AU708141B2 - Zinc phosphatizing using low concentrations of copper and manganese - Google Patents

Description

Zinc Phosphatising Using Low Concentrations of Copper and Manganese This invention relates to processes for phosphatising metal surfaces using aqueous, acidic phosphatising solutions which contain zinc and phosphate ions and a maximum of 70ppm of manganese ions and 30ppm of copper ions. The present invention also relates to the use of such a process as a preparatory treatment for metal surfaces for subsequent lacquering, in particular electrophoretic lacquering or powder lacquering. The process is applicable to the treatment of surfaces of steel, galvanised or alloy-galvanised steel, aluminium, aluminised or alloy-aluminised steel.

Metals are phosphatised with the objective of producing firmly bonded penetrating layers of metal phosphates on the metal surfaces, which alone improve corrosion resistance and, in combination with lacquers or other organic coatings, contribute to a substantial increase in lacquer adhesion and resistance to infiltration when subjected to corrosives. This type of phosphatising process has been known for a long time. In the case of preparatory treatment prior to lacquering, in particular electrophoretic lacquering, the low zinc phosphatising process in which the phosphatising solutions have relatively low concentrations of zinc ions of, for 2 instance, from 0.5 to 2g/L, is particularly suitable. One essential feature of these low 20 zinc phosphatising baths is the ratio, by weight, of phosphate ions to zinc ions, Swhich is usually greater than 8 and may have values of up to It has been shown that phosphate layers having much improved anti-corrosion and lacquer adhering properties may be formed by also using other polyvalent cations in the zinc phosphate baths. By way of example, low zinc processes with 25 the addition of eg., from 0.5 to 1.5g/L of manganese ions and, eg., from 0.3 to 2.0g/L of nickel ions find wide application as the so-called trication process for preparing metal surfaces for lacquering, for example for cathodic electrophoretic lacquering of car bodies.

Since nickel and also cobalt, which may be used as an alternative, are classified as critical from a toxicological and effluent point of view, there is a need for phosphatising processes which provide a similar level of performance as the trication process, but which manage with much lower bath concentrations of nickel and/or cobalt and preferably without these two metals.

49 350 discloses a phosphatising solution which contains, as essential constituents, from 3 to 20g/L of phosphate ions, from 0.5 to 3g/L of zinc ions, from 0.003 to 0.7g/L of cobalt ions or from 0.003 to 0.04g/L of copper ions or preferably from 0.05 to 3g/L of nickel ions, from 1 to 8g/L of magnesium ions, 0.01 to 0.25g/L of nitrite ions and from 0.1 to 3g/L of fluoride ions and/or from 2 to of chloride ions. Accordingly, this process describes a zinc/magnesium phosphatising procedure, wherein the phosphatising solution also contains one of 4x4 SC04054 the ions cobalt, copper or preferably nickel. This type of zinc/magnesium phosphatising procedure did not succeed industrially.

EP-B-18 841 relates to a chlorate/nitrite accelerated zinc phosphatising solution containing, inter alia, from 0.4 to lg/L of zinc ions, from 5 to 40g/L of phosphate ions and optionally at least 0.2g/L, preferably from 0.2 to 2g/L, of one or more ions selected from nickel, cobalt, calcium and manganese. Therefore, the optional manganese, nickel, or cobalt concentration is at least 0.2g/L. In the examples, nickel concentrations of 0.53 and 1.33g/L are quoted.

EP-A-459 541 concerns phosphatising solutions which are essentially free of nickel and which contain, apart from zinc and phosphate, from 0.2 to 4g/L of manganese and from 1 to 30mg/L of copper. DE-A-42 10 513 discloses nickel-free phosphatising solutions which contain, apart from zinc and phosphate, from 0.5 to of copper ions and hydroxylamine as accelerator. These phosphatising solutions optionally also contain from 0.15 to 5g/L of manganese.

