SE457642B - ACID WATER SOLUTION FOR BETWEEN METAL SURFACES - Google Patents

Abstract

Metal surfaces, particularly zinc and zinc alloy surfaces, are treated with an aqueous acidic solution containing effective amounts of A) hydrogen ions to provide a pH of about 1.5 to about 2.2, B) an oxidizing agent, C) at least one of iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum, lanthanide mixtures or cerium ions or mixtures thereof, or instead of C) iron and cobalt ions. Other treating solutions also incorporate D) chromium ions substantially all of which are in the trivalent state, and iron ions in combination with an additional metal from C) or cerium ions, or A), B), C) and D) and F), a bath soluble and compatible silicate compound or A), B), C) and D) and G), a mixture of 1-hydroxyethylidene-1,1 diphosphonic acid and citric acid or mixtures of A), B), C) and D) with two or more of E), F) and G). The treating solution may optionally further contain halide ions and a wetting agent. )

Description

457642 10 15 20 25 30 35 for an inferior corrosion protection in comparison with pickling film of yellow hexavalent chromium. This problem has been further accentuated by a transition from conventional cyanide-based zinc and cadmium plating processes to acidic and alkaline non-cyanide-based electroplating baths, which produce metal coatings that are less receptive to chromium pickling treatments.

Typical known compositions and methods for treating metal surfaces are found in U.S. Patent Nos. 2,393,663, 2,559,878, 3,090,710, 3,553,034, 3,755,018, 3,795,549, 3,880,772, 3,932,198, 4,126,490. , 4,171,231, GB patents 586,517 and 1,461,244 and DE patent 2,526,832.

In its broadest sense, the invention relates to an acidic aqueous solution for use in the treatment of receptive metal substrates for imparting to them a pickling film, which aqueous solution contains A) hydrogen ions corresponding to a pH of 1.2 - 2.5, B) a peroxide in an amount of 1 -20 g / l, based on an equivalent weight of hydrogen peroxide and C) chromium ions, most of which are present in the trivalent state, in an amount from 0.05 g / l up to the amount of saturation, which is characterized in that it also contains a combination of 'x D) iron ions in an amount of 0.05 - 0.5 g / l and E) ions of at least one of cobalt, nickel, molybdenum, manganese, minium, lanthanum, lanthanide mixture or cerium ions or mixtures thereof in an amount of 0.02 - 1.0 g / l. The invention is particularly applicable to, but not limited to, the treatment of alkaline and acidic, non-cyanide-based zinc and cadmium electroplates to impart improved corrosion protection to these. Particularly satisfactory results are obtained on decorative zinc and cadmium electroplating of the shiny and semi-shiny types, although improved effects are also obtained on zinc and zinc alloy substrates, such as galvanized zinc substrates, zinc die castings and cadmium substrates. mium or alloys of cadmium predominantly consisting of cadmium. Although the invention in its various aspects described herein is particularly directed to the treatment of zinc and zinc alloy surfaces, it has been found that favorable results are also obtained in the treatment of aluminum, aluminum alloy, magnesium and magnesium alloy surfaces to form a pickling film. or coating thereon. The invention is therefore broadly focused on the treatment of metal surfaces which are susceptible to the formation of a pickling film during the treatment with the solution according to the invention in accordance with the process parameters stated.

In accordance with the process of the invention, zinc, cadmium, zinc alloy, cadmium alloy, aluminum and magnesium surfaces are treated with the aqueous acidic treatment solution at a temperature between 4 - 66 ° C for a time which is usually between about 10 seconds. and up to about 1 minute to form the desired pickling film.

A treatment solution according to the present invention can be applied to a substrate to be treated by spraying, dipping, immersion or the like for a sufficient time to form the desired pickling film. The treatment solution is set at a temperature between about 4 - 66 ° C, preferably a temperature of about 21 - 32 ° C. Temperatures, above about 32 ° C, tend to cause a rapid loss of peroxide-type oxidizing agents when used, while temperatures below about 2106 lower the activity of the solution, and require increased treatment times to achieve a pickling film of the same. thickness or color intensity that can be achieved at the higher temperatures for shorter periods of time. Usually, treatment times of about 20 or 30 seconds up to about 1 minute are satisfactory and treatment times of about 30 seconds are usually preferred.

The solution used can be conveniently prepared by using a concentrate containing the active ingredients with the exception of any cerium ions and peroxide, which is adapted to be diluted with water, to which cerium ions, if used, and peroxide is added separately to form a solvent peroxide, to give a bath containing the active components within the specified concentration ranges. Peroxide, such as e.g. hydrogen peroxide, is supplied separately preferably in a commercially available and contains about 35 - hydrogen peroxide. snake, which is 40% by volume. The solution contains hydrogen ions in a quantity which gives a pH of 1.2 - 2.5, preferably a pH of 1.5 - 2.0. the solution to achieve the desired pH with various mineral acids and organic acids such as nitric acid, hydrochloric acid, formic acid, of which sulfuric acid, The acidification of can be accomplished if sulfuric acid, acetic acid or propionic acid, nitric acid and hydrochloric acid are preferred. The presence of sulphate ions in the solution has been found to be favorable in achieving the desired pickling of the substrate and E can be added by sulphate acid addition or sulphate salts of other solution components. The sulphate ion concentration can amount to up to 15 g / l, preferably to 0.5 - 5 g / l.

The solution contains as oxidizing agents peroxides which are bath-compatible, of which peroxides including hydrogen peroxide and metal peroxides such as alkali metal peroxides are preferred. Hydrogen peroxide of a commercial grade containing about 25-60% by volume of peroxide constitutes the preferred material. Other peroxides that can be used include zinc peroxide. 10 15 20 25 30 35 457642 The concentration of the peroxide is between 1 - 20 g / l, preferably between 3 - 7 g / l, calculated on a weight equivalent in relation to hydrogen peroxide.

The chromium ions, mainly in trivalent form, can be added in the form of some salt soluble and compatible salt such as chromium sulphate (Cr2 (SO4) 2), chromium alum (KCr (SO4) 2), chromium chloride (CrCl3), chromium bromide (CrBr3) , chromium fluoride (CrF3) or chromium nitrate (CrNO3).

The trivalent chromium ions can also be added by a reduction of a solution containing hexavalent chromium ions using a suitable reducing agent of any of the types known to give a substantially complete stoichiometric reduction of all hexavalent chromium to a trivalent state.

The concentration of the trivalent chromium ions in the treatment solution can vary from as little as 0.05 g / l up to the amount of saturation with quantities of about 0.2 - 2 g / l as preferred. Typically, the solution contains about 0.5 - 1 g / l of trivalent chromium ions.

The treatment solution contains iron ions in an amount of 0.05 - 0.5 g / l with concentrations of 0.1 - 0.2 g / l as preferred.

The iron in the solution is predominantly in a trivalent state due to the presence in the solution of oxidizing agent, although they can be added in the form of divalent iron. As is the case with the chromium ions, the iron ions can be added to the solution in the form of some soluble and compatible iron salt, such as ferrous ammonium sulphate, ferrous sulphate, ferrous nitrate or iron halide salts. Of these, ferrous sulphate constitutes the preferred material for economic reasons and because the use of this salt also contributes to introducing the desired sulphate ions into the solution.

In addition to the iron ions, the solution further contains at least one more metal ion selected from the group consisting of cobalt, nickel, molybdenum, manganese, aluminum, lanthanide mixture or cerium ions or mixtures thereof. Said metal ions or mixtures of metal ions are suitably supplied as in the case of the iron ions via soluble and compatible metal salts including sulphates, nitrates or halide salts. For economic reasons, the lanthanum anions are preferably not supplied as pure lanthanum compounds but as a mixture of rare earth metals of the metals of the lanthanide series (hereinafter referred to as "lanthanide mixture") containing lanthanum compounds as the predominant component.

A commercially available lanthanide mixture suitable for use in the practice of the invention is "Lanthanum-Rare Earth Chloride", product designation 5240 available from Molycorp, Inc. of White Plains, New York, USA. This product has the general formula La-RECl3. 6H - 60 The solution is prepared from a rare earth metal oxide (REO) concentrate containing at least 46% by weight REO comprising about 60% lanthanum oxide (Laz 20 and is available as a solution containing about 55% by weight solids.% 03), 21, 5% neodymium oxide (Nd2O3), 10% cerium oxide (CeO2), 7.5% praseodymium oxide (Pr 6011) and 1% of the remaining REO.

The presence of such other rare earth metals in the solution does not appear to have any detrimental effect at the low concentrations at which they are present, and may further contribute to the activation of the treatment solution in the formation of the pickling film.

The concentration of the metal ions E) for activation of the solution is adjusted to a concentration of 0.02 - 1 g / l with concentrations of 0.1 - 0.2 g / l being preferred.

