JPH0158280B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for anodizing aluminum in an electrolyte containing an organic acid. In recent decades, there has been a trend towards continuous improvement of aluminum surfaces for various applications (e.g. for construction or for the production of printing plates), e.g. when processing aluminum or its alloys in the form of strips, sheets or plates. Remarkable. The various properties desired for the surface include, for example, corrosion resistance, appearance, density, hardness, abrasion resistance, adsorption and adhesion of paints or synthetic resin films, colorability, gloss, and the like. Starting from rolled aluminum, chemical, mechanical and electrochemical surface treatment methods are developed, and combinations of various methods are also used in practice. (lithography) Processing of strip, sheet or plate materials of aluminum or aluminum alloys used as substrates for printing plates usually involves a mechanical or electrochemical roughening process followed by a roughening process. The combination of a treatment process by anodizing the aluminum surface with aluminum alloys has reached a tentative conclusion in the technological development. However, depending on the desired number of print runs of the printing plates to be treated, the aluminum material may be anodized without a separate roughening treatment, in which case the aluminum material will form a sufficiently adherent and strong aluminum oxide coating. The aluminum oxide film itself must have good adhesion to the photosensitive film to be applied. The anodized coating on the (lithographic) printing plate provides, inter alia, good dampening water guidance (=increased hydrophilicity) and increased abrasion resistance, thus reducing the image area of the printing plate, e.g. during the printing process. In addition, it has an increased adhesion strength to, for example, photoresist films. The following standard methods for anodizing aluminum in an aqueous electrolyte containing H ₂ SO ₄ are known from the prior art, e.g.
Werkstoff Aluminum und seine anodische
Oxydation”, Francke Publishing House (Bern), 760
Page (1948); “Praktische Galvanotechnik”;
Eugen G. Leuze Publishers (Saulgau), pp. 395 et seq. and 518/519 (1970); W. Hu¨bner and CTSpeiser
Co-author, “Die Praxis der anodischen Oxidation
des Aluminums”, Aluminum Verlag (Düsseldorf), pp. 137 et seq., 3rd edition (1977)],
It has now become clear that H ₂ SO ₄ is an electrolytic acid that can be used in most applications: - direct current - sulfuric acid method, in which usually per solution
10-22 in an aqueous electrolyte consisting of approximately 230 g _{of H2SO4}
anodized at a current density of 0.5-2.5 A/ ^dm2 for 10-60 minutes. In this case, the sulfuric acid concentration in the aqueous electrolyte solution can be as low as 8-10% by weight of H ₂ SO ₄ (approximately 100 g/H ₂ SO ₄ ) or as high as 30% by weight (365 g/H ₂ SO ₄ ). …“Hard anodizing” has a concentration of H ₂ SO ₄ of 166 g/(or about 230 g of H ₂ SO ₄ /
) using an aqueous electrolyte containing H ₂ SO ₄ at a treatment temperature of 0 to 5 °C, a current density of 2 to 3 A/dm ² , and a
It is carried out for 30-200 minutes at a voltage of 25-30V and an increasing voltage of about 40-100V at the end of the process. Known electrolytes other than sulfuric acid for the one-step oxidation process of metals, such as aluminum, or for the pretreatment steps prior to the actual oxidation, include in particular those described in the following publication: West German Patent No. 607 012 The book describes anodizing aluminum in an aqueous solution of oxalic acid or chromic acid. The oxidation product is later used as a base material for a photosensitive film (for example silver halide) which is to be filled into an oxide film to produce characters or pictures. A similar method is described in US Pat. No. 2,115,339. West German patent no.
No. 607474 also uses oxalic acid in aqueous solution as an electrolyte. In addition, further additives, such as organic acids, are mentioned, but are not described in detail. This oxidation product is suitable for coloring purposes. In addition to sulfuric acid, the electrolyte in the anodization of aluminum according to German Patent No. 623 847 contains sulfonated phenols. The pores formed during oxidation may be closed, for example with fat, and the reaction product is suitable for coloring purposes. West German patent no.
No. 825937 mentions aromatic hydrocarbon sulfonic acid as an additive to sulfuric acid or phosphoric acid during anodized bright coating treatment of aluminum. According to West German Patent No. 1251616, sulfuric acid and 1,8-dihydroxynaphthalene-3,6-
An aqueous electrolyte containing sulfonic acid is used for coloring aluminum by anodizing. West German Patent No. 1260266 (U.S. Patent No.
