DE3423990A1 - PEROXIDE-FREE CHROME (III) PASSIVATION SOLUTION AND METHOD FOR PASSIVATING SUBSTRATES WITH THIS SOLUTION - Google Patents

Description

Aqueous acidic chromium passivation solutions are found industrially Widely used to increase the corrosion resistance and appearance of various susceptible Metal surfaces, including surfaces made of zinc, zinc alloys, cadmium, cadmium alloys, and the like to improve. Such passivation solutions can be controlled to have a yellow or blue glossy coating on the surface give, of which the latter simulates a chrome deck coating.

The chromium passivation solutions usually contained Chromium (VI) ions, but these have been replaced by chromium (III) ions in recent years because chromium (III) ions containing wastewater can be treated more easily and effectively. Although initially the chromium (III) passivation solutions were less effective than the usual chromium (VI) passivation compositions, one is through research and development into chromium (III) passivation compositions that produce acceptable passivation films give on a variety of susceptible metal substrates. Typical for such procedures are described in the assignee of the present application's U.S. Patents 4,359,345; 4,359,346, 4,359,347, 4,359,348, 4,349,392, and 4,367,099; the teachings of this PS are, insofar as their content is contrary

status of the present application is relevant, by being mentioned in this description. examples for are other known compositions and methods for treating zinc and zinc alloy surfaces those disclosed in: U.S. Patents 2,393,663,

2 559 878, 3 090 710, 3 553 034, 3 755 018, 3 795 549,

3 843 430, 3 880 772, 3 932 198, 4 126 490, 4 171 231 and 4,263,059, GB-PS 586 517 and 1,461,244 and DE-PS 2,526,832.

Chromium passivation solutions of the kinds used industrially are used and are described in the above-mentioned PS, contain constant oxidizing agents from Peroxide type, particularly hydrogen peroxide, as one necessary component to produce acceptable passivation films. A constant problem with such Peroxide-type passivation solutions are associated with a high rate of consumption and a relatively rapid loss the peroxide oxidizing agent, which requires frequent replenishment and, because of the rapid rise in pH, careful Make control and adjustment of the same necessary. The peroxide consumption is partly based on its presence of various activating metal ions in the solution as well as of contaminating metal ions such as Zinc, Cadmium and Iron, for example, which are introduced by dissolving the metal from the substrates being treated

den and which tend to the decomposition of the oxidizing agent to catalyze. The frequent replenishment of hydrogen peroxide is not only time consuming, it is also relatively expensive. Such depletion of the solution of peroxide oxidizer occurs even if the bathroom is out of order overnight or over the weekend between shifts.

The advent of rapid treatment of metal surfaces, such as zinc, in which the aqueous acidic chromium passivation solution on the metal surface for short times, such as 1 to 10 seconds sprayed, has the problem exacerbated because of the loss of the peroxide component further increases with spray application; in addition, volatilization and pollution of the surrounding atmosphere created inadmissible workplace conditions. Quick dip application, at which passivation solution jets are directed against the surface to be treated, result also in an excessive loss of peroxide oxidizing agent.

When machining workpieces with openings that are not provided with a coating or on which no metal, e.g. zinc, has been electrodeposited, of which pipes are an example, causes dipping in a chromium passivation solution

Peroxide type quickly rusts the inside of the pipe within just a few seconds, leaving rust stains arise and peroxide oxidizers in the course of its Reacts with the exposed ferrous metal on the inside of the pipe is excessively consumed.

The invention is based on the object of a chromium (III) passivation solution which contains an oxidizing agent which is not of the peroxide type, is relatively low in volatility and is economical, no vapors polluting the environment are developed and in Sehnell passivation process can be used without incurring an undesirable loss of oxidizing agent; the solution is supposed to passivate of workpieces that have bare iron or steel surfaces, such as pipes and even serve to passivate the bare surfaces instead of oxidizing them quickly. In addition, a Method for using the solution indicated in a simple, economical and easily controllable manner will.