1i The phosphatising processes described in two last-mentioned documents fully satisfy the demands for anti-corrosion protection. In practice, however, phosphatising baths are used which have a relatively high concentration of manganese of about 1g/L. These phosphatising baths do not, therefore comply with modern ecological requirements for working with the lowest possible concentrations of heavy metals so that as small an amount as possible of metal-containing sludge is produced during the treatment of wash-water and effluents.

An object of the present invention is to provide a heavy metal depleted phosphatising process which achieves the performance of the trication phosphatising process on the various materials used in the automobile industry.

25 This object is achieved by a process for phosphatising metal surfaces of steel, galvanised or alloy-galvanised steel and/or of aluminium, in which the metal surfaces are brought into contact with a zinc-containing phosphatising solution by spraying or immersing for a period of between 3 seconds and 8 minutes, characterised in that the phosphatising solution contains: from 0.2 to 2g/L of zinc ions; from 3 to 50g/L of phosphate ions, calculated as P0 4 from 1 to 70mg/L of manganese ions; from 1 to 30mg/L of copper ions; and one or more accelerators selected from: from 0.3 to 4g/L of chlorate ions, from 0.01 to 0.2g/L of nitrite ions, from 0.05 to 2g/L of m-nitrobenzenesulfonate ions, from 0.05 to 2g/L of mnitrobenzoate ions, from 0.05 to 2g/L of p-nitrophenol, from 0.005 to 0.15g/L of hydrogen peroxide in free or bound form, from 0.1 to 10g/L of hydroxylamine in free or bound form, from 0.1 to 10g/L of a reducing sugar.

The zinc concentration is preferably between about 0.3 and about 2g/L, in particular between about 0.8 and about 1.6g/L. Zinc concentrations above 1.6g/L, for example between 2 and 3g/L, bring only very slight advantages to the process, S 4O but, on the other hand, increase the production of sludge in the phosphatising bath.

C04054 Such a zinc concentration may be produced in a working phosphatising bath if additional zinc gets into the phosphatising bath, when phosphatising galvanised surfaces, due to pickling erosion. Nickel and/or cobalt ions in the concentration ranges of from about 1 to about 50mg/L for nickel and from about 5 to about 100mg/L for cobalt, in combination with the lowest possible nitrate concentration of not more than about 0.5g/L improve the anti-corrosive effect and lacquer adherence as compared with phosphatising baths which do not contain any nickel or cobalt or which have a nitrate concentration of more than 0.5g/L. This achieves a beneficial compromise between the effectiveness of the phosphatising baths on the one hand and the requirements for effluent treatment of the rinsing water on the other hand.

German Patent application 195 00 927.4 discloses that amounts of lithium ions of from about 0.2 to about 1.5g/L improve the anti-corrosive effect achievable using zinc phosphatising baths. Lithium concentrations of 0.2 to about 1.5g/L, in particular from about 0.4 to about 1g/L, also have a beneficial effect on the anticorrosive effect achieved in the heavy metal depleted phosphatising process according to the present invention.

If the present process is intended for use as a spraying procedure, copper concentrations of from about 0.002 to about 0.01lg/L are particularly beneficial.

When used as an immersion procedure, copper concentrations of from 0.005 to 0.02g/L are preferred.

Apart from the previously mentioned cations, which are incorporated into the phosphate layer or which at least have a positive effect on crystal growth in the phosphate layer, the phosphatising baths generally contain sodium, potassium and/or ammonium ions to adjust the free acid. The expression free acid is familiar to those skilled in the phosphatising art. The method for determining free acid and total acid used for the present purposes is given in the exemplification. Free acid and total acid are an important regulating parameter for phosphatising baths since they have a large effect on the weight of the layer. Values for free acid between 0 and 1.5 points for partial phosphatising, of up to 2.5 points for strip phosphatising, and values for total acid between about 15 and about 30 points lie within the technically conventional range and are suitable in the context of the present invention.

