DE10236526A1 - Process for treating or pre-treating parts, profiles, strips, sheets and/or wires having metallic surfaces comprises using an aqueous acidic solution containing fluoride, zinc and phosphate - Google Patents

Abstract

Process for treating or pre-treating parts, profiles, strips, sheets and/or wires having metallic surfaces comprises using an acid aqueous solution containing fluoride, zinc and phosphate with 0.04 to less than 2 g/l sodium, 0.025-2.5 g/l potassium, 0.025-2.5 g/l sodium and potassium, 0.2-4 g/l zinc, 4-65 g/l phosphate, 0.33-0.5 g/l free fluoride, 0.1-5 g/l total fluoride and optionally at least 0.2 g/l nitrate in the phosphatizing solution:

Description

The invention relates to a method for coating metallic surfaces by zinc phosphating and the use of those coated by the process according to the invention Substrates.

The coating of metallic surfaces with phosphate layers can be done in many ways. Often Zinc, manganese and / or nickel ion-containing phosphating solutions are used. On Part of the in the bathrooms or systems on their surface metallic substrates to be coated also have a portion on aluminum or aluminum alloys, which may be too Can cause problems. The phosphate layer (s) should mostly together with at least a subsequently applied lacquer layer or lacquer-like Coating good corrosion protection and good paint adhesion exhibit. The simultaneous phosphating of substrates with different metallic surface has grown in importance. In particular, the proportion of aluminum-containing grows surfaces in such systems so that it lighter and more often as previously there are problems with phosphating in such systems.

With a larger proportion of aluminum-containing metallic surfaces, the one with the phosphating solution coming into contact will be a higher one Al dissolved. This usually occurs in the presence of alkali metal ions and fluoride ions on the one hand for the precipitation of alkali and fluoride-containing compounds like cryolite, if there is a sufficient content of alkali metal or Fluoride ions are present, and on the other hand, there may be an increased content on solved Aluminum as a bath poison prove that the formation of the phosphate layer seriously disabled, so then a thin one undefined, possibly hardly crystalline phosphate layer with poorer corrosion resistance and low paint adhesion is formed. With fluoride ions in excess can an Al-F complex form the one in the solution solved which is also with monovalent ions such as Sodium or / and Potassium lead to a precipitate can. The precipitation can collect in the wheel container as sludge and can be removed from there, but can also be on the aluminum-containing metallic surfaces disturbing precipitations cause.

So far, the influences have been that bad formation of the phosphate layer on the one hand or precipitation of rainfall such as. based on cryolite and lead to errors in the subsequent painting, little known. It was unclear under which chemical conditions The problems arise because they are not always and not predictable occurred. And it was unknown how to counteract these problems can be. It was known in the problem case the content of free Fluoride stronger to raise, but then sometimes also serious problems with Precipitation containing cryolite appeared.

EP-A1-0 452 638 teaches a method for phosphating surfaces made of steel, galvanized steel together with aluminum containing surface portions with a phosphating solution, which have a total content of sodium ions in the range of at least 2 g / L, a content of sodium and potassium ions together from 2 to 15 g / L and a manganese ion content of at least 1 g / L.

EP-A2-0 434 358 describes a method for phosphating metallic surfaces in the presence of aluminum, where the phosphating solution in addition to zinc, at least one complex fluoride and a so-called simple one Contains fluoride, where the molar ratio Complex fluoride to simple fluoride in the range of 0.01 to 0.5 lies. As a simple fluoride, a dissociated and undissociated hydrofluoric acid. In this method, at least one separate treatment container or a separate precipitation tank is used. This publication leads however no concrete measures on monovalent cations, which the avoidance of cryolite precipitation except by using additional ones separate container enable. The value of free acid FA should be 0.5 to 2 points, but was determined without the addition of KCI and would correspond to about 0.3 to 1.5 points FS-KCI. Very similar teaches EP-A2-0 454 361.

DE-A1-100 26 850 protects Phosphating process in which the precipitation of troublesome cryolite deposits in the area of the metallic surfaces to be coated by a limitation the aluminum content of the phosphating solution and by using a additional separate precipitation container, by the phosphating solution must circulate is avoided.

The object was therefore to propose a phosphating process for coating aluminum-containing surfaces, in which a separate precipitation area in the container of the phosphating solution or separate containers for precipitation and thus for avoiding precipitation on the metallic surfaces to be coated are not necessary. The phosphate layer should be closed, of good, fine-grained crystallinity, of sufficiently high corrosion resistance and of sufficiently good be paint liability. The process should be as simple, safe and cost-effective as possible.