The object is achieved by the solution of claim 1 and the method of claim 19. Preferred Embodiments are specified in the subclaims.

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Summary of the invention:

The advantages to which the invention leads are achieved from the compositional aspect by an aqueous one acidic chromium passivation solution containing: chromium ions, which are practically completely in the trivalent state, in an amount of about 0.05 g / l to saturation; Hydrogen ions to achieve a pH of from about 1.2 to about 2.5; Nitrate ions as the main oxidizing agent in an amount sufficient to activate the hydrated chromium (III) ions so that they become a Forming a chromate film on the substrate to be treated; and at least one additional metal ion from the group iron, Cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, cerium and lanthanide mixtures, as well as mixtures thereof, in one Amount sufficient to activate the bath and apply a chrome passivation film of the desired appearance the treated substrate, the solution may optionally but what is preferred also contain: halogen ions to give the coating additional hardness; one Bath-soluble and compatible silicate compound in an amount that improves the corrosion resistance of the passivation film and gives hardness; a bath soluble and compatible organic carboxylic acid in an amount that gives initial hardness and clarity to the passivation film; as well as a wetting agent such as Blancol N from GAF Corporation, that is a condensation product of an alkylnaphthalene

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sulfonate and formaldehyde. In addition, Dequest 2010, a phosphonate from Monsanto, has been shown to be beneficial to To effect clarification of the film when an aged bath is contaminated with significant amounts of iron and zinc ions has been.

In accordance with the method aspects of the invention, a receptive Metal substrate with an aqueous treatment solution composition given above at a temperature in the range from about 4 to about 65 C, preferably from about 21 to about 32 C a time that is typically im Ranging from one second to about a minute or more, kept in contact to provide the desired passivation coating to educate on it. The passivated substrate can then be dried directly after removing it from the bath or, if desired, a final rinse, preferably after an intermediate rinse with water Rinsing with a dilute aqueous silicate solution usually at a temperature of about 10 to Exposed to 65 C for a time usually ranging from about a second to a minute or more, to further improve the properties of the film, after which the surface is air-dried.

Further features of the invention and advantages to which they belong lead, are preferred from the following description

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Related embodiments emerge.

Description of preferred embodiments: The invention is particularly applicable, but not limited to, the treatment of zinc coatings made from Cyanide-containing and alkaline and acidic cyanide-free baths have been electrodeposited to the treated To give substrate improved corrosion resistance and a decorative appearance. Particularly satisfactory Results are obtained on decorative zinc coatings of the glossy or semi-glossy type, although also good effects on zinc and zinc alloy substrates such as galvanized substrates, zinc injection molded parts and substrates made of cadmium or alloys mainly composed of cadmium. It is also it has been found that good results in the passivation treatment of surfaces made of aluminum, aluminum alloy, Magnesium and magnesium alloy can be obtained. Good results are also with the treatment of workpieces with free surfaces made of ferrous metal, e.g. steel, with passivation of the free surfaces at the same time as the treatment of the surface provided with a coating, e.g. a zinc coating takes place. Accordingly, the invention in its broadest sense is directed to the treatment of metal surfaces, which is sensitive to the formation of a passivation film

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are borrowed when they are after with the aqueous acidic solution of the invention and under the process parameters disclosed below.

According to the compositional aspects of the invention, the treatment solution contains chromium ions as essential components, which are largely completely in the trivalent state, hydrogen ions to achieve a pH value ranging from about 1.2 to about 2.5, nitrate ion as the essential oxidizing agent in an amount effective to activation of hydrated chromium (III) - acts to create a chromate film on the surface that is being treated form; at least one other metal ion from the group: iron, cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, Cerium and lanthanide mixtures of the rare earth metals as well as mixtures thereof in an amount which has the effect that the gelatinous chromate film is given integral hardness, and optionally, but preferably, sulfate ions, halogen ions, one or more compatible wetting agents, a bath-soluble and compatible silicate compound, as well as soluble and compatible organic carboxylic acids as hardness builders.

