 10 μm aufweisen. Das erfindungsgemäße Verfahren setzt voraus, daß man auf Beschleuniger verzichtet, die Eisen(II) zu Eisen(III) oxidieren. Als Beschleuniger, der auf Eisen(II) nicht oxidierend wirkt, bietet sich insbesondere Hydroxylamin an. Demgemäß ist für das erfindungsgemäße Verfahren der Einsatz einer Phosphatierlösung bevorzugt, die als Beschleuniger zusätzlich etwa 0,1 bis etwa 3 g/1 Hydroxylamin in freier, ionischer oder gebundener Form enthält.In addition to the layer-forming cations mentioned, the phosphating solutions contain alkali metal and / or ammonium cations in order to adjust the value of the free acid to the desired range. Phosphating baths usually also contain so-called accelerators. These are substances that react with the hydrogen generated on the metal surface during the pickling reaction. This prevents a so-called polarization of the metal surface by covering it with hydrogen. As a result, the accelerators improve the uniform covering of the metal surface with finely divided phosphate crystals, which usually have a size between approximately 1 and approximately 10 μm. The process according to the invention presupposes that accelerators which oxidize iron (II) to iron (III) are dispensed with. Hydroxylamine is particularly suitable as an accelerator which does not have an oxidizing effect on iron (II). Accordingly, the use of a phosphating solution which additionally contains about 0.1 to about 3 g / 1 hydroxylamine in free, ionic or bound form as accelerator is preferred for the process according to the invention.
Hydroxylamin kann als freie Base, als Hydroxylamin-abspaltende Verbindung wie beispielsweise Hydroxylaminkomplexe sowie Ketoxime oder Aldoxime oder in Form von Hydroxylammoniumsalzen eingesetzt werden. Fügt man freies Hydroxylamin dem Phosphatierbad oder einem Phosphatierbad-Konzentrat zu, wird es aufgrund des sauren Charakters dieser Lösungen weitgehend als Hydroxylammonium-Kation vorliegen. Bei einer Verwendung als Hydroxylammonium-Salz sind die Sulfate sowie die Phosphate besonders geeignet. Im Falle der Phosphate sind aufgrund der besseren Löslichkeit die sauren Salze bevorzugt. Um einerseits ökonomischen Gesichtspunkten Rechnung zu tragen und andererseits die Phosphatierbäder mit nicht zu viel Sulfationen zu belasten, kann vorteilhafterweise eine Kombination von freiem Hydroxylamin und Hydroxylammoniumsulfat eingesetzt werden. Hydroxylamin oder seine Verbindungen werden der Phosphatierungslösung in solchen Mengen zugesetzt, daß die rechnerische Konzentration des freien Hydroxylamins zwischen etwa 0,1 bis etwa 3 g/1, vorzugsweise zwischen etwa 0,15 und etwa 1 g/1 liegt. Für die Angabe der Phosphatkonzentration wird der gesamte Phosphorgehalt des Phosphatierbades als in Form von Phosphationen P04 3' vorliegend angesehen. Demnach wird bei der Konzentrationsberechnung bzw. -bestimmung die bekannte Tatsache außer Acht gelassen, daß bei den im sauren Gebiet liegenden pH- Werten der Phosphatierbäder im Bereich von etwa 2,0 bis etwa 3,6 nur ein sehr geringer Teil des Phosphats tatsächlich in Form der 3-fach negativ geladenen Anionen vorliegt. Bei diesen pH-Werten ist vielmehr zu erwarten, daß das Phosphat vornehmlich als einfach negativ geladenes Dihydrogenphosphat-Anion vorliegt, zusammen mit undisoziierter Phosphorsäure und mit geringeren Mengen 2-fach negativ geladener Hydrogenphosphat-Anionen.Hydroxylamine can be used as a free base, as a hydroxylamine-releasing compound such as hydroxylamine complexes and ketoximes or aldoximes or in the form of hydroxylammonium salts. If free hydroxylamine is added to the phosphating bath or a phosphating bath concentrate, it will largely exist 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. In the case of the phosphates, the acid salts are preferred due to the better solubility. A combination of free hydroxylamine and hydroxylammonium sulfate can advantageously be used in order to take economic aspects into account on the one hand and on the other hand not to burden the phosphating baths with too much sulfate ions. Hydroxylamine or its compounds are added to the phosphating solution in amounts such that the calculated concentration of the free hydroxylamine is between about 0.1 to about 3 g / 1, preferably between about 0.15 and about 1 g / 1. For the indication of the phosphate concentration, the total phosphorus content of the phosphating bath is considered to be present in the form of phosphate ions P0 4 3 ' . Accordingly, the known fact that the pH values of the phosphating baths in the range from about 2.0 to about 3.6, which are in the acidic region, only a very small part of the phosphate is actually in the form is ignored when calculating or determining the concentration the triple negatively charged anions are present. At these pH values, it is rather to be expected that the phosphate is present primarily as a single negatively charged dihydrogen phosphate anion, together with undisociated phosphoric acid and with smaller amounts of double negatively charged hydrogen phosphate anions.