In the case of phosphatising baths which are intended to be suitable for different substrates, it has been conventional to add free and/or complexed fluoride in amounts of up to 2.5g/L of total fluoride, of which up to lg/L is free fluoride. The presence of this amount of fluoride is also of advantage in phosphatising baths according to the present invention. In the absence of fluoride, the aluminium concentration in the bath should not exceed 3mg/L. In the presence of fluoride, higher Al concentrations may be tolerated due to complex formation, provided the concentration of non-complexed Al does not exceed 3mg/L. The use of fluoride- C04054

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containing baths is therefore advantageous if the surfaces being phosphatised consist at least partly of aluminium or contain aluminium. In these cases, it is beneficial to use not complexed fluoride, but only free fluoride, preferably at a concentration of from 0.5 to 1.Og/L.

When phosphatising zinc surfaces, the phosphatising baths do not necessarily have to contain so-called accelerators. When phosphatising steel surfaces, however, the phosphatising solution should contain one or more accelerators. Such accelerators are common in the prior art as components of zinc phosphatising baths. They are understood to be substances which chemically bond the hydrogen being produced at the metal surface as a result of attack by the acid in the pickling solution and are themselves reduced. Oxidising accelerators also have the effect of oxidising to the trivalent state iron(ll) ions released on steel surfaces due to attack by the pickling solution so that they may be precipitated as iron(lll) phosphate.

Phosphatising baths according to the present invention may contain one or more of the following components as accelerators: from 0.3 to 4g/L of chlorate ions, from 0.01 to 0.2g/L of nitrite ions, from 0.05 to 2g/L of m-nitrobenzenesulfonate ions, from 0.05 to 2g/L of m-nitrobenzoate ions, from 0.05 to 2g/L of p-nitrophenol, from 0.005 to 0.15g/L of hydrogen peroxide in free or bound form, from 0.1 to of hydroxylamine in free or bound form, from 0.1 to 10g/L of a reducing sugar.

When phosphatising galvanised steel, the phosphatising solution should contain as little nitrate as possible. Nitrate concentrations of 0.5g/L should not be exceeded because at higher nitrate concentrations there is a risk of producing socalled "specks". These are white, crater-like defects in the phosphate layer. In addition, the adhesion of lacquer to galvanised surfaces is impaired.

The use of nitrite as an accelerator leads to technically satisfactory results, especially on steel surfaces. For industrial safety reasons (risk of evolving nitrous gases), however, it is recommended that the use of nitrite as an accelerator be avoided. This is also advisable for technical reasons when phosphatising galvanised surfaces because nitrate may be formed from nitrite which, as explained above, may lead to the problem of speck formation and to reduced adhesion of a lacquer to zinc.

For environmental reasons, hydrogen peroxide and, for technical reasons, hydroxylamine, which offers the possibility of a simplified formulation when more needs to be added to solutions at a later stage, are particularly preferred as accelerators. The mutual use of these two accelerators, however, is not advisable since hydroxylamine is decomposed by hydrogen peroxide. If hydrogen peroxide is used in free or bound form as an accelerator, concentrations of from 0.005 to 0.02g/L of hydrogen peroxide are particularly preferred. In this case, hydrogen peroxide may be added to the phosphatising solutions as such. It is also possible, however, to use hydrogen peroxide in bound form as compounds which provide C04054 cc .I

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hydrogen peroxide in the phosphatising bath due to hydrolysis reactions. Examples of such compounds are persalts, such as perborates, percarbonates, peroxosulfates or peroxodisulfates. Further suitable sources of hydrogen peroxide are ionic peroxides, such as alkali metal peroxides. A preferred embodiment of the present invention involves the use of a combination of chlorate ions and hydrogen peroxide when phosphatising by an immersion process. In this embodiment, the concentration of chlorate may be, for example, from 2 to 4g/L and the concentration of hydrogen peroxide may be from 10 to The use of reducing sugars as accelerators is known from US-A-5 378 292.

They may be used according to the present invention in amounts between about 0.1 and about 10g/L, preferably between about 0.5 and about 2.5g/L. Examples of this type of sugar are galactose, mannose and, in particular, glucose (dextrose).