When a pickling film with a light yellow appearance is desired, the treatment solution contains cerium ions in an amount sufficient to further activate the solution and impart a clear yellowish color to the pickling film on the treated substrate, preferably a shimmering light yellow color. The cerium ions can be added in the form of some soluble and compatible cerium salt including cerium sulphate (Ce (SO 4) 2 L 4 H 2 O, halide salts such as cerium chloride (CeCl 3 .6H 2 O) or nitrate salts such as cerium nitrates: at least some of the cerium ions solution in the tetravalent state 457642 to impart to the pickling film the characteristic yellow color of tetravalent cerium ion Peroxides act as reducing agents under the acidic conditions prevailing in the liquid of the treatment solution and reduce some of the tetravalent cerium ions to a trivalent state. However, the peroxides change from being a reducing agent to an oxidizing agent at the interface between the substrates to be treated due to the higher pH prevailing at the interface and oxidize at least some of the trivalent cerium ions to the tetravalent state deposited in the film and this gives it the characteristic yellow color.

Thus, when using oxidizing agents such as hydrogen peroxide, all the cerium ions can, if desired, be added from the beginning in the trivalent state, some of which are oxidized to the tetravalent state at the interface to the substrate. The pickling film may contain a mixture of trivalent and tetravalent cerium compounds and the yellow intensity of the film is dictated by the concentration of tetravalent cerium compounds present. In addition to imparting a light yellow color to the pickling film, the cerium ions also improve the corrosion resistance of the treated surface. Due to solubility difficulties, the cerium sulphate compound is added to the solution preferably in the form of an acidic solution, such as dilute hydrochloric acid solution containing the cerium sulphate dissolved therein.

For cost reasons, the cerium ions are preferably supplied as a commercially available mixture of rare earth metal salts of metals in the lanthanide series, which contain cerium compounds as the main component. One such commercially available material is a cerium chloride solution containing about 46% solids, of which CeCl 3 .6H 2 O dominates. The cerium chloride solution is derived from a rare earth metal oxide (REO) concentrate sold by Molycorp, Inc. of White Plains, New York, USA, under the product designation 5310 containing at least 99% total REO, of which CeO2 is 96%, La2O3 is 2, 7%, NÖ203 is 1% and Pr6O11 is 0.3%. A cerium sulphate solution is commercially available from the same source containing about 42% solids, of which Ce (SO 4) 2 .H 2 O predominates and which is also prepared from product 5310 containing other rare earth metal compounds in similar minor amounts. As mentioned above, the low solubility of cerium sulfate makes it desirable to add this component to the solution in the form of an aqueous acidic solution. Normally, the use of cerium sulfate in the high concentrations required to form a concentrate with other active ingredients other than the peroxide component causes a precipitation of the cerium compound. Even when cerium is added as a halide or nitrate salt, the presence of sulphate ions in the concentrate and entrained by other constituents causes precipitation.

The cerium concentrate is therefore preferably prepared as a separate additive component and may comprise aqueous acidic solutions of cerium (II) chloride or cerium (IV) sulphate with a cerium ion concentration of about 200 - 320 g / l and about 60 - 100 g / l, respectively. Such cerium concentrates may be included in commercially available materials of the type described above from Molycorp, Inc.

According to a preferred embodiment, optional components may include F) an organic carboxylic acid soluble and thus compatible in the solution in an amount of 0.05 - 4 g / l and having the formula (OH) aR (COOH) b, where a is 0 or an integer 1 to 6, b is an integer 1 to 3 and R is alkyl, alkenyl or aryl, containing 1 to 6 carbon atoms, and in the acidic aqueous solution soluble and compatible salts thereof, VG) a soluble in the solution and thus compatible silicate compound in an amount of 0.01 - 5 g / l, calculated as SiO2, H) a stabilizer consisting of a mixture of 1-hydroxyethylidene-1,1-diphosphonic acid and citric acid and in the solution soluble and thus compatible salts thereof in an amount of 0.05 - 3 g / l and 0.1 - 10 g / l, respectively, I) halide ions in an amount up to 8 g / l, J) a surfactant in an amount up to 1 g / l and K) sulphate ions in an amount up to 15 g / l. The organic carboxylic acid or a salt thereof having the above structural formula imparts to the deposited film increased clarity and initial hardness. The unexpected improvement in the clarity of the film is particularly pronounced in connection with the light yellow color shimmering films which are achieved with cerium ion-containing solutions. The concentration or concentration range of the clarity / hardness agent varies according to the molecular weight of the specific acid and / or metal salt used, with higher concentrations being required for an equivalent effect as the molecular weight of the additive increases. The concentration required to achieve optimal clarity and hardness is also dictated to some extent by the concentration of other metal ions in the solution, with higher concentrations occurring as the metal ion concentrations increase. The organic carboxylic acids or the metal salts thereof are generally used in amounts from 0.05 up to 4.0 g / l, with concentrations of 0.1 - 1.0 g / l generally being preferred.

The additive can be added as organic acid as such or as something in the solution soluble and thus compatible metal salt including alkali metal salts, ammonium salts and salts of other metal ions in the bath. For economic reasons, the organic acid is usually added as acid or as sodium or potassium salt.

Within the framework of the structural formula given above, the organic carboxylic acids which have proved to be particularly suitable are malonic acid, maleic acid, succinic acid, gluconic acid, tartaric acid and citric acid, of which succinic acid and / or succinate salts have proved to be particularly effective.

An additional optional component G) in the aqueous solution according to the invention is a silicate compound to provide improved corrosion protection and hardness to the pickling film formed on the treated substrate. The silicate compound may be an inorganic or organic silicate compound soluble in the solution and compatible therewith as well as mixtures thereof, which are present in an amount of 0.01 - 5 g / l, calculated as S102 with concentrations 457642 10 15 20 25 30 35 To prepare supplementation and renewal concentrate due to the improved stability and the extended service life. 1- and ammonium silicates, of which sodium silicate (Na (K 2 O.ysiocates, 2O.xSiO 2 (x = 2-4) and potassium silicate 2 (y = 3-5) are preferred for economic reasons. Organic silicas which can also be advantageously ammonium silicates including tetramethyllayltrimethylammonium silicate, disilicate and include quaternary ammonium silicate, fetisilicate and benzyltrimethylammonium silicate and disilicate. Such silicates which meet the requirements of the invention may be generally expressed in the form of alkyl. , alkylaryl or mixtures thereof, R 'represents either R or a hydrogen atom, x is 1-3 and y is 0-15.

Such water-soluble organic silicates, including their synthesis and characterization, are described in more detail in the literature, such as the article by Merrill and Spencer, Nary Ammonium Silicates and Colloid Chemistry.

"Some Quater", published in the Journal of Physical 55, 187 (1951), the contents of which are incorporated herein by reference in U.S. Pat. No. 3,993,548, to which reference is also made for further details.

The presence of the silicate compound in the bath according to the invention has unexpectedly also been found to contribute to improved clarity of the substance M 457642 'f ~ 1 ~ «. .. U. _ nlngs 1 men And follöktllgen is the use of the organic k b - -. n _. H N of ° XY1SYfaH GJ essential when a silicate is present in the solution.

S '~ - -. . . . if an optional but preferred component, no halide ions including chloro-1 bromine and fluorine ions can be obtained which has been found in fu _. _ _ _ _ _ improve the hardness of the pickling film on the treated substrate. The halide ions or mixtures thereof may conveniently t '- ... , _ illforas with the use of some alkali metal or ammonium Salt thereof as well as salts of the above metal ions. The concentration of the halide component is normally up to 8 g / l, with concentrations of about 0.1 - 2.5 g / l being typical.

It may be appropriate for the concentration of the total halide component to be up to 2 g / l, with concentrations aV 0.1 '0.5 g / l being typical.

In addition, the use of a small effective amount of various bath-compatible surfactants gives favorable results with the deposited pickling film. When such agent is used, it may be present in concentrations up to about 1 g / l with concentrations of about 50 - 100 mg / l being preferred.

Surfactants suitable for use in the solution include aliphatic fluorocarbonates available from 3M under the tradename "Fluorad FC 98", which is a non-foaming wetting agent and its use in a "such as, for example," Fluorad amount of about 100 mg / l improves the color and hardness of the pickling film.A second class of suitable surfactants are the sulfo derivatives of succinates.An example of this class is "Aerosol MA-80", which is the dihexyl ester of sodium sulphosuccinic acid and is commercially available from American Cyanamid Company. A third class of suitable surfactants are the sulfonates of the n-phthalates, which are linear alkylnaphthalene sulfonates, such as "Petro: BA", available from the Petrochemical Company.

Another optional ingredient in the treatment solution of the invention is a stabilizing agent consisting of a mixture of 1-hydroxyethylidene-1,1-diisophonic acid and citric acid and in the solution soluble and compatible salts thereof. . The use of the diphosphonic acid and citric acid seems to have an effect by not only holding back the loss and the amount of oxidizing agent of the Combination, a synergistic decomposing peroxide type, a fast g as observed chromium. the parts in or ammonium salts. A commercially available material suitable for use is sold under the tradename "Dequest (ïå010" by Montanto Chemical Company and includes 1-hydroxyethylidene-1,1 but also stabilizes the pH of the solution and prevents it from rising with the attendant disadvantages of it being taken into account. previously known pickling solutions containing t Typically the acid form of the two stabilizing constituents is added or as alkali metal diphosphonate.

The diphosphonic acid or diphosphonate component may be present in the solution in an amount of 0.05 - 3 g / l, with amounts of 0.1 0.5 g / l being preferred.