Die Phosphatierung schmelztauchverzinkter Stahlbänder wird durch Fluoridionen erleichtert und auch für die Phosphatierung von elektrolytisch verzinktem Stahlband kann die Anwesenheit von Fluoridionen für eine gleichmäßige Schichtausbildung vorteilhaft sein. Demnach besteht eine weitere bevorzugte Ausführungsform der Erfindung darin, Phosphatierlösungen einzusetzen, die bis zu etwa 0,8 g/1 Fluorid in freier oder komplex gebundener Form enthalten. Beispielsweise liegen für die Phosphatierung von elektrolytisch verzinktem Stahlband die bevorzugten Fluoridgehalte im Bereich von 0,0 bis etwa 0,5 g/1, insbesondere im Bereich von etwa 0,1 bis etwa 0,2 g/1.The phosphating of hot-dip galvanized steel strips is facilitated by fluoride ions and the presence of fluoride ions can also be advantageous for the phosphating of electrolytically galvanized steel strips for a uniform layer formation. Accordingly, a further preferred embodiment of the invention consists in using phosphating solutions which contain up to about 0.8 g / 1 fluoride in free or complex-bound form. For example, for the phosphating of electrolytically galvanized steel strip, the preferred fluoride contents are in the range from 0.0 to about 0.5 g / 1, in particular in the range from about 0.1 to about 0.2 g / 1.
Die Herstellung der Phosphatierungslösungen erfolgt im allgemeinen in der dem Fachmann bekannten Art und Weise. Phosphat wird beispielsweise in Form von Phosphorsäure in die Phosphatierungslösungen eingebracht. Die Kationen werden in Form säurelöslicher Verbindungen wie beispielsweise der Carbonate, der Oxide oder der Hydroxide der Phosphorsäure zugesetzt, so daß diese teilweise neutralisiert wird. Die weitere Neutralisation auf den erwünschten pH-Bereich erfolgt vorzugsweise durch Zugabe von Natriumhydroxid oder Natriumcarbonat. Als Quelle freier Fluoridanionen eignen sich beispielsweise Natrium- oder Kaliumfluorid. Als komplexe Fluoride können beispielsweise Tetrafluoroborat oder Hexafluorosilicat eingesetzt werden.The phosphating solutions are generally prepared in the manner known to the person skilled in the art. For example, phosphate is introduced into the phosphating solutions in the form of phosphoric acid. The cations are added in the form of acid-soluble compounds such as, for example, the carbonates, the oxides or the hydroxides of phosphoric acid, so that this is partially neutralized. The further neutralization to the desired pH range is preferably carried out by adding sodium hydroxide or sodium carbonate. Suitable sources of free fluoride anions are, for example, sodium or Potassium fluoride. For example, tetrafluoroborate or hexafluorosilicate can be used as complex fluorides.
Für die Erzeugung von Phosphatschichten mit einem Schichtgewicht im erwünschten Bereich setzt man vorzugsweise Phosphatierlösungen ein, die einen Gehalt an freier Säure im Bereich von etwa 0,4 bis etwa 4 Punkten und einen Gehalt an Gesamtsäure im Bereich von etwa 15 bis etwa 45 Punkten aufweisen. Die Begriffe „freie Säure" und „Gesamtsäure" sowie ihre Bestimmungsmethode wurden weiter oben bereits erläutert. Vorzugsweise liegen die Werte der freien Säure zwischen etwa 1,5 und etwa 3,5 und insbesondere zwischen etwa 2,0 und etwa 3,0 Punkten. Die Gehalte an Gesamtsäure liegen vorzugsweise im Bereich von etwa 25 bis etwa 35 Punkten.For the production of phosphate layers with a layer weight in the desired range, phosphating solutions are preferably used which have a free acid content in the range from about 0.4 to about 4 points and a total acid content in the range from about 15 to about 45 points. The terms "free acid" and "total acid" and their method of determination have already been explained above. The free acid values are preferably between about 1.5 and about 3.5 and in particular between about 2.0 and about 3.0 points. The total acid levels are preferably in the range of about 25 to about 35 points.
