DE19606017A1 - Zinc phosphating with low copper and manganese contents - Google Patents

Abstract

Process for phosphatizing metal surfaces of steel, zinc coated or zinc-alloy coated steel and/or of aluminium where the metal surfaces are brought into contact with a phosphatizing solution containing zinc through spraying or immersion for a time between 3 seconds and 8 minutes; the solution contains 0.2 to 3 g/l zinc ions, 3 to 50 g/l phosphate ions, calculated as PO4, 1 to 150 mg/l manganese ions, 1 to 30 mg/l copper ions and one or several accelerators.

Description

The invention relates to methods for phosphating metal surfaces with aqueous, sau Ren phosphating solutions, the zinc and phosphate ions and a maximum of 150 ppm manganese and Contain 30 ppm copper ions. The invention further relates to the use of such Process as pretreatment of the metal surfaces for a subsequent painting, esp in particular an electro-dip coating or a powder coating. The procedure is applicable for the treatment of surfaces made of steel, galvanized or alloy galvanized steel, Aluminum, aluminized or alloy-aluminized steel.

The phosphating of metals pursues the goal of being firmly adhered to the metal surface To produce metal phosphate layers that already improve the corrosion resistance and in conjunction with paints or other organic coatings to a white Significant increase in paint adhesion and resistance to infiltration in Korrosi contribute to stress. Such phosphating processes have long been known. For the Pretreatment before painting, especially electrocoating, are particularly suitable in particular the low-zinc phosphating processes, in which the phosphating solutions ver equally low levels of zinc ions of z. B. 0.5 to 2 g / l. An essential one The parameter in these low-zinc phosphating baths is the weight ratio of phosphate ions to zinc ions, which is usually in the range greater than 8 and can assume values up to 30.  

It has been shown that the use of other polyvalent cations in the zinc Phosphating baths Phosphate layers with significantly improved corrosion protection and paint adhesion properties can be trained. For example, low-zinc Process with the addition of z. B. 0.5 to 1.5 g / l of manganese ions and z. B. 0.3 to 2.0 g / l of nickel ions as a so-called trication process for the preparation of metal surfaces for the paintwork tion, for example for the cathodic electrocoating of car bodies Application.

Because nickel and the alternative cobalt can also be used from toxicological and waste water from a technical point of view, there is a need for phosphating processes, which have a similar level of performance as the trication procedures, but with essential lower bath concentrations of nickel and / or cobalt and preferably without them get along with both metals.

A phosphating solution is known from DE-A-20 49 350, which as essential components 3 up to 20 g / l phosphate ions, 0.5 to 3 g / l zinc ions, 0.003 to 0.7 g / l cobalt ions or 0.003 to 0.04 g / l copper ions or preferably 0.05 to 3 g / l nickel ions, 1 to 8 g / l magnesium ion nen, 0.01 to 0.25 g / l nitrite ions and 0.1 to 3 g / l fluorine ions and / or 2 to 30 g / l chlorine ions contains. This method therefore describes a zinc-magnesium phosphating, where the phosphating solution additionally one of the ions cobalt, copper or preferably nickel contains. Such zinc-magnesium phosphating was not possible in technology push through.

EP-B-18 841 describes a chlorate-nitrite-accelerated zinc phosphating solution, including tendency among other things 0.4 to 1 g / l zinc ions, 5 to 40 g / l phosphate ions as well as optional minimum at least 0.2 g / l, preferably 0.2 to 2 g / l, of one or more ions selected from nickel, Cobalt, calcium and manganese. Accordingly, the optional manganese, nickel or cobalt Content at least 0.2 g / l. In the exemplary embodiments, nickel contents of 0.53 and 1.33 g / l stated.  

EP-A-459 541 describes phosphating solutions which are essentially free of nickel and which contain 0.2 to 4 g / l manganese and 1 to 30 mg / l copper in addition to zinc and phosphate. Out DE-A-42 10 513 discloses nickel-free phosphating solutions which, in addition to zinc and Phos contain 0.5 to 25 mg / l copper ions and hydroxylamine as accelerator. Optional These phosphating solutions contain an additional 0.15 to 5 g / l manganese.