The citric acid or citrate component may be present in the solution in an amount of 0.1 - 10 9 / lf with 0.5 - 1.5 g / l being preferred.

The solution can be prepared using a concentrate containing the active ingredients with the exception of the oxidizing agent, which is diluted with water to prepare a solution containing the ingredients within the desired concentration range. Similarly, renewal of the solution on a continuous or batch basis can be accomplished using a concentrate of the active ingredients with the exception of the oxidizing agent, which is added to the solution separately. Typically, a supplement concentrate for the solution may contain about 10 - 30 g / l chromium ions, about 0.5 - 10 g / l iron ions, about 5 - 50 g / l of at least one more metal ion from the group consisting of cobalt, nickel, molybdenum, manganese, aluminum, lanthanum, lanthanide mixture or cerium ions or mixtures thereof. Furthermore, halide ions can be included up to an amount of 8 g / l and a surfactant in an amount of up to 1 g / l if used. Such a supplement concentrate can be diluted with about 98.5% by volume of water to give a solution which contains the active ingredients within the specified ranges. The oxidizing agent hydrogen peroxide is preferably supplied separately in a commercially available form containing about 35-40% by volume of hydrogen peroxide. According to the invention, zinc, zinc alloy, cadmium, cadmium alloy, aluminum and magnesium surfaces can be imparted a clear light yellow pickling film, which provides improved corrosion protection approaching or comparable to that previously achieved with use. of conventional pickling solutions containing hexavalent chromium.

The treatment solution reduces the problems of loss of oxidizing agent, as has been the case with previously used solutions. Thus, although improvements have been made with pickling compositions containing trivalent chromium to produce commercially acceptable pickling films, a constant problem with them has been the relatively rapid loss of the peroxide-type oxidizing agent, in particular hydrogen peroxide, which is present as a necessary ingredient for to achieve acceptable pickling films. Such pre-used solutions also undergo a relatively rapid increase in pH, which necessitates a careful control and addition of acids in order to maintain the pH value within the optimal operating range. The constant loss of peroxide-type oxidizing agents, in particular hydrogen peroxide, is due in part to the presence of activating metal ions in the solution as well as contaminating metal ions such as zinc or cadmium, which are added by dissolving metal from the substrates being treated and which tend to catalyze a decomposition of the peroxide oxidizing agent. The increasing loss of the peroxide-type oxidizing agent takes place not only during the process but also while the solution is standing overnight and over weekends, while the factory is closed.

Typically, a fresh solution containing 3% by volume of 35% hydrogen peroxide solution when left overnight is about 0.1% by volume per hour of hydrogen peroxide while a solution used containing about 2 to 10 g / l of contaminating zinc ions exhibits a loss. of hydrogen peroxide of as much as about 0.4% by volume per hour. It is obvious from the above that it is necessary to carefully monitor the composition of the solution and often renew the peroxide oxidant in order to maintain optimal efficiency, which is not only costly but also time consuming. A treatment solution according to the invention is effective in imparting improved corrosion protection to zinc, zinc alloys, cadmium and cadmium alloys as well as aluminum and magnesium surfaces and a desired surface finish, which may vary. from a clear gloss to a light blue gloss to a yellow color shimmering surface, which provides a pickling film with improved corrosion protection, hardness, durability, clarity and initial hardness, and a treatment solution that is stabilized against rapid loss of the peroxide oxidant and against a rapid increase of the pH value.

Concentrates containing trivalent chromium and containing metal ions and acid components in combination with an inorganic silicate compound tend to form precipitates upon prolonged storage due to the high concentrations and the acidic conditions. Such previously used concentrates are therefore normally diluted with water shortly after preparation to give a functional bath containing the active ingredients in desired concentrations. Concentrates with markedly improved stability and extended service life can be achieved by using organic silicates in combination with the trivalent chromium ions and optionally halide ions and a wetting agent. Such stable concentrates usually contain about 10 to 80 g / l of trivalent chromium ions, about 5 to 50 g / l of an organic quaternary ammonium silicate, calculated as SiO2, halide ions up to about 50 g / l and a surfactant in an amount up to about 5 g / l. Such stable concentrates are intended for use with a second concentrate containing the acid components, the additional metal ions in an amount of about 5 to 50 g / l, up to 80 g / l of the organic carboxylic acid and / or salt thereof if used. . Such a second concentrate may also optionally contain some or all of the halides and wetting agents if not used in the first trivalent chromium concentrate.

When preparing such a trivalent chromium / silicate concentrate, the organic silicate is first diluted with water to the desired concentration, after which the trivalent chromium component is added together with the halide and wetting agent if used.

A particularly suitable, commercially available organic silicate compound is "Quram 220" available from Emery Industries, which includes a quaternary amine silicate.

The diphosphonic acid and citric acid and / or the diphosphonate and citrate stabilizer can be added via any of said concentrates including the peroxide concentrate in an amount which gives the desired concentration in the working solution. Alternatively, the stabilizer may be prepared as a separate aqueous concentrate containing about 30 - 170 g / l diphosphonic acid / diphosphonate compound in admixture with about 160 - 500 g / l citric acid / citrate compound and added to the solution separately to give the desired operating concentration according to the above limits and typically 4 - 5 g / l stabilizer concentrate. In accordance with a preferred application, the stabilizer is added directly to the chromium-containing concentrate or the other concentrate used in conjunction with the organic silicate concentrate in amounts of 3 - 17 g / l diphosphonic acid / diphosphonate compound and 16 - 50 g / l citric acid / citrate compound.

The treatment solution can be applied to substrates in many different ways. In the final stage of the passivation treatment, the substrate is extracted from the treatment solution and dried, such as by means of hot circulating air. Such passivated substrates, in particular workpieces, treated mounted on a frame, are characterized as having a uniform pickling film over the entire surface and which does not require any further treatment. In the case of small workpieces which are treated in lumps, such as in a rotating drum, certain damages, such as scratches, may appear in the pickling film during the treatment and in such cases it is desirable to subject some workpieces to a silicate rinsing treatment to seal any surface defects and thereby improve the corrosion protection of parts treated in the drum.

When such a post-pickling treatment with silicate is used, the substrate after the pickling treatment is preferably subjected to at least one or more water rinsing steps, usually at room temperature, to remove residual pickling solution from the surface, after which the substrate is treated with silicate rinsing solution. 457642 10 15 20 25 30 35 16 A treatment solution can be prepared, which aims to reduce the problems of injuries in connection with the pickling of pickled workpieces during subsequent treatment. Thus, although improvements have been achieved with trivalent chromium pickling solutions and methods for producing commercially acceptable pickling films, such initially formed films have in some cases been found to lack sufficient initial hardness to enable the substrate to be handled in additional work steps without causing damage to the pickling film. In addition, such trivalent chromium coating compositions have in some cases been found to provide insufficient corrosion protection, hardness and durability and to give films which are somewhat obscure and lack optimal clarity.

The invention can be practiced in various ways and a series of specific embodiments are described below to illustrate the invention with reference to the following examples.

Examples 2.1 to 2.8 illustrate the invention utilizing iron and cobalt as metal activators and also comprising trivalent chromium to provide light blue pickling surfaces.

Examples 3.1 - 3.5 illustrate the invention, in which cerium is used as a metal activator and again comprises trivalent chromium, but this time gives a yellow pickling film reminiscent of pickles with hexavalent chromium. x Examples 4.1 - 4.3 illustrate the invention, using a carboxylic acid in solution of the same general type as shown in the examples regarding the second and third aspects. The carboxylic acid improves the initial hardness of the pickling film.

Examples 5.1 - 5.8 illustrate the invention, using a soluble silicate in the pickling bath and trivalent chromium in the solutions of the same general type as shown in the examples regarding the second and fourth aspects of the invention. The silicate improves the initial hardness of the pickling film and the corrosion resistance.

Examples 6.1 - 6.5 illustrate the invention, using a mixture of citric acid and a special phosphonic acid to reduce the loss of oxidizing agent and raise the pH value during the use of the solutions of the type described in connection with the second and fifth aspects. .

Examples 7.1 to 7.3 illustrate the invention, which relates to a silicate rinse after pickling and which makes the pickling film harder. 457642 10 15 20 25 30 18 Example gel 2.1 A bath was prepared containing the following components: ingredient concentration, g / l Cr2 (SO4) 3 2.2 NH4HF2 0.18 HZSO4 1.2: 1202 5.3 FeNH4SO4 * 0.25 CoSO4 ~ 7H2O 1.6 * ferrous ammonium sulphate = Fe (SO4) - (NH4) 2SO4-6H20 Steel sample plates were subjected to an alkaline electroplating step without the presence of cyanide to deposit a zinc plating, after which they were thoroughly rinsed with water and immersed under stirring in the baths described above for 20 seconds. At the end of the treatment, the pickled plates were rinsed in warm water and air dried. the coating on the plates after drying tat light clear blue color without any obscurity An inspection of of veiled an unfamiliarity. In addition, the coating could be likened to a light nickel-chrome electroplating and also possessed excellent “lightening” resistance when lightly touched with the finger.