• – an Natrium praktisch Null oder im Konzentrationsbereich von 0,04 bis weniger als 2 g/L,
• – an Kalium praktisch Null oder im Konzentrationsbereich von 0,025 bis 2,5 g/L,
• – an Natrium und Kalium zusammen im Konzentrationsbereich von 0,025 bis 2,5 g/L als Natrium, wobei der Kalium-Gehalt auf Mol-Basis auf Natrium umgerechnet wird,
• – an Zink im Konzentrationsbereich von 0,2 bis 4 g/L,
• – an Phosphat im Konzentrationsbereich von 4 bis 65 g/L berechnet als POa,
• – an freiem Fluorid im Konzentrationsbereich von 0,03 bis 0,5 g/L,
• – an gesamtem Fluorid im Konzentrationsbereich von 0,1 bis 5 g/L und
• – gegebenenfalls an Nitrat von mindestens 0,2 g/L,

wobei eine Zink-haltige Phosphatschicht auf den metallischen Oberflächen mit einem Schichtgewicht im Bereich von 0,5 bis 10 g/m² abgeschieden wird. Der Begriff "praktisch Null" soll für die verschiedensten Gehalte andeuten, daß hierbei untergeordnete Verunreinigungen, herausgelöste bzw. eingeschleppte Gehalte oder in einzelnen Fällen chemische Reaktionen geringe Gehalte bedingen können.The object is achieved by a method for treating or pretreating parts, profiles, strips, sheets and / or wires with metallic surfaces, in which at least 5% of these surfaces consist of aluminum and / or at least one aluminum alloy and, if appropriate, the further metallic surfaces in particular can consist of iron alloys, zinc and / or zinc alloys, with an acidic, aqueous solution containing zinc, fluoride and phosphate, the contents dissolved in the phosphating solution

• Practically zero sodium or in the concentration range from 0.04 to less than 2 g / L,
• - practically zero potassium or in the concentration range from 0.025 to 2.5 g / L,
• Sodium and potassium together in the concentration range from 0.025 to 2.5 g / L as sodium, the potassium content on a molar basis being converted to sodium,
• Zinc in the concentration range from 0.2 to 4 g / L,
• Phosphate in the concentration range from 4 to 65 g / L calculated as POa,
• Free fluoride in the concentration range from 0.03 to 0.5 g / L,
• - of total fluoride in the concentration range from 0.1 to 5 g / L and
• - if necessary, at least 0.2 g / L of nitrate,

wherein a zinc-containing phosphate layer is deposited on the metallic surfaces with a layer weight in the range from 0.5 to 10 g / m ² . The term "practically zero" is intended to indicate for a wide variety of contents that minor impurities, dissolved or entrained contents or, in individual cases, chemical reactions can result in low contents.

The term pretreatment is intended in Contrary to the term treatment in the sense of this application, that on the pretreatment layer still has at least one essential coating such as. at least one layer of a paint or / and a paint-like Material is applied.

Preferably there are at least 8% of these surfaces made of aluminum and / or at least one aluminum alloy, especially preferably at least 12%, at least 18%, at least 24%, at least 30%, at least 40%, at least 50%, at least 60%, at least 75% or at least 90%.

The dissolved levels can be at most types of ions often simultaneously in non-complexed and complexed condition side by side.

• – An Natrium im Konzentrationsbereich von 0,08 bis 1,8 g/L oder daß mindestens eine sehr geringe Menge zugesetzt wird,
• – an Kalium im Konzentrationsbereich von 0,05 bis 2,2 g/L oder daß mindestens eine sehr geringe Menge zugesetzt wird,
• – an Natrium und Kalium zusammen im Konzentrationsbereich von 0,05 bis 2,5 g/L als Natrium, wobei Kalium auf Mol-Basis auf Natrium umgerechnet wird,
• – an Zink im Konzentrationsbereich von 0,25 bis 3,5 g/L,
• – an Phosphat im Konzentrationsbereich von 5 bis 50 g/L berechnet als PO₄,
• – an freiem Fluorid im Konzentrationsbereich von 0,085 bis 0,35 g/L oder/und
• – an gesamtem Fluorid im Konzentrationsbereich von 0,2 bis 4 g/L.

The contents dissolved in the phosphating solution can preferably be:

• Sodium in the concentration range from 0.08 to 1.8 g / L or that at least a very small amount is added,
• Potassium in the concentration range from 0.05 to 2.2 g / L or that at least a very small amount is added,
• Sodium and potassium together in the concentration range from 0.05 to 2.5 g / L as sodium, potassium on a molar basis being converted to sodium,
• Zinc in the concentration range from 0.25 to 3.5 g / L,
• Phosphate in the concentration range from 5 to 50 g / L calculated as PO ₄ ,
• Free fluoride in the concentration range from 0.085 to 0.35 g / L or / and
• - of total fluoride in the concentration range from 0.2 to 4 g / L.

The content is particularly preferably of sodium and potassium together, calculated as sodium, 0.08 to 2.2 g / L, very particularly preferably 0.2 to 2 g / L, especially 0.3 to 1.8 g / L, especially up to 1.6 g / L. The zinc content is particularly high preferably 0.3 to 3 g / L, in phosphate 6 to 40 g / L, in free fluoride at least 0.08 g / L or up to 0.3 g / L or / and total fluoride 0.3 to 3 g / L, especially at least 0.4 g / L or up to 2.5 g / L of all fluoride.

It is particularly beneficial if the content of sodium, potassium and possibly other alkali metal ions Ammonium and nitrate ions if possible is kept low, especially if only an addition of each up to 1 g / L or practically zero is used, preferably from in each case up to 0.5 g / L or up to 0.2 g / L, where appropriate Addition of nitrate advantageously at least 0.4 g / L, however at not more than 6 g / L, particularly advantageously only up to 4 g / L, very particularly preferably only up to 2 g / L is kept.

