EP0313114A1 - Process for obtaining phosphate coatings - Google Patents

Process for obtaining phosphate coatings Download PDF

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Publication number
EP0313114A1
EP0313114A1 EP88201763A EP88201763A EP0313114A1 EP 0313114 A1 EP0313114 A1 EP 0313114A1 EP 88201763 A EP88201763 A EP 88201763A EP 88201763 A EP88201763 A EP 88201763A EP 0313114 A1 EP0313114 A1 EP 0313114A1
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Prior art keywords
iron
phosphating
oxidation
phosphate
ions
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EP88201763A
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German (de)
French (fr)
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EP0313114B1 (en
Inventor
Han Yong Dr. Oei
Werner Dr. Rausch
Klaus Dr. Wittel
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GEA Group AG
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Metallgesellschaft AG
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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
    • C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
    • C23C22/08—Orthophosphates
    • C23C22/10—Orthophosphates containing oxidants
    • 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

Definitions

  • the invention relates to a process for producing phosphate coatings on metal surfaces at least partially composed of iron or steel by means of phosphating solutions which contain layer-forming cations and are operated “on the iron side”, in which the iron II ion content is obtained by oxidation with oxygen-containing gases and precipitation is limited by iron phosphate.
  • phosphating processes uses phosphating solutions which contain oxidizing agents, such as chlorate or nitrite, which convert iron II to iron III, so that insoluble iron phosphate is formed.
  • oxidizing agents such as chlorate or nitrite
  • the phosphating solution is formulated from chemicals which do not convert the iron in solution into the trivalent state. This can be achieved, for example, by using nitrate or similarly weak oxidizing agents as accelerators.
  • the phosphating processes working on the iron side have the advantage of lower chemical consumption and the formation of thick layers, which are particularly suitable for corrosion protection in conjunction with corrosion protection oils or waxes and for cold forming.
  • the phosphating processes working on the iron side have numerous advantages, the accumulation of iron II ions in the phosphating solution poses certain problems.
  • iron content is too high, there is a tendency for spontaneous oxidation of the entire iron II to iron III and thus for such a strong formation of sludge that the phosphating bath is usually no longer usable. If the phosphate solution contains too much iron (II), there is also a tendency to form coarse-grained phosphate layers.
  • the object of the invention is to provide a method for producing phosphate coatings on at least partially iron or steel metal surfaces, which works on the iron side and does not have the known, in particular the aforementioned, disadvantages.
  • the object is achieved by designing the method of the type mentioned at the outset in accordance with the invention in such a way that the oxidation is carried out at a temperature of max. 50 ° C in the presence of iron II-oxidizing microorganisms.
  • DE-AS 24 30 776 describes a means for cleaning and non-layer-forming phosphating of iron surfaces in one operation with the aid of solutions containing phosphoric acid and / or phosphate, oxidizing agents and a culture suspension of lithotropic strains of iron bacteria (Ferrobacillus) and / which has a cleaning effect. or Thiobacillus ferrooxidans contain known.
  • the microorganisms here cause a complete oxidation of the iron II ions to iron III ions.
  • the iron content is no provision for the iron content to be limited to certain maximum values in the sense of controlling the iron II concentration as in the present invention. This also eliminates the possibility of working on the iron side, which is conceptually nonsensical in the case of non-layer-forming phosphating processes.
  • the setting of a maximum temperature of 50 ° C during the oxidation treatment of the phosphating solution is predetermined by the fact that the microorganisms die at higher temperatures.
  • the oxidation is carried out in the presence of Thiobacillus species, in particular of the Thiobacillus ferrooxidans strain.
  • this strain is also referred to as Ferrobacillus ferrooxidans or Ferrobacillus sulfooxidans, which distinguishes which medium the species is adapted to.
  • the term Thiobacillus ferrooxidans is used below.
  • a further preferred embodiment of the invention provides for the oxidation of the iron II ions to be carried out at a pH of the solution of 1.8 to 4, preferably 2.0 to 3.0.
  • the content of iron II ions is limited to a maximum of 10 g / l.
  • Thiobacillus ferrooxidans can be added directly to the phosphating bath. According to a preferred embodiment of the invention, however, a partial stream of the phosphating solution is branched off from the phosphating container and the oxidation of iron II and the iron phosphate separation are carried out in a zone separated from the phosphating zone. The solution freed from iron phosphate sludge is then returned to the phosphating tank, if necessary after the active solution components have been supplemented to the desired value. With this method of operation, it is in principle possible to carry out the phosphating even at a temperature above 50 ° C. if the phosphating solution is adequately cooled before it is regenerated. This cooling could be done in the simplest way by exchanging heat with already regenerated solution.
  • microorganisms Both in the oxidation in the phosphating bath itself and in a separate zone, it is expedient to provide the microorganisms with sufficient surface, for example in the form of packing, such as Raschig rings, for settlement so that they can fully develop their activity.
  • packing such as Raschig rings
  • the oxidation of the separated partial stream of the phosphating solution is carried out in a column provided with packing elements, which is charged with oxygen-containing gas from below and operated in an upward stream, and the iron phosphate formed is then separated from the phosphating solution. Due to the direct current flow of oxygen-containing gas and phosphating solution, the living conditions for the microorganisms are particularly favorable on the one hand, and on the other hand the iron phosphate sludge formed during the oxidation is discharged upwards with the phosphating solution so that blockages or sludge accumulations in individual areas of the apparatus cannot occur.
  • oxygen-containing gas air, and possibly also oxygen-enriched air, is particularly recommended as the oxygen-containing gas.
  • the carbon dioxide content of the air covers the carbon requirement essential for the microorganisms.
  • the other elements necessary for the multiplication and for the growth nitrogen, calcium and phosphorus are usually present in the phosphating solution. Possibly. it may be appropriate to add other additives, e.g. on magnesium, ammonium and / or sulfate ions, provided that the phosphating solution does not contain these components anyway.
  • phosphating solutions with layer-forming cations in the sense of the present invention are, in particular, those based on zinc, zinc / nickel, zinc / manganese and zinc / calcium phosphate.
  • the total acid score was 60 points and the bath temperature was 40 ° C. Degreased steel sheets of the VAT 1405 m quality were pushed through both baths.
  • the load on the baths was 0.12 m2 per liter and hour.
  • the total acid score was kept constant at 60 points by adding supplemental concentrate.

