CS386691A3 - Process of passivating additional rinsing of conversion layers - Google Patents

Description

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Technical field

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for passivating the surface-to-surface conversion layers, in particular galvanized steel, galvanized steel / aluminum alloys, as a coating preparation, and for the application of adhesives, using non-chromium-containing aqueous solutions. Further, the invention relates to the use of this method for preparing for subsequent electrocoating by dipping, in particular cathodic electrocoating by dipping, or for subsequent rinsing of metal surfaces having certain conversion layers.

Background Art

The phosphating process is used industrially to a large extent to prepare metal surfaces for subsequent pressurization. The phosphating layers obtained in this way cause, among other things, a better adhesion of the lacquer film to the metal, increase the corrosion resistance and suppress the blowing of the lacquer layer resulting from the corrosion stress of the lacquer film. Other layers, in particular those prepared by colorless, yellow or green chromating or layers obtained with titanium or zirconium-based solutions, also act in addition. The protective properties of such layers of conversion layers can be further improved when subjected to an aqueous after-treatment rinse.

Good operational technical properties are provided by passivating post-rinsing based on hexavalent and / or trivalent chromium. However, the toxicity of trivalent and especially hexavalent chromium compounds is preferred. U.S. Patent No. 4,376,000 discloses a polyvinylphenol-free after-rinse composition. However, this has to be used in a relatively high concentration, whereby undesirable loading of the waste water is caused, especially due to the high oxygen demand required for the degradation. U.S. Pat. No. 3,695,942 discloses the use of zirconium compounds for the post-processing of converting layers. The rinsing agent contains, in addition to zirconium, the alkali metal and ammonium. The presence of alkaline earth metal cations is explicitly warned. The compositions are used at a value of. however, these rinsing agents do not reach a qualitative level of chromium-containing compositions.

US Patent No. 3 Q95 970 describes acidic, aqueous compositions for post-rinsing a phosphate layer based on simple or complex fluorides, namely zirconium, chromium-fluoride and zirconfluoride compounds. With the exception of chromzirconium fluoride, the products disclosed in this patent specification are of the utmost importance. Chromzirconfluoride has the disadvantage of toxicity mentioned above.

According to an earlier design, the phosphated metal surfaces are rinsed with aqueous solutions containing aluminum umfluorozirconate with an aluminum: zirconium: fluorine molar ratio of 0.15 to 0.67 (: 1: 5 to 7), the total

the concentration of aluminum + zirconium + fluorine is 0.1 to 2.0 g / liter and the pH is set to between 3 and 5. Such additional rinsing results in high quality results. ·

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a process for passivating post-rinsing of constrictive layers on metals prior to painting or pre-coating adhesives, which does not have the disadvantages of the prior art, or has further improved the older process, which is characterized by with a very good adhesion of overlays and adhesives, and which would be virtually unnecessary to the environment. The above object has been solved by elaborating a method of the type described above according to the invention, the principle of which is to rinse the metal surfaces provided with the conical layers with an aqueous solution containing a tetravalent and / or trivalent cerium in the total amount of 0 From about 0.01 to about 1.0 g / liter, with a pH of from about 3 to about 6.

The process according to the present invention is suitable for all types of conversion layers which can be made on metals, in particular galvanized steel, galvanized steel, steel, aluminum, zinc, zinc alloys, aluminum and aluminum alloys. To these layers. bases of phosphate, such as zinc, iron, manganese, calcium, zinc and manganese and zinc and calcium, as well as other mixed products with two or more divalent cations are counted. The method is particularly suitable

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for the phosphate layers which have been formed by low-zinc phosphate-free processes or by the addition of other cations such as manganese, nickel, cobalt and magnesium. '

The process of the present invention is suitable for additionally rinsing convection layers made on the surface of aluminum or aluminum alloys by means of titanium or zirconium based solutions. Such solutions may contain, as an additional component, for example fluorides, phosphates, boron compounds and optionally, passivating components such as tannins. The process is also suitable for the post-treatment of chromate coatings, for example of the type described above, as well as icon layers which have been obtained on zinc or zinc compounds by means of a solution comprising at least two different multi-metal metal ions and a complexing agent. and having a pH of greater than 11.

After the conversion layer has been formed, the water is treated with water and subsequently treated by the method of the invention by dipping, spraying, pouring or rolling. In all test results, the anticorrosive effects of passivating after-rinsing according to the present invention correspond to at least the effect achieved by passivating post-rinse with its good effects of known solutions containing trivalent and / or tetravalent chromium.

A particularly preferred embodiment of the process according to the invention is that the metal surface provided with the conversion layer is rinsed with an aqueous solution in which the cerium concentration is between 0.05 and 0.15 g / liter.