3227639), in addition to sulfuric acid, 4-
Obtained in an aqueous electrolyte containing sulfophthalic acid or 5-sulfoisophthalic acid. In German Patent Application No. 1 446 002, uniformly colored aluminum oxide coatings are obtained in aqueous electrolytes based on sulfuric acid and sulfosalicylic acid.
Similarly, according to German Patent Application No. 1521016, an aqueous electrolyte containing naphthalene disulfonic acid and sulfuric acid is used for anodizing aluminum. West German Patent Application Publication No. 2713985
The use of sulfofumaric acid for the same purpose is known from the publication no. U.S. Pat. No. 4,022,670 discloses that, in addition to sulfuric or phosphoric acid, polybasic aromatic sulfonic acids, such as sulfophthalic acid or The use of sulfosalicylic acid has been described. According to DE 1 671 614 (=U.S. Pat. No. 3,511,661), lithographic printing plates are produced by anodizing an aluminum substrate in aqueous phosphoric acid. The surface after oxidation is composed of cells with pore diameters of 150-750·10 ^-10 m. Similar processes are described in US Pat. may also be present in the aqueous electrolyte. West German Patent Application Publication No. 2000227 (=
US Pat. No. 3,658,662) describes a process for anodizing aluminum in an aqueous sodium silicate solution, the material obtained being suitable as printing plate substrate material. It is known from U.S. Pat. No. 3,672,972 to simultaneously oxidize aluminum in an aqueous electrolyte and form boehmite in an oxide film, which electrolyte contains oxalic acid, sulfuric acid, phosphoric acid, malonic acid, sulfonic acid, etc. Contains salicylic acid/sulfuric acid mixture and aluminate ions. The surface has improved adhesion. US patent no.
Aluminum plates according to No. 3,915,811 are anodized in an aqueous ternary electrolyte containing phosphoric acid, sulfuric acid and an organic acid, such as acetic acid. US Pat. No. 3,988,217 describes a method in which aluminum is anodized and coated with resin simultaneously. The aqueous electrolyte includes an aliphatic amine or quaternary ammonium salt and a resin. The reaction product has a surface with improved adhesion and corrosion resistance. According to U.S. Pat. No. 4,115,211, the aqueous anodizing electrolyte for the pretreatment for the subsequent deposition of metal salts on aluminum contains, in addition to water-soluble metal salts, water-soluble acids such as oxalic acid, tartaric acid, citric acid, etc. Contains acids, colic acid, maleic acid, sulfuric acid, phosphoric acid, sulfamic acid, or nitric acid. German Patent No. 647 427 describes a pre-anodizing treatment of aluminum before applying an oxide coating, in which electrolysis is primarily carried out using - basic organic acids, such as acetic acid and also sulfuric acid or phosphorus. It is carried out in an aqueous solution containing acid and optionally boric acid. According to German Patent No. 703 314, a pretreatment of the aluminum before applying the oxide coating by anodization is carried out in an electrolyte with a pH of 4 to 10.
The electrolyte includes an alkali salt of an organic acid, such as tartaric acid or citric acid. The use of such electrolytes for the production of printing plates filled with photosensitive films is described in US Pat. No. 3,756,826. An aqueous electrolyte for anodizing aluminum containing sulfuric acid and phosphoric acid is known from US Pat. No. 2,703,781. DE 2707810 (US Pat. No. 4,049,504) describes the use of this method in the production of printing plate substrates. The process according to DE 1178272 for coloring aluminum by anodizing the aluminum is carried out in an aqueous electrolyte containing primarily sulfosalicylic acid and additionally sulfuric acid and maleic acid or maleic anhydride.