Abstract

In a process for obtaining phosphate coatings on metal surfaces consisting at least partially of iron or steel by means of phosphating solutions, which contain layer-forming cations and are operated on the iron side, wherein the content of iron (II) ions is limited by oxidation with oxygen-containing gases and precipitation of iron phosphate, the oxidation is carried out, in order to accelerate the oxidation of the iron(II) ions, at a temperature of at most 50 DEG C in the presence of microorganisms which oxidise iron(II), especially of Thiobacillus species, such as the strain Thiobacillus ferrooxidans. It is particularly advantageous here to branch a part stream of the phosphating solution off from the phosphating vessel and to carry out the oxidation and iron phosphate separation in a zone divided off from the phosphating zone, in particular in a column provided with packing, charged with oxygen-containing gas from below and operated with upward flow.

Description

Die Erfindung betrifft ein Verfahren zur Erzeugung von Phosphatüberzügen auf mindestens teilweise aus Eisen oder Stahl bestehenden Metalloberflächen mittels Phosphatierungslösungen, die schichtbildende Kationen enthalten und "auf der Eisenseite" betrieben werden, bei dem der Gehalt an Eisen II-Ionen durch Oxidation mit sauerstoffhaltigen Gasen und Fällung von Eisenphosphat begrenzt wird.The invention relates to a process for producing phosphate coatings on metal surfaces at least partially composed of iron or steel by means of phosphating solutions which contain layer-forming cations and are operated “on the iron side”, in which the iron II ion content is obtained by oxidation with oxygen-containing gases and precipitation is limited by iron phosphate.

Bei der Herstellung von Phosphatüberzügen auf Metalloberflächen mit z.B. einer Zinkphosphatlösung ist es generell üblich, zur Beschleunigung der Schichtausbildung der Phosphatierungslösung sogenannte Beschleuniger zuzusetzen. Soweit die Herstellung von Phosphatüberzügen auf Eisen- oder Stahloberflächen betroffen ist, ergeben sich aus der hiermit verbundenen Auflösung von Eisen, das zunächst in Form von Eisen II-Ionen in Lösung geht, besondere Probleme.When producing phosphate coatings on metal surfaces with e.g. In a zinc phosphate solution, it is generally customary to add so-called accelerators to accelerate the layer formation of the phosphating solution. As far as the production of phosphate coatings on iron or steel surfaces is concerned, the associated dissolution of iron, which initially dissolves in the form of iron II ions, poses particular problems.