Another preferred embodiment of the present invention involves using hydroxylamine as accelerator. Hydroxylamine may be used as the free base, as a hydroxylamine complex, as an oxime, which represents the condensation product of hydroxylamine with a ketone, or in the form of hydroxyl-ammonium salts. If free hydroxylamine is added to the phosphatising bath or to a phosphatising bath concentrate, it is mainly present as a hydroxylammonium cation due to the acidic character of these solutions. When used as a hydroxylammonium salt, the sulfates 20 and phosphates are particularly appropriate. In the case of phosphates, the acid salts are preferred due to the better solubility thereof. Hydroxylamine or compounds thereof are added to the phosphatising bath in amounts such that the theoretical concentration of free hydroxylamine is between 0.1 and 10g/L, preferably between 0.3 and 5g/L. In this case, it is preferred that the phosphatising baths contain only hydroxylamine as accelerator, if necessary together with a maximum of 0.5g/L of nitrate. Therefore, in a preferred embodiment, phosphatising baths are used which do not contain any of the other known accelerators, such as nitrite, oxo-anions of halogens, peroxides or nitro-benzenesulfonate. As a positive side effect, hydroxylamine concentrations above about 1.5g/L reduce the risk of rust formation at places on the components to be phosphatised which are inadequately surrounded by liquid.

In practice, it has been shown that the accelerator hydroxylamine may also be slowly inactivated if no metal parts to be phosphatised are introduced into the phosphatising bath. Surprisingly it has been shown that inactivation of hydroxylamine may be greatly retarded if one or more aliphatic hydroxycarboxylic or aminocarboxylic acids having from 2 to 6 carbon atoms are also added to the phosphatising bath in a total amount of from 0.01 to 1.5g/L. In this case, the carboxylic acids are preferably selected from glycine, lactic acid, gluconic acid, tartronic acid, malic acid, tartaric acid and citric acid, wherein citric acid, lactic acid and glycine are particularly preferred.

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When using the phosphatising process on steel surfaces, iron goes into solution in the form of iron(ll) ions. If the phosphatising baths according to the present invention do not contain substances which are able to oxidise iron(ll), the divalent iron is transformed into the trivalent state as a result of atmospheric oxidation so that it may precipitate as iron(lll) phosphate. This is the case, for example, when using hydroxylamine. Therefore, iron(ll) concentrations may be built up in phosphatising baths which are well above the concentrations contained in baths which contain oxidising agents. In this context, iron(ll) concentrations of up to ppm are normal, while values up to 500 ppm may also occur for short periods during the production cycle. In the phosphatising process according to the present invention, such iron(ll) concentrations are not damaging. When prepared using hard water, the phosphatising baths may also contain the hardness-producing cations Mg(ll) and Ca(ll) in a total concentration of up to 7mmol/L. Mg(ll) or Ca(ll) may also be added to the phosphatising baths in amounts of up to The ratio, by weight, of phosphate ions to zinc ions in the phosphatising baths may vary between wide limits, provided it is between 3.7 and 30. A weight ratio between 10 and 20 is particularly preferred. With respect to the data on phosphate concentration, the total phosphorus content of the phosphatising bath is regarded as being present in the form of phosphate ions P0 4 3 Therefore, when calculating the ratio, the fact that, at the pH of phosphate baths, which is generally from about 3 to about 3.6, only a very small proportion of the phosphate is actually in the form of triply charged anions, is ignored. Rather, at this pH it would be expected that the phosphate is mainly present as singly charged dihydrogen-phosphate anions, together with small amounts of undissociated phosphoric acid and doubly charged hydrogenphosphate anions.