Example gel 2.2 A bath was prepared containing: ingredient concentration, g / l Cr 2 (SO 4) 3 5.6 NH 4 HF 2 0.4 n 2 SO 4 2.7 21202 5.3 FeNH 4 SO 4 0.58 COSO 4 in 7H 2 O 3, 75 The bath in Example 2.2 was similar to that in Example 2.1 with the difference that trivalent chromium, ammonium bifluoride, sulfuric acid, the iron and cobalt components were all present in higher concentrations. Zinc-plated sheets treated with the bath of Example 2.2 gave results which were essentially equivalent to those obtained with the bath of Example 2.1.

Example 2.3 A bath was prepared containing: ingredient concentration Q / l Cr 2 (SO 4) 3 3.0 NH 4 HF 2 0.24 H 2 SO 4 1.54 H 2 O 2 5.3 FeNH 4 SO 4 0.25 NiNH 4 SO 4 * 2.1 * nickel ammonium sulfate - NiSO 4 ° (NH 4) 2 SO 4 '6H20 Zinc-plated sample plates treated with this bath under the same conditions as in Example 2.1 were observed after drying and were found to have a coating which was very light with a clear bluish coloration and without any haze. The coating also showed good "lightening" resistance when lightly touched with the finger. 457642 10 l5 20 25 30 35 20 Example 2.4 A bath was prepared identically to that in Example 2.3 with the difference that 1.6 g / l nickel sulphate was used instead of 2 The zinc-plated sample plates treated in the manner described in Example 2.1 using the treatment solution of Example 2.4 gave results which were substantially comparable to those obtained with the treatment bath of Example 2.3 except that the coating had a slightly less bluish color.

Examples 2.5A to 2.5E A series of pickling solutions were prepared for treating zinc plated steel sheets to evaluate their relative corrosion resistance to a 5%, salt spray solution after pickling. solutions SA, SB, SC and 5D are given in la: neutral The composition of the following table Table la concentration g / 1 ingredient Zrâê Zrëš - šräå šiäâ cr2 (so4) 3 3.0 3.0 3.0 3.0 NH4nF2 0.24 0.24 0.24 0.24 n2so4 1.54 1.54 1.54 1.54 Hzoz 5.3 5.3 5.3 5.3 PeNn4so4 - 0.25 0.25 0.25 CQSO3 - - 1 , 6 _ N1NH4so4 - - - 2-1 Solution 2.5A contained only trivalent chromium ions, solution 2.5B also contained iron (II) ions, solution 2.5C contained a combination of iron and cobalt ions while solution 2.5D contained a combination of iron and nickel ions. In addition to the above solutions, a traditional pickling solution containing hexavalent chromium (Example 2.5E) was prepared to serve as a control sample containing 0.63 g / l sodium dichromate, 0.63 g / l ammonium bifluoride, .01 g / l sulfuric acid and 0.65 g / l nitric acid. This solution was called solution 2.5E. In Double sets of steel sheets measuring 7.6 x 10.2 cm were cleaned and galvanized using a zinc plating electrolyte without cyanide for 15 minutes at a current density of 2.2 A / cm 2, after which they were thoroughly rinsed. Each set of zinc-plated sheets was then immersed in the respective treatment solution for a period of 20 seconds, after which they were rinsed in hot water, air-dried and then aged for 24 hours before performing salt spray tests in accordance with ASTM regulations. The plates were exposed to the influence of 5% neutral salts for a total of 43 hours. For further comparative purposes, a double set of zinc sheets was also subjected to the neutral salt spray without any pickling treatment. The results are shown in table lb below.

Table lb results of spraying experiments with neutral salt x eczema test proportion white proportion EÉl__ plÉt_ corrosion,% red rust,% 2.5F untreated 50 50% 2,511. 5A 45 - 55 0 2.5B SB 10 - 15 0 2.5C SC less than 2 0 2.5D 5D less than 10 0 2.5B SE 45 - 55 0 In the light of these experimental results it is obvious that the untreated zinc plated sheets are clearly failed, 457642 10 15 20 25 30 35 22 the plate treated with solution 2.5A is failed, the plates treated with solution 2.5B are approved at the limit, the plates treated with solutions 2.5C and 2.5D pass the test and the plate treated with solution 2.5E is failed.

Example 2.6 A bath was prepared containing: ingredient concentration g / l cr2 (so4) 3 3.0 Na4HF2 0.24 H2so4 1.54 FeNH4so4 0.24 Hzoz 5.3 Mnso4-H2O 1.0 Electroplated zinc sheets prepared according to The procedure given in Example 2.5 was immersed in the bath of Example 2.6 for 30 seconds, rinsed with hot water, air dried and aged for 24 hours before being subjected to a 5% neutral salt spray test. For comparative purposes, zinc sheets were treated with solutions 2.5A and 2.5E in Example 2.5 and subjected to the same salt spray evaluation.

After 48 hours of salt spraying, an inspection of the plates at hand indicated that the plates treated with the solution of Example 2.6 had superior corrosion resistance compared to the plates treated with solutions 5A and 5E.

Example 2.7 A bath was prepared containing: Ingredient concentration g / l Cr 2 (SO 4) 3 3.0 NH 4 HF 4 0.24 112304 1.54 FeNn 4 SO 4 0.24 3202 5.3 HZMQG 4 - H 2 O 1.0 Electroplated zinc sheets according to Example 2.5 were immersed in the bath of Example 2.7 for 30 seconds, rinsed in hot water, air dried and aged for 24 hours before being subjected to spray testing with 5% neutral salt. For comparative purposes, zinc sheets were treated with solutions 2.5A and 2.5E in Example 2.5 and subjected to the same salt spray evaluation.

After 48 hours of salt spraying, an inspection of the plates was performed and this showed that the plates treated with the solution in Example 2.7 had superior corrosion resistance compared to the plates treated with the solutions 2.SA and 2.5E.

Example 2.8 A bath was prepared containing: ingredient concentration 5 / l Cr2 (SO4) 3 3.0 NH4HF2 0.24 HZSO4 1.54 FeNH4SO4 0.24 H2O2 5.3 (No4) 4 (NiMoo24H6) 4-4n2o 1.0 Electroplated zinc sheets prepared according to the procedure described in Example 2.5 were immersed in the bath of Example 2.8 for 30 seconds, rinsed with hot water, air dried and allowed to age for 24 hours before being sprayed with 5%. neutral salt. For comparative purposes, zinc sheets were treated with the solutions 2.5A and ZQSE in Example 2.5 and subjected to the same saline test.

After 48 hours of salt spraying, an inspection of the plates was performed and this revealed that the plates treated with the solution of Example 2.8 had superior corrosion resistance compared to the plates treated with the solutions 2.5A and 2.5E.

A relative comparison of the plates prepared according to Examples 2.6, 2.7 and 2.8 reveals that the solution of Example 2.6 containing iron ions and molybdic acid and the solution of Example 2.8 containing iron ions in combination with ammonium 6-molybdone nickelate showed superior corrosion resistance to the plates treated with the solution. Example 2.6 containing iron ions in combinations with manganese ions. The sheets treated according to Examples 2.7 and 2.8 also showed superior corrosion resistance compared to sheets treated with the solution 2.5B in Example 2.5 containing only iron ions while plates treated with the solution according to Example 2.6 containing both iron and manganese ions showed a corrosion resistance. , which to some extent could be compared with that of the plates treated with solution 2.5B.

Example 3.1 A concentrate 3.1A was prepared comprising an aqueous acidic solution containing 25 g / l trivalent chromium ions added as chromium sulphate ("Korean MF" from Allied Chemical Company), 12 g / l ammonium chloride, 12 g / l iron (II) ammonium sulphate and 4% by volume of concentrated sulfuric acid A second aqueous acidic concentrate 3.lB was prepared containing 60 g / l of trivalent cerium ions added as Ce (SO 4) 2'4H 2 O and 5% by volume of concentrated sulfuric acid.

A bath was prepared comprising water containing 2% by volume of concentrate 3.1A, 2% by volume of concentrate 3.lB and 1.5% by volume of a 38% solution of hydrogen peroxide. Electroplated zinc sheets immersed in this bath for 40 - 60 seconds showed light yellow, shimmering staining films on the surface.

Example 3.2 A concentrate 3.2A was prepared in the same manner as concentrate 1A in Example 1 containing 25 g / l of trivalent chromium ions, 20 g / l of sodium chloride, 40 g / l of ferrous sulphate and 4% by volume of concentrated sulfuric acid.

A bath was prepared comprising water containing 2% by volume of concentrate 3.2A, 2% by volume of concentrate 3.lB according to Examples 3.1 and 1.5 - 3% by volume of a 38% solution of hydrogen peroxide. Electroplated zinc sheets immersed in the bath gave the same results as in Example 3.1.

Example 3.3 A concentrate 3.3A was prepared in the same manner as concentrate 3.1A in Example 3.1 except that 6% by volume nitric acid was used instead of 4% by volume sulfuric acid.