Meet the phosphating processes described in the last two documents the demands on corrosion protection. In practice, however, Phos phatizing baths used, which have a relatively high manganese content of about 1 g / l. These phosphating baths therefore do not meet the modern ecological requirements to work as low as possible on heavy metals, so that in the treatment of Rinse and waste water produce as little metal-containing sludge as possible.

The invention has for its object to provide a low-heavy phosphating process To provide the efficiency of the trication-phosphating process on the different materials used in automotive construction. This task will solved by a process for phosphating metal surfaces made of steel, galvanized or galvanized steel and / or aluminum, where the metal surfaces by spraying or dipping for a time between 3 seconds and 8 minutes with a zinc containing phosphating solution in contact, characterized in that the phosphating solution

0.2 to 3 g / l zinc ions
3 to 50 g / l phosphate ions, calculated as PO₄,
1 to 150 mg / l manganese ions,
1 to 30 mg / l copper ions and
one or more accelerators selected
0.3 to 4 g / l chlorate ions,
0.01 to 0.2 g / l nitrite ions,
0.05 to 2 g / l m-nitrobenzenesulfonate ions,
0.05 to 2 g / l m-nitrobenzoate ions,
0.05 to 2 g / l p-nitrophenol,
0.005 to 0.15 g / l hydrogen peroxide in free or bound form,
0.1 to 10 g / l hydroxylamine in free or bound form,
0.1 to 10 g / l of a reducing sugar
contains.

The zinc concentration is preferably in the range between about 0.3 and about 2 g / l and in particular between about 0.8 and about 1.6 g / l. Zinc levels above 1.6 g / l, for example between 2 and 3 g / l bring little advantages for the process, but can be others increase the amount of sludge in the phosphating bath. Such zinc levels can change set a working phosphating bath if, when phosphating galvanized surfaces additional zinc gets into the phosphating bath. Nickel and / or Cobalt ions in the concentration range from about 1 to about 50 mg / l for nickel and about 5 to about 100 mg / l for cobalt improve in conjunction with the lowest possible nitrate content of no more than about 0.5 g / l corrosion protection and paint adhesion to phospha animal baths that do not contain nickel or cobalt or that contain more than 0.5 g / l nitrate exhibit. This creates a favorable compromise between the performance of the phospha animal baths on the one hand and the requirements for wastewater treatment of rinsing water on the other hand reached.

From the German patent application with the file number 195 00 927.4 it is known that Lithium ions in the amount range from about 0.2 to about 1.5 g / l with zinc phosphating baths improve achievable corrosion protection. Lithium contents in the range from 0.2 to approximately 1.5 g / l and in particular from about 0.4 to about 1 g / l also have an effect in the case of the invention moderate low-metal phosphating processes favorably on the achieved corrosion protection out.  

If the process according to the invention is to be used as a spray process, copper is used te in the range from about 0.002 to about 0.01 g / l are particularly favorable. When using as Dipping processes copper contents in the range of 0.005 to 0.02 g / l are preferred.

Except for the cations mentioned above, which are incorporated into the phosphate layer or which at least have a positive effect on the crystal growth of the phosphate layer the phosphating baths usually sodium, potassium and / or aminonium ions for adjustment free acidity. The term free acid is known to the person skilled in the art on the phosphating gene bids commonly. The method of determination of the free acid and of the selected in this document Total acid is given in the example section. Free acid and total acid make you important control parameters for phosphating baths, since they have a great influence on the Have layer weight. Free acid values between 0 and 1.5 points for partial phosphate tion, with band phosphating up to 2.5 points and the total acid between about 15 and about 30 points are in the technically usual range and are within this scope suitable.

It is common for phosphating baths that should be suitable for different substrates become free and / or complex-bound fluoride in amounts up to 2.5 g / l total flow orid, of which up to 1 g / l free fluoride is added. The presence of such amounts of fluoride is also advantageous for the phosphating baths according to the invention. In the absence of fluoride the aluminum content of the bath should not exceed 3 mg / l. In the presence of fluoride higher Al contents are tolerated as a result of the complex formation, provided the concentration of not complexed Al does not exceed 3 mg / l. The use of fluoride-containing baths is therefore advantageous if the surfaces to be phosphated are at least partially made of aluminum exist or contain aluminum. In these cases it’s cheap, not complex, but only free fluoride, preferably in concentrations in the range of 0.5 to 1.0 g / l put.

