Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
  • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
  • C23C22/364—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also manganese cations
  • C23C22/365—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also manganese cations containing also zinc and nickel cations
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
  • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
  • C23C22/362—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also zinc cations

Definitions

• the invention relates to a method for coating metallic surfaces by zinc phosphating and the use of the substrates coated by the method according to the invention.
• Metallic surfaces can be coated with phosphate layers in a variety of ways. Zinc, manganese and / or nickel ion-containing phosphating solutions are often used. Some of the metallic substrates to be coated on the surface of the baths or systems also have a proportion of aluminum or aluminum alloys, which may lead to problems.
• the simultaneous phosphating of substrates with different metallic surfaces has increased in importance. In particular, the proportion of aluminum-containing surfaces in such systems increases, so that problems with phosphating in such systems occur more easily and more frequently than in the past.
• alkali and fluoride-containing compounds such as cryolite are precipitated on the one hand if a sufficient content of alkali metal or fluoride ions is present, and on the other hand an increased content of dissolved aluminum can occur prove to be bad poison that seriously impedes the formation of the phosphate layer, so that a thin, undefined, possibly hardly crystalline phosphate layer with poor corrosion resistance and low paint adhesion is formed becomes.
• an Al-F complex can form which is dissolved in the solution, but which can also lead to precipitation with monovalent ions such as sodium and / or potassium.
• the precipitate can collect as sludge in the bath tank and be removed from there, but can also cause troublesome precipitations on the aluminum-containing metallic surfaces.
• EP-A1-0 452 638 teaches a process for phosphating surfaces made of steel, galvanized steel together with aluminum-containing surface portions with a phosphating solution which has a total content of sodium ions in the range of at least 2 g / l, a content of sodium and potassium ions from 2 to 15 g / L and a manganese ion content of at least 1 g / L.
• EP-A2-0 434 358 describes a process for phosphating metallic surfaces in the presence of aluminum, in which the phosphating solution contains, in addition to zinc, at least one complex fluoride and a so-called simple fluoride, in which the molar ratio of complex fluoride to simple fluoride is in the range from 0.01 to 0.5.
• a dissociated and undissociated hydrofluoric acid is referred to as simple fluoride.
• at least one separate treatment container or a separate precipitation container is used.
• This publication does no concrete measures regarding monovalent cations, which make it possible to avoid the cryolite precipitation except by using additional separate containers.
• the value of the free acid FA should be 0.5 to 2 points, but was determined without the addition of KCI and would correspond to approximately 0.3 to 1.5 points FS-KCI.
• EP-A2-0 454 361 teaches very similar things.
• DE-A1-100 26 850 protects a phosphating process in which the precipitation of troublesome cryolite deposits in the area of the metallic surfaces to be coated by limiting the aluminum content of the phosphating solution and by using an additional separate precipitation container through which the phosphating solution has to 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 paint adhesion.
• the process should be as simple, safe and cost-effective as possible.
• 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,
• a zinc-containing phosphate layer being deposited on the metallic surfaces with a layer weight in the range from 0.5 to 10 g / m 2 .
• pretreatment is intended to mean that at least one essential coating, such as e.g. at least one layer of a lacquer or / and a lacquer-like material is applied.
• At least 8% of these surfaces preferably consist of aluminum and / or at least one aluminum alloy, particularly preferably at least 12%, at least 18%, at least 24%, at least 30%, min. at least 40%, at least 50%, at least 60%, at least 75% or at least 90%.
• the dissolved contents can often be present simultaneously in a non-complexed and complexed state.
• 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,
• the sodium and potassium content, calculated as sodium, is particularly preferably 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 preferably 0.3 to 3 g / L, phosphate 6 to 40 g / L, 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 total fluoride.