A further preferred embodiment of the process according to the present invention is that the surfaces of the cores provided with the conversion layers are rinsed with solutions containing trivalent and tetravalent cerium in a weight ratio of 9 to 2 (Ce III / 1 / Ce IV). By using a mixture of trivalent and tetravalent cerium within said mass ratio range, a higher anticorrosive effect is obtained than when using a cerium compound in only one oxidation step.

A further advantageous embodiment of the method according to the invention is that the surfaces of the metals provided with the inverted layers are rinsed with a solution. wherein the trivalent and / or tetravalent cerium is present as nitrate and / or sulfate. Furthermore, it is expedient for the compounder to be added at least in part as fluoride, hexafluoro zirconate, hexafluorotitanate, hexafluorosilicate, hexafluoroaluminate, tetrafluoroborate or as carboxylic acid salts, hydroxycarboxylic acids or amino acids. Suitable carboxylic acids include, for example, acetic acid, oxalic acid and malonic acid, suitable hydroxycarboxylic acids are, for example, glycolic acid, lactic acid, tartaric acid and citric acid, and suitable amino acids are. for example nitrilotriacetic acid and ethylenediaminetetraacetic acid. The addition of cerium as compounds with the above-mentioned acids positively influences the solubility of especially tetravalent cerium. • y

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Another advantageous embodiment of the present invention is that the coating surfaces are rinsed with an aqueous solution which additionally contains inolybdate and / or tungstate. Preferably, these compounds are added in the form of their alkaline salts.

The pH value of the solution for additional rinsing is expediently carried out using simple mineral acids such as nitric acid or hydrofluoric acid. If alkaline chemicals are required to adjust the pH, volatile bases such as ammonia, ethanolamine, diethanolamine and triethanolamine may be used. However, according to a further preferred embodiment of the process according to the present invention, the pH is adjusted by means of alkaline hydroxides, since the alkali hydroxides, in particular hydroxidesodium, have the advantage over volatile bases that they do not cause destabilization of these solutions for additional rinsing.

The post-rinse goat used in the process of the invention is conveniently prepared by diluting the concentrate.

Another advantageous embodiment of the method according to the invention is that, following the passivating additional rinsing, the completely desalinated water is further flushed. This rinsing removes any adhering salts or salt solutions that may affect the paint's adhesion and corrosion protection.

The application of passivating post-rinse solutions to metal surfaces provided with a conversion layer takes place by conventional methods such as. such as dipping, pouring, spraying, and roll coating. The processing time is in the range of about 1 second to 2 minutes. The rinsing temperature may be in the range of room temperature to about 80 ° C. Temperatures in the range of 20 to 50 ° C are normally preferred. It is recommended to use salt-free water, especially fully desalinated water, to prepare solutions for additional treatment. Water with a high salt content is not suitable for the preparation of the bath. in

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The process of the present invention serves for preparation surfaces coated with conversion layers for painting or applying adhesive. It improves the adhesion of the organic film, improves the bubble film's resistance to bubble formation during corrosion, and suppresses the leaching caused by the blowing, leaving the film damage sites. The process is suitable for pre-powder coating, lacquer coating with low solvent and varnishes which contain substantially water as solvent. A particularly advantageous use of the process of the present invention is the preparation of metal surfaces provided with conversion layers for subsequent electrocoating by dipping, in particular cathodic electrocoating by dipping.

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The process is particularly advantageous for the post-rinsing of metal surfaces having phosphate layer conversion layers prepared by chromium-free zirconium and / or tetrane, fluorine and optionally O 2, or a base layer. plex metal oxides. EXAMPLES OF THE INVENTION

The process of the present invention is illustrated by the following examples. Example 1

Degreased steel sheets, electrolytically galvanized steel and AlngSi alloys were treated with a manganese modified low-zinc phosphating process by spraying for 2 minutes at 55 ° C. · The phosphatizing solution had the following composition: ku - 8- '~; : Zn 0.7 g / 1 η Λ 1 - ϋΟ Mn 1.0 g / 1 -Ni 1.0 g / 1, -; To 2.9 g / 1 ell &amp; ·. Ϊ ·? 5 5 5 5 5 5 5 5 5 5 5 5 5 ° ° ° 03 03 03 03 03 03 03 03 03 03 03 03 03 03 03 , 1 g / l - ap 0.3 g / l i <0 Z Z 0.07 g / l. On metal substrates, crystalline, uniformly phosphate layers of surface weight in the range of 2.5 to 3 g / m < 2 &gt; The plates were then rinsed with water and then rinsed additionally.