If the content of free fluoride in the phosphating solution is too high, there is an increased formation of cryolite or / and related Al-F-containing Connections that can lead to paint defects in the subsequent painting.

The content of dissolved including complexed Zinc can be particularly preferred at 0.4 to 2.5 g / L 0.5 to 2.2 g / L, with a content during application the phosphating solution in Diving at 0.5 to 2.5 g / L and especially at 0.7 to 2.0 g / L or when applied by spraying at 0.3 to 2 g / L and in particular at 0.5 to 1.5 g / L is preferred.

The phosphate content can be in particular 6 to 40 g / L PO ₄ , especially at least 8 g / L or up to 36 g / L.

The one with the phosphating solution accordingly The applied phosphate layer can either directly on a metallic surface, on an activated metallic surface such as through an activation based on titanium phosphate or at least one previously applied Pre-coating such as B. on a first phosphate layer, which is not or is not used solely for activation, or / and at least a different chemically composed layer such as on a layer containing complex fluoride, silane and / or polymer is applied become.

To assess whether disruptive precipitation products excreted on a coated aluminum-containing metallic surface a sample of the surface of an Al-containing surface after crushing it to a suitable sample format placed in a scanning electron microscope and there by means of energy dispersive or wavelength dispersive Analysis for the presence of sodium or potassium, which is common are not built into the crystal lattices of the zinc phosphates, representative of the remaining Alkali or alkaline earth metals or ammonium, parallel to this with which sodium and potassium could be precipitated. If Areas under the scanning electron microscope, in particular on crystalline precipitation products with cube-like Allow crystals to be detected using EDX sodium and / or potassium, is from a precipitation a substance containing sodium and / or potassium, e.g. cryolite went out.

In the method according to the invention can the levels of dissolved Aluminum in the phosphating solution preferably in the concentration range from 0.002 to 1 g / L, especially from at least 0.005 g / L, especially preferably 0.008 to 0.7 g / L, especially 0.01 to 0.4 g / L lie. A higher one Aluminum content as 0.1 g / L is here for the process according to the invention not harmful.

In the process according to the invention, the total content of silicon complex fluoride and boron complex fluoride together in the phosphating solution can preferably be 0.01 to 8 g / L - optionally converted on a molar basis to SiF ₆ , it not being necessary for both groups of fluoride complexes to occur simultaneously.

In the process according to the invention, the contents of complex-bound fluoride in the phosphating solution can preferably be 0.01 to 8 g / L, calculated as SiF ₆ , the conversion being carried out on a molar basis.

In the method according to the invention, the contents dissolved in the phosphating solution can
of sodium 0.05 to 2 g / L,
of potassium practically zero or 0.030 to 1.5 g / L,
of silicon complex fluoride 0.01 to 4 g / L or / and
boron complex fluoride is preferably 0.01 to 4 g / L, the latter
calculated as SiF ₆ or BF ₄ .

In particular, levels of sodium in the range from 0.05 to 2 g / L, in potassium from practically zero or in the range from 0.05 to 1 g / L, in silicon complex fluoride in the range from 0.03 to 3.2 g can be present / L or / and boron complex fluoride in the range from 0.03 to 3.5 g / L, the latter calculated as SiF ₆ or BF ₄ . This variant particularly preferably has more sodium than potassium.

In the method according to the invention, the contents dissolved in the phosphating solution can alternatively be used
of sodium practically zero or 0.060 to 1.8 g / L,
of potassium 0.035 to 1.4 g / L,
of sodium and potassium in the concentration range from 0.05 to 2 g / L as sodium, potassium on a molar basis being converted to sodium,
of silicon complex fluoride 0.02 to 1 g / L or / and
boron complex fluoride is preferably 0.02 to 3 g / L,
the latter calculated as SiF ₆ or BF ₄ .

The contents of sodium 0.05 to 1.9 g / L, potassium 0.05 to 4 g / L, silicon complex fluoride 0.03 to 0.8 g / L or / and boron complex fluoride can be dissolved in the phosphating solution , 03 to 3.5 g / L, the latter calculated as SiF ₆ or BF ₄ . This variant particularly preferably has more potassium than sodium. It is particularly preferred that the sodium and potassium content of the phosphating solution together is in the concentration range up to 1.8 g / L, very particularly preferably up to 1.5 g / L, in particular up to 1.1 g / L, given as sodium, where mole-based potassium is converted to sodium.

In the method according to the invention, the dissolved contents in the phosphating solution
of nickel practically zero or 0.001 to 3 g / L or / and
manganese is preferably practically zero or preferably 0.002 to 5 g / L,
in particular 0.02 to 2 g / L of nickel, particularly preferably 0.1 to 1.5 g / L or in particular of manganese 0.05 to 4 g / L, particularly preferably 0.1 to 3 g / L. The manganese content is very particularly preferably less than 1 g / L, since this can save chemicals.