A bath was prepared comprising water containing 2% by volume of concentrate 3.3A, 2% by volume of concentrate 3.lB according to Example 3.1 and 1.5 - 3% by volume of a 38% solution of hydrogen peroxide. Electroplated zinc plates immersed in the bath gave results similar to those in Example 3.1. 45 3.442 10 15 20 25 30 35 26 Example 3.4 A concentrate 3.4A was prepared in the same way as concentrate 3.2A in Example 3.2 with the difference that 6% by volume of nitric acid was used instead of 4% by volume of sulfuric acid.

A bath was prepared comprising water containing 2% by volume of concentrate 3.4A, 2% by volume of concentrate 3.lB according to Example 3.1 and 1.5 - 3% by volume of a 38% solution of hydrogen peroxide. Electroplated zinc sheets immersed in the bath gave results similar to those in Example 3.1.

Examples 3.5A - 3.5G A series of seven aqueous sample solutions were prepared each containing 1 g / l trivalent chromium ions, lg / l nitric acid, lg / l sulfuric acid, 7 g / l hydrogen peroxide and with a nominal pH of about 1 , 5. To each sample solution was added controlled amounts of metal ions to evaluate the effect of such additives on the color, hardness and salt spray resistance of the pickling films produced on electroplated zinc sheets immersed in each bath with gentle stirring for a period of about 30 seconds at a temperature of about 21 ° C.

The cerium ions were added as a CeCl3 solution containing about 300 g / l cerium ions, the manganese ions were added as MnSO4'H2O, the iron (III) ions were added as Fe2 (SO4) 3 dissolved in a dilute sulfuric acid solution, the molybdenum ions were added as sodium molybdate in the form of dry molybdate the lanthanum anions were added as a LaCl 3 solution containing about 85 g / l lanthanum anions and the cobalt ions were added as cobalt sulphate.

The sample solutions were designated as Examples 3.5A - 3.5G and the concentration of metal ions are summarized in the following Table 2. 457642 27 ~ + ou m + mA w + O2 m + mm ~ + = z m + wu A m + HU con fl amuwe I- iNO (\ l Um.m hm.m mm.m Qm.m Um.m mm.m H \ m G0 fl umuuGwU: Oxc0nHHmuw2 N a fi wßmü 457642 10 15 20 25 30 35 28 Each plate was subjected to water rinsing and air drying after immersion in the respective test bath and Visually inspected visually for color and clarity, all plates as well as a clear yellow clear as air-drying film were treated by a comparative forearm 3. It was further pickled in solutions 3.5A - 3.5G had e light yellow color varying in clarity from film to film, which was slightly unclear or is shown in Table 3. Each plate was tested immediately for hardness of the bite with light rubbing with the finger.The results of the hardness test of the pickling film on specimens in solutions 3.5 A - 3.5G is apparent from the loss that after 24 hours of aging a v plate film hard and rub resistant. The advantage of a pickling film, which is hard immediately after air drying, is that it can be handled for further processing without being damaged by the coated film. The solutions 3.5A - 3.5G were exposed with neutral salt for a period area, expressed, in%, Each plate treated with also for spray testing of 72 hours and the surface where a white corrosive coating is formed is also given in Table 3 below.

Table 3 Test results sample- .neutral salt spraying pel clarity hardness 72 h -% white corrosion 3.5A slightly cloudy soft 50 3.5B slightly cloudy soft 100 3.5C slightly cloudy hard 10 3.5D cloudy hard 0 3.5E slightly cloudy soft 100 3.5F clear soft 2 3.5G clear hard 0 In the light of the values obtained in Table 2 regarding clarity and hardness, examples 3.5G are definitely approved, examples 3.5C and 3.5F are acceptable while examples 3.5A, 3.5B 10 15 20 25 30 35 457642 29 and 3.5E are less acceptable from a general appearance point of view. From a corrosion protection point of view, examples 3.5D, 3.5F and 3.5G are definitely approved, 3.5C is approved at the limit, while examples 3.5A, 3.5B and 3.5E must be considered unacceptable on the basis of ASTM corrosion data during a 72 hour spray evaluation with neutral salt . It should be noted, however, that each of the sheets exhibits improved corrosion protection compared to an untreated electroplated zinc sheet and the pickling films which did not pass the 72 hour neutral salt spray test are in any case acceptable for less exposed functional purposes. The corrosion resistance of the material according to Example 3.5G is substantially comparable to that obtained with conventional known pickling solutions with hexavalent chromium of known type. It should also be noted that variations in the types, combinations and concentrations of metal ions contained in the sample solutions can be made to optimize and improve the clarity, hardness and corrosion resistance of the plates compared to the results given in Table 3. The conditions of the 72 hour spray test The neutral salt is relatively strict and is generally applied to parts that are exposed to external influences, such as car components. The 72-hour neutral salt spray test normally applies to yellow pickles containing hexavalent chromium, although some specifications require only 48 hours and others 96 hours of exposure. The 72-hour test was thus chosen because it was moderately difficult.

Examples 4.1A - 4.lG A series of concentrates containing trivalent chromium were prepared suitable for dilution with water for the preparation of a working bath in further combination with an oxidizing agent and cerium or lanthanum anions as follows: 457642 10 15 20 25 30 35 '_ cr Concentrate 4.lA _______________ ingredient +3 CoSO4 ° 7H2O iron (II) ammonium sulphate sodium fluoroborate succinic acid nitric acid (100%) Concentrate 4.lB ______________ ingredient Cr + 3 NaCl iron (II) ammonium sulphate sodium succinate 100% nitric acid .lC ______________ ingredient Cr + 3 iron (III) ammonium sulphate sodium succinate NaCl nitric acid (100%) Concentrate 4.lD _______________ ingredient cr + 3 iron (III) ammonium sulphate succinic acid NaCl nitric acid (100%) 30 concentration g / lf 24 25 12 15 25 60 concentration ¶ / l 24 20 25 55 60 concentration ¶ / l 24 50 55 20 60 concentration Q / l 24 50 25 20 60 l0 15 20 25 30 35 Concentrate 4.lE ingredient Cr + 3 iron (III) ammonium sulphate NaCl malonic acid nitric acid (100%) Conc concentrate 4.lF ingredient Cr + 3 Fe2 (SO4) 3 NaCl gluconic acid nitric acid (100%) Concentrate 4.lG ingredient Cr + 3 iron (III) ammonium sulphate NaCl maleic acid nitric acid (100%) Exemgel 4.2A - 4.2G 31 concentration g / l 24 50 20 25 60 concentration 3 / l 24 30 20 20 60 concentration ¶ / 1 24 50 20 25 60 457642 A cerium ion concentrate was provided containing about 80 g / l cerium (IV) ions in the form of cerium (IV) sulphate in predicted sulfuric acid solution. An oxidate was also provided containing A series of baths were prepared suitable to give a yellow pickling film on a substrate each containing 2% by volume concentrate, 2% by volume% of either of the chromium concentrates 4.1A - 4.lG. 35% hydrogen peroxide. % oxidant concentrate and 2% cerium 457642 10 15 20 25 30 35 32 4.lA - 4.lG.

Steel plates were subjected to an alkaline electroplating step without cyanide to deposit a zinc plating thereon, after which they were thoroughly rinsed with water and immersed with stirring in the test baths for a period of about 30 seconds at a temperature of about 21 ° C and with a pH of about 1.5 - 2.0. After finishing pickling treatment, the pickled plates were rinsed in warm water and air dried. An inspection of the coating on each of the plates, which were immersed in the sample solutions, indicated that a clear, hard, yellow pickling film had formed.

Examples 4.3A - 4.3G A lanthanum anion concentrate was provided containing about 60 g / l lanthanum anions in the form of a solution of lanthanum chloride.

An oxidizing agent concentrate was also provided containing about 35% hydrogen peroxide. A series of baths were prepared suitably to provide a blue-gloss betnin support each containing 2% by volume of lanthanum anion concentrate, 2% by volume of oxidizing agent concentrate and 2% by volume of one of the chromium concentrates 4.1A - 4.1G in Example 4.1. gs film on a Zinc plated sheet of the type described in Example 4.2 was immersed under the conditions set forth in Example 4.2, after which they were rinsed in hot water and air dried.

Inspection of the coating on each of the plates after drying gave the impression that an exceptionally light, clear, hard and bluish colored pickling film was formed.

The yellow pickled plates of Examples 4.2A, 4.2B and 4.2C obtained using the baths containing the concentrates 4.lA, 4.lB and 4.lC, respectively, were aged for at least 24 hours and then subjected to corrosion tests. by spraying with neutral salt according to ASTM method B-ll7. Table 4 below shows the results of measured corrosion resistance using these baths: Table 4 Exe chromium neutral salt spray test concentrate concentrate 72 h 96 h 4.2A 4.1A ready with some clear with some dark spots dark spots 4.2B 4.lB finished with some finished with some dark spots dark spots 4.2C 4.lC finished with some dark dark spots spots - l% white spots The results above show that plates treated with bath containing concentrate A, B and C passed the 96 hour test.

Similar results were obtained with plates obtained using the other concentrates.