Bei einer Kategorie von Phosphatierungsverfahren arbeitet man mit Phosphatierungslösungen, die Eisen II in Eisen III überführende Oxidationsmittel, wie z.B. Chlorat oder Nitrit, enthalten, so daß unlösliches Eisenphosphat gebildet wird. Mit zunehmendem Durchsatz an behandelten Oberflächen entstehen dann erhebliche Schlammengen, die physikalisch entfernt werden müssen. Bei einigen Verfahren bereitet jedoch die physikalische Schlammentfernung Schwierigkeiten bzw. ist schwer durchführbar, so daß es vorteilhafter ist, das Phosphatierverfahren so zu leiten, daß praktisch kein oder nur wenig Schlamm gebildet wird.One category of phosphating processes uses phosphating solutions which contain oxidizing agents, such as chlorate or nitrite, which convert iron II to iron III, so that insoluble iron phosphate is formed. With increasing throughput of treated surfaces, considerable amounts of sludge then arise which have to be physically removed. In some processes, however, the physical removal of sludge is difficult or difficult to carry out, so that it is more advantageous to conduct the phosphating process in such a way that practically no or only a little sludge is formed.

Bei dieser Kategorie von Phosphatierverfahren, die "auf der Eisenseite" arbeiten, wird die Phosphatierungslösung aus Chemikalien formuliert, die das in Lösung gehende Eisen nicht in den dreiwertigen Zustand überführen. Dies gelingt beispielsweise durch Verwendung von Nitrat oder ähnlich schwachen Oxidationsmitteln als Beschleuniger. Neben des geringen Schlammanfalles haben die auf der Eisenseite arbeitenden Phosphatierverfahren den Vorzug eines geringeren Chemikalienverbrauchs und der Ausbildung dicker Schichten, die insbesondere für den Korrosionsschutz in Verbindung mit Korrosionsschutzölen oder Wachsen und für die Kaltumformung geeignet sind. Obgleich die auf der Eisenseite arbeitenden Phosphatierverfahren zahlreiche Vorzüge aufweisen, wirft die Anreicherung von Eisen II-Ionen in der Phosphatierungslösung gewisse Probleme auf. Bei einem zu hohen Eisengehalt ist eine Neigung zu einer spontanen Oxidation des gesamten Eisen II zu Eisen III und somit zu einer derartig starken Schlammbildung vorhanden, daß meist das Phosphatierbad nicht mehr verwendbar ist. Bei einem zu hohen Eisen II-Gehalt der Phosphatierungslösung ist zudem eine Tendenz zur Ausbildung grobkörniger Phosphatschichten gegeben.In this category of phosphating processes, which work "on the iron side", the phosphating solution is formulated from chemicals which do not convert the iron in solution into the trivalent state. This can be achieved, for example, by using nitrate or similarly weak oxidizing agents as accelerators. In addition to the low amount of sludge, the phosphating processes working on the iron side have the advantage of lower chemical consumption and the formation of thick layers, which are particularly suitable for corrosion protection in conjunction with corrosion protection oils or waxes and for cold forming. Although the phosphating processes working on the iron side have numerous advantages, the accumulation of iron II ions in the phosphating solution poses certain problems. If the iron content is too high, there is a tendency for spontaneous oxidation of the entire iron II to iron III and thus for such a strong formation of sludge that the phosphating bath is usually no longer usable. If the phosphate solution contains too much iron (II), there is also a tendency to form coarse-grained phosphate layers.

Es hat nicht an Versuchen gefehlt, die Eisen II-Konzentration in Phosphatierbädern, die auf der Eisenseite arbeiten, derart zu begrenzen, daß keine Nachteile entstehen. So ist es bekannt, bei der Herstellung von Phosphatüberzügen auf Eisen- oder Stahloberflächen im Tauch- oder Flutverfahren mit wäßrigen sauren Zinkphosphatlösungen bestimmter Zusammensetzung zu arbeiten, bei der man durch geeignete Bemessung von Chlorat oder einem gleichwirkenden Eisen II zu Eisen III oxidierenden Beschleuniger einen Eisen II-Gehalt von 0,05 bis 1 Gew.% einstellt (EP-Bl 45 110). Die Verwendung von Chlorat als Oxidationsmittel hat jedoch den Nachteil, daß der bei der Oxidation gebildete Schlamm voluminös ausfällt. Darüber hinaus entsteht bei der Oxidation von Eisen II zu Eisen III aus dem Chlorat Chlorid, das sich im Bad anreichert und die korrosionsschützenden Eigenschaften des Phosphatüberzuges beeinträchtigen kann.There has been no lack of attempts to limit the iron II concentration in phosphating baths which work on the iron side in such a way that there are no disadvantages. Thus, it is known to work in the production of phosphate coatings on iron or steel surfaces by immersion or flooding with aqueous acidic zinc phosphate solutions of a certain composition, in which an iron II is oxidized by suitable measurement of chlorate or an iron II which has the same effect to iron III Content of 0.05 to 1% by weight (EP-Bl 45 110). The use of However, chlorate as the oxidizing agent has the disadvantage that the sludge formed during the oxidation turns out to be bulky. In addition, the oxidation of iron II to iron III from the chlorate produces chloride, which accumulates in the bath and can impair the corrosion-protective properties of the phosphate coating.