In the method according to the invention, the dissolved contents in the phosphating solution
on dissolved iron ²⁺ ions practically zero or 0.005 to 3 g / L or / and
of complexed iron ³⁺ ions practically zero or 0.005 to 1 g / L
preferably be
in particular of dissolved iron ²⁺ ions 0.02 particularly preferably up to 2 g / L, particularly preferably 0.1 to 1.5 g / L or particularly of complexed iron ions ³⁺ 0.002 to 0.5 g / L, 0.005 to 0.1 g / L. Such contents occur in particular in processes which run on the iron side, that is to say that the phosphating solution, if appropriate also with the accelerator (s) present, has a composition such that it dissolves dissolved Fe ²⁺ in the solution at a somewhat increased content can hold. The complexed iron ³⁺ ions are particularly preferably predominantly or exclusively in the form of a fluoride complex (s).

In the method according to the invention, the dissolved contents in the phosphating solution
of silver practically zero or 0.001 to 0.080 g / L or / and
copper practically zero or preferably 0.001 to 0.050 g / L,
in particular 0.002 to 0.030 g / L of silver, particularly preferably up to 0.015 g / L or in particular of 0.002 to 0.015 g / L of copper, particularly preferably up to 0.010 g / L.

In the method according to the invention, the dissolved contents in the phosphating solution
on titanium practically zero or 0.001 to 0.200 g / L or / and
zirconium preferably practically zero or 0.001 to 0.200 g / L,
in particular titanium in the range from 0.002 to 0.150 g / L, particularly preferably in the range up to 0.100 g / L or in particular zirconium in the range from 0.002 to 0.150 g / L, particularly preferably in the range up to 0.100 g / L. Above all, it is preferred not to add either a titanium or a zirconium compound to the phosphating solution. In addition, it can be advantageous to avoid titanium-containing alloys as metallic surfaces that are to be phosphated.

In the coating method according to the invention, the phosphating solution can have the following contents:
Zinc in the range of 0.4 to 2.5 g / L,
Manganese in the range from 0.3 to 2.0 g / L,
Weight ratio zinc: manganese in the range from 0.7: 1 to 1.8: 1,
Phosphate calculated as PO ₄ in the range from 7 to 35 g / L,
Zinc: phosphate weight ratio in the range from 0.01 to 0.2,
Free fluoride content 0.05 to 0.6 g / L or / and
Content of complex fluoride in the range from 0.1 to 4.5 g / L, as SiF ₆ .

In the coating method according to the invention, the phosphating solution can have the following contents:
Zinc in the range of 0.5 to 1.9 g / L,
Manganese in the range of 0.4 to 0.95 g / L,
Weight ratio zinc: manganese in the range from 0.8: 1 to 1.6: 1,
Phosphate calculated as PO ₄ in the range from 8 to 30 g / L,
Zinc: phosphate weight ratio in the range from 0.012 to 0.16,
Free fluoride content 0.06 to 0.4 g / L or / and
Complex fluoride content in the range from 0.2 to 4 g / L, as SiF ₆ .

In the method according to the invention, the dissolved contents in the phosphating solution
of practically zero ammonium or 0.01 to 50 g / L or / and
practically zero in nitrate or 0.01 to 30 g / L, in particular 0.012 to 20 g / L in ammonium, particularly preferably 0.015 to 5 g / L or 0.05 to 20 g / L in particular in nitrate, particularly preferably 0.1 to 12 g / L. Ammonium ions can be an alternative to other monovalent cations, but low or medium contents of ammonium ions usually do not lead to precipitations, or only rarely. At the same time, the pH can be influenced with the addition of ammonia without increasing the sodium and potassium content.

In the method according to the invention, the dissolved contents in the phosphating solution
of sulfate practically zero or 0.005 to 5 g / L or / and
of chloride practically zero or preferably 0.020 to 0.5 g / L,
in particular sulfate 0.01 to 4 g / L, particularly preferably 0.02 to 3 g / L or in particular chloride 0.050 to 0.3 g / L, particularly preferably at least 0.075 g / L or up to 0.15 g / L.

It is usually advantageous to add at least one accelerator to the phosphating solution. In the method according to the invention, the phosphating solution can contain at least one accelerator selected from the group of compounds or ions based on
at least one nitrogen-containing compound in the concentration range from 0.01 to 8 g / L, chlorate
in the concentration range from 0.01 to 6 g / L,
Hydroxylamine in the concentration range from 0.01 to 3 g / L and peroxide including water-soluble organic peroxide in the concentration range from 0.001 to 0.200 g / L, calculated as H ₂ O ₂ .

The phosphating solution particularly preferably contains at least a certain nitrate content as an accelerator, but a Addition of at least one further accelerator is advantageous. The content of the nitrogen-containing compounds may be in each case preferably with m-nitrobenzenesulfonate 0.01 to 2 g / L, for nitrite 0.001 to 0.400 g / L or for nitroguanidine 0.01 to 3.5 g / L. The chlorate-based content is preferred practically zero or in the range of 0.05 to 4 g / L or particularly preferably in the range of 0.1 to 3 g / L. The salary based on Hydroxylamine is preferably practically zero or in the range of 0.05 to 2 g / L or particularly preferably in the range from 0.2 to 1.5 g / L. The content based on m-nitrobenzenesulfonate is preferably practically zero or in the range of 0.05 to 1.5 g / L or particularly preferably in the range from 0.15 to 1 g / L. The Content based on nitrite is preferably practically zero or in the range from 0.005 to 0.350 g / L or particularly preferably in the range from 0.010 to 0.300 g / L. The content based on nitroguanidine is preferably practically zero or in the range of 0.1 to 3 g / L or particularly preferably in the range from 0.3 to 2.5 g / L. The salary based on peroxide including water-soluble organic peroxide is preferably practically zero or in the range from 0.003 to 0.150 g / L or particularly preferably in the range from 0.005 to 0.100 g / L.

