DE2715292A1 - PROCESS FOR THE PRODUCTION OF CORROSION-RESISTANT ADHESIVE COATINGS ON ALUMINUM SURFACES AND Aqueous-ACID SOLUTIONS FOR CHEMICAL CONVERSION COATINGS - Google Patents

Description

PATENT LAWYERS DR. A. VAN DERWERTH DR. FRANZ LEDERER REINER F. MEYER

DlPL- ING. (1934-1974) DIPL-CHEM. DIPL-ING.

AMCHEM PRODUCTS, INC., Brookside Avenue, Ambler, Pemsylvania, USA

8000 MUNICH 80 LUCILE-GRAHN-STRASSE

TEUFON: (089) 472947 TELEX: 524624 LEOER O TEUGR .: LEATHER PATENT

April 4, 1977 1191 / 1191A

Process for the production of corrosion-resistant adhesive coatings on aluminum surfaces and aqueous acidic solutions for chemical conversion coatings

The invention relates to improved aqueous acidic solutions for chemical conversion coatings and methods for Manufacture of adhesive, corrosion-resistant coatings with them on aluminum surfaces.

First of all, it should be noted that the term "aluminum" used here is not only pure aluminum, but also alloys in which aluminum predominates, e.g. aluminum alloys with smaller proportions of metals like magnesium, manganese, copper and silicon. However, the coating solutions and methods are believed to be in accordance with of the invention are generally used on aluminum surfaces that have a bright, shiny appearance, such as aluminum strips or sheets and in front

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any aluminum can or can material. Probably the most popular aluminum alloy currently used in the can industry is the aluminum alloy Mr. 3004

Aqueous-acidic coating solutions, the chemical conversion coatings on aluminum surfaces, which are corrosion-resistant and thereby protect the surface from decomposition through corrosive attack, form effectively, are already known. Such chemical conversion coatings should also support overlying siccative coatings, which are either decorative or functional (such as paints, varnishes, printing inks, etc.) are to be firm and strong on the underlying aluminum surface to adhere.

An important area for the coating of aluminum nowadays, with which the invention actually deals directly concerned is the coating of aluminum cans or cans. The chemical used in aluminum cans Conversion coatings not only have to be corrosion-resistant and have good adhesion, they should also be uniform be clear and colorless so that the cans, although coated, retain their bright, shiny natural appearance of the underlying aluminum as normally desired by the final product when the Can can also be partially covered with colored paints or printing inks.

In addition to the above properties, as are well desirable for all aluminum coatings, is a highly desirable property for coated aluminum cans their resistance to discolouration when they are / exposed ater moderately hot V, for example in the range of 60 to about 77 ⁰ C. In For certain uses, aluminum is treated in this way, a process that is used in

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referred to in the can industry as "pasteurizing ¹¹ cans or cans; however, this treatment tends to cause an uncoated or even a coated aluminum surface to turn black or otherwise discolor, rendering the can unsightly.

Currently there are aqueous-acidic chemical conversion coating solutions, which form uniformly clear, colorless coatings on aluminum surfaces that form the various meet the requirements mentioned above. Unfortunately, the best of these solutions contain chromic acid, phosphoric acid and hydrofluoric acid; and their use leads, because of the presence of hexavalent chromium, a very toxic material, to waste disposal problems.

There is therefore a need for chemical conversion coating solutions that do not contain hexavalent chromium, firmly adhering, corrosion-resistant conversion coatings capable of forming, which are resistant to discoloration during pasteurization, clear and colorless, and Form a good basis for siccative treatment on aluminum surfaces.

When examining the state of the art, eich shows as far as known that hitherto colorless coatings could be obtained by using aqueous coating solutions that contain hexavalent chromium and / or form coatings that require the application of a post-rinse treatment require with hexavalent chromium; or that when using coating and rinsing solutions, those of hexavalent Chromium-free, coatings were formed on aluminum surfaces, all of which were colored or discolored. As an aside, it should be noted that many earlier

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propose to speak out against the presence of phosphate.

Now, however, a coating solution has been found which makes the use of hexavalent chromium or the like poisonous Materials no longer required and yet a clear and colorless coating on an aluminum surface forms without turning black or otherwise discoloring, even when exposed to boiling water.

In accordance with one aspect of the invention, aqueous-acidic chemical conversion coating solutions are used provided on aluminum surfaces that have a pH in the range from 1.5 to 4.0 and at least 10 ppm zirconium and / or titanium, at least 10 Ppm phosphate and also fluoride in an amount not less than 13 ppm and at least sufficient to form of a soluble complex with the total zirconium and titanium present, the above essentially are free from solids that tend to precipitate and have a uniformly clear and colorless coating an aluminum surface that turns black after 2 minutes of treatment in boiling water resists.

Such solutions can be used to treat a brightly shiny aluminum surface in such a way that the bright, shiny appearance of the surface remains unchanged and yet a uniformly colorless coating on the surface is formed, which is corrosion-resistant and to which the overlying siccative coatings adhere excellently. Further, the coatings obtained are able to resist blackening or other discoloration if they are exposed to boiling water, and not only for the specified minimum time, namely at least about

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2 min, but - as will be seen from the later examples - if the solutions are put together like this that they give optimal resistance to blackening or other discoloration, the coatings can withstand boiling tap water for as long as 15 minutes and even up to about 30 minutes.

No components other than those specified above and their associated components Cations are necessary in the aqueous-acidic coating solutions according to the invention, and yet they are able to do so Solutions the aforementioned types of coatings on an aluminum surface in the absence of toxic and others Form materials that create waste disposal problems. In particular, the invention Solutions of, for example, seaworthy chrome and Elements like manganese, iron, cobalt, nickel, molybdenum and tungsten as well as other troublesome ones Substances such as ferricyanide and perrocyanide, be free and are usually free of this. So the coating solution according to the invention is frai of such chemicals, their Presence requires special treatment of the solution to be discarded before either is completely discarded or is only fed to a sewage disposal system.