• the content of sodium, potassium and possibly further alkali metal ions, ammonium and nitrate ions is kept as low as possible, in particular if only an addition of up to 1 g / L or practically zero is used , preferably in each case optionally up to 0.5 g / L or up to 0.2 g / L, an addition of nitrate advantageously being at least 0.4 g / L but not more than 6 g / L , particularly advantageously only up to 4 g / L, very particularly preferably only up to 3.5 or 3 or 2.5 or 2 g / L.
• cryolite and / or related compounds containing Al-F which can lead to paint defects in the subsequent painting.
• the content of dissolved, including complexed zinc can be in particular 0.4 to 2.5 g / L, particularly preferably 0.5 to 2.2 g / L, with a content in the application of the phosphating solution in dipping being 0.5 up to 2.5 g / L and in particular at 0.7 to 2.0 g / L or in the case of application in 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 in particular be 6 to 40 g / L PO 4 , especially at least 8 g / L or up to 36 g / L.
• the phosphate layer applied with the phosphating solution according to claim 1 can either be applied directly to a metallic surface, to an activated metallic surface such as, for example, by activation based on titanium phosphate, or to at least one previously applied pre-coating, such as to a first phosphate layer, which does not or not serves only for activation, and / or to at least one other such a chemically composed layer such as, for example, be applied to a layer containing complex fluoride, silane and / or polymer.
• a sample of the surface of an Al-containing surface is, if necessary, brought to a suitable sample format in a scanning electron microscope and analyzed there using energy-dispersive or wavelength-dispersive analysis for the presence of sodium or potassium, which are usually not built into the crystal lattices of the zinc phosphates, representative of the other alkali or alkaline earth metals or ammonium, which could be precipitated in parallel with the sodium and potassium. If areas under the scanning electron microscope, particularly on crystalline precipitation products with cube-like crystals, allow detection of sodium or / and potassium, precipitation of a substance containing sodium or / and potassium, such as e.g. Cryolith ran out.
• the content of dissolved aluminum in the phosphating solution can preferably be in the concentration range from 0.002 to 1 g / L, in particular from at least 0.005 g / L, particularly preferably from 0.008 to 0.7 g / L, especially at 0.01 up to 0.4 g / L.
• An aluminum content higher than 0.1 g / L is not detrimental to 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.
• the sum of the contents of complex-bound fluoride in silicon complex fluoride and in boron complex fluoride is preferably 0.01 to 8 g / L, particularly preferably 0.02 to 5.3 g / L, very particularly preferably 0.02 to 4 g / L, in particular less than 3 or 2 g / L or even not more than 1 , 8 g / L. It is particularly preferred if the content of silicon complex fluoride is not more than 1.8 g / L.
• 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.
• the contents of sodium in the phosphating solution can be 0.05 to 2 g / L, potassium practically zero or 0.030 to 1.5 g / L, 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 .
• the contents of silicon complex fluoride are preferably 0.01 to 2.5 g / L and / or boron complex fluoride is preferably 0.01 to 2.8 g / L.
• 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 .
• levels of sodium in the range from 0.05 to 2 g / L, in potassium of practically zero or in the range from 0.05 to 1 g / L, in silicon complex fluoride in the range from 0.03 to 2.5 can be present g / L or / and boron complex fluoride in the range of 0.03 to 2.8 g / L.
• This variant particularly preferably has more sodium than potassium.
• the contents dissolved in the phosphating solution can alternatively be used virtually zero or 0.060 to 1.8 g / L of sodium, 0.035 to 1.4 g / L of potassium, sodium and potassium in the concentration range of 0.05 to 2 g / L as sodium, potassium on a molar basis Sodium is converted, preferably 0.02 to 1 g / L of silicon complex fluoride or / and 0.02 to 3 g / L of boron complex fluoride, the latter calculated as SiF 6 or BF.
• 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 2.5 g / L or 0.03 to 1.8 g / L, the latter calculated as SiF 6 or BF.
• 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, with mole-based potassium being converted to sodium.