In the process according to the invention, the total content of all cations in the phosphating solution can preferably be in the concentration range from 0.35 to 80 g / L, calculated on a molar basis as Zn, and the total content of all anions without accelerator, but including nitrate, in the concentration range from 4 to 120 g / L, calculated on a mole basis as PO _{4 are} preferably. Alternatively or additionally, at least one accelerator other than the abovementioned can also be used, in particular based on a nitro compound such as, for example, based on nitrobenzoate and / or nitrophenol. The phosphating solution preferably does not contain an accelerator based on hydroxylamine.

In the method according to the invention the content of magnesium in the phosphating solution may be preferred amount to not more than 1 g / L, particularly preferably less than 0.5 g / L, most preferably not more than 0.15 g / L.

In the method according to the invention it is preferred that on the surfaces so phosphated of aluminum and / or at least one aluminum alloy none or almost no precipitate Base of aluminum fluorocomplexes of ammonium, alkali or / and Alkaline earth metal on the metallic surface, under the phosphate layer or / and between the zinc phosphate crystals in the phosphate layer is deposited - at least their amounts should be limited so that the rainfall does not give rise to paint defects in the subsequent painting.

Preferably in the method according to the invention with solutions worked that are essentially free of ions or compounds or / and their derivatives based on barium, lead, cadmium, chromium, Hafnium, cobalt, lithium, molybdenum, Niobium, tantalum, vanadium, tungsten, precious metals such as Silver, bromine, Iodine, phosphoric acids, high-order Alcohols from 8 carbon atoms, carboxylic acids and / or other organic acids like gluconic acid, Silanes, siloxanes and / or organic polymers, copolymers and nomopolymers such as. Resins and optionally also are essentially free of colloidal and other particles. Essentially means in this case in particular without intentionally adding such ions or connections so that impurities, Avarice reactions and kidnappings are most likely at such levels lead in small quantities can. Preferably also - in many cases - no copper added. The method according to the invention is preferably operated without current; however, it is fundamental possible, the phosphating solution to be used electrolytically, where appropriate the content of accelerators can be reduced or even avoided.

To determine the free acidity 10 ml of the phosphating solution without dilution Dissociation shift of the complex fluoride to saturation mixed with KCI and using dimethyl yellow as an indicator Titrated with 0.1 M NaOH until the change from red to yellow. The The amount of 0.1 M NaOH consumed in ml gives the value of the free Acid (FS-KCI) in points.

To determine the total content of phosphate ions, 10 ml of the phosphating solution are diluted with 200 ml of deionized water and titrated with bromocresol green as an indicator with 0.1 M NaOH until the color changes from yellow to turquoise. Following this titration, after adding 20 ml of 30% neutral potassium oxalate solution against phenolphthalein as an indicator, titrate with 0.1 M NaOH until the color changes from blue to violet. The consumption of 0.1 M NaOH in ml between the envelope with bromocresol green and the envelope with phenolphthalein corresponds to the total acid according to Fischer (GSF) in points. If this value is multiplied by 0.71, the total content of phosphate ions in P ₂ O ₅ or multiplied by 0.969 for PO ₄ results (see W. Rausch: "The phosphating of metals". Eugen G. Leuze-Verlag 1988, pp. 300 ff).

The so-called S-value results by dividing the value of the free acid KCI by the value of the total acidity according to Fischer.

The total acid diluted (GS _diluted ) is the sum of the divalent cations contained and free and bound phosphoric acids (the latter are phosphates). It is verified by the consumption of 0.1 molar sodium hydroxide solution using the indicator phenolphthalein in 10 ml phosphating solution diluted with 200 ml of deionized water. This consumption of 0.1 M NaOH in ml corresponds to the total acid score.

In the method according to the invention can the free acid content KCI preferably in the range of 0.3 to 6 points, the content of total acidity dilute preferably in the range of 8 to 70 points or / and the content of total acidity Fischer are preferably in the range of 4 to 50 points. Preferably is the area of free acid KCI at 0.4 to 5.5 points, especially at 0.6 to 5 points. The range of total acid diluted is preferably 12 to 50 points, especially at 18 to 44 points. The range is preferably of total acidity Fischer at 7 to 42 points, especially at 10 to 30 points. The S value as a ratio the number of free acid points KCI to those of total acid Fischer is preferably in the range of 0.01 to 0.40 points, in particular in the range of 0.03 to 0.35 points, especially in the range of 0.05 up to 0.30 points.

In the coating method according to the invention the pH of the phosphating solution can range from 1 to 4 are preferably in the range from 2.2 to 3.6, particularly preferably in the range of 2.8 to 3.3.