It is surprising that such excellent results are obtained using the solutions according to the invention can be, in particular because it was previously assumed that the introduction of phosphoric acid or phosphates in aqueous-acidic coating solutions based on zirconium or titanium have an adverse effect on them became. In addition, this view was very understandable, since both zirconium phosphate and titanium phosphate in aqueous Media were extremely insoluble - after all this

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was a well-known analytical method for determination the amount of zirconium and titanium in aqueous solution in introducing phosphate into the solution to zirconium or titanium phosphate to fail. Earlier attempts to put together aqueous-acidic solutions that were not just zirconium and fluoride but also phosphate, and they used to form coatings on aluminum of the type to which the invention relates related to form, resulted in the formation of zirconium phosphate precipitate, which, as explained below becomes extreme in an industrial coating process is undesirable. According to the invention, however, it is possible to compose the aqueous-acidic coating solutions in such a way that they contain practically no zirconium or titanium phosphate solids which tend to precipitate.

Zirconium and / or titanium must or must be contained in the aqueous-acidic solutions according to the invention, as coatings with satisfactory properties can only be guaranteed if they are zirconium and / or titanium directly or indirectly bound to the aluminum surface. Satisfactory coatings can be formed from coating solutions containing down to 10 ppm zirconium and / or titanium; depending on other parameters of the coating process however, larger amounts of these ingredients may be required.

Zirconium and / or titanium can in fact be used in concentrations up to their solubility limits in the aqueous-acidic Coating solution can be used, which, however, depend on other parameters, including in particular the acidity of the coating solution and the fluoride and phosphate concentration therein. This should be controlled that way be that the precipitation of zirconium and titanium phosphate is avoided, which is undesirable for several reasons.

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Precipitation not only reduces the levels of the constituents, but can also affect the coating process adversely affect, both on the aluminum surface and elsewhere, any type of precipitation e.g. clog spray nozzles. Should the zirconium and / or titanium quantities exceed their solubility limits and If precipitates are encountered, the amount of phosphate should be reduced and / or the pH of the coating solution should be lowered and / or the amount of fluoride can be increased.

Phosphate must be present in the aqueous-acidic coating solutions according to the invention for several reasons. For one, the presence of phosphate in the coating solution enables a simple test to confirm that Formation of the coating. This is crucial in an industrial operation where perhaps very large amounts of aluminum are treated in a relatively short time in order to form a coating thereon, which is invisible to the eye. Without a test, there could be a change in the operating parameters of the coating solution can easily take place unnoticed, e.g. insufficient replenishment of the coating solution as a result of mechanical or human error that renders them ineffective.

In order to determine whether the aqueous-acidic coating solutions according to the invention are working as they should or not to form chemical conversion coatings on the aluminum surface, samples of the coated aluminum only need to be taken occasionally and kept at a relatively high temperature for a relatively short time, e.g. 5 m ir! at about 538 ⁰ C, and subjected to the appearance of the sample after this so-called "muffle test" are observed. A discoloration or color change to a light golden brown or even darker shades

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of brown or purple indicates the presence of zircon and phosphorus in the coating. Are zircon and phosphorus If not deposited, the aluminum surface shows a matt gray appearance after the muffle test. An electron probe analysis properly coated surfaces treated in accordance with the present invention also show the presence of both zirconium and phosphorus.

Another reason for the presence of phosphate in the solutions according to the invention is that it is used for Corrosion resistance and the adhesive properties of the coatings, especially the coatings that are made of Coating solutions with a pH <5.5 were formed »

It has been found that, in order to provide coatings with satisfactory properties, the aforementioned Muffle test able to discolour, it is necessary that the coating solution contains at least 10 ppm of phosphate; and larger amounts may be required for optimal results, depending on others Coating process parameters as explained below. On the other hand, concentrations can be too high to phosphate reduce the corrosion resistance of the coatings formed; the phosphate concentration should therefore not> 1,000 tpm. When choosing the phosphate concentration, the ones given here should also be used Guidelines regarding the tendency of phosphate to precipitate zirconium or titanium are taken into account.

Fluoride must be present in a concentration that is at least suitable for combination with all of the zirconium and / or titanium is sufficient to form a soluble complex, e.g. a fluozirconate or fluotitanate, because this leads to the formation of zirconium and / or titanium phosphate

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Precipitation prevented. The minimum amount of fluoride depends on this on the amount of zirconium and / or titanium in the solution. As a general guideline, however, it can be noted that that when there are 10 ppm zirconia in solution, the minimum fluoride level is 13 ppm; and if 10 ppm titanium in Solution, the minimum fluoride quantity is 25 ppm.

There are other considerations that affect the desired concentration of fluoride. The coating solution according to the invention dissolves aluminum during its use; consequently, the concentration of aluminum dissolved in the solution increases if only aluminum comes into contact with the coating solution by immersion or even by spraying or, according to the flow coating technique, when excess or unreacted spray solution is recycled. The dissolved aluminum has ^to% of complexing adverse effect on the coating process, if not adequately fluoride is present in the coating solution it. The amount of fluoride required in the solution depends on the extent to which aluminum builds up in it, and this in turn depends on factors such as the shape of the aluminum surface to be treated and the way in which the surface is brought into contact with the solution will.

From a practical point of view, when operating on an industrial scale, the coating solution should of course be one Contain excess fluoride, i.e. one in excess of the amount associated with aluminum (and any other metal constituent in the solution, which is able to form complexes with fluoride) complexes, exceeding the amount here of simplicity is referred to as "available or available fluoride", including HF and fluoride ion any fluoride present.