DE 1 496 719 A1 uses electrolytes consisting of tartaric acid, sulfuric acid or sulfates, and sulfamic acid, sulfosalicylic acid or sulfophthalic acid for the same purpose. According to West German Patent Application No. 2,243,178 (=U.S. Pat. No. 3,804,731), an oxide film generated by hard anodizing on an aluminum alloy containing at least 1% copper is formed by aromatic sulfonic acid. and in an electrolyte based on sulfuric acid and optionally containing oxalic acid or maleic acid. The anodic oxidation coloring of aluminum according to German Patent Application No. 1496722 uses (a) malonic acid, tartaric acid, citric acid, diglycolic acid, malic acid, succinic acid, glutaric acid, itaconic acid, maleic acid, pyromellitic acid, among others. (benzenetetracarboxylic acid), trimellitic acid (benzenetricarboxylic acid), citraconic acid, acetylene dicarboxylic acid,
It is carried out in an aqueous electrolyte containing at least a dibasic organic carboxylic acid from the group of aconitic acid, glycosylic acid and phthalic acid and (b) oxalic acid or glycosylic acid. Two-stage and multi-stage oxidation processes or one-stage oxidation processes with non-oxidizing after-treatment steps are also known from the prior art, including, for example: German Patent No. 629 629 describes a method for anodizing aluminum, in which the surface is first electrolytically treated in sulfuric acid and subsequently in an organic acid solution (malonic acid or oxalic acid). The printing plate base material is based on the West German Patent Application Publication No.
Publication No. 1471707 (=U.S. Patent No. 3181461 specification)
The aluminum oxide coating produced by anodization is further processed with fillers, such as silicates, dichromic acid, oxalates or dyes, in an aqueous solution. In DE 1621478 (=US Pat. No. 4,153,461) polyvinylphosphonic acid is used in aqueous solution for the same purpose. Electrochemical silicate treatment under anodizing conditions of already anodized printing plate substrates made of aluminum has been described in West German patent application no.
Publication No. 2532769 (= US Patent No. 3902976 specification)
It is described in. The method for anodizing aluminum according to West German Patent Application No. 1496874 uses a sulfuric acid-based aqueous electrolyte in the first step, and sulfuric acid, sulfosalicylic acid, sulfophthalic acid,
Use those based on ligninsulfonic acid or resorcinsulfonic acid. West German Patent Application No. 2211553 (=
^The aluminum oxide film obtained by anodization from U.S. Pat. Alternatively, it is known to carry out non-electrolytic post-treatment (sealing) using N,N,N-amino-trimethanephosphonic acid. According to West German Patent Application No. 2520955, aluminum is first anodized and then a water bath containing 0.5 to 200 g of a coloring metal salt and phosphonic acid is used to electrolytically color an oxide film using alternating current. do. Phosphonic acids include in particular amino-substituted mono- or polyphosphonic acids, such as aminomethanephosphonic acid, n-propylamino-
Di(methanephosphonic acid) or hydrazine-tetra(methanephosphonic acid) may be mentioned. These compounds are used as "barrier film formers" for already anodized aluminum, for which purpose boric acid, citric acid or tartaric acid are also often used. DE 2805219 (U.S. Pat. No. 4,090,880) describes a method for producing anodized metal (in particular aluminum) printing plate substrates, in which, before the oxidation step, Optionally, the substrate is subsequently treated with compounds which have the effect of rendering it hydrophilic in aqueous solution, such as silicates, silicic acid, polyacrylic acid, zirconium fluoride or fluorozirconic acid. According to German Patent Application No. 2836878, the hydrophobic aluminum oxide coating on hydrated aluminum is produced in a first anodization step in an aqueous electrolyte based on ammonia, citric acid and phosphoric acid, and in a second anodization step. It is produced by treatment in an aqueous electrolyte based on azelaic acid (1,9-nonadic acid) in an anodizing process. The reaction product is used as an electrolytic capacitor. A two-stage anodization of aluminum printing plate substrates is known from US Pat. No. 3,940,321, in which they are first treated in sulfuric acid and then in phosphoric acid. The previously known processes based on sulfuric acid give oxide films on aluminum that can be used in many fields of use, but have some drawbacks, for example when used for the production of substrates for printing plates. There is.
The disadvantages are, on the one hand, the increased sensitivity of the resulting coatings to alkalis and "haze formation", and on the other hand, the oxidation process used in particular in "hard anodizing",
The relatively high residence time of aluminum in the electrolyte is advantageous in the continuous anodization of aluminum, which is advantageous in terms of energy and economy to obtain and maintain a low electrolysis temperature. For industrially usable anodization processes, phosphoric acid as the sole electrolyte or in mixtures has hitherto been of no importance or of only secondary importance.
In the case of this acid, only relatively thin films can be obtained by film growth. However, this thin coating is not thick enough to compete with coatings produced, for example, from borates or citric acid, for example as conversion coatings for capacitors [M.Schenk, ed.