In the coating method according to the invention can with the phosphating solution Substrates with a predominantly aluminum, iron, copper, or tin Zinc-containing metallic surface to be coated, wherein always a minimum content of aluminum and / or at least one Aluminum alloy occurs, especially surfaces of at least one of the Materials based on aluminum, iron, copper, steel, zinc or / and Alloys containing aluminum, iron, copper, magnesium, Tin or zinc. When coating tapes according to the invention these are mostly tapes Aluminum or / and on at least one aluminum alloy.

In the coating method according to the invention can the phosphating solution to the surface the substrates are brought in by flooding, lance application, roll coating, Spraying, spraying, Brushing, dipping, atomizing, rolling, with individual process steps can be combined with each other - in particular spraying, spraying and diving, in particular spraying and squeezing or spraying and squeezing on the belt can be used.

A slow moving belt with one Surface containing aluminum can be coated according to the invention e.g. also in the no-rinse process. The phosphating solution is preferably on Tape by roll coating, spraying, Spraying, dipping and / or squeezing applied.

In the method according to the invention the phosphate coating may preferably be at a temperature in the range of 20 to 70 ° C are applied, in particular in the range from 32 to 65 ° C., particularly preferably in the range of 40 to 60 ° C.

In the coating method according to the invention can the metallic substrates are coated in a time up to 20 minutes be, tape before preferably in a time of 0.1 to 120 seconds and particularly preferably coated in a time of 0.3 to 60 seconds and parts preferably in a time of 1 to 12 minutes and particularly preferably coated in a time of 2 to 8 minutes become.

The layer weight of the coating according to the invention is preferably in the range from 0.9 to 9 g / m ² , particularly preferably at least 1.2 g / m ² or at least 1.6 g / m ² or at most 8 g / m ² , at a maximum of 7.2 g / m ² , at a maximum of 6 g / m ² or at a maximum of 5 g / m ² . It is preferred that phosphating is carried out in a so-called "layer-forming" manner (see Werner Rausch: The Phosphating of Metals, Saulgau 1988), because then a closed phosphate layer is formed which is clearly visible to the naked eye.

It was surprising that a simple, safe, inexpensive To develop phosphating processes that are closed on the one hand good phosphate layers of sufficiently high quality, also with regard to corrosion resistance and paint adhesion, allowed to train, at the same time the problems with Al-F-containing that have always recurred rainfall avoided on aluminum-containing surfaces could become. This procedure has also proven itself with increased proportions on aluminum-containing surfaces in the mix of metallic surfaces to be phosphated.

The according to the inventive method coated substrates can are used in the production of tapes or parts of components or body parts or pre-assembled elements in the automotive or aerospace industry, in the construction industry, in the furniture industry, for the Manufacture of equipment and systems, especially household appliances, measuring devices, control devices, test equipment; Construction elements, claddings and small parts; as Wire, wire winding, wire mesh, sheet metal, cladding, shielding, Body or part of a body, as part of a vehicle, trailer Motorhomes or missiles, as an electronic or microelectronic component, as a cover, Casing, Lamp, lamp, traffic light element, piece of furniture or Furniture element Element of a household appliance, Frame, profile, molded part of complicated geometry, guardrail, Radiator- or fence element, bumper, Part of or with at least one tube and / or a profile, window, Door or bicycle frame or as a small part such as a screw, nut, flange, spring or an eyeglass frame.

Examples and comparative examples

The subject of the invention is based on exemplary embodiments explained in more detail:

The examples are as follows listed Underlying substrates or process steps:

• a) Die Substratoberflächen wurden in einer 2%-igen wässerigen Lösung eines mildalkalischen Reinigers über 5 Minuten bei 58 bis 60°C gereinigt und hierbei gründlich entfettet.
• b) Es folgte eine Spülung mit Leitungswasser über 0,5 Minuten bei Raumtemperatur.
• c) Dann wurden die Oberflächen durch Tauchen in einem titanphosphathaltigen Aktivierungsmittel über 0,5 Minuten bei Raumtemperatur aktiviert.
• d) Danach wurden die Oberflächen über 3 Minuten bei 55°C durch Tauchen in die Phosphatierungslösung phosphatiert.
• e) Anschließend wurde zuerst mit Leitungswasser gespült, dann mit einer Zirkonfluorid enthaltenden wässerigen Lösung nachgespült und schließlich mit vollentsalztem Wasser gespült.
• f) Dann wurden die beschichteten Substrate im Trockenofen bei 80°C über 10 Minuten getrocknet. Ein Teil der Prüfbleche wurde hiernach entnommen und auf Alkali- und Fluorid-haltige Niederschläge geprüft. In diesem Zustand wurde auch das Schichtgewicht ermittelt.
• g) Schließlich wurden die trockenen Prüfbleche mit einem kathodischen Tauchlack versehen und mit den weiteren Schichten eines in der Automobilindustrie für Karossen üblichen Lackaufbaus beschichtet.