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The concentration of "available fluoride ^11" can conveniently be measured as follows. First, a constant ionic strength buffer is prepared containing 40.8 g / l sodium acetate, 28.5 ml / l glacial acetic acid, and 58.0 g / l sodium chloride in deionized water and is adjusted with NaOH to a pH in the range of 5.0 to 5.3 A sample of the coating solution diluted with this constant strength buffer is then treated with an Orion pH keter (Model No. 9409) with a fluoride ion Specific Orion Electrode (Model No. 90-01) and the resulting reading will indicate the concentration of "Available Fluoride" in the coating solution.

While the general problem is to prevent That there is too little available fluoride rather than too much should be avoided, such a high concentration use of available fluoride that the aluminum surface suffers an improper etching, * resulting in a matt and tire-like appearance on the surface and the corrosion resistance and adhesive properties of the Coating impaired. It is difficult to get precise cut-off values for the concentrations of available fluoride which lead to such problems as these will vary depending on other parameters of the coating process including, for example, the pH of the solution and the contact time and temperature. According to the experience gained however, these problems can be avoided if the "available fluoride" is in one concentration not> 500 tpm.

The pH of the coating solution must be in the range from 1.5 to 4.0, since phosphate precipitation occurs at higher pH values can be a problem. A coating solution with a pH in the range from 2.6 to 3.1 is preferably used.

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The pH of the solution can be adjusted using any acid or base as a means of adjusting the pH, that does not interfere with the coating process, e.g. perchloric acid or sulfuric acid - although when using Sulfuric acid it is recommended that the pH of the coating solution is not <2, as sulfuric acid is below this value adversely affects the coating process. However, the preferred pH adjusters are. Nitric acid and Ammonium hydroxide

The aqueous-acidic coating solution according to the invention can be obtained from numerous readily available sources for zirconium and / or titanium, fluoride and phosphate soluble therein. Commonly used are zircon and titanium preferably as a soluble fluozirconate and / or pluotitanate compound supplied, e.g., fluozirconic acid and ammonium and alkali metal fluozirconates; titanium becomes similar preferably supplied as a soluble pluotitanate compound, e.g. as pluotitanic acid and ammonium and alkali metals luo titanate. However, the solution can also be made of zirconium fluoride (ZrF,) and / or titanium fluorides (TiP ^, TiP.) and also from a mixture of soluble compounds, one of which is zirconium or titanium and the other Contains fluoride, e.g. with zirconium nitrate, Zirconium sulfate and titanium (IV) sulfate on the one hand and Hydrofluoric acid and its water-soluble salts (e.g. ammonium and alkali metal salts) on the other hand. Zirconium carbonates, such as Ammonium and alkali metal zirconium carbonates can also be used.

Likewise, the aqueous-acidic coating solution according to the invention can be obtained from a number of readily available sources of phosphate getting produced. In general terms, the phosphate is preferably supplied as orthophosphoric acid, am-

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Inonium and alkali metal phosphates can also be used as well as other forms of phosphoric acid, such as meta-, pyro-, tripoly- and hypo-porms and their salts.

In general terms, the same also applies to fluoride A source of fluoride, which is able to complex aluminum, can be used which is soluble in the coating solution and does not contain any ingredient that adversely affects the coating process. However, if pluoride is used as a Complex fluoride added to the titanium or zirconium can reduce the amount of available fluoride resulting from hydrolysis derived from such a complex fluoride may not be sufficient to complex the aluminum, but the extent can the hydrolysis must be such that non-complexed zirconium or titanium with phosphate leads to an undesirable precipitate combined. To avoid this problem, the solution should then also contain a further source of fluoride, which is able to complex the aluminum that * forms as the process progresses. Examples for aluminum Complexing sources of fluoride are hydrofluoric acid, its salts and ammonium bifluoride (NH, F »HF) as well as alkali metal bifluorides. Hydrofluoric acid is a particularly good source of fluoride because it easily provides enough fluoride to remove the aluminum to complex, but it is not a source of externally introduced cations, which interfere with the coating process can.

It will of course be understood that whenever waste disposal is a problem and aluminum products after Coating should also be used in the food or beverage industry, the coating solutions of course should be free of chromium and other toxic materials such as iron cyanides. Equally important Is it possible, even if for other reasons, that the

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appropriate solutions of everything that forms pesticides easily separate from the solution, should be kept free.

The incorporation of fluoboric acid into the coating solution has been found to reduce the gloss or hardness of paint films can improve, which are then applied to erfindungsgeaäß coated aluminum surfaces, and also the upright Preservation of the stability of the coating solution, when made with hard water, aids. The calcium and magnesium ions in hard water have an affinity for fluoride; and if they are the zirconium and / or titanium fluoride complex remove the fluoride, the decomplexed zirconium and / or titanium that is formed can easily be carried along with it combine the phosphate to form an undesirable precipitate of insoluble zirconium and / or titanium phosphate. Presumably, fluoboric acid, when present, acts as a buffered fluoride source for the calcium and magnesium ions in hard water. Too much fluoboric acid can, however reduce the corrosion resistance of the coating. Generally speaking, solutions are therefore preferred which contain fluoboric acid at a concentration in the range of 8 to 200 ppm.

It has also been found that certain polyhydroxy compounds are advantageously added to the coating solution can be used to form coatings, the better adhesion for subsequently applied paint or printing ink coatings offer, namely any organic compound soluble in the coating solution, which after dissolving at least 40 ppm polyhydroxy compounds with no more than 6 carbon atoms and of course the ability of Coating solution for forming coatings with the desired corrosion resistance and adhesion for paints does not

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disturbs. Examples of such polyhydroxy compounds are gluconic acid, salts of gluconic acid, sorbitol, mannitol, dextrose, Ethylene glycol and glycerin.

Particularly preferred polyhydroxy compounds are gluconic acid and its alkali metal and ammonium salts, as well as in Compounds soluble in the coating solution, the gluconates and / or provide gluconic acid, e.g. stable glueonolactones, such as glucono-tf-lactone and glueono-y-lactone.