Schließlich ist es bekannt, die Eisen II-Konzentration von auf der Eisenseite arbeitenden Phosphatierungslösungen durch Oxidation des Eisen II mittels Luft zu begrenzen (DE-Al-33 45 498). Dieses Verfahren hat jedoch den Nachteil, daß die Oxidationsgeschwindigkeit relativ gering ist. Bei Phosphatierbädern, die eine hohe Durchsatzleistung aufweisen, d.h. durch die große Oberfläche pro Badvolumen durchgesetzt werden, ist die in Lösung gehende Menge an Eisen II-Ionen in der Regel höher, als die durch Oxidation mit sauerstoffhaltigem Gas in Eisen III überführbare Menge. Eine Begrenzung der Eisen II-Konzentration auf einen bestimmten Maximalwert ist bei derartigen Verfahren praktisch nicht durchführbar.Finally, it is known to limit the iron II concentration of phosphating solutions working on the iron side by oxidation of the iron II by means of air (DE-Al-33 45 498). However, this method has the disadvantage that the rate of oxidation is relatively slow. For phosphating baths that have a high throughput, i.e. Due to the large surface area per bath volume, the amount of iron II ions in solution is generally higher than the amount that can be converted into iron III by oxidation with oxygen-containing gas. Limiting the iron II concentration to a certain maximum value is practically not feasible with such methods.

Aufgabe der Erfindung ist es, ein Verfahren zur Erzeugung von Phosphatüberzügen auf mindestens teilweise aus Eisen oder Stahl bestehenden Metalloberflächen bereitzustellen, das auf der Eisenseite arbeitet und die bekannten, insbesonderen vorgenannten, Nachteile nicht aufweist.The object of the invention is to provide a method for producing phosphate coatings on at least partially iron or steel metal surfaces, which works on the iron side and does not have the known, in particular the aforementioned, disadvantages.

Die Aufgabe wird gelöst, indem das Verfahren der eingangs genannten Art entsprechend der Erfindung derart ausgestaltet wird, daß man die Oxidation bei einer Temperatur von max. 50°C in Gegenwart von Eisen II-oxidierenden Mikroorganismen vornimmt.The object is achieved by designing the method of the type mentioned at the outset in accordance with the invention in such a way that the oxidation is carried out at a temperature of max. 50 ° C in the presence of iron II-oxidizing microorganisms.

Zwar ist aus der DE-AS 24 30 776 ein Mittel zur Reinigung und nichtschichtbildenden Phosphatierung von Eisenoberflächen in einem Arbeitsgang mit Hilfe von Lösungen, die Phosphorsäure und/oder Phosphat, Oxidationsmittel sowie eine Reinigungswirkung zeigende Kultursuspension von lithotropen Stämmen von Eisenbakterien (Ferrobazillus) und/oder des Thiobazillus ferrooxidans enthalten, bekannt. Jedoch bewirken hierbei die Mikroorganismen neben der Reinigung entsprechend den Ausführungen in Spalte 5, Zeilen 50ff eine komplette Oxidation der Eisen II-Ionen zu Eisen III-Ionen. Eine Begrenzung des Eisengehaltes auf bestimmte Höchstwerte im Sinne einer Steuerung der Eisen II-Konzentration wie bei der vorliegenden Erfindung, ist nicht vorgesehen. Damit entfällt auch die Möglichkeit des Arbeitens auf der Eisenseite, was übrigens bei Verfahren der nichtschichtbildenden Phosphatierung begrifflich unsinnig ist.DE-AS 24 30 776 describes a means for cleaning and non-layer-forming phosphating of iron surfaces in one operation with the aid of solutions containing phosphoric acid and / or phosphate, oxidizing agents and a culture suspension of lithotropic strains of iron bacteria (Ferrobacillus) and / which has a cleaning effect. or Thiobacillus ferrooxidans contain known. However, in addition to cleaning in accordance with the statements in column 5, lines 50ff, the microorganisms here cause a complete oxidation of the iron II ions to iron III ions. There is no provision for the iron content to be limited to certain maximum values in the sense of controlling the iron II concentration as in the present invention. This also eliminates the possibility of working on the iron side, which is conceptually nonsensical in the case of non-layer-forming phosphating processes.