The test sheets consisted of a mix of sheets each in a ratio of 1: 1 1 a) from an aluminum alloy AA6016 with a thickness of approx. 1.15 mm, b) from a cold-rolled continuous annealed sheet made of unalloyed steel DC04B with a thickness of approx. 0 , 8 mm and c) made of galvanized sheet metal on both sides, automotive quality, grade DC05, ZE75 / 75, steel, each with a thickness of approx. 0.85 mm. The surface area of each individual sheet, of which a total of at least 3 were used per experiment, was 400 cm ² (measured over both surfaces).

• a) The substrate surfaces were cleaned in a 2% aqueous solution of a mildly alkaline cleaner for 5 minutes at 58 to 60 ° C and degreased thoroughly.
• b) This was followed by rinsing with tap water for 0.5 minutes at room temperature.
• c) Then the surfaces were activated by immersion in an activating agent containing titanium phosphate for 0.5 minutes at room temperature.
• d) The surfaces were then phosphated for 3 minutes at 55 ° C. by immersing them in the phosphating solution.
• e) Then it was rinsed first with tap water, then rinsed with an aqueous solution containing zirconium fluoride and finally rinsed with demineralized water.
• f) Then the coated substrates were dried in a drying oven at 80 ° C. for 10 minutes. Part of the test panels were then removed and tested for precipitates containing alkali and fluoride. The layer weight was also determined in this state.
• g) Finally, the dry test sheets were provided with a cathodic dip coating and coated with the other layers of a coating structure which is customary for bodies in the automotive industry.

The composition of each phosphating is listed in Table 1.

Table 1

Composition of the phosphating solutions in g / L or with information on the free acid (FS-KCI), total acid diluted (GS _diluted ) and total acid Fischer (GSF) in points, the S-value (ratio FS-KCI: GSF), to cryolite -Precipitation on the sheets or on the layer weight

No aluminum, no calcium, no magnesium and no iron added on purpose. Such levels in the phosphating solution resulted from trace contamination of the water, the additives and of the sheet metal surfaces. For dissolved aluminum in the phosphating solution Depending on the sample, the content was in the range of a few mg / L. There was a low content of dissolved iron (II) ions in the phosphating solution due to the composition of the phosphating solution, where however, a significant iron content only becomes apparent at a higher throughput of sheets in the phosphating solution could have stopped. Besides, was the phosphating solution each nitroguanidine as an accelerator with a content in the range from 0.6 to 0.8 g / L added. Fluorides or phosphates of Al, Fe, Zn and possibly other cations can be found in the so-called "mud". These precipitation products however, practically do not settle on the sheet metal surfaces. The term "cryolite on sheet metal" refers to precipitation on phosphated Sheets with mostly cuboid Crystals, the morphology of which is evident in the scanning electron microscope was recognizable and their composition by qualitative evidence the Na or / and K contents by EDX were successful. In addition, F contents could also be added can be detected with the micro probe.

Adequate coating quality was retained despite the significant variation in the chemical composition the phosphating solution preserved in wide areas.

The phosphate layers of the examples according to the invention were sufficiently fine crystalline and sufficiently closed. Your corrosion resistance and adhesive strength corresponded to typical quality standards of similar ones Zinc phosphate layers. All sheets according to the invention showed different than the sheets of the comparative examples did not precipitate cryolite or chemically related phases. In the sheets of the comparative examples resulted from these precipitates on the phosphate layer or between the zinc phosphate crystals in the phosphate layer compared to the sheets coated according to the invention one different surface properties. The surface texture of the coated substrates of the comparative examples can by Painting to paint defects such as unacceptably rough paint surfaces or vesicle in the varnish layer and thus necessarily for rework e.g. by Sand the painted surface to lead. With the method according to the invention it was not necessary to have a separate area in the container of the phosphating for the precipitation to use or even not necessary a separate, additional Use precipitation container.

Claims (19)