Passivating additional rinsing was performed by dipping at a temperature of 30 ° C for one minute. The final treatment was the shower with completely desalinated water. : · '·; · Λ <

The varnishing was carried out by cathodic electro-matting of the base, by application of the putty and by the application of the topcoat. The total coating layer thickness was about 90 µm. - row .... ‘ř> * ·

The sheets were pinned to a metal substrate using a steel needle and subjected to various tests. The results of the tests are summarized in Tables 1 to 3 below.

The post-rinsing composition of the present invention was made by dissolving 0.08 g of Ce 2+ + supplied as Ce 2 H 2 O 2 O 2 H 2 O and 0.020 g of Ce 2+ +. / shipped '2 j as

Ce / SO4 / o. 4 HgO / in one liter of water. For st

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Fumilization of tetravalent cerium, 0.1 g / l of fluoride in the form of hydrogen fluoride was added to the bath. Finally, the bath value of the bath was adjusted to 4.0-4.5 with ammonia. A slight haze that occurs when preparing the solution had no effect on the passivating properties of the after-rinse aid.

The solutions used for comparison purposes have the following composition: 1. Cr 2 / Cr 3 + solution: 0.2 g / l Cf 2 O 3 0.037- / 1 Cr 3, and a pH of 3.5 to 4.0 Al - Zr - P: 0.014 0/1 A1 0.14 s / l and 0.17 g / l P i pH value in the range 3.5 to 4.0. It is clear from the tables that the method of the present invention exhibits at least the same, in part even superior, effects to the anticorrosive agent than the particularly recognized highly effective Cro + / Cr 3+ solution. 5a

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immersing the conversion coating for 10 seconds at a temperature of 50 ° C with the following composition: titanium 0.17 g / l fluorine 1.24 g / l phosphorus pentoxide 0.09 g / l KH "0, 91 g / 1 fc &amp; nin 0.11 g / 1 sodium '0.003 s /' bioside 0.10 g / 1

The plates are then rinsed with water and rinsed additionally. To do this, the sheets are immersed in the post-rinse solution for 5 seconds at 35 ° C and finally the excess solution is removed by pressing. After a drying time of 30 seconds in a circulating drier at a temperature of 60 ° C, the sheets are varnished with a two-layer food varnish, the first layer of which is made of epoxy-phenolic resin. and the second layer is an organosol. The overall thickness of the varnish is in the range of 10 to 15 µm. £ g? with

Finally, sheet-metal discs of 60 mm in diameter are punched out of the processed, about 0.25 mm thick sheets, and cups of 26 mm in diameter and 25 mm in height are produced by deep drawing.

These cups are subjected to a sterilization test by subjecting them to a pressurized container for 40 minutes to an aqueous solution of 3% sodium chloride, 1% acid, citric acid and 0.5% lactic acid at 121 ° C.

Errors then found on the cups / nail polish,

bliny./ is judged to be peeled throughout, cup surface = - unusable /, / 15 - no lacquer errors = excellent /. 9mi

The post-rinse solution used (A) contains 0.110 g / l of trivalent cerium (supplied as clarine nitrate hexahydrate) and 0.020 g / l of quadruple cerium (supplied as ethyl sulfate sulfate). up to 4.5

The value of the solution is adjusted to the range

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For comparison purposes, a portion of the sheets is additionally rinsed with an aqueous solution of 0.6 g / l of polyvinylphenol of pHasi 5 / solution for rinsing B / a with a 0.014 g / l aluminum, 0.14 g / l zirconium, 0.17 g / l solution. 1 fluorine and 0.016 g / l pH between 3.5 and 4.0 / solution oro additional rinse 0 /. Results of Sterilization Test / Scale Scale: 1 / Unusable up to 15 = Rinse A Solution Rating A / According to the Invention / 12 to 13 B / Comparative / 6 C / Comparative / 11

The comparison of the values in the table shows that the process of the present invention provides substantially better

higher values, especially in comparison with the comparative example with a polyvinyl-based post-rinse junction. nylphenol. Example 3

Purified and degreased hot-galvanized steel sheets are dipped in a 55 ° C solution for 30 seconds to form a conversion coating, giving the following composition:

Co2 ”: 0.3 y / i Pe3 + 0.2 g / l h ° 3 1.3 g / l heg &amp; hydrohexheptanoic acid 2.2 g / l HaOH 2-7.4 g / l

The plates are then rinsed with water and rinsed additionally. For this purpose, the sheets are dipped for 5 seconds at 30 [deg.] C. in a solution for additional treatment and finally the excess solution is removed by squeezing. After a drying time of 30 seconds in a circulating dryer at a temperature of 75 ° C, the treated sheets are coated with epoxy primer and acrylate coating varnish. The layer thickness of the total coating is about 25 µm. Finally, the treated pellets are subjected to the following tests:

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I The adhesion of the varnish is determined by the so-called P-Bend Test, in which the sheets are bent by 180 0 and the different gradients of curvature are given as n-multiples.