The trivalent chromium ions can be introduced in the form of any bath-soluble and compatible salt, such as chromium sulfate, Cr ₂ (SO ₄ ) ₃ , chromium-alum QcCr (SO ₄ ) J, chromium chloride, CrCl ₃ ,

Chromium bromide, CrBr ₃ , chromium fluoride, CrF ₃ , chromium nitrate, Cr (NO ₃ J ₃ , and the like. The chromium (III) ions can also be introduced by reducing a chromium (VI) -containing solution, preferably with sulfur dioxide or hydrogen sulfite, forming a mixture of chromium (III) ions and sulfate compounds One material of the foregoing which has been found to be particularly suitable for use in the practice of the invention is Chrometan from British Chromium.

The concentration of the chromium (III) ions in the treatment solution can range from about 0.05 g / l to saturation lie; Concentrations from about 0.2 to about 4 g / L are preferred. Typically a bath contains about 0.5 to about 2 g / l chromium (III) ions.

The treatment bath contains hydrogen ions in an amount which provides a pH of about 1.2 to about 2.5. A hydrogen ion concentration ranging from about 1.5 to about 1.8 is preferred for producing clear to pale blue passivation films. The acidification of the operating bath to the desired pH value can be done with a variety of Mineral acids and organic acids can be made, such as hydrochloric acid, formic acid, acetic acid, and propionic acid like that. Preferably the pH adjustment is done with Nitric acid and / or sulfuric acid made, with which

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at the same time the desired nitrate ions and sulfate ions are introduced into the bath. It has been found that the presence of sulfate ions favors the desired passivation of the substrate. The sulfate ions can by adding sulfuric acid and / or alkali metal or ammonium sulfate and as metal salts of the others Bath components are introduced. In general, the sulfate ion concentration ranges up to about 15 g / L, preferably amounts of about 0.5 to about 5 g / l.

Another essential part of the bathroom are those Nitrate ions as the main oxidizing agent. The nitrate ions can be in the form of nitric acid, alkali and ammonium nitrate as well as nitrates in the bath Metal ions are introduced. If desired, additional oxidizing agents can be included in small amounts but the nitrate ions themselves are preferred. The nitrate ions can be in concentrations of about 0.5 g / l is present in the bath until saturation, an amount of about 5 to about 50 g / l is preferred. Of the A certain concentration range of the nitrate ions is to a certain extent dependent on the amount of chromium (III) ions present as well as the other bath components and finally by the Process parameters prescribed. With the so-called "high-speed" processes are higher concentrations of the active ingredients required for the formation of a

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adequate passivation film in a relatively short time, such as one second to 10 seconds to effect. In the case of conventional passivation processes, on the other hand, time periods from about 10 seconds to about 1 minute, with the active ingredients in correspondingly lower Concentrations can be used.

Another essential bath component is at least one further metal ion from the group: iron, cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, cerium, lanthanide mixtures and mixtures thereof. The metal ions or mixtures of metal ions listed above are usually introduced in the form of bath soluble or compatible metal salts, including the sulfates, nitrates, halides, and the like. For economic reasons, lanthanum ions are not used in the form of a pure lanthanum compound, but rather as a mixture of salts of the metals of the lanthanide series (hereinafter referred to as "lanthanide mixture"), which contains lanthanum compounds as the predominant component. A commercially available mixture of lanthanides suitable for use in practicing the invention is Lanthanum - Rare Earth Chloride, Product Code 524 0 from Molycorp Inc. of White Plains, New York. This product has the general formula La-RECl, (6H ₀ O) and is available as an approximately 55 to 60% solution (weight percent solids)

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available. The solution is made from a concentrate of rare earth oxides containing a minimum of 46% by weight total REO, consisting of: about 60% lanthanum oxide (La ₃ O), 21.5% neodymium oxide (Nd ₃ O ₃ ) , 10% cerium oxide (CeO ₃ ), 7.5% praseodymium _{oxide (Pr 6} O ₁₁ ) and 1% other REO. The presence of such other rare earth metals in the solution does not appear to be detrimental at the low concentrations in which they are present and they can help activate the treatment solution to form the passivation film.