While larger amounts can be used, the polyhydroxy compound does not use an amount > about 1,000 ppm is recommended, the preferred range is between 40 and 400 ppm of the polyhydroxy compound.

The coating solutions of the present invention usually contain

(a) 10 to 125 ppm zircon (or an equivalent amount of titanium);

(b) 10 to 1,000 ppm phosphate and

(c) 10 to 500 ppm available fluoride.

The coating solutions particularly preferred for the use according to the invention are those with a pH in the range from 2.6 to 3.1 and included

Component approximate concentration

in tpm

Zr 45 to 125

PO ₄ 50 to 200

available fluoride 10 to 200

The preferred source of Zr in the above solution is ammonium fluozirconate and the preferred source of phosphorus

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ph.at Orth.oph.03ph.orsa.xire. Hydrofluoric acid is preferred as Source of available fluoride is used and nitric acid is used to adjust the pH. the Use 8 to 200 ppm of pluoboric acid and 40 to 400 ppm of a polyhydroxy compound, as preferred Gluconic acid is beneficial for the reasons stated above.

Although presently generally speaking, preference is given to coating solutions zirconium-based solutions are used, preferred titanium-based solutions are those with the following Held:

Component approximate concentration

in tpm

Ti 20 to 65

PO. 50 to 200 4

available fluoride 1t) up to 200

The preferred source of titanium is pluotitanic acid. the further preferred components and amounts are as described above for the preferred zirconium-containing solution.

There are certain general considerations that should be kept in mind for best results. Is at a relatively high pH worked, should relatively small amounts of zirconium or titanium and / or Phosphate can be used to prevent precipitation. Will the coating solution and the aluminum surface for brought together for a relatively short time, should contain relatively high amounts of zirconium or titanium and phosphate be used. Similarly, at a relatively low contact temperature between the coating solution and relatively high amounts of the aluminum surface

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Components are used. The general rule is that, ever the lower the amount of phosphate used in the solution, the greater the amount of zirconium and / or Titanium that can be used.

According to a further aspect of the invention, methods for producing uniformly clear and colorless, however, indicated firmly adhering chemical conversion coatings that provide a good base for subsequently applied Form siccative coatings on aluminum surfaces, covering the aluminum surface with an aqueous acidic chemical conversion coating solution, as here is described, brought into contact.

The aluminum surface to be brought into contact with the coating solution should of course be clean. Each The cleaning agents currently available, such as alkaline or acidic cleaning agents, can * be used for cleaning the aluminum surface using conventional techniques be used. As previously indicated, the method is currently preferred for aluminum can material bright shiny surface applied.

The aluminum surface can be contacted with the coating solution by any suitable method e.g. by spraying or dipping or by roller or flow coating or by misting. For For many purposes, the coating solution can be applied extremely economically by spraying. The covering can either be applied to individual objects, such as cans or cans, or to objects that have not yet been finished Workpieces, e.g. aluminum strips or sheets, which then processed into finished products.

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The temperature at which the process is carried out must of course be such that the reactive components of the solution form a bond with the aluminum surface, but is otherwise not very critical - it can be carried out, for example, at room temperature. The coating solution is brought into contact with the aluminum surface but preferably at a temperature of at least about 27 ⁰ C, on the other hand preferably is avoided a high temperature, since then obtain a stunpfes, ripe-like appearance can ground v /. This occurs at temperatures which depend on numerous parameters of the coating, including, for example, the contact time and the reactivity of the solution, which in turn depends on the pH and the concentration of the components in the solution. An upper temperature limit of around 66 C is recommended; preferably the solution is brought into contact with the aluminum surface at a temperature in the range from about 27 to 33 ° C.

Satisfactory coatings can be formed by applying the coating solution to the aluminum surface for at least 5 seconds and preferably for at least 15 seconds is brought into contact. The lower the temperature of the coating solution, the longer the contact time should be while the higher the temperature of the solution, the shorter the contact time required. in the in general, it is unnecessary to bring the surface into contact with the coating solution for more than 1 minute.

The aqueous-acidic coating solution is able to form a very thin and very light coating. The coating weight varies depending on the concentration of the various ingredients in the coating solution, the temperature and the application time. For those mentioned here For purposes, the coating should preferably weigh about

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2 to about 20 mg / 929 cm (sqft), preferably about 5 to about 10 mg / 929 cm. Coatings of such weight can be formed by operating within the conditions described above. Higher coating weights can create problems in the aluminum can coating industry because the equipment that applies paints or printing inks to coated aluminum cans have tight tolerances for fitting the cans with very thin coatings, and cans with relatively thick coatings can jam the equipment.

According to the invention it is possible to form very uniform coatings, which allows the colors to be applied to apply evenly and with the desired coverage on the coated aluminum surface. In the Aluminum can industry ground coatings of paints and printing inks on coated aluminum cans with the aid an automatic Y / al ζ enbe layering machine, chine applied, in the paints and printing inks applied to a salt and then to the surface of the coated Can be applied when the roller rolls over the surface of the coated can. The can doesn't have one uniform coating, the subsequently applied colored agent can cover the desired areas or areas do not cover the can.

After applying the coating solution to the aluminum surface, it should be rinsed with water, including ground a final rinse with deionized water. Rinse with v / ater that has a small amount of dissolved Contains solids can lead to a coating with poor paint adhesion. It is not necessary, the coated aluminum surface secured according to the invention with some kind of an aqueous chromium solution to rinse, e.g. with the solution of hexavalent chromium,

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v / how it is conventionally used in many other chemical conversion coating processes.

After the coated surface has been rinsed with water or otherwise treated as described above, the coating should dry out. This can be done by any convenient drying method, such as oven drying or by forced circulation of hot air.