Phosphatising baths are generally sold in the form of aqueous concentrates which are adjusted to the application concentration by addition of water on site. For stability reasons, these concentrates contain an excess of free phosphoric acid so that, on dilution to the bath concentration, the free acid value is initially too high and the pH is too low. The free acid value is lowered to the desired range by adding alkalis, such as sodium hydroxide, sodium carbonate or ammonia. Furthermore, it is known that the concentration of free acid may rise with time during the use of phosphatising baths due to consumption of the layer-forming cations and optionally by decomposition reactions of the accelerator. In this case, the free acid value has to be re-adjusted to the desired range by adding alkali from time to time. This means that the concentrations of alkali metal ions or ammonium ions in the phosphatising baths may vary between wide limits and that they tend to increase over the lifetime of the phosphatising baths as a result of neutralising the free acid.

The weight ratio of alkali metal ions and/or ammonium ions to, for example, zinc ions, may therefore be very low in freshly prepared phosphatising baths, for C04054 zL example and in the extreme may even be 0, while it generally increases over time as a result of bath maintenance procedures, so that the ratio may become >1 and values up to 10 and above may be acceptable. Low zinc phosphatising baths generally require the addition of alkali metal ions or ammonium ions in order to be able to adjust the free acid to the required range with the desired weight ratio of PO4 3 Zn>8. Analogous considerations may also be used with respect to the ratios of alkali metal ions or ammonium ions to other bath constituents, for example to phosphate ions.

In the case of lithium-containing phosphatising baths, the use of sodium compounds for adjusting the free acid should be avoided because the beneficial effect of lithium on the anti-corrosive effect is suppressed by too high a concentration of sodium. In this case basic lithium compounds are preferably used for adjusting the free acid. Potassium compounds are also suitable for assisting this procedure.

In principle, it does not matter in what form the layer-forming or layerinfluencing cations are introduced into the phosphatising baths. Nitrates should be avoided, however, in order not to exceed the preferred upper limit for nitrate concentration. The metal ions are preferably used in the form of those compounds which do not introduce foreign ions to the phosphatising solution. Therefore it is most beneficial to use the metals in the form of oxides or carbonates thereof.

Lithium may also be used as sulfate and copper preferably as acetate.

Phosphatising baths according to the present invention are suitable for phosphatising surfaces of steel, galvanised or alloy-galvanised steel, aluminium, aluminised or alloy-aluminised steel. The expression "aluminium" as used herein includes industrially conventional aluminium alloys, such as AIMg.5Sil.4. The materials mentioned may, as is increasingly conventional in the automobile industry, also be present side-by-side.

Thus, parts of the car body may also consist of already prepared material, such as a material prepared by the Bonazink® process. In this case, the basic material is first chromatised or phosphatised and then coated with an organic resin.

The phosphatising process according to the present invention then leads to phosphatising of damaged areas in this prepared layer or to phosphatising of the untreated other side.

The process is applicable to immersion, spraying or spray/immersion procedures. It may be used, in particular, in the automobile industry, where treatment times between 1 and 8 minutes, in particular from 2 to 5 minutes, are conventional. Use for strip phosphatising in steel works, wherein the treatment times are between 3 and 12 seconds, however, is also possible. When used in strip phosphatising processes, it is advisable to set the bath concentrations in the upper half of each of the preferred ranges according to the present invention. For C04054 example, the zinc concentration may be from 1.5 to 2.5g/L and the concentration of free acid may be from 1.5 to 2.5 points. Galvanised steel, in particular electrolytically galvanised steel, is particularly suitable as a substrate for strip phosphatising.

As is also conventional in the case of other known phosphatising baths, appropriate bath temperatures are between 30 and 70 0 C, regardless of the field of application, the temperature range between 45 and 600C being preferred.

The phosphatising process according to the present invention is particularly intended for treating the metal surfaces mentioned prior to lacquering, for example before cathodic electrophoretic lacquering, as is conventional in the automobile industry. Furthermore, it is suitable as a preparatory treatment prior to powder lacquering, as is used for example for domestic appliances. The phosphatising process is to be regarded as one step in the technically conventional preparatory treatment chain. In this chain, phosphatising is conventionally preceded by the steps of cleansing/degreasing, intermediate rinsing and activating, wherein activating is generally performed using activating agents which contain titanium phosphate. Phosphatising according to the present invention may optionally be followed by a passivating post-treatment, with or without intermediate rinsing.