Example gel 5.1 A bath suitable for depositing a yellow pickling film on a receptive substrate was provided by preparing a concentrate containing trivalent chromium designated as "concentrate 5.1A" having a composition as follows: Concentrate 5.1A ingredient concentration 5 / l Cr +3 50 iron (III) ammonium sulphate 30 sodium chloride 20 nitric acid (100%) 59 succinic acid 20 The trivalent chromium ions were added as Cr2 (SO4) 3. A cerium ion concentrate called "concentrate 5.lB" was supplied containing about 80 g / l cerium ions in the form of cerium sulphate in a dilute (approximately 5%) sulfuric acid solution. An oxidizing agent concentrate was also provided containing about 35% hydrogen peroxide. A sodium silicate concentrate was also provided containing 300 g / l of sodium silicate, calculated as SiO 2.

A yellow pickling bath was prepared comprising water containing 2% by volume of concentrate 5.1A, ionic concentrate 5.1B, 2% by volume and 0.4% by volume of 10% by volume of cerium% of the oxidizing agent concentrate-% of the sodium silicate concentrate.

Steel sheets were subjected to an alkaline electroplating step without any cyanide to deposit a zinc plating thereon, after which they were thoroughly rinsed with water and immersed with stirring in the pickling bath for a period of about 30 seconds at a temperature of about 21 ° C and a pH. of about 1.5 - 2.0. The plates were then taken out of the bath 20 and dried with recirculating hot air.

The plates were visually inspected after drying and found to have a very hard, clear, yellow pickling film. After aging for at least 24 hours, the plates were subjected to a corrosion test by spraying with neutral salt according to ASTM method B-117. The plates thus treated showed excellent salt spray resistance after being subjected to this test for more than 96 hours. Example 5.2 A bath suitable for depositing a yellow pickling film on a receptive substrate was prepared by preparing a concentrate containing trivalent chromium designated "concentrate 5.2A" having a composition as follows: Concentrate 5.2A ingredient concentration g / l Cr + 3 'so iron (III) ammonium sulphate 40 sodium chloride 20 nitric acid (100%) 60 sodium silicate (calculated as S102) 10 A bath for yellow pickling was prepared comprising water containing 2% by volume of concentrate 5.2A, 2 volumes -% cerium ion concentrate 5.lB according to Example 5.1 and 2% by volume of oxidant concentrate according to Example 5.1.

Plates prepared according to the method described in Example 5.1 were immersed in the bath for about 30 seconds at a temperature of about 210 DEG C. and a pH of about 1.5 to 2.0. The treated plates were dried with recirculating hot air and the dried plates were found to have a very hard, clear, yellow pickling film. After aging, the plates were subjected to corrosion testing by neutral salt spraying as described in Example 5.1 and were found to have excellent salt spray resistance after a treatment for more than 96 hours.

Example 5.3 A bath suitable for depositing a yellow pickling film on a receptive substrate was prepared by preparing a concentrate containing trivalent chromium designated "concentrate 5.3A" having a composition as follows: 457642 10 15 20 25 30 35 36 Concentrate 5.3A Ingredient concentration ~ g / 1 +3 Cr 50 iron (III) ammonium sulphate 40 nitric acid (100%) 60 sodium chloride 20 A bath was prepared comprising water containing 2% by volume of concentrate 5.3A, 2% by volume of cerium ion-containing concentrate 5.lB according to examples 5.1, 2% by volume of oxidizing agent concentrate according to Example 5.1 and 0.5% by volume of sodium silicate concentrate according to Example 5.1.

Electroplated zinc sheets were treated in the bath according to the procedure described in Example 5.1 and after drying were found to have an excellent, clear yellow pickling film.

The plates also showed excellent resistance to the salt spray test, which indicated excellent corrosion protection.

Example 5.4 A bath suitable for depositing a yellow pickling film on a receptive support was prepared by preparing a concentrate containing trivalent chromium together with a quaternary amine silicate designated "concentrate 5.4A" a composition as follows: with Concentrate 5.4A _______________ ingredient concentration g / l cr * 3 20 quaternary amine silicate * 15 sodium chloride 15 * "Quram 220" calculated as SiO2 10 15 20 25 30 35 457642 37 The concentrate 5.4A containing trivalent chromium was stored for a long time and was found to show excellent stability during long-term storage.

In addition, a second concentrate designated "concentrate 5.4B" was prepared having a composition as follows: Concentrate 5.4B ingredient concentration g / l nitric acid (100%) 60 sulfuric acid (100%) 30 ferrous sulfate 25 cerium chloride 120 A bath was prepared comprising water and containing 2% by volume of concentrate 5.4A, 2% by volume of concentrate 5.4B and 2% by volume of oxidizing agent concentrate of the kind described in Example 5.1.

Zinc-plated sheets were treated with the bath according to the procedure under the conditions described in Example 5.1, after which the sheets were dried with recirculating hot air. The plates were found to have an excellent hard and clear yellow pickling film and showed excellent resistance to salt spray testing and showed no formation of white after being subjected to neutral salt spray testing for a period of 96 hours.

Example 5.5 A second series of electroplated zinc sheets were treated with the bath described in Example 5.4 under the same conditions, after which the sheets were rinsed with water and then rinsed for 30 seconds in an aqueous solution at room temperature containing 10 g / l sodium silicate, calculated as SiO 2. After this rinsing, the plates were dried with hot air. 457642 l0 l5 20 25 30 35 38 The plates were inspected and found to have a very hard, clear, yellow pickling film.

After aging, the plates were subjected to a corrosion test by spraying with neutral salt and showed excellent durability after being subjected to this test for 96-140 hours. These tests also showed that cooling with silicate is the nitrate ions in the pickling bath a formation of some turbidity in when one applied it is desirable to have a certain amount to in some cases avoid the pickling film as a result of the last dipping step.

Example 5.6 A bath suitable for depositing a blue light pickling film on a receptive substrate was prepared by preparing a concentrate designated "concentrate 5.6A" having a composition as follows: Concentrate 5.6A _______________ ingredient concentration g / l nitric acid (100 %) 30 sulfuric acid (100%) 20 succinic acid 20 La-RE-Cl 3 - 80 a A pickling bath was prepared comprising water containing 3% by volume of concentrate 5.4A according to Example 5.4, 3% by volume of concentrate 5.6A and 3% by volume oxidant concentrate according to Example 5.1 Electroplated zinc sheets were treated with the bath according to the procedure described in Example 5.1 and after drying the sheets were found to have an excellent bluish light pickling film.

The plates also showed excellent corrosion resistance, as evidenced by the presence of white corrosion after being subjected to corrosion testing by spraying with neutral salt for a period of from 48 up to 72 hours. Examples 5.7.1 and 5.7.2 A concentrate containing trivalent chromium was prepared as 'concentrate 5.7A' having a composition as follows: Concentrate 5.7A ingredient concentration g / l Cr + sodium chloride sodium silicate ( calculated as S102) A bath (Example 5.7.1) suitable for depositing a yellow pickling film on a receptive substrate was prepared using 2% by volume of concentrate 5.7A, 2% by volume of concentrate 5.4B in Example 5.4 and 2 volumes. -% oxidant concentrate in Example 5.1 In addition, a bath was prepared (Example 5.7.2) suitable for depositing a blue light pickling film using 2% by volume concentrate 5.7A, 2% by volume concentrate 5.6A in Examples 5.6 and 2 volume% oxidant concentrate according to Example 5.1.

Sheets treated in accordance with the procedure described in Example 5.1 exhibited excellent pickling films and excellent corrosion protection.

Example 5.8 A bath suitable for depositing a blue light pickling film on a receptive substrate was prepared by preparing a concentrate containing trivalent chromium designated "concentrate 5.8A" having a composition as follows: 457642 10 15 20 25 30 35 40 Concentrate 5.8A ingredient concentration g / l - +3 'Cr 30 sodium chloride 13 sodium gluconate 10 quaternary amine silicate * 15 * "Quram 220", calculated as SiO2 A second concentrate called "concentrate 5.8B" was prepared with a composition as follows: Concentrate 5.8B ingredient concentration g / l nitric acid (100%) 60 sulfuric acid (10%) - 30 Ål2 (504) 3 30 A bath was prepared comprising water containing 3% by volume of concentrate S.8A, 3% by volume of concentrate 5.8B and 3% by volume of % oxidant concentrate according to Example 5.1.

Electroplated zinc sheets were used in accordance with the procedure described in Example 5.1 and were found to have a clear, light pickling film after drying. Examination of these plates during corrosion testing by spraying with neutral salt showed a corrosion resistance of at least 12 and up to 24 hours.

Example gel 6.1 A bath suitable for depositing a yellow pickling film on a receptive substrate was prepared by preparing a concentrate containing trivalent chromium designated "concentrate 6.1A" having a composition as follows: Concentrate 6 .1A ingredient concentration g / l Cr + 3 quaternary ammonium Silicate 15 NaCl 15 The trivalent chromium ions were added as Cr2 (SO4) 3 while the silicate compound was added as "Quram 220" from Emery Industries.

A cerium ion concentrate designated "concentrate 6.lB" was prepared with a composition as follows: Concentrate 6.lB ingredient concentration g / l HNQ3 (100%) 60 H2so4 (100%) 30 Fe (so) 25 É3 4 3 - ce 120 The cerium ions were added as a cerium chloride solution containing about 300 g / l Ce + 3 ions. In addition, an oxidizing agent concentrate containing about 35% hydrogen peroxide was used.