The concentration of the additional metal ions will be in the range from about 0.02 to about 1 g / l, preferably from about 0.1 to about 0.2 g / L controlled. It is true that such metal ions can be present in concentrations above 1 g / l, such as up to about 10 g / l can be used, but the use of such high concentrations results in dull films of one yellow hue instead of the desired clear or pale blue films. That is why the high concentrations inexpedient from the standpoint of appearance.

As another optional but preferred component, the bath contains halogen ions, including chloride, Bromide and fluoride ions which, as has been found, the Hardness of the passivation film on the treated substrate

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raise. The halogen ions or mixtures thereof can easily be in the form of any alkali metal or Ammonium salt and a salt of those listed above Metal ions are introduced. The total halogen ion concentration in the bath can normally be up to about 2 g / l; concentrations of about 0.1 are typical up to about 0.5 g / l.

Optionally, but preferably, the bath contains an organic carboxylic acid of the structural formula listed below:

(OH) _a R (COOH) _b
in which:

a is an integer from 0 to 6; b is an integer from 1 to 3; and R is alkyl, alkenyl or aryl with 1 to 6 Carbon atoms;

as well as the bath-soluble and compatible salts of the acid.

The bath-soluble and compatible carboxylic acid or its salt may be present in an amount suitable for the deposited gelatinous chromate film gives increased clarity and initial hardness. The particular concentration or concentration range of the clearing-hardening agent, if applied varies, depending on the molecular weight of the

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added acid and / or its metal salt, higher concentrations being required with increasing molecular weight are to get equivalent effect. The one required to achieve optimal clarity and hardness particular concentration is to some extent also dependent on the concentration of the silicate and the other Metal ions present in the bath are also determined, with higher concentrations as the metal ion concentration increases are to be used. In general, the additive can be organic carboxylic acid or metal salt thereof in amounts up to about 4.0 g / l can be used, quantities in the range from about 0.1 to about 1.0 g / l are typical.

The carboxylic acid additive can be used as the organic acid by itself or as any bath soluble and compatible metal salt including the alkali metal salts, ammonium salts and salts of the particular metal ions additionally present in the bath are introduced into the bath. the end For economic reasons, this additive is usually in the form of the acid itself or its sodium or potassium salt used.

As particularly suitable organic carboxylic acids that fall under the general formula given above, have proven: malonic acid, maleic acid, succinic acid, gluconic acid, tartaric acid and citric acid, of which

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Succinic acid and its salts have been found to be particularly effective.

An optional but preferred component of the treatment bath is a silicate compound which is present in an amount to provide improved corrosion protection and hardness to the passivation film on the treated substrate. The silicate compound is a bath-soluble and compatible inorganic or organic silicate or a mixture of such compounds and is in an amount of about 0.01 to about 5 g / l, calculated on SiO ₃ , preferably about 0.1 to about 0.5 g / l before. If inorganic silicates are used, concentrations above about 2 g / l in the treatment bath are unsuitable because of the tendency of the silicate with the metal ions present in the bath to form fine flaky precipitates under acidic conditions, which contribute to the instability of the bath. On the other hand, organic silicates give the bath stability and are preferred for the formation of make-up and refill concentrates because of their improved stability and longer service life.

Inorganic silicates suitable for practicing the invention include alkali metal and ammonium silicates. For economic reasons, sodium silicate [Na ₂ O (XSiO ₂ ) (x = 1-4) and potassium silicate are used

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) (y = 1-5) J preferred. Organic silicates, which are also used with a satisfactory result can include: tetramethylammonium silicate, phenyltrimethylammonium silicate, disilicate and trisilicate, and benzyl trimethyl ammonium silicate and disilicate. Such silicates that meet the purposes of the invention can be represented by the following general formula

ROR ': xSiO ₂ : yH ₂ O

in which: R is a quaternary ammonium radical which is substituted by four organic groups which are selected are from the group alkyl, alkylene, alkanol, aryl, alkylaryl or mixtures thereof; R 'either R or hydrogen; χ a number from 1 to 3 and y 0 to 15.