• the dissolved contents in the phosphating solution in nickel can be practically zero or 0.001 to 3 g / L or / and in manganese practically zero or 0.002 to 5 g / L, in particular in nickel 0.02 to 2 g / L , particularly preferably 0.1 to 1.5 g / L or in particular 0.05 to 4 g / L of manganese, 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.
• the dissolved contents of dissolved iron 2+ ions in the phosphating solution can be practically zero or 0.005 to 3 g / L o- the / and on complexed iron 3+ ions are preferably practically zero or 0.005 to 1 g / L, in particular on dissolved iron 2+ ions 0.02 to 2 g / L, particularly preferably 0.1 to 1.5 g / L L or in particular on complexed iron 3+ ions 0.002 to 0.5 g / L, particularly preferably 0.005 to 0.1 g / L.
• the complexed iron 3+ ions are very particularly preferably predominantly or exclusively in the form of a fluoride complex (s).
• the dissolved contents in the phosphating solution in silver can be practically zero or 0.001 to 0.080 g / L or / and in copper practically zero or 0.001 to 0.050 g / L, especially in silver 0.002 to 0.030 g / L, particularly preferably up to 0.015 g / L or in particular on copper 0.002 to 0.015 g / L, particularly preferably up to 0.010 g / L.
• the dissolved contents in the phosphating solution of titanium can be practically zero or 0.001 to 0.200 g / L or / and zirconium practically zero or 0.001 to 0.200 g / L, in particular titanium in the range from 0.002 to 0.150 g / L 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.
• the phosphating solution can have the following contents: zinc in the range from 0.4 to 2.5 g / L, manganese in the range from 0.3 to 2.0 g / L,
• the phosphating solution can have the following contents: zinc in the range from 0.5 to 1.9 g / L, manganese in the range from 0.4 to 0.95 g / L,
• Free fluoride content 0.06 to 0.4 g / L or / and complex fluoride content in the range 0.2 to 4 g / L as SiF 6 .
• the zinc content of the phosphating solution is greater than its manganese content.
• the dissolved contents in the phosphating solution of ammonium can be practically zero or 0.01 to 50 g / L or / and practically zero of nitrate or 0.01 to 30 g / L, in particular 0.012 to 20 g of ammonium / L, particularly preferably 0.015 up to 5 g / L or in particular 0.05 to 20 g / L of 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.
• ammonium can be added as a bifluoride.
• the pH can be influenced with the addition of ammonia without increasing the sodium and potassium content.
• the dissolved contents in the phosphating solution of sulfate can be practically zero or 0.005 to 5 g / L or / and of chloride practically zero or 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 of chloride 0.050 to 0.3 g / L, particularly preferably at least 0.075 g / L or up to 0.15 g / L.
• 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,
• the phosphating solution particularly preferably contains at least a certain nitrate content as accelerator, but the addition of at least one further accelerator is advantageous.
• the nitrogen Compounds containing the content is optionally preferably 0.01 to 2 g / L for m-nitrobenzenesulfonate, 0.001 to 0.400 g / L for nitrite or 0.01 to 3.5 g / L for nitroguanidine.
• the chlorate-based content is preferably practically zero or in the range from 0.05 to 4 g / L or particularly preferably in the range from 0.1 to 3 g / L or from 0.15 to 1.8 g / L L.
• the content based on hydroxylamine is preferably practically zero or in the range from 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 from 0.05 to 1.5 g / L or particularly preferably in the range from 0.15 to 1 g / L.
• the nitrite-based content 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 from 0.1 to 3 g / L or particularly preferably in the range from 0.3 to 2.5 g / L.
• the content 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.
• the total content of all accelerators is preferably less than 5 g / L, particularly preferably less than 4 g / L, in particular less than 3.5 g / L, less than 3 g / L or less than 2.5 g / L ,
• 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 of 4 to 120 g / L, calculated on a mole basis as PO preferably.
• 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.
• the magnesium content in the phosphating solution can preferably be not more than 1 g / L, particularly preferably less than 0.5 g / L, very particularly preferably not more than 0.15 g / L.