Treatment baths containing chromic acid are widely used for this type of passivating post-treatment. For reasons of industrial safety, to protect the environment and also for waste disposal reasons, however, there is a tendency to replace these chromium-containing passivating baths with chromium-free treatment baths. For this purpose, purely inorganic bath solutions, in particular those based on zirconium compounds, or else organic-reactive bath solutions, for example those based on poly(vinylphenols), are known. It is known, from German Patent application 195 11 573.2, that specific phosphatising processes may be followed by a passivating postrinsing using an aqueous solution having a pH of from about 3 to about 7 which contains from 0.001 to 10g/L of one or more of the following cations: lithium ions, copper ions and/or silver ions. This type of post-rinsing is also suitable for improving the anti-corrosive effect of the phosphatising process according to the present invention. An aqueous solution which contains from 0.002 to lg/L of copper ions is preferably used for this purpose. The copper is preferably used as the acetate. It is particularly preferred for such a post-rinsing solution to have a pH of from 3.4 to 6 and a temperature of from 20 to 500C.

An intermediate rinsing procedure using fully deionised water is generally performed between this post-passivating procedure and the lacquering procedure which conventionally follows it.

C04054 9 Examples The phosphatising process according to the present invention and comparison processes were tested on ST 1405 steel sheets and on electrolytically galvanised steel sheets such as are used in the automobile industry. The following procedure, conventional when producing car bodies, was performed as an immersion process: 1. Cleansing with an alkaline cleanser (Ridoline® 1501, Henkel KGaA), made up as 2 in town water, 55 0 C, 4 minutes.

2. Rinsing with town water, room temperature, 1 minute.

3. Activating with a titanium phosphate-containing activating agent (Fixodine@ 950, Henkel KGaA), made up as 0.1 in fully deionised water, room temperature, 1 minute.

4. Phosphatising with phosphatising baths in accordance with Table 1, 4 minutes, temperature 55 0 C. In addition to the cations mentioned in Table 1, the nitrate-free phosphatising baths contained 0.1g/L of iron(ll) and, if required, sodium ions to adjust the free acid value. Li-containing phosphatising baths did not contain sodium. All the baths contained 0.95g/L of SiF 6 2 and 0.2g/L of F- and, as accelerator, 1.7g/L of hydroxylammonium sulfate.

The free acid value was 1.0 1.1 points, the total acid value was 23 points. The value in points of free acid is to be understood to be the consumption in mL of 0.1N caustic soda solution by 10mL of bath solution, when titrated to give a pH of 3.6. Similarly the value in points of total acid is the consumption in mL to give a pH of 8.2.

Rinsing with town water, room temperature, 1 minute.

6. Post-passivating with a chromium-free passivating agent based on complex zirconium fluorides (Deoxylyte® 54 NC, Henkel KGaA) 0.25 strength in fully deionised water, pH 4.0, temperature 40 0 C, 1 minute.

7. Rinsing with fully deionised water.

8. Air-blowing with compressed air.

The area-specific weight ("layer weight") was determined by dissolution in strength chromic acid solution in accordance with DIN 50942. They were 2 The phosphatised specimen sheets were coated with a cathodic electrophoretic lacquer from BASF (FT 85-7042). The anti-corrosive effect for electrolytically galvanised steel was tested over 5 cycles in a test under changing climatic conditions according to VDA 621-415. The result is given in Table 1 as the lacquer penetration at a scratch (half-width of scratch). Table 1 also contains the results, as a "K value", of a stone impact test according to a VW standard (the smaller K, the better the lacquer adhesion).