For the phosphating of zinc surfaces, it would not be absolutely necessary that the Phosphating baths contain so-called accelerators. For phosphating steel surfaces However, it is necessary for the phosphating solution to have one or more accelerators contains. Such accelerators are in the prior art as components of zinc phospha  animal baths common. This is understood to mean substances that are caused by the pickling attack bind the acid produced on the metal surface chemically by be reduced yourself. Oxidizing accelerators continue to have the effect of: the pickling attack on steel surfaces released iron (II) ions to the trivalent stage oxidize so that they can precipitate as iron (III) phosphate.

The phosphating baths according to the invention can act as one or more of the accelerators contain the following components:

0.3 to 4 g / l chlorate ions,
0.01 to 0.2 g / l nitrite ions,
0.05 to 2 g / l m-nitrobenzenesulfonate ions,
0.05 to 2 g / l m-nitrobenzoate ions,
0.05 to 2 g / l p-nitrophenol,
0.005 to 0.15 g / l hydrogen peroxide in free or bound form,
0.1 to 10 g / l hydroxylamine in free or bound form,
0.1 to 10 g / l of a reducing sugar.

When phosphating galvanized steel, it is necessary that the phosphating solution contains as little nitrate as possible. Nitrate concentrations of 0.5 g / l should not be exceeded because at higher nitrate concentrations there is a risk of so-called "speck formation" consists. This means white, crater-like defects in the phosphate layer. Furthermore paint adhesion on galvanized surfaces is impaired.

The use of nitrite as an accelerator leads in particular to steel surfaces technically satisfactory results. For reasons of occupational safety (risk of development nitrous gases) it is advisable to avoid nitrite as an accelerator. For the phosphating of galvanized surfaces, this is also advisable for technical reasons. since nitrite can form nitrate, which, as explained above, is a problem with the stip pen formation and reduced paint adhesion to zinc.

Hydrogen peroxide is for reasons of environmental friendliness, for technical reasons The simplified formulation options for replenishing solutions is hydroxylamine as Accelerators particularly preferred. Sharing these two accelerators  is not advisable, however, since hydroxylamine is decomposed by hydrogen peroxide. You sit down Concentrate is hydrogen peroxide in free or bound form as an accelerator ions of 0.005 to 0.02 g / l hydrogen peroxide are particularly preferred. The what can peroxide be added to the phosphating solution as such. However, it is also possible Lich to use hydrogen peroxide in bound form as compounds in the phospha Tierbad deliver hydrogen peroxide by hydrolysis reactions. Examples of such connections are persalts such as perborates, percarbonates, peroxosulfates or peroxodisulfates. As another Sources of hydrogen peroxide come from ionic peroxides such as alkali metal peroxides oxides into consideration. A preferred embodiment of the invention is that in the Phosphating in the immersion process a combination of chlorate ions and hydrogen per oxide is used. In this embodiment, the concentration of chlorate can be exemplified in the range of 2 to 4 g / l, the concentration of hydrogen peroxide in the range of 10 up to 50 ppm.

The use of reducing sugars as accelerators is known from US-A-5 378 292. In the context of the present invention, they can be used in amounts between about 0.01 and about 10 g / l, preferably used in amounts between about 0.5 and about 2.5 g / l. Examples Such sugars are galactose, mannose and especially glucose (dextrose).

Another preferred embodiment of the invention is as an accelerator To use hydroxylamine. Hydroxylamine can be used as a free base, as a hydroxylamine complex, as Oxime, which is a condensation product of hydroxylamine with a ketone, or in Form of hydroxylammonium salts can be used. If you add free hydroxylamine Phosphating bath or a phosphating bath concentrate too, it becomes due to the acid cha of these solutions are largely present as a hydroxylammonium cation. In a ver When used as a hydroxylammonium salt, the sulfates and the phosphates are particularly suitable net. In the case of the phosphates, the acid salts are preferred due to the better solubility. Hydroxylamine or its compounds are added to the phosphating bath in such quantities set that the calculated concentration of free hydroxylamine between 0.1 and 10 g / l, is preferably between 0.3 and 5 g / l. It is preferred that the phosphating baths as contain only accelerator hydroxylamine, at most together with a maximum of 0.5 g / l nitrate Accordingly, in a preferred embodiment, phosphating baths are used which  none of the other known accelerators such as nitrite, oxo anions from halo genes, contain peroxides or nitrobenzenesulfonate. Reduce as a positive side effect Hydroxylamine concentrations above about 1.5 g / l increase the risk of rust formation insufficiently flooded areas of the components to be phosphated.