After the chemical conversion coating is applied and usually after being coated, rinsed with water and dried, the coated surface can be subjected to sanitary or decorative coating treatments v / grounding, including e.g. the application of siccative coatings. Occasionally the sanitary cover applied after the water rinse, and then the chemical conversion coating and the sanitary coating are applied dried at the same time. ■

Before aluminum cans are filled with beer, the cans should first be filled with the coating solution according to the invention treated, and then sanitary and / or decorative coatings should be applied. Be on it the cans filled with beer and sealed, whereupon the cans filled with beer are subjected to pasteurization v / earth.

The coating solution according to the invention can be prepared extremely conveniently by using an aqueous concentrate the ingredients is diluted with a suitable amount of water.

According to a further embodiment of the invention, a concentrate is therefore made available so that if

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a coating solution from about 0.5 "to about 10 percent by weight Concentrate, the amounts of the ingredients present in the coating solution are as follows:

(a) at least about 10 ppm zirconium or titanium;

(b) at least about 10 ppm phosphate and

(c) fluoride in an amount at least sufficient to be combined with substantially all of the Zr or Ti into a complex, and the pH of the coating solution is within the range of 1.5 to 4.0.

The preferred concentrates are such that when the coating solution contains from about 0.5 to about 10 percent by weight of the concentrate, the coating solution (a) about 45 to about 125 ppm zircon, added as a fluozirconate such as sodium or potassium fluozirconate, preferably ammonium fluozirconate, (b) about 50 to about 200 ppm phosphate, added as H ₅ PO ₄ , (c) about 8 to about 200 ppm HBP ₄ , (d) about 10 to about 50 ppm HP and (e) nitric acid in in an amount such that the pH of the coating solution is between 2.6 and 3.1.

A polyhydroxy compound, preferably gluconic acid, can also be contained in these concentrates in such an amount that the coating solution contains 40 to 400 ppm of it.

With continuous coating it is of course important to keep the solution appropriately supplemented, to maintain the efficiency of the coating process. It has been found that a number of the ingredients decrease during the formation of the coating. Zircon and / or phosphorus get into the coating, available Fluoride is formed by complexing with dissolved aluminum and hydrogen is formed with oxidation of the aluminum surface

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consumed. The constituents also decrease as the solution is dragged out on the aluminum surface. Of the The extent or the speed of the decrease of the constituents by dragging further depends on the shape of the surface to be coated and the manner in which the coating solution with the aluminum surface is brought into contact, for example greater losses occur due to dragging out when spraying cans than when spraying strips or sheets.

The coating solution can be supplemented either by determining the amount of each component individually in the coating solution and its replacement according to its decrease or by adding an aqueous concentrate the ingredients in approximately the exact proportions to the solution are made in order to make the ingredients effective To obtain operating quantities.

Where aluminum in the coating solution increases slightly, will recommended that the concentrate for supplementing or topping up a relatively high proportion of available Fluoride to complex the dissolved aluminum contains. Preferred sources of available fluoride are HF or ammonium bifluoride or a mixture thereof.

The following recipe is a recommended aqueous concentrate to supplement the coating solution:

(A) about 5 to about 10 g / l Zr or about 2.5 to about

5 g / l Ti;

(B) about 5 to about 10 g / L PO .; and

(C) a material that is a source of about 5 to about Represents 20 g / l available fluoride, preferably HP and / or ammonium bifluoride.

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When using a polyhydroxy compound this should be in the refill concentrate in an amount of about 5 to about 20 g / l are present.

If fluoboric acid is used, it should be included in this concentrate be contained in an amount of about 1 to about 5 g / l.

Examples

The following examples illustrate the practice of the invention. Comparative examples are also specified.

Unless otherwise stated, the aluminum surfaces treated with the solutions given in the examples were drawn and stretched aluminum cans which, if necessary, were first degreased in an aqueous-acidic cleaner containing sulfuric acid and detergents. Unless otherwise stated, the coating solutions were applied by spraying for about 25 seconds at a temperature of about 45 ^° C (110 ^° F). After treatment with the above solutions in the examples, the aluminum surfaces were rinsed in deionized v / ater and dried in an oven for 2 minutes at about 204 ° C (400 ⁰ P).

Then the aluminum surfaces were checked for corrosion resistance tested by subjecting them to a pasteurization test. In this test, the aluminum surface became immersed in water at the specified temperature for a specified period of time. One only The cleaned aluminum surface turns black after a few minutes when subjected to the pasteurization test. the end

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The following examples show that the previous treatment of the aluminum surfaces with according to the invention Coating solutions resulted in coated surfaces that did not turn black or otherwise discolor or which have resisted blackening or other discoloration. The test results were like evaluated as follows: 5: perfect, no blackening; 3+: acceptable and 0: complete failure, 3 strong blackening.

Aluminum surfaces treated with the solutions described in the examples were also tested for their paint adhesion tested. After drying the treated surface as described above, part of the surface was covered with a white base coat (No. 12V / 100A white polyester paint from H.C.I.) and the other part of the surface with a vinyl interior lacquer (modified vinyl epoxy lacquer C-5054 by Mobil). After the paint had dried or hardened, the painted surface was either converted into a immersed in boiling aqueous solution of detergent or saline solution. After removing the painted surface it was rinsed from the solution with water and excess water was wiped off. The painted surface was then cross-hatched using a sharp metal object was used to linearly expose aluminum that peeked through the paint or varnish, and then tested for paint adhesion. In this test, a cellophane tape was stuck over the cross-hatched area placed and then peeled off with a quick drag against itself so that it is cross-hatched from the Area v / eg pulled. The test results were rated as follows: 10: perfect if the tape is none at all Color decreased from the surface, 8: acceptable and 0: complete failure.

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The various compositions of the first 6 examples and the first 7 comparative examples are listed in Table I and comprise compositions according to the invention and comparative compositions. Table II gives the results of the pasteurization and paint adhesion tests. The solutions in Table I were adjusted to a pH of 2.7 by adding concentrated nitric acid or ammonium hydroxide. The surfaces were exposed to either boiling tap water for 15 minutes or (71 ^° C, 160 ^° F) hot tap water for 45 minutes, as indicated in Table II.