Such water-soluble organic silicates, their preparation and their properties are in the literature fully described, e.g., by Merrill and Spencer, "Some Quaternary Ammonium Silicates" in the Journal of Physical and Colloid Chemistry, 55, 187 (1951). Similar silicates including typical syntheses are in U.S. Patent 3,993,548. The content of these two publications is incorporated herein by mentioning them.

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The use of a small effective amount of one of the various bath-compatible wetting agents also works good results on the nature of the deposited passivation film. When a wetting agent is used it can be used in amounts up to about 1 g / l, amounts in the range from being preferred about 50 to about 100 mg / l. Suitable wetting agents for use in the treatment bath include aliphatic ones Fluorocarbon sulfonates, from 3M under the Names Fluorad available commercially, e.g. Fluorad FC 98; this is a non-foaming wetting agent and its use in an amount of about 100 mg / 1 improves the color and hardness of the passivation film. A second The class of sulfoderivatives of the succinates is a class of suitable wetting agents. An example of this class is Aerosol MA-80, which is a dihexyl ester of the sodium salt of sulfosuccinic acid, commercially available from American Cyanamid Company available. A third class of suitable wetting agents is that of the sulfonates of naphthalene, the straight-chain Alkyl naphthalene sulfonates are such as Petro Ba from Petrochemical Company.

Particularly favorable results are obtained when using polymeric wetting agents, such as the bath-soluble ones Salts of sulfated alkylphenoxy-poly (ethylene-oxy-ethanol), such as Alipal CO433 e.g. sulfonated alkylnaphthalene, such as

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Nekal BX78 and bath-soluble and compatible salts sulfonated naphthalene-formaldehyde condensates, such as Blancol N. 1-Hydroxi-ethylidene-1fl-diphosphonate (Dequest 2010), used in amounts up to about 1 g / l, has proven to be a particularly good means of clearing the passivation film proven from aged baths that contained significant amounts of contaminating zinc and iron ions, which e.g. by loosening the zinc and iron surfaces of the objects that have been treated, got into the bathroom.

In accordance with the method aspects of the invention, a chromium (III) bath, as described above, is applied to a substrate by spraying, dipping, flooding or the like. The solution can Behändlungs at a temperature in the range of about 4 to about 65 C, are preferably applied from about 21 to about 32 ⁰ C. The time that the substrate is in contact with the solution can range from about 1 second to about 1 minute or longer. In the conventional passivation process, the contact times during which the workpiece is immersed in the aqueous acidic solution are in the range of about 10 seconds to about 1 minute, depending on the desired film thickness, the required preparation (the amount of cleaning) of the substrate and the Production speed of the workpieces. Thieves-

The correct contact time required to achieve the desired passivation film is determined by the pH certainly. In general, a pH of about 1.5 usually takes about 10 to 20 seconds to get a To produce passivation film of more satisfactory Color and of good protection against corrosion. On the other hand, a pH of about 2.5 makes a contact time of it takes about 35 to about 50 seconds to arrive at a similar movie.

In the high-speed passivation process of the common types used for treating coil steel, wire and tubes in a continuous process the passivation must be performed in view of the rapid passage of the workpieces through the passivation section can be effected in a few seconds. Contact times are from only about 1 to about 10 seconds economically feasible and the aqueous solution is made by spraying or nozzling at high speed as well applied by dipping to achieve even contact. In terms of the shorter available Time the concentration of the active ingredients is increased to a comparable in the shorter time To obtain passivation film deposition.