“Werkstoff Aluminum und seine anodische
Oxydation”, Francke Publishers (Bern), 324
(1948)]. The strong redissolving ability of phosphoric acid for aluminum oxide is not only a possible explanation for this situation (Sienck, op. cit., p. 385), but also
Provides a possible explanation why thicker and more wear-resistant oxide films are not produced under economically acceptable conditions, or only under difficult conditions. The coarse pore structure of the oxide films produced in phosphoric acid (Sienck, supra, p. 585) and their low abrasion resistance are probably also attributable to this redissolution. Anodized coatings on aluminum belong to two main types. One type is a so-called barrier film, which occurs when the electrolyte used during anodization has only a small ability to dissolve oxides. Such coatings are mostly non-porous and their thickness is limited to approximately 13.10 ^-10 m/V. As soon as this critical thickness is achieved, an effective barrier to subsequent ion or electron flow generally exists. The current drops to a current corresponding to a low conductivity value and oxide film formation ceases. For example, boric acid and tartaric acid are used as electrolytes in this method. On the other hand, if the electrolyte exerts a sufficient dissolving effect on the oxide, the barrier film does not reach a critical thickness, ie the current continues to flow and a "porous" oxide structure is obtained by its action. The porous film is of considerable thickness, i.e. several
The thickness may be 10 ^-7 m, but the metal/
A thin oxide barrier film is always present at the oxidized metal interface. Electron microscopy reveals the presence of billions of closely packed amorphous oxide cells throughout the oxide film, generally aligned perpendicular to the metal/metal oxide interface. It is shown that there is. Sulfuric acid is the most commonly used electrolyte in this case, but phosphoric acid is also used. The aluminum oxide film formed by anodization is harder than the surface film oxidized in air. Anodized aluminum produced by the various aforementioned methods can be seen in action.
Substances which additionally influence adhesion and structure, especially after anodization, are also used in the printing plate sector, and improvements are nevertheless still desired. This includes, for example, removing defects that appear scattered in an oxide film or when applying a photoresist film, avoiding premature and unexpected image collapse on the printing press, or on the printing press. Fast and reliable inking. Even longer life on the printing press is desirable, as well as sealing or other forms of sealing or other forms of coating as a pre-step to later applying the photosensitive film to the substrate in a subsequent second and therefore additionally carried out processing step. An improved method of performing post-treatment that is more economical than conventional anodization would be desirable. Improved corrosion resistance and economical production over known anodizing methods for protective and decorative purposes are desirable. The object of the present invention is therefore to provide an improvement in which an aluminum oxide coating is produced which is sufficient for practical use, and the pores of this coating are also modified (sealing), so that the product is on the one hand suitable for e.g. architectural applications. on the other hand, exhibits improved adhesion, gives high print runs, results in low wear on the press, has improved shelf life, and not to mention in terms of hydrophilicity. The object of the present invention is to propose a particularly economical method for producing anodized aluminum, which can be used as an improved printing plate substrate. The present invention provides an aqueous electrolyte containing at least one polybasic organic acid after mechanically, chemically and/or electrochemically roughening the aluminum or aluminum alloy plate, sheet or strip material. We start with the method of anodizing inside. The process according to the invention consists in that the polybasic organic acid has at least 5 acid functions and belongs to the group of phosphonic acids, sulfonic acids or carboxylic acids. Additionally, the aqueous electrolyte may contain an inorganic acid from the group consisting of phosphoric acid, phosphorous acid and mixtures of phosphoric acid and sulfuric acid or phosphorous acid. The method according to the invention can be carried out continuously or batchwise. The aluminum materials treated by the method according to the invention are generally first cleaned, for which purpose various organic solvents or aqueous alkaline solutions are used. For alkaline degreasing, for example, aqueous solutions of sodium hydroxide, potassium hydroxide, trisodium phosphate and sodium silicate are used, which may also contain surfactants. Environmental and health organic solvents such as trichlorethylene, 1,
Degreasing with 1,1-trichloroethane and perchlorethylene is less commonly used. “Pure Aluminum”, 1100, 3003 and A-19 aluminum alloys are used and advantageous for offset printing; typical analyzes (% by weight) of these alloys for offset printing are as follows: is:

[Table] The metal surface may be smooth or roughened. Conventional techniques can be used to roughen the surface. These include, among others, chemical etching in alkaline or acidic solutions, roughening by dry polishing with metal brushes, wet polishing with a suspension of brushes and abrasive particles, roughening with shots and/or Electrochemical roughening in hydrochloric acid or nitric acid may be mentioned. The surface roughness and structure are different for each of these methods. The average roughness Rz is in the range of approximately 1-15 μm. The roughness is DIN (German Industrial Standard) 4768.