• the process according to the invention it is preferred that on the phosphated surfaces of aluminum and / or at least one aluminum alloy there is no or almost no precipitation product based on aluminum fluorocomplexes of ammonium, alkali metal and / or alkaline earth metal on the metallic surface, under which Phosphate layer or / and between the zinc phosphate crystals is deposited in the phosphate layer - at least their amounts should be so limited that the precipitation does not give rise to paint defects in the subsequent painting.
• the process according to the invention is preferably carried out using solutions which are essentially free from 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, phosphonic acids, higher-quality alcohols from 8 carbon atoms, carboxylic acids and / or other organic acids such as gluconic acid, silanes, siloxanes or / and organic polymers, copolymers and homopolymers such as resins and, if appropriate, also essentially free of colloidal and other particles.
• This essentially means in particular without intentionally adding such ions or compounds, so that impurities, pickling reactions and carry-over can most likely lead to such contents in small amounts.
• impurities, pickling reactions and carry-over can most likely lead to such contents in small amounts.
• no copper is added.
• the method according to the invention is preferably operated without current; in principle, however, it is possible to use solution electrolytically, where appropriate the content of accelerators can be reduced or even avoided.
• the so-called S-value results from dividing the value of the free acid KCI by the value of the total acid according to Fischer.
• the total acid diluted (GS ver diluted) is the sum of the included divalent cations and free and bound phosphoric acids (the latter are phosphates). It is determined by the consumption of 0.1 molar sodium hydroxide solution using the indicator phenolphthalein in 10 ml phosphating solution diluted with 200 ml deionized water. This consumption of 0.1 M NaOH in ml corresponds to the total acid score.
• the free acid KCI content can preferably be in the range from 0.3 to 6 points, the total acid content preferably diluted in the range from 8 to 70 points or / and the total acid content Fischer preferably in the range from 4 to 50 Points.
• the range of the free acid KCI is preferably 0.4 to 5.5 points, in particular 0.6 to 5 points.
• the range of total acid diluted is preferably 12 to 50 points, in particular 18 to 44 points.
• the range of total Fischer acid is preferably from 7 to 42 points, in particular from 10 to 30 points.
• the S value as the ratio of the number of points of the free acid KCI to those of the total acid Fischer is preferably in the range from 0.01 to 0.40 points, in particular in the range from 0.03 to 0.35 points, especially in the range from 0.05 to 0.30 points.
• the pH of the phosphating solution can be in the range from 1 to 4, preferably in the range from 2.2 to 3.6, particularly preferably in the range from 2.8 to 3.3.
• substrates with a metallic surface predominantly containing aluminum, iron, copper, tin or zinc can be coated with the phosphating solution, a minimum content of aluminum and / or at least one aluminum alloy always occurring, in particular surfaces of at least one of the materials Base aluminum, iron, copper, steel, zinc and / or alloys containing aluminum, iron, copper, magnesium, tin or zinc.
• the coating of strips according to the invention is usually a strip made of aluminum or / and on at least one aluminum alloy.
• the phosphating solution can be brought onto the surface of the substrates by fluorination. lance application, roll coating, spraying, spraying, brushing, dipping, atomizing, rolling, it being possible for individual process steps to be combined with one another - in particular spraying, spraying and dipping, in particular spraying and squeezing or spraying and squeezing on the belt can be used.
• a slow moving belt with a surface containing aluminum can be coated according to the invention, e.g. also in the no-rinse process.
• the phosphating solution is preferably applied to the belt by roll coating, spraying, spraying, dipping or / and squeezing.
• the phosphate coating can preferably be applied at a temperature in the range from 20 to 70 ° C., in particular in the range from 32 to 65 ° C., particularly preferably in the range from 40 to 60 ° C.