In some cases there was more than one sample of the aluminum surface treated in the same way. In these cases, several ratings are given in the tables below listed.

Table I. 6 ^M 4 and your amounts in g / l H ₅ PO ₄ Solution components H ₂ SiF ₆ H ₂ TiF ₆ HF 0.294 at
game - 0.164 0.050 0.294 1 0.240 0.264 - 0.164 0.050 0.294 2 - 0.264 - 0.164 0.050 0.294 3 - 0.264 - 0.164 0.050 0.294 4th 0.240 0.264 - - - 0.294 5 0.240 0 - 0.164 - 0 6th 0.240 - 0 0 0 - C-1 + 0 0.264 - - 0.050 - C-2 0.240 0.264 - - 0.050 0.294 C-3 0.240 - - - 0.050 - C-4 - - 0.442 0.050 0.294 C-5 0.240 - 0.442 - 0.050 ■ - C-6 - - 0.164 0.050 C-7 0.240

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1 3+ 2 3 3 CVJ 4th 3 5 4+ 6th 4+ C-1 + O C-2 O C-3 O C-4 O C-5 O C-6 O C-7 O

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Table II Pasteurization test Paint adhesion test + ⁴

At- (212 ⁰ P) 100 ⁰ C 71 ° C (160 ° F) white base Yinyl interior 15 min 45 min coating varnish

4- 10.9 +, 9 +, 9 10,10,10,10,10

3 10.9 +, 9 +, 9 10,10,10,10

3- 9,9,9,8 10,10,10,10

5+ 9 +, 8 +, 8.8 10,10,10,10

4+ 10,10,9 +, 9 10,10,10,10,10

4+ 10,10,10,10 10,10,10,10

0 0,0,0,0 10,10,9 +, 8

0 9.8 +, 8.6 10, 10, 10, 10

0 6, <5, <5, O 10,10,10,10

0 0,0,0,0 10,10,10,9+

0 0,0,0,0 10,9 +, 9 +, 9 +

0 0,0,0,0 10,10,10

0 7.6, <5, <5 10,10,10,9+

+ only cleaned, not treated. ++ 0.7% Orvus-K-detergent, 100 ⁰ C, 15 min

The examples listed in Table III below illustrate the influence of a change in the phosphate concentration in pluozirconate solutions. The solutions of these examples had a pH of 2.5, except for Example C-9 which had a pH of 3.25. When Pasteurisiertest an aluminum can lid without painting in tap water 45 min was immersed at 71 ° C (160 ⁰ F). Part adhesion to both the white base coat and the vinyl interior paint was tested by dipping painted cans in a boiling 1-soak detergent (Joy solution) for 15 minutes, followed by standard cross-hatching and treatment with the tape.

709841/1001

at
game, H ₅ PO ₄ (NH ₄ ) ₂ ZrP ₆ Table III 3teurization ~ Te their quantities in g / l 10.10, 10 10 C-8 0 0 , 24 Solution components and 0 10.10, 10, 10 7th 0.05 0 , 24 HP Pas 3 10.10, 10, 10 8th 0.10 0 , 24 0.05 4- 10.10, 10, 10 9 0.49 0 , 24 0.05 4- 10.10, 10, 10 0.98 0 , 24 0.05 3+ 10.7 C-9 0.98 0 0.05 0 O
co 0.05 co 0.05 ■> «. . Parbhaft test
v / white base coat vinyl interior paint 100 8,7,0,0 9 +, 9 +, 9.9 9 +, 8 +, 8.5 9 +, 9 +, 9.9 9 +, 9 +, 9 +, 9 + 0.0

cn κ> co

Example 11

This example illustrates the use of a make-up solution and a make-up solution in a continuous process for coating cans in which 400 cans were drawn over. The make-up concentrate contained 4.8 g / l ammonium fluozirconate, 3 g / l phosphoric acid, 0.44 g / l hydrofluoric acid, 2.64 g / l fluoboric acid, 11.4 g / l nitric acid and 1.92 g / l sodium gluconate. This make-up concentrate was then diluted 2.5% in aqueous solution. The pH of the solution was 2.70. The make-up solution was made from 24 g / l ammonium fluozirconate, 9.4 g / l phosphoric acid, 11.7 g / l hydrofluoric acid, 0.68 g / l fluoboric acid, 21.4 g / l nitric acid and 0.4 g / l sodium gluconate .

When treating the alurainium cans, make-up solution was added as needed to keep the bath at a pH of 2.70 + 0.02. (The pH was measured after 10 cans were coated. Later calculations showed that an average of about 0.3 ml of supplementary solution was needed per can.) A pasteurization test was immersed in boiling tap water for 15 minutes. The paint adhesion was tested by immersion in boiling water with 0.7 % detergent (Orvus K) for 15 minutes, then cross-hatching and treating with tape. The test results are shown in Table IV below.

7098A1 / 1001

-n- - 2715292 Vinyl interior Tabel IV Paint adhesion test paint white ground 10.10 transfer 10.10 Number of behan Pasteurisa 10.10 10.10 Delten cans tion test 10.10 10.10 1 3 10.10 10.10 50 4+ 10.8+ 10.10 51 4+ 8 +, 7 10.10 100 4+ 9 +, 8 10.10 101 3 9 +, 9 10.10 150 4+ 10.8+ 10.10 151 4+ 10.8+ 10.10 200 4+ 10.9 10.10 201 4+ 9+, 9+ 10.10 250 4+ 9.9 10.10 251 4+ 10.10 10.10 300 4+ 10.9+ 10.10 301 4th 10.10 350 4+ 10.10 351 4+ 400 4th

Table IV shows the results of the pasteurization and paint adhesion tests. When coating v / ere the doses 3, 80, 160, 240, 320 and 399 about 5.Min subjected to a temperature of about 538 ⁰ C (1000 ⁰ F). The whole surface of these cans turned evenly brown. It should be noted that when the first 100 cans were coated, the solution was clear. Then the coating solution became slightly cloudy and was still when the 400th can was treated. If the bath was centrifuged after the end of the test, no sludge or precipitate was isolated.