Die Einstellung einer Temperatur von maximal 50°C bei der Oxidationsbehandlung der Phosphatierungslösung ist dadurch vorgegeben, daß bei höheren Temperaturen die Mikroorganismen absterben.The setting of a maximum temperature of 50 ° C during the oxidation treatment of the phosphating solution is predetermined by the fact that the microorganisms die at higher temperatures.

Gemäß einer bevorzugten Ausgestaltung der Erfindung nimmt man die Oxidation in Gegenwart von Thiobazillus-Arten, insbesondere des Stammes Thiobazillus ferrooxidans, vor. In der Literatur wird dieser Stamm auch als Ferrobazillus ferrooxidans oder Ferrobazillus sulfooxidans bezeichnet, wodurch unterschieden wird, an welches Medium die Art adaptiert ist. Im folgenden wird die Bezeichnung Thiobazillus ferrooxidans verwendet.According to a preferred embodiment of the invention, the oxidation is carried out in the presence of Thiobacillus species, in particular of the Thiobacillus ferrooxidans strain. In the literature, this strain is also referred to as Ferrobacillus ferrooxidans or Ferrobacillus sulfooxidans, which distinguishes which medium the species is adapted to. The term Thiobacillus ferrooxidans is used below.

Die Effektivität der Oxidation der Eisen II-Ionen mittels Thiobazillus ferrooxidans in Phosphatierlösungen ist am größten, wenn diese Lösungen auf einen pH-Wert von 1,8 bis 4, vorzugsweise 2,0 bis 3,0 eingestellt sind. Demzufolge sieht eine weitere bevorzugte Ausführungsform der Erfindung vor, die Oxidation der Eisen II-Ionen bei einem pH-Wert der Lösung von 1,8 bis 4, vorzugsweise 2,0 bis 3,0 vorzunehmen.The effectiveness of the oxidation of the iron II ions by means of Thiobacillus ferrooxidans in phosphating solutions is greatest when these solutions are adjusted to a pH of 1.8 to 4, preferably 2.0 to 3.0. Accordingly, a further preferred embodiment of the invention provides for the oxidation of the iron II ions to be carried out at a pH of the solution of 1.8 to 4, preferably 2.0 to 3.0.

Gemäß einer weiteren vorteilhaften Ausführungsform wird der Gehalt an Eisen II-Ionen auf höchstens 10 g/l begrenzt.According to a further advantageous embodiment, the content of iron II ions is limited to a maximum of 10 g / l.

Thiobazillus ferrooxidans kann direkt dem Phosphatierbad zugesetzt werden. Gemäß einer bevorzugten Ausgestaltung der Erfindung zweigt man jedoch einen Teilstrom der Phosphatierungslösung aus dem Phosphatierbehälter ab und nimmt die Oxidation des Eisen II und die Eisenphosphatabtrennung in einer, von der Phosphatierungszone abgetrennten Zone vor. Die von Eisenphosphatschlamm befreite Lösung wird dann, ggf. nach einer Ergänzung der wirksamen Lösungsbestandteile auf den Sollwert, in den Phosphatierbehälter zurückgeführt. Bei dieser Arbeitsweise ist es prinzipiell möglich, die Phosphatierung selbst bei einer Temperatur oberhalb 50°C vorzunehmen, wenn für eine hinreichende Kühlung der Phosphatierungslösung vor ihrer Regenerierung gesorgt wird. Diese Kühlung könnte in einfachster Weise im Wärmeaustausch gegen bereits regenerierte Lösung erfolgen.Thiobacillus ferrooxidans can be added directly to the phosphating bath. According to a preferred embodiment of the invention, however, a partial stream of the phosphating solution is branched off from the phosphating container and the oxidation of iron II and the iron phosphate separation are carried out in a zone separated from the phosphating zone. The solution freed from iron phosphate sludge is then returned to the phosphating tank, if necessary after the active solution components have been supplemented to the desired value. With this method of operation, it is in principle possible to carry out the phosphating even at a temperature above 50 ° C. if the phosphating solution is adequately cooled before it is regenerated. This cooling could be done in the simplest way by exchanging heat with already regenerated solution.