• the metallic substrates can be coated in a time of up to 20 minutes, tape being coated preferably in a time of 0.1 to 120 seconds and particularly preferably in a time of 0.3 to 60 seconds, and parts preferably be coated in a time of 1 to 12 minutes and particularly preferably in a time of 2 to 8 minutes.
• 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.
• the substrates coated by the process according to the invention can be used in the production of strips or parts, for the production of components or body parts or preassembled elements in the automotive or aerospace industry, in the construction industry, in the furniture industry, for the Manufacture of devices and systems, in particular household appliances, measuring devices, control devices, test devices, construction elements, cladding 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, motor home or missile, as electronic or microelectronic component, as cover, housing, 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 made 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.
• test sheets consisted of a mix of sheets each in a ratio of 1: 1: 1 a) from an aluminum alloy AA6016 sanded with abrasive paper 240 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.
• a pilot plant with a 220 l bath volume was used in the exemplary embodiments, and a pot with a 10 l bath volume was used in the remaining exemplary embodiments. It was stirred and heated quickly in each case.
• 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.
• composition of the respective phosphating solution is listed in Table 1.
• Table 1 composition of the phosphating solutions in g / L or with information on the free acid (FA-KCI), total acid diluted (GS ve r Patnt) and Fischer total acid (GSF) in points, the S-value (ratio FS-KCI: GSF ), to cryolite deposits on the sheets or to the layer weight
• Fluorides or phosphates of Al, Fe, Zn and possibly other cations can be found in the so-called "sludge". However, these precipitation products practically do not settle on the sheet metal surfaces.
• the term "cryolite on sheet metal” refers to precipitates on phosphated sheets with predominantly cube-like crystals, the morphology of which was clearly visible in the scanning electron microscope and the composition of which was achieved by qualitative detection of the Na and / or K contents by EDX. In addition, F-contents could also be detected with the microsensor. The precipitation products appeared as the beginning of precipitation on surfaces of the aluminum alloy.
• Adequate coating quality was maintained over a wide range despite the significant variation in the chemical composition of the phosphating solution.
• the phosphate layers of the examples according to the invention were sufficiently fine-crystalline and sufficiently closed. Their corrosion resistance and adhesive strength corresponded to typical quality standards of similar zinc phosphate layers. Unlike the sheets of the comparative examples, all of the sheets according to the invention showed no precipitation of cryolite or chemically related phases. In the sheets of the comparative examples, due to these deposits on the phosphate layer or between the zinc phosphate crystals in the phosphate layer, the surface properties differed from the sheets coated according to the invention. The surface finish of the coated substrates of the comparative examples can lead to painting errors such as unacceptably rough paint surfaces or bubbles in the paint layer and thus inevitably lead to reworking, for example by sanding the painted surface. With the method according to the invention it was not necessary to use a separate area in the container of the phosphating solution for the precipitation or even not necessary to use a separate, additional precipitation container.
• AA6016 sheets prepared in this way were subjected to an exposure test according to VDA standard 621-414.
• the sheets that were chemically on the border between precipitation and non-precipitation of the cryolite were mainly selected.
• these sheets were provided with the following paint structure for the outdoor weathering test: BASF Cathoguard ® 400 and three-layer paint structure as at DaimlerChrysler in Sindelfingen.
• the entire four-layer paint structure had an average thickness of 110 ⁇ m.
• Table 2 shows the results of the corrosion test after 6 and 9 months of outdoor exposure in Frankfurt / Main.
• Table 2 Results of the outdoor weathering test according to VDA standard 621-414 on overpainted sheets made of AA6016 in correlation with the Na and F fre i content

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• 2003
  • 2003-07-09 AU AU2003250917A patent/AU2003250917A1/en not_active Abandoned
  • 2003-07-09 US US10/519,006 patent/US20050205166A1/en not_active Abandoned
  • 2003-07-09 DE DE50310042T patent/DE50310042D1/de not_active Expired - Lifetime
  • 2003-07-09 JP JP2005505061A patent/JP4233565B2/ja not_active Expired - Fee Related
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