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At the end of the passivation treatment, the object is pulled out and dried, for example by means of warm air fed into the Ural River. It is also to be considered to rinse the workpieces one or more times with water in order to remove residual passivation solution from the surfaces, after which the substrates with a dilute silicate rinse solution at a temperature in the range from room temperature to about 65 ⁰ C for the Can be contacted for periods of about 1 second to 1 minute or longer. Such dilute silicate rinsing solutions contain as their essential components at least one bath-soluble and compatible inorganic or organic silicate compound of the same type as above in connection with the silicates which have been described as suitable for use in the aqueous acidic passivation solution. The silicate compound can be present in an amount from 1 to about 40 g / l, preferably in an amount from about 5 to about 15 g / l, calculated on SiO ₂ . The substrate rinsed with silicate can be dried after being removed from the rinsing solution, for example with circulating warm air.

In order to further illustrate the invention, the following examples are based on the invention but is not limited.

example 1

A chromium (III) concentrate, designated "Concentrate A" was prepared to form an aqueous solution containing: 30 g / l of chromium (III) ions introduced as Chromium sulfate, 30 g / l citric acid, 90 g / l sodium nitrate, 11 g / l nickel ions introduced as nickel sulfate, and 30 g / l of a wetting agent, namely a polymeric alkyl naphthalene sulfonate (Blancol N from GAF). A second aqueous concentrate, designated "Concentrate B" was made made by dissolving 600 g / l sodium nitrate in water.

The above concentrates were suitable for mixing the operating baths of the following Make examples.

Example 2

An operating bath that is used for the formation of a passivation coating suitable under normal operating conditions including contact times in the range of 10 to 60 seconds was made by mixing 0.5 to about 3 volume percent of Concentrate A with about 1 to about 3 volume percent of the concentrate B prepared in water to give a series of test solutions. The pH of the operating solution was with nitric acid to a value in a range of about

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1.5 to about 2.5. The Betriebsbad was reacted with steel test panels, which were provided with a deposited from a cyanide-free acidic Zinkglanzbad zinc coating at a temperature in the range of 15 to 32 ⁰ C with agitation provided by air or by mechanical means in contact. In addition, operating solutions of the above compositions have been used for passivating fasteners galvanized in barrel plating apparatus, various pressings galvanized in the frame and long galvanized threaded pins under the conditions used in the industry.

In each case a chromium passivation film was obtained, which was clear, hard and deep blue.

It should be noted that the passivation treatment like usually after galvanizing or electrodeposition of another metal has been carried out and which for The time available for passivation treatment was largely determined by the machine cycle and the sequence of steps the workpieces passing through the passivation section of the process. To get the desired Cleaning of the workpieces before electroplating and the desired thickness of the electroplated coating to achieve, there will therefore be changes in the

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final passivation treatment of the galvanized Workpieces available time. An adaptation to this is by adjusting the pH value of the Activation solution possible so that the appropriate color and the desired corrosion protection is achieved within the specified time range available will. For example, when contact times of about 10 to about 20 seconds are available, pH becomes preferred set to about 1.5. If more time is available, e.g. from about 35 to about 50 seconds, there is a pH of about 2.5 gives equivalent results.

Example 3

An acidic passivation solution suitable for rapid application was prepared by mixing about 5 to about 10 volume percent Concentrate A and about 3 to about 10 volume percent Concentrate B of Example 1 in water. A number of operating baths were prepared and the pH was adjusted to within the range of about 1.5 to about 2 with nitric acid. The passivation solution was controlled in a temperature range of about 21 to about 32 ⁰ C.

Solutions of the type described above were for use under so-called tendon deposition conditions, "high-speed conditions", suitable and have been used in series with processes for the electroplating of

Steel coils, strips, wires and tubes used in a continuous manner. Stood under such conditions Contact times of as little as about 1 to about 10 seconds to achieve a suitable passivation treatment Disposal. The passivation solution can be sprayed under high pressure or by dipping the strip or passing object into the solution through which it is passed quickly from the inlet to the outlet, be applied.

Among the compositional and Operating parameters were galvanized workpieces under simulated tendon deposition conditions used in technology provided with a hard, clear, shiny blue passivation film.