Die Temperatur der Phosphatierlösung liegt im erfindungsgemäßen Verfahren vorzugsweise im Bereich von etwa 50 bis etwa 70 °C und insbesondere zwischen 53 und 65 °C.The temperature of the phosphating solution in the process according to the invention is preferably in the range from about 50 to about 70 ° C. and in particular between 53 and 65 ° C.
Im erfindungsgemäßen Verfahren bringt man das ein- oder beidseitig verzinkte Stahlband mit der Phosphatierlösung für eine Zeitdauer im Bereich von etwa 2 bis etwa 30 Sekunden dadurch in Kontakt, daß man die Phosphatierlösung auf das verzinkte Stahlband aufspritzt oder indem man das verzinkte Stahlband in die Phosphatierlösung eintaucht. Dabei ist die Spritzbehandlung technisch einfacher durchführbar und demgemäß bevorzugt. Besonders bevorzugt sind Behandlungszeiten zwischen 3 und 15 Sekunden. Nach der erwünschten Behandlungsdauer wird die Phosphatierlösung von dem verzinkten Stahlband mit Wasser abgespült.In the process according to the invention, the steel strip galvanized on one or both sides is brought into contact with the phosphating solution for a period of time in the range from about 2 to about 30 seconds by spraying the phosphating solution onto the galvanized steel strip or by immersing the galvanized steel strip in the phosphating solution . The spray treatment is technically easier to carry out and is therefore preferred. Treatment times between 3 and 15 seconds are particularly preferred. After the desired duration of treatment, the phosphating solution is rinsed off with water from the galvanized steel strip.
Das erfindungsgemäße Verfahren setzt voraus, daß nicht unkontrolliert Eisen(II)- Ionen in die Phosphatierlösung eingetragen werden. Wie bereits erwähnt sind daher Ergänzungslösungen vorzuziehen, die kein Eisen(II) enthalten. Weiterhin sollte bei der Phosphatierung von nur einseitig verzinktem Stahlband verhindert werden, daß die unverzinkte Stahlseite mit der Phosphatierlösung in Kontakt kommt und hierbei durch eine Beizreaktion Eisen(II)-Ionen in die Phosphatierlösung gelangen. Demgemäß führt man das erfindungsgemäße Verfahren im Falle der Phosphatierung von einseitig verzinktem Stahlband derart aus, daß man nur die verzinkte Bandseite mit der Phosphatierlösung in Kontakt bringt. Man vermeidet also durch geeignete technische Maßnahmen wie beispielsweise einer Abdeckung der unverzinkten Bandseite, daß diese in Kontakt mit der Phosphatierlösung kommt.The process according to the invention assumes that iron (II) ions are not introduced into the phosphating solution in an uncontrolled manner. As already mentioned, supplementary solutions that do not contain iron (II) are therefore preferable. Furthermore, at The phosphating of steel strip, which is only galvanized on one side, prevents the non-galvanized steel side from coming into contact with the phosphating solution and iron (II) ions thereby getting into the phosphating solution through a pickling reaction. Accordingly, the process according to the invention is carried out in the case of phosphating single-sided galvanized steel strip in such a way that only the galvanized strip side is brought into contact with the phosphating solution. Appropriate technical measures such as, for example, covering the non-galvanized strip side prevent it from coming into contact with the phosphating solution.