Sowohl bei der Oxidation im Phosphatierungsbad selbst wie in einer separaten Zone ist es zweckmäßig, den Mikroorganismen ausreichend Oberfläche, z.B. in Form von Füllkörpern, wie Raschigringen, zur Besiedelung zur Verfügung zu stellen, damit sie ihre Tätigkeit voll entfalten können.Both in the oxidation in the phosphating bath itself and in a separate zone, it is expedient to provide the microorganisms with sufficient surface, for example in the form of packing, such as Raschig rings, for settlement so that they can fully develop their activity.

Optimale Bedingungen sind dann gegeben, wenn man entsprechend einer weiteren bevorzugten Ausführungsform der Erfindung die Oxidation des abgetrennten Teilstromes der Phosphatierungslösung in einer mit Füllkörpern versehenen, von unten mit sauerstoffhaltigem Gas beaufschlagten und im Aufwärtsstrom betriebenen Kolonne vornimmt und das gebildete Eisenphosphat anschließend von der Phospatierungslösung abtrennt. Durch die Gleichstromführung von sauerstoffhaltigem Gas und Phosphatierungslösung sind einerseits die Lebensbedingungen für die Mikroorganismen besonders günstig, andererseits wird der bei der Oxidation gebildete Eisenphosphatschlamm mit der Phosphatierungslösung nach oben ausgetragen, so daß es nicht zu Verstopfungen oder Schlammansammlungen in einzelnen Apparatebereichen kommen kann.Optimal conditions are met if, according to a further preferred embodiment of the invention, the oxidation of the separated partial stream of the phosphating solution is carried out in a column provided with packing elements, which is charged with oxygen-containing gas from below and operated in an upward stream, and the iron phosphate formed is then separated from the phosphating solution. Due to the direct current flow of oxygen-containing gas and phosphating solution, the living conditions for the microorganisms are particularly favorable on the one hand, and on the other hand the iron phosphate sludge formed during the oxidation is discharged upwards with the phosphating solution so that blockages or sludge accumulations in individual areas of the apparatus cannot occur.

Als sauerstoffhaltiges Gas empfiehlt sich insbesondere die Verwendung von Luft, ggf. auch von mit Sauerstoff angereicherter Luft. Durch den Kohlendioxidgehalt der Luft wird dabei der für die Mikroorganismen unerläßliche Kohlenstoffbedarf gedeckt. Die weiteren, für die Vermehrung und für das Wachstum erforderlichen Elemente Stickstoff, Kalzium und Phosphor, liegen in der Phosphatierungslösung in der Regel vor. Ggf. kann es zweckmäßig sein, weitere Zusätze, z.B. an Magnesium-, Ammonium- und/oder Sulfationen, vorzunehmen, sofern die Phosphatierungslösung diese Komponenten nicht ohnehin enthält.The use of air, and possibly also oxygen-enriched air, is particularly recommended as the oxygen-containing gas. The carbon dioxide content of the air covers the carbon requirement essential for the microorganisms. The other elements necessary for the multiplication and for the growth nitrogen, calcium and phosphorus are usually present in the phosphating solution. Possibly. it may be appropriate to add other additives, e.g. on magnesium, ammonium and / or sulfate ions, provided that the phosphating solution does not contain these components anyway.

Beispiele für Phosphatierungslösungen mit schichtbildenden Kationen im Sinne der vorliegenden Erfindung sind insbesondere solche auf Basis Zink-, Zink/Nickel-, Zink/Mangan- und Zink/Kalziumphosphat.Examples of phosphating solutions with layer-forming cations in the sense of the present invention are, in particular, those based on zinc, zinc / nickel, zinc / manganese and zinc / calcium phosphate.

Die Erfindung wird anhand der nachfolgenden Beispiele beispielsweise und näher erläutert.The invention is illustrated by the following examples, for example and in more detail.

Beispiel.Example.