Example 4

An aqueous acidic operating bath was created by preparing an aqueous solution containing 2% by volume of concentrate A and 3% by volume of concentrate B, as described in Example 1, was prepared and heated to a temperature of 24 ° C held. The pH of the solution was adjusted to various values using nitric acid. There were test panels and workpieces galvanized from an acidic solution using the above Solution at different pH values and in

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different times according to the usual dipping method and movement by means of air as well as according to the drum method passivated.

The treated articles were subjected to a salt spray test with 5% saline solution for white corrosion, subjected. A pH of 1.5 and a treatment time of about 10 to about 20 seconds in the above Tests were carried out for both rack-treated panels and drum-coated workpieces as found optimal. A pH of about 1.7 to about 2 with a treatment time of about 15 to about 25 seconds were found to be optimal for the above compositional and process parameters. At a pH of 2 to about 2.5 was achieved in contact times of about 25 to about 40 seconds, optimal protection. In each case, test panels that had been rack treated had 5% salt spray resistance in the Ranges from about 16 to 24 hours while drum treated test pieces have 5% salt spray resistance from about 8 to about 16 hours.

Example 5

Aqueous, acidic operating solutions for tendon treatment of workpieces were produced by the formation of aqueous solutions containing 10% by volume of concentrate A and

contained varying amounts of concentrate B in the range from about 2 to about 10% by volume. Adjusting the pH different values were brought about by the addition of nitric acid.

Steel test panels measuring 10.15 15.25 cm, the Had been galvanized in an acid sulphate-bright zinc bath, were controlled with passivation solutions under different pH values, treatment times and various amounts of concentrate B. The tests were carried out under conditions equivalent to the Passage of galvanized coil material or galvanized strip material through a solution tank with a linear Mimicked speeds of about 45.7 to 61 m / min. This was achieved using a container with a cell immersed in it, in which a nozzle arrangement was built, which one down directed stream of solution at a rate of 94.6 l / min onto a stationary one suspended in the cell Plate caused. The treated test panels were subjected to a salt spray test with 5% saline solution for white corrosion subjected. The results obtained at the various conditions and concentrations are listed in Table 1 below.

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Table 1

IT , 0 Handling
time, s Concentrate B
Vol% corrosion
5% salt spray, h. 1.5 , 0 2 - 2-3 8-10 1.5 2 - 6-10 20 - 24 1.8-2 5 - 2-3 8-10 1.8-2 5 - 6-10 20 - 24 Example 6 - 4th - 4th - 10 - 10

An operating solution was prepared by forming an aqueous solution containing 2% by volume of Concentrate A and Contained 3% by volume of concentrate B of Example 1 and adjusted to a pH of about 2 with nitric acid was. The plant bath was divided into four separate samples and each sample was divided into different amounts Iron ions in conjunction with 3 g / l zinc ions added to an aged bath of the technique, which is made with zinc and Iron ions contaminated after prolonged use, mimic them. Test plates that are galvanized in an acid bath were immersed in each sample bath for about 20 seconds, and the resulting passivation film was observed. The clarifying agent Dequest was added to two of the sample baths in 2010. The results that are in Table 2 summarized show the advantage of is achieved by using this additive in the presence of high iron contamination.

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Zn ions, Table 2 Appearance Fe ions, ppm 3 Dequest
g / iq / i decently blue 25-50 3 0 decently blue 25-50 3 0.1-0.4 cloudy, cloudy 150 3 0 decently blue 150 0.1-0.4

Example 7

A powdery dry concentrate was produced, that contained: 54 wt .-% chromium sulfate (Chrometan), 2% by weight of wetting agent (Alipal CO433), 3% by weight of wetting agent (Nekal BX78), 10% by weight citric acid, 20% by weight sodium metasilicate and 10% by weight nickel sulfate hexahydrate.

It was a working solution by dissolving 15 g / l des dry concentrate in water and adding 50 g / l sodium nitrate. The working solution was with Nitric acid adjusted to a pH of about 1.7 to about 2.