(October 1970 edition), the roughness Rz is 5
is the arithmetic mean of the individual roughness of each of the two adjacent reference lengths. The individual roughness is defined as the distance between two lines parallel to the average line that touch the highest and lowest points of the cross-sectional curve within each reference length. Each reference length is 1/2 of the length projected perpendicularly to the mean line of the cross-sectional curve portion used for direct evaluation. The mean line is a line parallel to the general direction of the cross-sectional curve of a geometrically ideal cross-sectional shape, and the mean line connects the cross-sectional curve with the total area of the material portion above this mean line. Divide so that the total area excluding material below is equal. Practical practice of the invention has shown that for best results, clean surfaces should be anodized immediately before air oxides form. The cleaned, degreased and optionally roughened plate may be additionally etched to remove air oxides before being treated with the method of the invention. This etching is carried out using known etching agents, such as acidic and alkaline solutions, followed by rinsing. A method for removing air oxides is, for example, decoating the plate with a phosphoric acid/chloro acid solution. Metal surfaces should therefore advantageously be rinsed with water immediately after cleaning, roughening (if this step is required) and etching and anodizing while still wet, but this careful measure should not be strictly followed. Useful products can be obtained even if these rules are not followed. Polybasic organic acids which are suitable for the process of the invention are, for example, condensation products of benzenephosphonic acid and formaldehyde (polybenzenephosphonic acid), hydrolyzed copolymers of methyl vinyl ether and maleic anhydride, copolymers of methyl vinyl ether and maleic acid, etc. Copolymer, polyvinyl sulfonic acid, polystyrene sulfonic acid, alginic acid, poly-n-butyl-benzenesulfonic acid (condensation product of n-butyl-benzenesulfonic acid and formaldehyde),
Poly-diisopropylbenzenesulfonic acid (condensation product of diisopropylbenzenesulfonic acid and formaldehyde), polyvinylphosphonic acid, poly-diisopropyl-naphthalene disulfonic acid (condensation product of diisopropyl-naphthalene-disulfonic acid and formaldehyde), poly-2-ethyl - hexanephosphonic acid, poly-decyl-benzenesulfonic acid, polyacrylic acid, polymethacrylic acid, diethylenediamine-pentaacetic acid, polynaphthalenesulfonic acid (condensation product of naphthalenesulfonic acid and formaldehyde) and mixtures of these acids. . All of the above acids are water soluble. The preferred acids in the process of the invention are phosphonic acids. Good electrolytes for producing printing plate substrates include polybenzenephosphonic acid, hydrolyzed copolymers of methyl vinyl ether and maleic anhydride, copolymers of methyl vinyl ether and maleic acid, polyvinyl sulfonic acid, polyvinylphosphonic acid, -diisopropyl-naphthalene-sulfonic acid, poly-2-ethyl-hexanephosphonic acid and mixtures of these acids.
Very suitable electrolytes include polybenzenephosphonic acid, condensation products of benzenephosphonic acid and formaldehyde, polyvinylphosphonic acid, poly-2-ethylhexanephosphonic acid and mixtures of these acids. Possible electrolyte concentrations are from about 0.01% to saturation (although solutions above about 30% are often inappropriate due to viscosity) and do not depend significantly on chemical structure. At the lower end of the concentration range, the conductivity of the solution is very small; for example, for an aqueous polyvinylphosphonic acid solution with a concentration of 0.001%, the resistance is 61.000 Ω.