Es wurden zwei Phosphatierbäder mit folgender Zusammensetzung angesetzt: Zn 16,5 g/l P₂O₅ 19,8 g/l NO₃ 21,1 g/l Two phosphating baths with the following composition were prepared: Zn 16.5 g / l P₂O₅ 19.8 g / l NO₃ 21.1 g / l

Die Gesamtsäure-Punktzahl betrug 60 Punkte und die Badtemperatur 40°C. Durch beide Bäder wurden entfettete Stahlbleche der Qualität USt 1405 m durchgesetzt.The total acid score was 60 points and the bath temperature was 40 ° C. Degreased steel sheets of the VAT 1405 m quality were pushed through both baths.

Die Belastung der Bäder betrug 0,12 m² pro Liter und Stunde.The load on the baths was 0.12 m² per liter and hour.

Während des Durchsatzes wurde die Gesamtsäure-Punktzahl durch Zugabe von Ergänzungskonzentrat auf 60 Punkte konstant gehalten.During the throughput, the total acid score was kept constant at 60 points by adding supplemental concentrate.

Nachdem in beiden Bädern die Eisen II-Konzentration auf 8,2 g/l angestiegen war, wurde Luft eingeleitet. Bad B erhielt einen Zusatz von ca. 1 g/l Thiobazillus ferrooxidans. Hiernach wurden beide Bäder in gleicher Weise weiter belastet.After the iron II concentration had risen to 8.2 g / l in both baths, air was introduced. Bath B received about 1 g / l of Thiobacillus ferrooxidans. Afterwards, both baths were subjected to the same load.

Der Verlauf der jeweiligen Eisen II-Konzentration ist aus Tabelle 1 zu entnehmen. In der 1. Spalte ist der Durchsatz an der Metalloberfläche mit m²/l aufgeführt. In der 2. Spalte ist die Eisen II-Konzentration von Bad A und in der 3. Spalte die Eisen II-Konzentration von Bad B angegeben. TABELLE 1 m²/l Bad A g/l Fe(II) Bad B g/l Fe(II) 0 0 0 1 2,4 2,4 2 4,5 4,5 3 6,5 6,5 4 8,2 8,2 Einleiten von Luft Einleiten von Luft + Thiobazillus ferrooxidans 5 9,4 8,6 6 10,4 8,9 7 11,3 9,2 8 12,0 9,3 9 12,6 9,2 The course of the respective iron II concentration is shown in Table 1. In the 1st column the throughput on the metal surface is listed with m² / l. The 2nd column shows the iron II concentration of bath A and the 3rd column shows the iron II concentration of bath B. TABLE 1 m² / l Bad A g / l Fe (II) Bad B g / l Fe (II) 0 0 0 1 2.4 2.4 2nd 4.5 4.5 3rd 6.5 6.5 4th 8.2 8.2 Introducing air Introduction of air + Thiobacillus ferrooxidans 5 9.4 8.6 6 10.4 8.9 7 11.3 9.2 8th 12.0 9.3 9 12.6 9.2

Mit dem Bad A konnten bei 12 g/l Fe(II) keine hochwertigen Phosphatschichten mehr erzeugt werden. Die mit dem Bad B entsprechend dem erfindungsgemäßen Verfahrenen erhaltenen Phosphatüberzüge waren nach 9 m²/l Durchsatz noch excellent.With bath A it was no longer possible to produce high-quality phosphate layers at 12 g / l Fe (II). The phosphate coatings obtained with bath B in accordance with the process according to the invention were still excellent after 9 m² / l throughput.

Claims (6)