The concentrations of zirconium, available fluoride and phosphate were determined over the entire run. the Zirlcon concentration increased from an initial value of 46 ppm at 111 tpm while performing. The phosphate concentration rose from 70 tpm to 110 tpm in operation. The available fluoride concentration increased from 85 ppm about 95 ppm and eventually dropped to 87 ppm.

709841/1001

Examples 12-26, as set out in Tables V and VI below, illustrate the improved ink adhesion achieved through the use of polyhydroxy compounds in the coating solution of the present invention. In particular, Table V shows the use of various concentrations of sodium gluconate in a coating solution containing ammonium fluozirconate and / or pluotitanic acid, phosphoric acid and hydrofluoric acid. Table VI illustrates the results obtained using polyhydroxy compounds other than sodium gluconate. In these examples, the coating solutions were applied by 15 sec long spraying at a temperature of 32 ° C (90 ⁰ P), and the thus coated aluminum cans were then coated with a white polyester color (the Acme Printing Ink Co., in the trade as M61513, slot white) coated. An alkydamine topcoat was applied to the wet paint coat prior to curing. Cure occurred for 6 minutes at 190 ° C (375 ° F).

709841/1001

Table V

(all solutions with ENT, adjusted to pH 2.7)

at (NH ₇ I Jz ₃ ZrP / - H ₂ TiP ₆
(g / l) H, P0 _A HP Sodium- game (g / l) 0 j 4
(g / l) (g / l) gluconate
(rJl) O 12th 0.120 0 0.098 0.010 0 co 13th 0.120 0 0.098 0.010 0.04 14th 0.120 0 0.098 0.010 0.08 15th 0.120 0 0.098 0.010 0.195 O 16 0.120 0.041 0.098 0.010 0.40 CD 17th 0.120 0.041 0.098 0.010 0 18th 0.120 0.082 0.098 0.010 0.195 19th 0.120 0.082 0.098 0.010 0 20th 0.120 0.098 0.010 0.195

Pasteurization adhesion 1 % test, 100 ⁰ C, Joy, 100 ⁰ C, (212OF). 15 min (212 ⁰ F), 15 min

5.5 0.0

4+ 8.8

4+ 8.9+ ^ '

4 9 +, 9 +

4.4 5.9

4.4 9.9+

4-, 3 + 7.9

3 +, 3 + 9 +, 9 +

KJ

5292

Table VI

(all solutions with ENT, adjusted to pH 2.7)

Bei- (NH ^) ₉ ZrPr- Η, ΡΟ, HP additive pasteurization adhesion game Λ, fs ^b ? _ / 7n (g / l) (0.1 g / l) 10O ⁰ C (212 ⁰ P), 1 % Joy, 10O ⁰ C t ^{g / 1J} Jflil 15 min (212 ⁰ F), 15 min

21 0.120 0.098 0.010 without 4 +, 4 + 0.5

-J 22 0.120 0.098 0.010 sorbitol 4 +, 4 + 0.9+

co 23 0.120 0.098 0.010 mannitol 4+, 4 + 9.9+

24 0.120 0.098 0.010 Dextrose 4 +, 4 + 5.9 ^, '

25 0.120 0.098 0.010 ethylene glycol 4 +, 4 + 7.9 ^ '- *

26 0.120 0.098 0.010 glycerine 4 +, 4 + 0.6 '

The next two groups of examples illustrate the use of previously known coating solutions that incorporate a Contains phosphate, eluoride and either zirconium or titanium. The examples show the less than desirable results obtained when these coating solutions are used to coat aluminum. Examples C-10, C-11, C-12 and C-13 show the use of ÜberzuglÖ surigen according to Examples 7, 9, 14 and 15 of US Pat. No. 3,109,757 on aluminum tin cans.

For Examples C-10, C-11, C-12, and C-13, the following became Concentrate made:

Weight percent ZnO 8.0 H ₃ PO ₄ (75 %) 39.5 Ni (NOj) ₂ -6H ₂ O 6.75 ENT ₃ (38 ° Be.) 2.87 H ₂ O 42.88

100.00

This concentrate was diluted with water to a strength of 4 volume percent and 0.25 w / v. ~% Caustic soda added. A glycerophosphate compound and a complex ketal fluoride were added to the diluted solution in the amounts shown in Table VII. The solutions were ^{heated to about 63 °} C. (145 ^° I ") and sprayed onto aluminum cans for 30 seconds. In Example C-12, Cu (NO ^) p« 6H ₂ 0 was added in such an amount that 0.005 % copper ions resulted .

Table VII shows the properties of the coating solution and the coating it formed.