Process for the treatment or pretreatment of parts, profiles, strips, sheets or / and wires with metallic surfaces, in which at least 5% of these surfaces consist of aluminum or / and at least one aluminum alloy and, if appropriate, the further metallic surfaces predominantly made of iron alloys, zinc or / and zinc alloys, with an acidic, aqueous solution containing fluoride, zinc and phosphate, characterized in that the dissolved contents in the phosphating solution - practically zero in sodium or in the concentration range from 0.04 to less than 2 g / L, - practically zero in potassium or in the concentration range from 0.025 to 2.5 g / L, - in sodium and potassium together in the concentration range from 0.025 to 2 , 5 g / L as sodium, the potassium content on a molar basis being converted to sodium, - calculated for zinc in the concentration range from 0.2 to 4 g / L, - for phosphate in the concentration range from 4 to 65 g / L as PO ₄ , - of free fluoride in the concentration range of 0.03 to 0.5 g / L, - of total fluoride in the concentration range of 0.1 to 5 g / L and - optionally of nitrate of at least 0.2 g / L , wherein a zinc-containing phosphate layer is deposited on the metallic surfaces with a layer weight in the range from 0.5 to 10 g / m ² . A method according to claim 1, characterized in that the contents in the phosphating solution dissolved Aluminum are in the concentration range of 0.002 to 1 g / L. A method according to claim 1 or 2, characterized in that the total content of silicon complex fluoride and boron complex fluoride together in the phosphating solution is 0.01 to 8 g / L - possibly converted on a molar basis as SiF ₆ , it not being necessary for both groups of fluoride complexes to occur simultaneously . Method according to one of the preceding claims, characterized in that the contents of complex-bound fluoride in the phosphating solution are 0.01 to 8 g / L, calculated on a molar basis as SiF ₆ . Method according to one of the preceding claims, characterized in that the levels of sodium dissolved in the phosphating solution in the concentration range from 0.050 to 2 g / L, in potassium practically zero or in the concentration range from 0.030 to 1.5 g / L, in sodium and potassium in the concentration range from 0.025 to 1.5 g / L as sodium, with potassium being converted to sodium on a molar basis, of silicon complex fluoride in the concentration range of 0.01 to 4 g / L or / and of boron complex fluoride in the concentration range of 0.01 to 4 g / L, calculated as SiF ₆ or BF ₄ . Method according to one of the preceding claims, characterized in that the dissolved contents in the phosphating solution of sodium practically zero or in the concentration range from 0.060 to 1.8 g / L, of potassium in the concentration range from 0.035 to 1.4 g / L, of sodium and potassium in the concentration range from 0.05 to 2 g / L as sodium, potassium on a molar basis being converted to sodium, of silicon complex fluoride in the concentration range of 0.02 to 1 g / L or / and of boron complex fluoride in the concentration range of 0, 02 to 3 g / L, calculated as SiF ₆ or BF ₄ . Method according to one of the preceding claims, characterized in that that the dissolved Contents in the phosphating solution on Nickel are practically zero or in the range of 0.001 to 3 g / L or and of manganese are practically zero or in the range of 0.002 to 5 g / L. Method according to one of the preceding claims, characterized in that the dissolved contents in the phosphating solution of dissolved iron ²⁺ ions are practically zero or are in the concentration range from 0.005 to 3 g / L or / and practically zero of complexed iron ions or are in the concentration range of 0.005 to 1 g / L. Method according to one of the preceding claims, characterized in that that the dissolved Contents in the phosphating solution on Silver are practically zero or in the concentration range of 0.001 up to 0.080 g / L or / and of copper are practically zero or in the concentration range of 0.001 to 0.050 g / L. Method according to one of the preceding claims, characterized in that the dissolved contents in the phosphating solution are practically zero on titanium or are in the concentration range from 0.001 to 0.200 g / L or / and are practically zero on zirconium or are in the concentration range from 0.001 to 0.200 g / L. Method according to one of the preceding claims, characterized in that that the dissolved Contents in the phosphating solution on Ammonium are practically zero or in the concentration range of 0.01 up to 50 g / L or / and of nitrate are practically zero or are in the concentration range of 0.01 to 30 g / L. Method according to one of the preceding claims, characterized in that that the dissolved Contents in the phosphating solution on Sulphate are practically zero or in the concentration range of 0.005 up to 5 g / L or / and of chloride are practically zero or are in the concentration range from 0.020 to 0.5 g / L. Method according to one of the preceding claims, characterized in that the phosphating solution contains at least one accelerator selected from the group of compounds or ions based on nitrogen-containing compounds in the concentration range from 0.01 to 8 g / L, chlorate in the concentration range from 0 , 01 to 6 g / L, hydroxylamine in the concentration range from 0.01 to 3 g / L and peroxide including water-soluble organic peroxide in the concentration range from 0.001 to 0.200 g / L calculated as N ₂ O ₂ , with contents in the specified concentration range. Method according to one of the preceding claims, characterized in that that the Magnesium content in the phosphating solution is not more than 1 g / L, preferably not more than 0.15 g / L. Method according to one of the preceding claims, characterized in that that on the surfaces so phosphated of aluminum and / or at least one aluminum alloy none or almost no precipitate based on aluminum fluorocomplexes of ammonium, alkali or / and Alkaline earth metal on the metallic surface, under the phosphate layer or / and between the zinc phosphate crystals in the phosphate layer is deposited. Method according to one of the preceding claims, characterized in that that the pH is kept in the range of 2 to 4. Method according to one of the preceding claims, characterized in that that the Free acid KCI content in the range of 0.3 to 6 points, the total acidity diluted in the range from 8 to 70 points or / and the total acidity Fischer is in the range of 4 to 50 points. Method according to one of the preceding claims, characterized in that that phosphate coating at 20 to 70 ° C is applied. Use of the process according to at least one of claims 1 to 18 coated substrates in tape production, for manufacturing of components or body parts or pre-assembled elements in the automotive or aerospace industry, in the construction industry, in the furniture industry, for the production of devices and systems, in particular household appliances, measuring devices, control devices, test devices, Construction elements, claddings and small parts; as Wire, wire winding, wire mesh, sheet metal, cladding, shielding, Body or part of a body, as part of a vehicle, trailer Motorhomes or missiles, as an electronic or microelectronic component, as a cover, Casing, Lamp, lamp, traffic light element, piece of furniture or Furniture element Element of a household appliance, Frame, profile, molded part of complicated geometry, guardrail, Radiator- or fence element, bumper, Part of or with at least one tube and / or a profile, window, Door or Bicycle frame or as a small part such as a screw, nut, Flange, spring or an eyeglass frame.