Test panels were galvanized in an acidic zinc chloride bath, rinsed with water and then for 15 to Immersed in the manually moved working solution for 20 seconds. The plates were then rinsed with water and using

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Hot air dried. Examination of the test panels showed that a clear blue passivation film appeared of the zinc surface, similar to that obtained in Examples 2, 3 and 4.

The embodiments described above are preferred. Of course, many different modifications, changes and deviations are possible, without departing from the scope of the invention.

Claims (20)

Expectations 1. Aqueous acidic peroxide-free solution for treatment 'receptive metal substrates for imparting a chromium passivation film, characterized in that it contains the following components: chromium ions, which are essentially completely in the trivalent state; Hydrogen ions to achieve an acidic pH; Nitrate ions as the main oxidizing agent in an amount sufficient to activate the hydrated chromium (III) ions so that they become a Forming a chromate film on the substrate; and at least one European Patent Attorneys Approved representatives helmet European Patent Office Deutsche Bank AG Hamburg, No. 05/28 4Θ7 (BbZ 20070000) Poetecheck Hamburg 2842-206 Dresdner Bank AO Hamburg, No. Θ33ΘΟ3Β (BIjZ 2OO 8OO σο) additional metal ion from the group: iron, cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, cerium, Lanthanide mixtures as well as mixtures thereof in an amount sufficient for the formation of the chromate passivation film to activate effectively. 2. Solution according to claim 1, characterized in that it contains the chromium (III) ions in an amount of about 0.05 g / l to saturation. 3. Solution according to claim 1, characterized in that it contains the chromium (III) ions in an amount of about 0.2 to contains about 4 g / l. 4. Solution according to claim 1, characterized in that it contains the chromium (III) ions in an amount of about 0.5 contains up to about 2 g / l. 5. Solution according to claim 1, characterized in that it has a pH of about 1.2 to about 2.5. 6. Solution according to claim 1, characterized in that it has a pH of about 1.5 to about 1.8. 7. Solution according to claim 1, characterized in that it contains the nitrate ions in an amount of about 0.5 g / l contains until saturation. 8. Solution according to claim 1, characterized in that it contains the nitrate ions in an amount of about 5 to about Contains 50 g / l. 9. Solution according to claim 1, characterized in that it contains the additional metal ion in an amount of from about 0.02 to about 1 g / l. 10. Solution according to claim 1, characterized in that it contains the additional metal ion in an amount of about Contains 0.1 to about 0.2 g / l. 11. Solution according to claim 1, characterized in that it additionally contains sulfate ions in an amount up to about 15 g / l. 12. Solution according to claim 1, characterized in that it also contains sulfate ions in an amount of about
Contains 0.5 to about 5 g / l. 13. Solution according to claim 1, characterized in that it additionally contains halogen ions in an amount up to
contains about 2 g / l. 14. Solution according to claim 1, characterized in that it also contains halogen ions in an amount of about Contains 0.1 to about 0.5 g / l. 15. Solution according to claim 1, characterized in that it additionally contains an organic carboxylic acid in an amount of up to about 4 g / l. ( 16. The solution according to claim 1, characterized in that it additionally contains a bath-soluble and bath-compatible silicate in an amount of up to about 5 g / l, calculated on SiO ₂ . 17. Solution according to claim 1, characterized in that it also contains at least one bath-soluble and compatible Contains wetting agents in an amount up to about 1 g / l. 18. Solution according to claim 1, characterized in that they additionally contain at least one bath-soluble and compatible wetting agent in an amount of about 50 to contains about 100 mg / l. 19. method of treating a susceptible metal substrate; to give it a chromate passivation film, characterized in that the substrate with an aqueous acidic peroxide-free solution according to any one of claims 1 to 18 at one temperature in the range of about 4 to about 65 ° C, sufficient time for a passivation film to form thereon Brings contact. 20. The method according to claim 19, characterized in that one controls the temperature of the solution so that it is in the range of about 21 to about 32 ⁰ C.