A series of 1 liter baths were prepared comprising 3% by volume of concentrate 6.1A, 3% by volume of concentrate 6.1B and 3% by volume of the oxidizing agent concentrate. To mimic an aged bath used to passivate the zinc workpieces, 1 g / l zinc powder is dissolved in each sample solution. Such a test solution without any other additives was called test solution 6.1.1 and served as a control test. To a second sample solution designated 6.1.2 was added 1 g / l of lemon - 457642 10 15 20 25 30 35 42 Syfa 0Ch 0,4 g / l 1-hydroxyethylidene-1,1-2010 ") as a stabilizer. To a designated 6.1. 3 was added 1 g / l of citric acid hydroxyethylidene-1.1 diphosphonate (Dequest third sample solution ch 0.08 g / l 1-diphosphonate ("Dequest 2010").

Each sample solution was stirred at room temperature to mimic current commercial practice. The pH at the beginning and end and the peroxide concentration measured in volume% 35% hydrogen peroxide concentrate remaining in the bath were analyzed over a one-day period. The results were as follows - n Hydrogen peroxide concentration and pH test sample Example 6.1.1 6.1.2 6.1.3 time HZO2 pH H2O2 pH H202 pH start 2.56% 1.6 2.95% 1.6 3.05% 1.4 after 3 , 5 h 2.39% - 2.92% - 2.84% - after 21 h 0.83% - 1.72% - 2.37% 1.7 after 26 h 0.50% 2.5 1, 42% 1,8 - - The results in the table above show that the control sample 6.1.1 without any stabilizer rapidly lost the peroxide oxidizing agent, which should be present in a concentration of at least 2% by volume in order to maintain a reasonable passivation. An almost complete addition of the oxidizing agent in sample 6.1.1 would therefore be necessary after a period of about 1 day. In contrast, sample 6.1.3 showed only a minor loss of peroxide after 21 hours, while sample 6.1.2 containing a smaller quantity of "Dequest 2010" in combination with 1 g / l citric acid also showed a surprisingly high peroxide stability in relation to to the material sample 6.1.1 10 15 20 25 30 35 457642 43 The stabilization of the pH value is also shown by the values in the table above.The control sample 6.1.1 had an increase of the pH value to 2.5 after 26 hours, which would need - added an addition of acid to the bath to maintain the pH within the preferred range 1.5 - 2.0.

However, both sample 6.1.2 and sample 6.1.3 were essentially stable and remained within the optimum pH range during the test period.

Example 6.2 An aqueous stabilizer concentrate was prepared containing 270 g / l citric acid and 110 g / l 1-hydroxyethylidene-1,1-diphosphonate ("Dequest 2010"). These solutions were prepared as described in Example 6.1 containing 3% by volume of concentrate 6.1A, 3% by volume of concentrate 6.lB, 3% by volume of oxidizing agent concentrate and 1 g / l of zinc powder for aging the baths. A control sample designated 6.2.1 which lacked any stabilizer had an initial peroxide concentration of 3% by volume but after standing for 18 hours under the conditions given in Example 6.1 it showed a peroxide residue content of only 1,05%, which necessary supplementation. A second sample solution designated 6.2.2 was stabilized by the addition of 2.5 ml / l stabilizer concentrate and had an initial peroxide concentration of 3% and after 18 hours a residual peroxide content of 2.43 E.

Example 6.3 To evaluate the effect of the peroxide and pH stabilizer in this aspect of the invention under actual commercial conditions, the stabilizer concentrate defined in Example 6.2 was used to stabilize a trivalent chromium pickling solution having a composition similar to that of the bath of Example 6.1 containing trivalent chromium ions, iron and cerium ions and maintaining a pH of about 1.5 - 2.0 at a temperature of about 210 ° C and containing hydrogen peroxide as oxidizing agent. During normal operation, in the absence of stabilizer, the commercial bath required a renewal of the peroxide oxidant by the addition of 3% by volume of 35% hydrogen peroxide concentrate each morning at the beginning of operation as well as the addition of an additional 1% by volume of peroxide oxidation concentrate after about 4 hours of operation. to keep the bath at a minimum amount of oxidizing agent of 2% by volume.

By adding 1 liter of stabilizer concentrate per 378.5 l of bath, the required amount of freshly added peroxide oxidant concentrate was reduced to only 1% by volume each day and only 2% by volume addition after standing for one weekend to restore the bath to proper operating conditions. things.

Furthermore, an addition of the stabilizer concentrate to the bath further stabilized the pH value during the 6-day test period, the pH value remaining substantially constant and the addition of acid to control the pH value being avoided. The same commercial bath without any stabilizer concentrate, on the other hand, required constant monitoring of the pH value and periodic addition of acid to maintain the pH value within the desired range 1.5 - 2.0.

Light zinc-plated parts made with use. of the above commercial baths was subjected after aging for at least 24 hours to a corrosion test by spraying with neutral salt according to ASTM method B-177. The excellent corrosion resistance of the yellow pickling film was evident by the absence of white corrosion on the parts after 96 hours of salt spray testing.

Example 6.4 The stabilization of a commercial bath with a composition and using the procedure as described in Example 6.3 was achieved by preparing an aqueous stabilizer concentrate containing about 30 - 170 g / l -hydroxyethylidene-1,1-diphosphonate ("Dequest 2010") in a mixture with about 160 - 500 g / l citric acid. The stabilizer concentrate was added to the commercial bath to give a concentration of 1-hydroxyethylidene-1,1-diphosphonate of about 0.05 - 3 g / l and a concentration of citric acid of about 0.1 - 10 g / l. The results obtained were similar to those obtained in Example 6.3.

Example Gel 6.5 A bath suitable for depositing a yellow pickling film on a receptive substrate was prepared by preparing a concentrate designated "concentrate 6.5A" having a composition as follows: Concentrate 6.5A Ingredient concentration g / l HNO3 (100%) 60 HZSO4 (100%) Fe2 (SO4) 3 FeCl3 5 diphosphonate * 5.5 citric acid _ 36 ce * 120 * "Dequest 2010" A bath was prepared comprising 3% by volume of chromium ion concentrate 6.1A in Example 6.1, 3% by volume % concentrate 6-5A O fi h 3 volume% oxidant concentrate containing about 35% hydrogen peroxide.

Steel plates were subjected to an alkaline electroplating step without any cyanide to deposit a zinc plating, after which they were thoroughly rinsed with water and, while stirring, were immersed in the pickling bath for a period of about 30 seconds at a temperature of about 30 seconds. 210 C and at a pH between about 1.5 - 2.0. The sample plates were then taken out of the bath and dried with recirculating hot air.

The test plates were visually inspected after drying and found to have a uniform, clear, yellow pickling film. The small addition of ferric chloride to the bath resulted in an improvement in the color intensity of the yellow pickling film compared to that obtained using the pickling bath in Example 6.1.

After aging, the test plates were subjected to neutral salt spray testing in accordance with the procedure described in Example 6.3, and similar results were obtained.

Example gel 7.1 A bath suitable for depositing a yellow pickling film on a receptive substrate was prepared as follows: A concentrate containing trivalent chromium designated "concentrate 7.lA" was prepared with a composition as follows: Concentrate 7.lA ingredient concentration ¶ / l cr * 3 25 iron (III) ammonium sulphate 30 sodium chloride 20 nitric acid (100%) 60 succinic acid 20 A 7.1B cerium ion concentrate was prepared containing about 30 9/1 cerium (IV) ions in the form of cerium (IV) sulphate in a dilute (about 5 -percent) sulfuric acid solution. An oxidizing agent concentrate was also prepared containing about 35% hydrogen peroxide. A yellow pickling bath was prepared comprising water containing 2% by volume of concentrate 7.1A, 2% by volume of cerium ion concentrate 7.1B and 2% by volume of oxidant concentrate 7.1C.

An aqueous silicate rinse solution was prepared containing 10 g / l sodium silicate, calculated as S102.

Steel plates were subjected to an alkaline electroplating step without cyanide to deposit a zinc plating, after which they were thoroughly rinsed with water and, with stirring, immersed in the pickling bath for about 30 seconds at about 210 DEG C. and at a pH of about 1.5 to 2.0. . The plates were taken out of the bath, rinsed with tap water and then treated with the silicate rinsing solution for about 30 seconds at about 210 DEG C. The silicate rinsed plates were then taken out of the solution and dried with recirculating hot air.