Vorzugsweise setzt man das erfindungsgemäße Verfahren ein, um Phosphatschichten mit Schichtgewichten im Bereich von 1 bis 2 g/m zu erzeugen. Insbesondere stellt man den Gehalt an Eisen(II)-Ionen im Phosphatierbad so ein, daß man Schichtgewichte von 1,5 ± 0,3 g/m erhält. Die Kontrolle des Gehalts an Eisen(II)-Ionen kann mit bekannten analytischen Techniken und besonders einfach durch Eintauchen entsprechender kommerziell erhältlicher Meßstreifen in die Behandlungslösung erfolgen.The process according to the invention is preferably used to produce phosphate layers with layer weights in the range from 1 to 2 g / m 2. In particular, the iron (II) ion content in the phosphating bath is adjusted so that layer weights of 1.5 ± 0.3 g / m are obtained. The iron (II) ion content can be checked using known analytical techniques and particularly simply by immersing corresponding commercially available measuring strips in the treatment solution.
Vor dem Aufbringen der Phosphatierungslösung muß die Metalloberfläche vollständig wasserbenetzbar sein. Dies ist in kontinuierlich arbeitenden Bandanlagen in der Regel gegeben. Falls die Bandoberfläche jedoch beölt sein sollte, ist dieses Öl vor der Phosphatierung durch einen geeigneten Reiniger zu entfernen. Die Verfahren hierfür sind in der Technik geläufig. Vor der Phosphatierung erfolgt üblicherweise eine Aktivierung mit im Stand der Technik bekannten Aktivierungsmitteln. Üblicherweise werden Lösungen bzw. Suspensionen eingesetzt, die Titanphosphate und Natriumphosphate enthalten. Auf die Aktivierung folgt die Anwendung des erfindungsgemäßen Phosphatierverfahrens, dem man vorteilhafterweise eine passivierende Nachspülung folgen läßt. Dabei erfolgt zwischen Phosphatierung und passivierender Nachspülung üblicherweise eine Zwischenspülung mit Wasser. Für eine passivierende Nachspülung sind . chromsäurehaltige Behandlungsbäder weit verbreitet. Aus Gründen des Arbeits- und Umweltschutzes sowie aus Entsorgungsgründen besteht jedoch die Tendenz, diese chromhaltigen Passivierbäder durch chromfreie Behandlungsbäder zu ersetzen. Hierfür sind rein anorganische Badlösungen, insbesondere auf Basis von Hexafluorozirkonaten, oder auch organisch-reaktive Badlösungen, beispielsweise auf Basis von substituierten Poly(vinylphenolen) bekannt. Weiterhin können Nachspüllösungen eingesetzt werden, die 0,001 bis 10 g/1 eines oder mehrerer der folgenden Kationen enthalten: Lithiumionen, Kupferionen, Silberionen und/oder Wismutionen.The metal surface must be completely water wettable before applying the phosphating solution. This is usually the case in continuously operating conveyor systems. However, if the belt surface is oiled, this oil must be removed by a suitable cleaner before phosphating. The procedures for this are common in the art. Before phosphating, activation is usually carried out using activation agents known in the art. Solutions or suspensions are usually used which contain titanium phosphates and sodium phosphates. The activation is followed by the use of the phosphating process according to the invention, which is advantageously followed by a passivating rinse. An intermediate rinse with water usually takes place between phosphating and passivating rinsing. For a passivating rinse. treatment baths containing chromic acid widely spread. For reasons of work and environmental protection and for disposal reasons, however, there is a tendency to replace these chromium-containing passivation baths with chromium-free treatment baths. Purely inorganic bath solutions, in particular based on hexafluorozirconates, or also organic-reactive bath solutions, for example based on substituted poly (vinylphenols), are known for this. Rinse solutions which contain 0.001 to 10 g / l of one or more of the following cations can also be used: lithium ions, copper ions, silver ions and / or bismuth ions.
Die erfindungsgemäß phosphatierten Metallbänder können direkt mit einer organischen Beschichtung versehen werden. Sie können jedoch auch im zunächst unlackierten Zustand nach Schneiden, Formen und Fügen zu Bauteilen wie Automobilkarosserien oder Haushaltsgeräten zusammengefügt werden. Die hiermit verbundenen Umformvorgänge werden durch die Phosphatschicht erleichtert. Ist die korrosive Beanspruchung der fertigen Bauteile gering, wie beispielsweise bei Haushaltsgeräten, können die aus dem voφhosphatierten Metall zusammengebauten Geräte direkt lackiert werden. Für höhere Korrosionsschutzanforderungen, wie sie beispielsweise im Automobilbau gestellt werden, ist es vorteilhaft, nach dem Zusammenbau der Korosserien nochmals eine Phosphatierbehandlung folgen zu lassen. The metal strips phosphated according to the invention can be provided directly with an organic coating. However, they can also be assembled in the initially unpainted state after cutting, shaping and joining to form components such as automobile bodies or household appliances. The associated forming processes are facilitated by the phosphate layer. If the corrosive stress on the finished components is low, as is the case with household appliances, for example, the devices assembled from the phosphated metal can be painted directly. For higher corrosion protection requirements, such as those made in automobile construction, it is advantageous to have a phosphating treatment again after assembling the bodies.