In practice, it has been shown that the hydroxylamine accelerator also slowly enters can be activated if there are no metal parts to be phosphated in the phosphating bath to be brought. It has surprisingly been found that the inactivation of the hydroxylamine can be significantly slowed down if you add one or more to the phosphating bath re aliphatic hydroxy or amino carboxylic acids with 2 to 6 carbon atoms in one Ge total amount of 0.01 to 1.5 g / l added. The carboxylic acids are preferably selected from glycine, lactic acid, gluconic acid, tartronic acid, malic acid, tartaric acid and citric acid, citric acid, lactic acid and glycine are particularly preferred.

When the phosphating process is applied to steel surfaces, iron goes in the form of Iron (II) ions in solution. If the phosphating baths according to the invention are not substances contain that have an oxidizing effect on iron (II), the divalent iron only goes into Result from air oxidation into the trivalent state, so that it is called ferric phosphate can fail. This is the case, for example, when using hydroxylamine. Therefore iron (II) contents can build up in the phosphating baths, which are well above the Ge hold lying, which contain oxidizing agent-containing baths. In this sense, iron (II) - Concentrations up to 50 ppm normal, with values up to shortly in the production process 500 ppm can occur. Such eggs are for the phosphating process according to the invention Sen (II) concentrations are not harmful. When mixed in hard water, the phosphating agents can continue to bath the hardness cations Mg (II) and Ca (II) in a total concentration up to 7 mmol / l. Mg (II) or Ca (II) can also be used in the phosphating bath in quantities up to 2.5 g / l can be added.

The weight ratio of phosphate ions to zinc ions in the phosphating baths can vary within a wide range, provided it is in the range between 3.7 and 30. A weight ratio between 10 and 20 is particularly preferred. For the indication of the phosphate concentration, the total phosphorus content of the phosphating bath is considered to be in the form of phosphate ions PO₄ ^3- . Accordingly, the known fact that the pH values of the phosphating baths, which are usually in the range from about 3 to about 3.6, only a very small part of the phosphate is actually in the form of the triple negative charged anions. 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 smaller amounts of undissociated phosphoric acid and double negatively charged hydrogen phosphate anions.

Phosphating baths are usually sold in the form of aqueous concentrates which are adjusted to the application concentrations on site by adding water. For reasons of stability, these concentrates can contain an excess of free phosphoric acid, so that when diluted to a bath concentration, the value of the free acid is initially too high or the pH is too low. By adding alkalis such as sodium hydroxide, sodium carbonate or ammonia, the value of the free acid is reduced to the desired range. Furthermore, it is known that the free acid content during use of the phosphating baths can increase over time due to the consumption of the layer-forming cations and, if appropriate, through decomposition reactions of the accelerator. In these cases it is necessary to readjust the value of the free acid to the desired range from time to time by adding alkalis. This means that the contents of alkali metal or ammonium ions in the phosphating baths can fluctuate within wide limits and tend to increase over the course of the service life of the phosphating baths due to the dulling of the free acid. The weight ratio of alkali metal and / or ammonium ions to zinc ions, for example, can therefore be very low in freshly prepared phosphating baths, for example <0.5 and in extreme cases even 0, while it usually increases over time due to bath maintenance measures, so that the ratio <1 and can take values up to 10 and larger. Low-zinc phosphating baths generally require additives of alkali metal or ammonium ions in order to be able to adjust the free acid to the desired value range at the desired weight ratio PO₄ ^3- : Zn <8. Analogous considerations can also be made about the quantitative ratios of alkali metal and / or ammonium ions to other bath components, for example phosphate ions.

In the case of lithium-containing phosphating baths, the use of is preferably avoided Sodium compounds to adjust the free acid, because of too high sodium concentration  the beneficial effect of lithium on corrosion protection is suppressed. In this Traps are preferably used to adjust the free acid basic lithium compound fertilize. In the alternative, potassium compounds are also suitable.

In principle, it does not matter in what form the layer-forming or layer-influencing Cations are introduced into the phosphating baths. However, nitrates should be avoided in order to not to exceed the preferred upper limit of the nitrate content. Preferably you bet the metal ions in the form of such compounds that no foreign ions in the phosphating solution enter the solution. It is therefore most favorable to use the metals in the form of their oxides or their carbo to use nate. Lithium can also be used as sulfate, copper preferably as acetate will.