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'· Ζ' '· ..... rr «r« mmn .-- »w» nur- ~> - ^ / 4 í \ t > yf · *, * χ-. 1 - -J «· * J * ** '”' i—, 'ί -', γ γ T «- i -, · '- Xo —r' / -> <· -, 's - · · /. - “>. * · ”Thickness. / n «0 *, 1 -, 2, .... // Tn /. As "tested, the proportion of the varnished surface of the varnish is given to the total curved surface.%. IT and other processed sheets are scribed up to the metal substrate and shears are cut using the scissors on the sheet. The value to be tested is the blowing pressure (mm), which starts from the scratch or from the cutting edge.

The rinsing solution according to the invention is 110

Ce P + / aooavan A 4 "Crude Nitrate Hydrate" and 0.020 g / L As the Cerium Sulfate Tetrahydrate, the value as hexa- / feed of this solution is between 4.0 and 4.5.

For comparison purposes, the additional rinse solution (3), containing 0.014 g / l aluminum, 0.14 g / l zirconium, 0.17 g / l fluorine and 0.016 g / l, is in the range of 3, 5 to 4.0, as well as a post-rinse solution (0), containing 2.0 g / l Cr ^ +, 0.8 g / l Cr ^ +, 0.2 g / l fluorine and 0.3 g / l zinc . Test results are shown in the following tables:

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A / according to the invention / 100 50 10 «<5 '3 / comparative / ICO r- r - OJ 15 3 0 / comparative /. 100 80! 1 V io 5 Corrosion resistance in the fog test solution for blowing / am / after 1008 h additional rinsing at scratch. at edge A / according to the invention / 0 - 1 ... .6-8 B / comparative / 1 • '<1 - 1 8 -9 C / comparative / 1 - 3 9-10

A comparison of the values shown in the tables shows that the process of the present invention is in any case equally good, or better, especially in the case of. compared to the anticorrosive protection of a recognized high-performance reference solution for post-rinsing on Cro + / Cr ^ r.

Claims (5)

> i ’ - 18 - • 'Wť ^ L AA3fS0V PATE N T O V E CLAIMS A method for passivating post-rinsing of conversion layers on a metal surface, in particular steel, galvanized steel, galvanized steel alloys and / or aluminum, as a preparation for coating or applying adhesives using non-chromium-containing aqueous solutions, characterized in that with conversion layers, rinse with an aqueous solution containing Ce 'α / or Ce'J in a total amount of 2.01 and: δ 1.0 g / l, the pH value of which is according to claim 1, by rinsing the coating solutions with the aqueous solutions with an aqueous solution having a cerium concentration in the range of 0.05-1.15 g / l. Method according to claim 1, characterized in that the surfaces of the metal surfaces provided with the conversion layers are rinsed with a water solution containing Ce 2+ and Ce 4+ in the limiting medium 9 to 2. with the conversion layers, rinse with aqueous 3h-1-in solution in which Ce and / or Ce are occupied in the form of nitrate and / or sulphate. Method according to claims. 1 characterized by the fact that the surfaces of the cores provided with the conversion layers are rinsed with an aqueous solution in which the Ce @ + + and / or Ce @ 4 4 is at least partially bound via the anionic fluoride . , hexafluorozirconate, hexarluorotitanate, hexafluorosilicate and tetrafluoroborate, optionally as a salt of carboxylic acids, hydroxycarboxylic acids and / or aminocarbosyl acids. y ' 5. A method according to claim 1, wherein the surface coatings provided with the conversion layers are rinsed with an aqueous solution which additionally contains molybdate and / or tungstate. Method according to claim 1, characterized in that the surfaces of the layers provided with the conversion layers are rinsed with an aqueous solution, the pH of which is adjusted using simple mineral acids such as nitric acid and / or hydrofluoric acid, optionally using alkali hydroxides, preferably with sodium hydroxide. to Method according to claims. 1 to characterized by those on. passivating additional rinsing with salted water. 7 that it is rinsed completely Use of the method according to one or more of the claims. 1 to 8 for the preparation of metal surfaces provided with convertible layers, for the following electromaching processes, in particular cathodic electrocoating. • y h: K • f • 'i. · ·' ·· ' - 20 - Use of the method according to one or more of claims 1 to 6. 0 to additionally rinse the metal surfaces provided with the phosphate conversion layers, the layers produced by the acidic processes based on zirconium and / or non-titanium, fluorine and optionally PO 4, or complex methoxide layers. ::