Ausführungsbeispieleembodiments
Das erfindungsgemäße Verfahren zur Steuerung des Schichtgewichts wurde in einer Bandanlage zur Phosphatierung von beidseitig elektrolytisch verzinktem Stahl eφrobt. Die elektrolytisch verzinkten Metallbänder wurden nach der Verzinkung mit einer Titanphosphat-haltigen Aktivierlösung (FixodineR 950, Henkel KGaA, Ansatzkonzentration 0,5 Gew.-%) aktiviert und unter den in der Tabelle angegebenen Bedingungen phosphatiert. Außer den in der Tabelle angegebenen Werten wies das Phosphatierbad in diesem Beispiel folgende Zusammensetzung auf:The method according to the invention for controlling the layer weight was tested in a belt system for the phosphating of galvanized steel on both sides. After galvanizing, the electrolytically galvanized metal strips were activated with an activation solution containing titanium phosphate (Fixodine R 950, Henkel KGaA, batch concentration 0.5% by weight) and phosphated under the conditions given in the table. In addition to the values given in the table, the phosphating bath in this example had the following composition:
3,5 g/1 Zink, 3,0 g/1 Mangan, 3,0 g/1 Nickel, 17 g/1 Phosphationen, 15 g/1 Nitrationen3.5 g / 1 zinc, 3.0 g / 1 manganese, 3.0 g / 1 nickel, 17 g / 1 phosphate ions, 15 g / 1 nitrate ions
Die Werte entsprechen dem kommerziell eingesetzten Phosphatierverfahren GRANODINER 5854 (Henkel KGaA). The values correspond to the commercially used phosphating process GRANODINE R 5854 (Henkel KGaA).
1414
Tabelle: Einfluß des Eisen(II)-Gehalts auf das SchichtgewichtTable: Influence of the iron (II) content on the layer weight
BandgeBehandFreie Gesamt TempeFe(II)- Schichtschwindiglungszeit Säure -säure ratur Gehalt gewicht keit SekunPunkte Punkte °C mg/1 g/m2 m/min denBelt treatment-free total tempeFe (II) - layer shrinkage time acid-acid temperature content weight seconds points points ° C mg / 1 g / m 2 m / min den
Vergl.l 45 12 2,5 30 58 «0 2,0Compare l 45 12 2.5 30 58 «0 2.0
Beisp.1 45 12 2,5 30 58 20 1,7Ex. 1 45 12 2.5 30 58 20 1.7
Beisp.2 45 12 2,5 30 58 35 1,4Ex. 2 45 12 2.5 30 58 35 1.4
Vergl.2 90 6 2,5 30 58 «0 1,7Compare 2 90 6 2.5 30 58 «0 1.7
Beisp.3 90 6 2,5 30 58 20 1,5Ex. 3 90 6 2.5 30 58 20 1.5
Vergl.3 180 3 2,5 30 58 «0 1,2Compare 3 180 3 2.5 30 58 «0 1.2
Beisp.4 180 3 2,5 30 58 20 1,1 Ex. 4 180 3 2.5 30 58 20 1.1

Claims

Patentansprüche claims
1. Verfahren zur Steuerung des Schichtgewichts bei der Phosphatierung von ein- oder beidseitig verzinktem Stahlband mit einer Phosphatierlösung, die 1 bis 6 g/1 Zinkionen und 10 bis 30 g/1 Phosphationen enthält, dadurch gekennzeichnet, daß man in der Phosphatierlösung einen Gehalt an Fe(II)-Ionen im Bereich von 3 bis 100 mg/1 einstellt.1. A method for controlling the layer weight in the phosphating of one or both sides galvanized steel strip with a phosphating solution containing 1 to 6 g / 1 zinc ions and 10 to 30 g / 1 phosphate ions, characterized in that a content of in the phosphating solution Fe (II) ions in the range of 3 to 100 mg / 1.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß man der Phosphatierlösung zur Verringerung des Schichtgewicbts um 0, 1 g/m2 zwischen 3 und 20 mg/1 Fe(II)-Ionen zusetzt.2. The method according to claim 1, characterized in that the phosphating solution to reduce the layer weight by 0, 1 g / m 2 between 3 and 20 mg / 1 Fe (II) ions is added.