It is. Nevertheless, even at a concentration of only 0.05%, an oxide film is formed produced by anodization, which gives the aluminum substrate corrosion resistance, aging resistance, hydrophilicity and printing technology properties, and which The properties are better than those of typical known products, such as aluminum plates which are anodized in a conventional manner and then sealed non-electrolytically in a hot aqueous solution of polyvinylphosphonic acid in a second step. The current supply capacity increases rapidly with increasing electrolyte concentration, resulting in shorter processing times and
and reduce the required voltage. Electrolyte concentration 1-5%
There is almost no difference in the properties of the products, and characteristic properties are obtained even at 30%, despite the often high viscosity of the electrolyte. Furthermore, at constant voltage, increasing concentration results in a decrease in the rate of film thickness growth. A particularly good concentration range considering the desired properties, easy processing, film thickness achieved and cost of the electrolyte is approximately
0.8 to about 5%. The relationship between the weight of the oxide film produced by anodization and the DC voltage used is approximately linear. In a test using 1% aqueous polyvinylphosphonic acid, the film weight was approximately 40 mg/m ² at 10 V (DC),
At 110V (DC), it is approximately 860mg/ ^m2 . These numbers are measured with an electrolysis time of 60 seconds. The electrolytically applied coatings at all magnitudes of voltage above about 5 V provide corrosion resistance and printing properties superior to those of the prior art. When the voltage is 70V (DC), the stability of the oxide film will also increase due to the large film weight and large film thickness. When the voltage exceeds 70V, the film stability decreases again. This is believed to be due to a loss of film density, since the breakdown strength limit of the film was exceeded and pits formed in the film. This view is confirmed by examination under a transmission electron microscope, in which pits are visible. Therefore, corrosion resistance is more advantageous when working at 70V or less. With plates in which electrolysis is carried out using low voltages, printing tests last for a long time. 10, 20 and 40V
Comparative tests on diazo-coated aluminum plates electrolytically treated show that the press life is inversely proportional to the electrolytic voltage and the oxide film thickness. Printing test results demonstrate that low voltage promotes good adhesion to photosensitive films, especially diazo-based films, where 1
~30V, especially the 10-30V range is excellent. Although direct current is preferred for this method, superimposed tributary currents may also be used. A square wave of pulsed power supply is particularly suitable. The strength of the current is highest at the beginning of the method according to the invention and decreases over time, while an oxide layer forms on the metal surface and the current supply capacity decreases. The current supply capacity decreases within 30 seconds to a level that minimizes subsequent current consumption. This is an important factor for the economy of the process, since a useful film has already been formed. When a 1% aqueous polyvinylphosphonic acid solution is used as the electrolyte, the current strength drops dramatically to about 10 A/dm ² depending on the load voltage and sample geometry. This reduction in current strength to a very small level is characteristic of the method according to the invention,
In contrast, in conventional anodization using the electrolytes mentioned at the outset, the current decreases gradually and remains at a level of 10-15 A/dm ² for the remainder of the process. Current density 1 to 5, especially 1.3A/dm ² to 4.3A/
dm ² represents an advantageous process condition and is excellent. The temperature at which the method is carried out may vary from about -2°C (near the freezing point of the electrolyte) to about 60°C. surface hardness test,
According to oxide film stability tests, streak adhesion, hydrophilicity and aging properties, best results are achieved at 10°C. However, the decrease in performance from 10°C to room temperature or up to 40°C is not significantly large. Working at very low temperatures requires expensive cooling capacities, and for this reason temperatures of about 10 to 35°C are advantageous, as they also offer the greatest economic efficiency and the least loss of capacity. Particularly good is processing at a working temperature of about 20-25°C. More than 60% of the aluminum oxide film is formed during the first 5 seconds (approximately 0.08 minutes) of anodization. For use in printing technology, no more than 5 minutes are used, since then no film is formed anymore. However, as discussed above, as long as the voltage is low, time is not a barrier. A time of 0.16 to 1 minute is excellent. From a methodological point of view, the process requires shorter (processing) times and lower temperatures (with little need for additional heating or cooling) compared to the conventional two-step method, which includes anodization followed by a characteristic hot immersion treatment. (no room temperature) and low current consumption are overall advantageous economical factors. In the embodiment of the process according to the invention, in which an inorganic acid is added in addition to the at least one polybasic organic acid, the following process parameters are preferably observed: It can be written as follows. An aqueous electrolyte consisting of 100 g of phosphoric acid with a concentration of 1% polyvinylphosphonic acid was used at a temperature of 20 °C and a direct current of 10 V, with a cleaned and etched aluminum plate as the anode and carbon as the cathode. Use a stick.