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at
game Weight per
z ent
Glycerine
phosphate Weight per
cent
(NH ₄ ) ^ ZrFg Weight per
z ent Table VII Appearance d.
Coating
solution Pasteurizer
test, 10O ⁰ C
(212 ⁰ F), 15 min Paint adhesion test,
1% Joy, 100 ° C
(212 ⁰ F), 15 min C-10 0.1 0.05 0 Appearance of
overdone
Cans before
Pasteurize very much
Precipitation 1 9+ C-11 0.4 0.05 0 light gray very much
Precipitation 1 9+ -J C-12 0.2 0 0.033 light gray very much
Precipitation 0 9
4 I. σ
co
OO C-13 0.2 0 0.33 dark gray whiter
Precipitation 0 9+ oj ψ dark gray

Example C-U

This example demonstrates the use of a coating solution of the type described in Example 8 of U.S. Patent 2,813,814. A concentrate with the following ingredients has been presented here;

MnCO ₃
H ₃ PO ₄ (75 %) 183.4
555.3 ENT ₃ (70 %) 22.5 HH ₄ NO ₃ 77.3 HaHF ₂ 6.0 K ₂ TiP ₆ 15.8 HoO 573.5 all in all 1,433.8

In the above recipe, manganese carbonate and phosphoric acid were converted to hangan dihydrogen phosphate. 840 g of the above concentrate were added to 4 l of water, then 44.8 g of MnCO ₃ and 9.2 g of NaHF _{2 were} added. The solution was warmed to 93 ° C (20O ⁰ F) and sprayed on an aluminum can for 30 seconds. The coating solution contained significant amounts of precipitate and formed a gray coating on the can. The Korrosxonsbeständigkeit vnirde tested by 15-minute immersion of the box in water at 10O ⁰ C. The can became very dark and was given an O rating. The adhesion of the white basecoat was determined by dipping the can in 1 % Joy. tested at 10O ⁰ C for 15 min. The can passed the adhesion test and received a rating of 9+.

709841/1001

From the above examples it can be seen that the invention provides a coating solution that is hexavalent in nature Is chromium-free and is able to form a colorless pale coating on an aluminum surface, without changing their appearance. The coated surface resists discoloration even after one Treatment in boiling water and has excellent adhesion for overlying siccative coatings. The coating solution can be used extremely advantageously in industrial continuous coating will.

7098A1 / 1001

Claims (16)

Claims Process for the production of chemical urination coatings on an aluminum surface as a basis for subsequently applied siccative coatings, in which the surface with an aqueous-acidic chemical Conversion coating solution is contacted, characterized in that to form uniformly clear, colorless, firmly adhering coatings a solution free of hexavalent chromium, which at least 10 ppm zirconium and / or titanium, at least 10 ppm but no more than 1,000 ppm phosphate and fluoride in an amount not less than 15 ppm and in one to form a soluble complex with the whole contains sufficient amount of zirconium and titanium present, has a pH in the range of 1.5 to 4.0 and is practically free from precipitate-prone pesticides. 2. The method according to claim 1, characterized in that it on aluminum can material with a bright, shiny surface by spraying the solution at a temperature is carried out in the range of about 27 to about 33 ° C. 3. The method according to claim 1 or 2, characterized in that the surface after coating so-called Is subjected to pasteurization conditions. 4. Means for performing the method according to any one of claims 1 to 3 in the form of aqueous-acidic chemical Conversion coating solutions containing phosphoric acid and hydrofluoric acid, characterized in that they are free of hexavalent chromium and at least 10 ppm zirconium and / or titanium, but at least 10 ppm 709841/1001 - 97 - no more than 1,000 ppm phosphate and fluoride in an amount no less than 13 ppm and in one to form contain a sufficient amount of a soluble complex with all the zirconium and titanium present, have a pH in the range from 1.5 to 4.0 and are practically free of precipitating pesticides are. 5. Means according to claim 4, characterized in that it contains available fluoride in a concentration not exceeding 500 ppm. 6. Composition according to claim 4 or 5, characterized in that the pH of the solution is in the range from 2.6 to 3.1. 7. Agent according to one of claims 4 to 6, characterized in that that it additionally contains pluoboric acid in a concentration in the range from 8 to 200 ppm. 8. Agent according to one of claims 4 to 7, characterized in that that there is additionally an organic polyhydroxy compound with no more than 6 carbon atoms in one Concentration of at least 40 and no more than Contains 1,000 ppm. 9. Composition according to claim 8, characterized in that it contains 40 to 400 ppm of gluconic acid and / or its salts. 10. Agent according to one of claims 4 to 9, characterized in that that it (a) 10 to 125 phr of zircon, (b) 10 to 1,000 ppm phosphate and (c) Contains 10 to 500 ppm of available fluoride. 709841/1001 11. Gown according to one of claims 4 to 10, characterized in that that it (a) 45 to 125 ppm zircon, (b) 50 to 200 ppm phosphate and (c) Contains 10 to 200 ppm of available fluoride. 12. Agent according to one of claims 4 to 9, characterized in that that it (a) 20 to 65 ppm titanium, (b) 50 to 200 ppm phosphate and (c) Contains 10 to 200 ppm of available fluoride. 13. Means for carrying out the method according to any one of claims 1 to 3 in the form of aqueous concentrates for preparing and / or supplementing the aqueous-acidic coating solutions according to one of claims 4 to 12, characterized in that when the concentrate is mixed with water to a concentration of 0.5 to 10 percent by weight of the concentrate is diluted, the resulting dilute solution has a pH in the range from 1.5 to 4.0 and essentially off (a) at least 10 ppm zirconium and / or titanium, (b) at least 10 ppm phosphate, (c) Fluoride in one to form a complex with practically all of the zirconium and / or titanium sufficient amount and (d) water
consists. 14. Composition according to claim 13, characterized in that, when the concentrate is diluted, the resulting 709841/1001 dilute solution has a pH fourth in the range 2.6 to 3.1 and is essentially off (a) 45 to 125 ppm zircon, (b) 50 to 200 ppm phosphate, (c) 8 to 200 ppm HBP ₄ , (d) 10 to 50 ppm HP, (e) nitric acid in a range sufficient to adjust the pH of the solution in the range mentioned Amount and (f) water
consists. 15. Composition according to claim 13 or 14, characterized in that it consists of an aqueous, of precipitate practically free solution (a) 5 to 10 g / l zirconium or 2.5 to 5 g / l titanium, (b) 5 to 10 g / l phosphate and (c) there is a source of 5 to 20 g / L available fluoride. 16. Means according to claim 15, characterized in that the available fluoride is added as plus acid and / or ammonium bifluoride. 709841/1001