3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß man der Phosphatierlösung zur Erhöhung des Schichtgewichts um 0,1 g/m i und 20 mg/1 Fe(II)-Ionen durch Oxidation zu Fe(III)-Ionen entzieht.3. The method according to claim 1, characterized in that the phosphating solution to increase the layer weight by 0.1 g / m i and 20 mg / 1 Fe (II) ions is removed by oxidation to Fe (III) ions.
4. Verfahren nach einem oder mehreren der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Phosphatierlösung zusätzlich eines oder mehrere der folgenden Kationen enthält:4. The method according to one or more of claims 1 to 3, characterized in that the phosphating solution additionally contains one or more of the following cations:
1 bis 5 g/1 Manganionen, 1 bis 4 g/1 Magnesiumionen, 0,8 bis 4,5 g/1 Nickelionen.1 to 5 g / 1 manganese ions, 1 to 4 g / 1 magnesium ions, 0.8 to 4.5 g / 1 nickel ions.
5. Verfahren nach einem oder mehreren der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die Phosphatierlösung als Beschleuniger zusätzlich 0,1 bis 3 g/1 Hydroxylamin in freier, ionischer oder gebundener Form enthält. lo5. The method according to one or more of claims 1 to 4, characterized in that the phosphating solution additionally contains 0.1 to 3 g / 1 hydroxylamine as an accelerator in free, ionic or bound form. lo
6. Verfahren nach einem oder mehreren der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Phosphatierlösung einen Gehalt an freier Säure im Bereich von 0,4 bis 4 Punkten und einen Gehalt an Gesamtsäure im Bereich von 15 bis 45 Punkten aufweist.6. The method according to one or more of claims 1 to 5, characterized in that the phosphating solution has a free acid content in the range from 0.4 to 4 points and a total acid content in the range from 15 to 45 points.
7. Verfahren nach einem oder mehreren der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß die Phosphatierlösung eine Temperatur im Bereich von 50 bis 70 °C aufweist.7. The method according to one or more of claims 1 to 6, characterized in that the phosphating solution has a temperature in the range of 50 to 70 ° C.
8. Verfahren nach einem oder mehreren der Ansprüche 1 bis 7, dadurch gekennzeichnet, daß man die Phosphatierlösung für eine Zeitdauer im Bereich von 2 bis 30 Sekunden durch Spritz- oder Tauchbehandlung mit dem ein- oder beidseitig verzinktem Stahlband in Kontakt bringt.8. The method according to one or more of claims 1 to 7, characterized in that the phosphating solution is brought into contact with the steel strip galvanized on one or both sides for a period of time in the range from 2 to 30 seconds by spraying or dipping treatment.
9. Verfahren nach einem oder mehreren der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß man im Falle der Phosphatierung von einseitig verzinktem Stahlband nur die verzinkte Bandseite mit der Phosphatierlösung in Kontakt bringt.9. The method according to one or more of claims 1 to 8, characterized in that in the case of phosphating one-sided galvanized steel strip, only the galvanized strip side is brought into contact with the phosphating solution.
1 O.Verfahren nach einem oder mehreren der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß man Phosphatschichten mit Schichtgewichten im Bereich von 1 bis 2 g/m2 erzeugt. 1 O.Verfahren according to one or more of claims 1 to 9, characterized in that one generates phosphate layers with layer weights in the range of 1 to 2 g / m 2 .
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AU3253499A (en) 1999-09-20
ATE239807T1 (en) 2003-05-15
EP1090160B1 (en) 2003-05-07
DE19808755A1 (en) 1999-09-09
WO1999045171A1 (en) 1999-09-10
US6461450B1 (en) 2002-10-08
JP2002505383A (en) 2002-02-19
DE59905477D1 (en) 2003-06-12
KR20010074665A (en) 2001-08-08

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