C04054 Table I Phosphatising baths, post-passivation and anti-corrosive results (steel: salt spray test; galvanised steel: changing climate test) Bath components Comp. 1 Comp. 2 Ex. 1 Ex. 2 Ex. 3 Zn(11y 1.0 1.0 1.0 10 P4-14 14 14 14 14 M I 1.0 10. 0.04 10.07 0.05 CUI 0.007 0.007 0.007 0.007 NiI)- LOII Lacquer penetration 0.8 1.3 0.9 0.8 0.7 steel Lacquer penetration 1.4 2.2 1.6 1.6 1.4 galvanised steel [Kvalue 1 8 6 A5 0 0e 0

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Claims (10)

1. A process for phosphatising metal surfaces of steel, galvanised or alloy- galvanised steel and/or of aluminium, in which the metal surfaces are brought into contact with a zinc-containing phosphatising solution at a temperature between and 700C and in which the ratio by weight of phosphate ions to zinc ions is between

3.7 and 30, by spraying or immersing for a period between 3 seconds and 8 minutes, characterised in that the phosphatising solution does not contain lanthanum compounds but does contain 0.2 to 2g/L of zinc ions, 3 to 50g/L of phosphate ions, calculated as P0 4 1 to 70 mg/L of manganese ions, 1 to 30mg/L of copper ions and one or more accelerators selected from 0.3 to 4g/L of chlorate ions, 0.01 to 0.2g/L of nitrite ions, 0.05 to 2g/L of m-nitrobenzenesulfonate ions, 0.05 to 2g/L of m-nitrobenzoate ions, 0.05 to 2g/L of p-nitrophenol, 0.005 to 0.15g/L of hydrogen peroxide in free or bonded form, 0.1 to 10g/L of hydroxylamine in free or bonded form and 0.1 to 10g/L of a reducing sugar. 2. A process according.to claim 1 wherein the phosphatising solution also contains from 1 to 50mg/L of nickel ions and/or from 5 to 100mg/L of cobalt ions. 3. A process according to one or both of claims 1 and 2 wherein the phosphatising solution also contains from 0.2 to 1.5g/L of lithium ions.

4. A process according to any one of claims 1 to 3 wherein the phosphatising solution contains from 5 to 20mg/L of copper ions when used in an immersion process and from 2 to 10mg/L of copper ions when used in a spray process.

5. A process according to any one of claims 1 to 4 wherein the phosphatising solution also contains fluoride in amounts of up to 2.5g/L of total S 25 fluoride, of which up to lg/L is free fluoride, each being calculated as F.

6. A process according to any one of claims 1 to 5 wherein the phosphatising solution contains as accelerator from 5 to 150mg/L of hydrogen peroxide in free or bound form.

7. A process according to any one of claims 1 to 5 wherein the phosphatising solution contains as accelerator from 0.1 to 10g/L of hydroxylamine in the free or bound form.

8. A process according to claim 7 wherein the phosphatising solution also contains a total of from 0.01 to 1.5g/L of one or more aliphatic hydroxycarboxylic or aminocarboxylic acids having from 2 to 6 carbon atoms.

9. A process according to any one of claims 1 to 8 wherein the phosphatising solution contains not more than 0.5g/L of nitrate. A process according to any one of claims 1 to 9 wherein, after treating the metal surface with the phosphatising solution and before lacquering, a c^ passivating post-rinsing is performed using an aqueous solution having a pH of C04054 from 3 to 7 which contains a total of from 0.001 to 10g/L of one or more of the following cations: lithium ions, copper ions and/or silver ions.

11. A process for phosphatising metal surfaces of steel, galvanised or alloy- galvanised steel and/or of aluminium, in which the metal surfaces are brought into contact with a zinc-containing phosphatising solution at a temperature between and 70 0 C and in which the ratio by weight of phosphate ions to zinc ions is between 3.7 and 30, by spraying or immersing for a period between 3 seconds and 8 minutes, substantially as hereinbefore described with reference to any one of the examples.

12. Metal surfaces of steel, galvanised or alloy-galvanised steel and/or of aluminium, phosphatised by the process according to any one of claims 1 to 11. Dated 28 May, 1999 Henkel Kommanditgesellschaft Auf Aktien 15 Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON o *o S S S S C04054