The plates were visually inspected after drying and found to have a very hard, clear yellow pickling film. After aging for at least 24 hours, the plates were subjected to a corrosion test by spraying with neutral salt according to ASTM method B-117. The sheets treated according to the invention showed excellent salt iron resistance after a period of more than 96 hours. Examples 7.2.1 - 7.2.14 A series of concentrates containing trivalent chromium were prepared suitable for dilution with water for the preparation of a functional bath in combination with an oxidizing agent and cerium lanthanum anions as follows: 457642 10 15 20 25 30 35 Concentrate 7.2A Ingredient cr * 3 CoSO4'7H2O iron (II) ammonium sulphate sodium fluoroborate succinic acid nitric acid (100%) Concentrate 7.2B ingredient Cr + 3 NaCl iron (II) ammonium sulphate sodium succinate nitric acid (100%) Concentrate 7.2C ______________ ingredient III + ammonium sulphic acid sodium succinate NaCl nitric acid (100%) Concentrate 7.2D ingredient Cr + 3 iron (III) ammonium sulphate succinic acid NaCl nitric acid (100%) 48 concentration 3 / l 24 25 12 15 25 60 concentration 5/1 24 20 25 55 60 concentration g / l 24 50 55 20 60 concentration Q / l 24 50 25 20 60 10 l5 20 25 30 35 457642 49 Concentrate 7.2.E ÉE fl šÉÉÅÉE§§ concentration 3 / l + Cr 24 iron (III) ammonium sulphate 50 NaCl 20 malonic acid 25 nitric acid (100%) 60 Concentrate 7.2F Ingredient concentration ¶ / l r + 3 C 24 Fe2 (SO4) 3 30 NaCl 20 gluconic acid 20 nitric acid (100%) 60 Concentrate 7.2G ingredient concentration 3 / l cr + 3 24 iron (III) ammonium sulphate 50 NaCl 20 maleic acid ~ 25 nitric acid (100%) 60 A cerium ion concentrate was prepared containing about 80 g / l of cerium (IV) ions in the form of cerium (IV) sulphate in dilute sulfuric acid solution. An oxidizing agent concentrate was also prepared containing about 35% hydrogen peroxide.

A series of baths (Examples 7.2.1 - 7.2.7) were prepared suitably to give a yellow pickling film on a support each containing 2% by volume of cerium ion concentrate, 2% by volume of oxidizing agent concentrate and 2% by volume of one of chromium cone - centers 7.2A - 7.2G. A lanthanum anion concentrate was prepared containing about 60 g / l of lanthanum anions in the form of a solution of lanthanum chloride.

An oxidizing agent concentrate was also prepared containing about 35% hydrogen peroxide. A series of baths (examples suitable for giving a layer each containing% lanthanum anion concentrate, 2% by volume oxidant concentrate and 2% by volume of one of the chromium concentrates 7.2A - 7.2G. 7.2.8 - 7.2.l4) were prepared 1 blue light pickling film on a less than 2 volume 10 Zinc plated steel plates of the type described in Example 7.1 was treated in the baths (Examples 7.2.1 - 7.2.14) under the conditions set forth in Example 7.1, after which the pickled plates was subjected to a post-treatment by rinsing in silicate using an aqueous silicate rinsing solution, in which the silicate concentration ranged from about 1 to about 40 g / l, calculated as SiO 2, at a temperature between 10 - 660 ° C. thereafter and was subjected to corrosion testing by spraying with neutral salt as described in Example 7.1. Similar results as those reported for Example 7.1 were obtained.

Examples 7.3.1 - 7.3.6 A series of baths were prepared as follows: Finished bath 7.3A ingredient concentration g / l 30 cr2 (so4) 3 2.2 NH4HF2 0.18 H2so4 1.2 3202 5.3 FeNs4so4 * 0.25 coso4-7H2o 1.6 * ferrous ammonium sulphate = Fe (SO4) '(NH4) 2504'5H 0 2 10 15 20 25 30 Finishing bath 7.3B ingredient cr2 (so4) 3 NH4HFz HZSO4 H2 ° 2 FeNH4SO4 COSO4'7H2O Finishing bath 7.3C ingredient Cr2 (SO4) 3 NH4HF2 HZSO4 3202 FeNH4SO4 NiNH4SO4 * * nickel ammonium sulphate = NiSO4 '(NH4) 2SO4 ° 6H2O Finished fl bath 7.3D ingredient cr2 (so4) 3 NH4HF2 HZSO4 FeNH2SO4S4 51 , 4 2.7 5.3 0.58 3.75 concentration ¶ / 1 3.0 0.24 1.54 5.3 0.25 2.1 concentration 5 / l 3.0 0.24 1.54 0 , 24 5,3 1,0 457642 457642 52 Finished bath 7.3E Å fl igååiågå concentration / l ____________ šL_ 5 Cr2 (SO4) 3 3,0 NH4HF2 0,24 112504 1,54 FeNí4SO4 0,24 10 HZOZ 5,3 H2Moo4 .H20 1, Finished bath 7.3F 15 in rediens concentration / l -3 -_-- _________ í._ Cr2 (SO4) 3 3.0 NH4HF2 0.24 H 20 2504 154 FeNH4SO4 0.24 HZOZ 5.3 (NH4) 4 (NiMoO24H6) 4.4H2O 1.0 25 Zinc plated sheets were processed in said bath (Examples 7.3.1 - 7.3.6) under the conditions described in Example 7.1, after which they were rinsed with water and subjected to a post-treatment in aqueous silicate in a rinsing solution in which the silicate concentration, calculated as SiO , ranging from about 1 to about 40 g / l, at a temperature between about 10 - 66 ° C. The pickled and rinsed plates were subjected to drying after drying by neutral salt spraying as described in Example 7.1 and similar results were obtained.

Claims (7)

B) UI S * 457642 Claim 1. Acidic aqueous solution for use in the treatment of receptive metal substrates to impart to them a pickling film, which aqueous solution contains A) hydrogen ions corresponding to a pH of 1.2 - 2.5, B) a peroxide in an amount of 1-20 g / l, based on an equivalent weight of hydrogen peroxide, and C) chromium ions, substantially all of which are present in the trivalent state, in an amount of from 0.05 g / l up to saturation, characterized in that it also contains a combination of D) iron ions in an amount of 0.05 - 0.5 g / l and E) ions of at least one of cobalt, nickel, molybdenum , manganese, aluminum, lanthanum, lanthanide mixture or cerium ions or mixtures thereof in an amount of 0.02 - 1.0 g / l. Aqueous solution according to Claim 1, characterized in that it also contains, as optional components, F) an organic carboxylic acid soluble and thus compatible in the solution in an amount of 0,05 - 4 g / l and having the formula (OH) aR (COOH) b where a is o or a nelcai 1-s, 'b is an integer 1-3 and' R is alkyl, alkenyl or aryl containing 1-6 carbon atoms, and in the acidic aqueous solution soluble and compatible salts thereof, G) a silicate compound soluble in the solution and compatible therein in an amount of 0.61-5 g / l, calculated as SiO 2, H) a stabilizer consisting of a mixture of 1-hydroxyethyl diphosphonic acid and citric acid and in the solution soluble and compatible salts thereof in an amount of 0.05-3 9 / l and 0.1-10 g / l, respectively, I) halide ions in an amount up to 8 g / l, J ) a surfactant in an amount up to 1 g / l and K) sulphate ions in an amount up to 15 g / l. Aqueous solution according to claims 1 - 3, characterized in that component E) consists of cerium ions. Aqueous solution according to any one of claims 1 to 4, characterized in that the hydrogen ions in A) are provided by a mineral acid, which is sulfuric acid, nitric acid or hydrochloric acid. Aqueous solution according to any one of claims 1 n a d in that it has a pH of 1.5 1.6 - 1.8. - 5, characterized in that 2.0, preferably aqueous solution according to any one of claims 1 - 6, characterized in that the peroxide B) is present in an amount of 3-7 g / l. Aqueous solution according to one of Claims 1 to 7, characterized in that the peroxide B) is hydrogen peroxide. Aqueous solution according to one of Claims 1 to 8, characterized in that component E) is present in an amount of 0.1 to 0.2 g / l. Aqueous solution according to any one of claims 2 to 9, characterized in that the halide ions, when included, are present in an amount of 0.1-2.5 g / l, preferably up to 2 g / l l and in particular in an amount of 0.1-0.5 g / l. Aqueous solution according to claim 1, in that component E) consists of cobalt ions in an amount of 0.02-1 g / l, preferably in an amount of 0.1-0.2 g / l. Aqueous solution according to claim 11, characterized in that component E) in addition consists of cerium ions in an amount of 0.5 - 10 g / l. 10 15 20 sf 457642 1 Aqueous solution according to claim 2, characterized in that the carboxylic acid P) is present in an amount of 0.1 - 1 g / l. 1 Aqueous solution according to claim 13, characterized in that the carboxylic acid consists of malonic acid, maleic acid, succinic acid, gluconic acid, tartaric acid or citric acid. 1 Aqueous solution according to Claim 2, characterized in that the silicate compound G) consists of an alkali metal or ammonium silicate compound in an amount of up to 2 g / l, calculated as SiO 2. 1 Aqueous solution according to one of Claims 1 to 14, characterized in that the silicate compound G) consists of a quaternary ammonium silicate in an amount of 0.01 to 5 g / l, preferably 0.1 to 0.5 g / l. l, calculated as SiO2. n a d 1 Aqueous solution according to any one of claims 1 to 14, characterized in that the silicate compound G) has the structural formula ROR ': xSiO2: yH2O where R represents a quaternary ammonium radical substituted by four organic radicals selected from alkyl, alkylene, alkanol, aryl or alkylaryl or mixtures thereof, R 'represents R or a hydrogen atom, x is an integer 1-3 and y is 0 or an integer 1-15.