1. Verfahren zur Erzeugung von Phosphatüberzügen auf mindestens teilweise aus Eisen oder Stahl bestehenden Metalloberflächen mittels Phosphatierungslösungen, die schichtbildende Kationen enthalten und auf der Eisenseite betrieben werden, bei dem der Gehalt an Eisen II-Ionen durch Oxidation mit sauerstoffhaltigen Gasen und Fällung von Eisenphosphat begrenzt wird, dadurch gekennzeichnet, daß man die Oxidation bei einer Temperatur von max. 50°C in Gegenwart von Eisen II-oxidierenden Mikroorganismen vornimmt.1. A process for producing phosphate coatings on metal surfaces at least partially composed of iron or steel by means of phosphating solutions which contain layer-forming cations and are operated on the iron side, in which the content of iron II ions is limited by oxidation with oxygen-containing gases and precipitation of iron phosphate , characterized in that the oxidation at a temperature of max. 50 ° C in the presence of iron II-oxidizing microorganisms. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß man die Oxidation in Gegenwart von Thiobazillus-Arten, insbesondere des Stammes Thiobazillus ferrooxidans, vornimmt.2. The method according to claim 1, characterized in that one carries out the oxidation in the presence of Thiobacillus species, in particular the strain Thiobacillus ferrooxidans. 3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß man die Oxidation der Eisen II-Ionen bei einem pH-Wert der Lösung von 1,8 bis 4, vorzugsweise 2,0 bis 3,0 vornimmt.3. The method according to claim 1 or 2, characterized in that one carries out the oxidation of the iron II ions at a pH of the solution of 1.8 to 4, preferably 2.0 to 3.0. 4. Verfahren nach Anspruch 1, 2 oder 3, dadurch gekennzeichnet, daß man den Gehalt an Eisen II-Ionen auf höchstens 10 g/l begrenzt.4. The method according to claim 1, 2 or 3, characterized in that one limits the content of iron II ions to at most 10 g / l. 5. Verfahren nach einem oder mehreren der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß man einen Teilstrom der Phosphatierungslösung aus dem Phosphatierbehälter abzweigt und die Oxidation und Eisenphosphatabtrennung in einer von der Phosphatierungszone abgetrennten Zone vornimmt.5. The method according to one or more of claims 1 to 4, characterized in that a partial stream of the phosphating solution is branched off from the phosphating tank and the oxidation and iron phosphate removal is carried out in a zone separated from the phosphating zone. 6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß man die Oxidation des abgetrennten Teilstromes der Phosphatierungslösung in einer mit Füllkörpern versehenen, von unten mit sauerstoffhaltigem Gas beaufschlagten und im Aufwärtsstrom betriebenen Kolonne vornimmt und das gebildete Eisenphosphat anschließend von der Phosphatierungslösung abtrennt.6. The method according to claim 5, characterized in that one carries out the oxidation of the separated partial stream of the phosphating solution in a column provided with packing, charged from below with oxygen-containing gas and operated in an upward flow, and then separates the iron phosphate formed from the phosphating solution.
EP88201763A 1987-10-21 1988-08-18 Process for obtaining phosphate coatings Expired - Lifetime EP0313114B1 (en)

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DE3735538 1987-10-21

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Publication number Priority date Publication date Assignee Title
US11323884B2 (en) * 2017-06-27 2022-05-03 Allot Ltd. System, device, and method of detecting, mitigating and isolating a signaling storm

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* Cited by examiner, † Cited by third party
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WO2001011110A1 (en) * 1999-08-09 2001-02-15 Nippon Steel Corporation Zinc-based metal plated steel sheet treated with phosphate being excellent in formability and method for production thereof
SG11201505264XA (en) * 2013-03-06 2015-08-28 Ppg Ind Ohio Inc Methods for treating a ferrous metal substrate

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1107481B (en) * 1959-06-10 1961-05-25 Dr Stefan Klinghoffer Process for the pretreatment of wires for the purpose of drawing
US3144361A (en) * 1955-11-10 1964-08-11 Klinghoffer Stefan Pretreating iron or steel
DE1223657B (en) * 1961-08-09 1966-08-25 Chemische Und Lackfabrik Process for phosphating metal surfaces
FR2367704A1 (en) * 1976-10-18 1978-05-12 Gen Mining & Finance Corp METHOD FOR OXIDIZING SOLUTIONS OF A FERROUS SALT
DE3345498A1 (en) * 1983-12-16 1985-06-27 Metallgesellschaft Ag, 6000 Frankfurt Process for producing phosphate coatings

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3144361A (en) * 1955-11-10 1964-08-11 Klinghoffer Stefan Pretreating iron or steel
DE1107481B (en) * 1959-06-10 1961-05-25 Dr Stefan Klinghoffer Process for the pretreatment of wires for the purpose of drawing
DE1223657B (en) * 1961-08-09 1966-08-25 Chemische Und Lackfabrik Process for phosphating metal surfaces
FR2367704A1 (en) * 1976-10-18 1978-05-12 Gen Mining & Finance Corp METHOD FOR OXIDIZING SOLUTIONS OF A FERROUS SALT
DE3345498A1 (en) * 1983-12-16 1985-06-27 Metallgesellschaft Ag, 6000 Frankfurt Process for producing phosphate coatings

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11323884B2 (en) * 2017-06-27 2022-05-03 Allot Ltd. System, device, and method of detecting, mitigating and isolating a signaling storm

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JPH01152281A (en) 1989-06-14
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DE3735538A1 (en) 1989-05-03

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