Phosphating baths according to the invention are suitable for phosphating surfaces Steel, galvanized or galvanized steel, aluminum, aluminized or alloy aluminized steel. The term "aluminum" includes the technically common aluminum alloys such as AlMg0.5Si1.4. The materials mentioned can - as is becoming increasingly common in automotive engineering - also coexist.

Parts of the body can also consist of pre-treated material such as this for example using the Bonaz® process. Here the basic material becomes next chromated or phosphated and then coated with an organic resin tet. The phosphating process according to the invention then leads to phosphating Damage to this pretreatment layer or to untreated backs.

The process is suitable for use in immersion, spray or spray / immersion processes. It can be used in particular in automobile construction, where treatment times between 1 and 8 minutes, especially 2 to 5 minutes, are usual. Use in band phosphatics tion in the steel mill, with treatment times between 3 and 12 seconds, is dependent but also possible. It is recommended for use in tape phosphating processes worth the bath concentrations in the upper half of the preferred according to the invention Areas. For example, the zinc content can range from 1.5 to 2.5 g / l the free acid content is in the range of 1.5 to 2.5 points. As a substrate for the  Strip phosphating is particularly suitable for galvanized steel, in particular electrolytically ver zinc-coated steel.

As is also common with other phosphating baths of the prior art, they are suitable neten bath temperatures regardless of the application between 30 and 70 ° C, the Temperature range between 45 and 60 ° C is preferred.

The phosphating process according to the invention is in particular for the treatment of the named Metal surfaces before painting, for example before a cathodic electrot also painted, as is common in automotive engineering. It is still suitable as a front treatment before powder coating, such as that used for household appliances becomes. The phosphating process is part of the technically usual pretreatment chain to see. In this chain, the steps of phosphating are usually Reini gene / degreasing, rinsing and activation upstream, the activation more common done with titanium phosphate-containing activating agents. The phosphatie according to the invention passivation, with or without intermediate rinsing, if necessary, a passivating aftertreatment consequences. Treatments containing chromic acid are suitable for such a passivating aftertreatment baths widely used. For reasons of work and environmental protection as well as for disposal However, there is a tendency to pass these chromium-containing passivation baths with chromium-free be to replace action pools. For this purely inorganic bath solutions, especially on the Basis of zirconium compounds, or also organic reactive bath solutions, for example on Basis of poly (vinylphenols), known. From the German patent application with the file character 195 11 573.2 is known, certain phosphating processes a passivating Rinsing with an aqueous solution with a pH in the range from about 3 to about 7 to follow, which contains 0.001 to 10 g / l of one or more of the following cations: Lithium ions, copper ions and / or silver ions. Such a rinse is also suitable to improve the corrosion protection of the phosphating process according to the invention. Before an aqueous solution containing 0.002 to 1 g / l copper ions is preferably used for this. The copper is preferably used as acetate. One of the is particularly preferred like rinse solution that has a pH in the range of 3.4 to 6 and a temperature in the Has range of 20 to 50 ° C.

Between this post-passivation and the painting that usually follows usually an intermediate rinse with deionized water.

Embodiments

The phosphating and comparison methods according to the invention were carried out on Stahlble Chen ST 1405 as well as on electrolytically galvanized steel sheets, such as those used in automobile construction Ver find application, checked. The following, more common in body production, Ver Driving course executed as a diving process:

• 1.Clean with an alkaline cleaner (Ridoline® 1501, Henkel KGaA), batch 2% in City water, 55 ° C, 4 minutes.
• 2. Rinse with city water, room temperature, 1 minute.
• 3. Activation with an activating agent containing titanium phosphate (Fixodin® 950, Henkel KGaA), approach 0.1% in deionized water, room temperature, 1 minute.
• 4. Phosphating with phosphating baths according to Table 1, 4 minutes, temperature 55 ° C.
  In addition to the cations listed in Table 1, the nitrate-free phosphating baths contained 0.1 g / l of iron (II) and, if necessary, sodium ions to adjust the free acid. Li-containing phosphating baths did not contain sodium. All baths contained 0.95 g / l SiF₆- and 0.2 g / l F⁻ as well as 1.7 g / l hydroxylammonium sulfate as accelerators.
  The free acid score was 1.0-1.1 and the total acid was 23-25. The free acid score is understood to mean the consumption in ml of 0.1 normal sodium hydroxide solution in order to titrate 10 ml of bath solution up to a pH of 3.6. Similarly, the total acid score indicates consumption in ml up to a pH of 8.2.
• 5. Rinse with city water, room temperature, 1 minute.  
• 6. Post-passivation with a chrome-free post-passivation agent based on complex Zirconium fluoride (Deoxylyte® 54 NC, Henkel KGaA) 0.25% in deionized water, pH 4.0, temperature 40 ° C, 1 minute.
• 7. Rinse with deionized water.
• 8. Blow dry with compressed air.

The mass per unit area ("layer weight") was obtained by dissolving in 5% chromic acid solution determined according to DIN 50942. It was in the range 2.5-4.5 g / m².

The phosphated test panels were coated with a cathodic dip coating from BASF (FT 85-7042) coated. The corrosion protection effect for electrolytically galvanized steel was tested in an alternating climate test according to VDA 621-415 over 5 laps. As a result, the Paint infiltration at the Ritz (half the width of the Ritz) included in Table 1. Table 1 contains also as "K values" the results of a stone chip test according to the VW standard (the smaller K, the better the paint adhesion).

The corrosion protection for steel sheets was tested with a salt spray test according to DIN 50021 (1008 Hours) checked. Table 1 shows the paint infiltration at the Ritz (half the width of the Ritz).

Claims (10)

Characterized 1. A process for phosphating metal surfaces of steel, galvanized or alloy galvanized steel and / or aluminum, in which zen the metal surfaces by fuel or diving takes for a period of between 3 seconds and 8 minutes with a zinc-containing phosphating solution in contact, characterized in that the phosphating
0.2 to 3 g / l zinc ions
3 to 50 g / l phosphate ions, calculated as PO₄,
1 to 150 mg / l manganese ions,
1 to 30 mg / l copper ions and
one or more accelerators selected
0.3 to 4 g / l chlorate ions,
0.01 to 0.2 g / l nitrite ions,
0.05 to 2 g / l m-nitrobenzenesulfonate ions,
0.05 to 2 g / l m-nitrobenzoate ions,
0.05 to 2 g / l p-nitrophenol,
0.005 to 0.15 g / l hydrogen peroxide in free or bound form,
0.1 to 10 g / l hydroxylamine in free or bound form,
0.1 to 10 g / l of a reducing sugar
contains. 2. The method according to claim 1, characterized in that the phosphating solution additional contains 1 to 50 mg / l nickel ions and / or 5 to 100 mg / l cobalt ions.   3. The method according to one or both of claims 1 and 2, characterized in that the Phosphating solution additionally contains 0.2 to 1.5 g / l lithium ions. 4. The method according to one or more of claims 1 to 3, characterized in that the phosphating solution when used in the immersion process 5 to 20 mg / l copper ions, at Spray application contains 2 to 10 mg / l copper ions. 5. The method according to one or more of claims 1 to 4, characterized in that the phosphating solution also contains fluoride in amounts of up to 2.5 g / l total fluoride, thereof contains up to 1 g / l free fluoride, each calculated as F⁻. 6. The method according to one or more of claims 1 to 5, characterized in that the phosphating solution as accelerator 5 to 150 mg / l hydrogen peroxide in free or ge bound form contains. 7. The method according to one or more of claims 1 to 5, characterized in that the phosphating solution as an accelerator 0.1 to 10 g / l hydroxylamine in free or in a bunch whose form contains. 8. The method according to claim 7, characterized in that the phosphating solution additionally a total of 0.01 to 1.5 g / l of one or more aliphatic hydroxy or aminocarbon contains acids with 2 to 6 carbon atoms. 9. The method according to one or more of claims 1 to 8, characterized in that the phosphating solution contains no more than 0.5 g / l nitrate. 10. The method according to one or more of claims 1 to 9, characterized in that after treating the metal surfaces with the phosphating solution and before painting passivation rinsing with an aqueous solution with a pH in the loading  ranges from 3 to 7, the total of 0.001 to 10 g / l of one or more of the following Cations contain: lithium ions, copper ions and / or silver ions.