The aluminum oxide film forming the surface film initially forms very rapidly. During this time, the voltage is approximately constant. Although the strength of the current is not a top variable,
It is determined by other conditions selected, in particular voltage and electrolyte concentration. Immediately after the start of electrolysis, the strength of the current begins to decrease. A binary system consisting of phosphoric acid and an organic acid has a concentration of
It has about 10 g/ to about 200 g/H ₃ PO ₄ . Preferably at least about 0.25%, preferably at least about 0.5%, of a polybasic organic acid is used with 20 g/~100 g/H ₃ PO ₄ and to ensure the above-mentioned properties and advantages of the anodized aluminum plate. added. In ternary systems in which sulfuric acid or phosphorous acid is added to phosphoric acid, such mixtures may vary over a whole range of compositions. If non-porosity is to be ensured, a high proportion of polyhydric organic acids, ie about 1% or more, is required when the ratio of H ₂ SO ₄ to H ₃ PO ₄ is high. However, very high ratios of H ₂ SO ₄ to H ₃ PO ₄ may prevent the formation of non-porous coatings, while low ratios of H ₂ SO ₄ to H ₃ PO ₄ may prevent non-porous coatings. This is already achieved with a proportion of polybasic organic acids of about 0.5%. Higher contents of organic acids are in no case harmful. If the inorganic acid content is sufficiently low, the electrodeposition produces in all cases a non-porous coating, which is determined primarily by the concentration of the polybasic organic acid. The current supply capacity increases rapidly with increasing electrolyte concentration, resulting in shorter processing times and lower voltage requirements. The relationship between the weight of the aluminum oxide film produced and the DC voltage used is approximately linear. At all voltages above approximately 5 V, the electrodeposited coating provides corrosion resistance and print-technical properties superior to state-of-the-art products. The electrolytic voltage may be in the range of 5 to 75 V (DC) or higher. In the presence of strong inorganic acids, high weight electrodeposited oxide films can be easily obtained without the need for high voltages or long processing times. The desired products according to the invention are advantageously obtained using voltages of about 5 V to 40 V in both binary and ternary systems. The strength of the current is the dependent variable, while the uniform composition of the electrolyte and the voltage are independent variables. Current density 0.2A/dm ² ~6A/d
m ² indicates favorable processing conditions and is excellent. The temperature at which the method is carried out may likewise vary from about -2°C (near the freezing point of the electrolyte) to about 60°C. It is also possible to carry out the anodization of the aluminum material by classical methods, in particular with aqueous sulfuric acid, even before applying the aluminum oxide coating by the method according to the invention (ie using polybasic organic acids). In this case, the holes are sealed by the subsequent method according to the invention, so that a surface which is likewise improved in practice is produced. Applications of the materials anodized by the method according to the invention include, in particular, their use as substrates in the production of printing plates with photosensitive films. When the substrate is coated by the manufacturer of the presensitizing printing plate or by the user, the substrate is coated with one of the following photosensitive materials: As a photosensitive film, in principle, optionally All coatings are suitable which give a printable image-like surface after exposure with subsequent development and/or fixing. In addition to films containing silver halide, which are used in many areas, for example "Light-Sensitive Systems" (Jaromir Kosar, John Wiley & Sons, New York, 1965) ] are known: colloidal films containing chromates and dichromates (ibid., Chapter 2); films containing unsaturated compounds, in which the compounds are isomerized upon exposure to light. membranes containing photopolymerizable compounds, in which the monomers or prepolymers polymerize upon exposure, optionally with an initiator (ibid., Chapter 4); and membranes containing o-diazo-quinones, such as naphthoquinone diazide, p-diazo-quinone or diazonium salt condensates (ibid., Chapter 7). Suitable films also include electrophotographic photosensitive films, such as those containing inorganic or organic photoconductors. Of course, in addition to the photosensitive material, these films may also contain other components, such as resins, dyes or softeners. In particular, the following photosensitive substances or compounds can be used for coating the substrates produced by the method according to the invention: US Pat. Nos. 3,175,906, 3,046,118
No. 2063631, No. 2667415 and No. 3867147
condensation products of iminoquinonediazide, o-quinonediazide and aromatic diazonium compounds with suitable binders, as described in the patent specification, the substances described in the last-mentioned patent specification being generally preferred. There is. Furthermore, photosensitive polymer systems based on ethylenically unsaturated monomers, which have a photopolymerization initiator and may also contain a polymeric binder, are suitable. Additionally, photodimeric systems, such as systems based on polyvinyl cinnamate and diallyl phthalate prepolymers, are suitable. Such systems are described, for example, in U.S. Pat. No. 3,497,356;
No. 3615435, No. 3926643, No. 2670286, No.
3376138 and 3376139. The density and alkali resistance of aluminum oxide coatings can be determined by the potassium zincate test for anodized substrates. This test is described in US Pat. No. 3,940,321. The evaluation criterion is the dissolution rate (in seconds or minutes) of the film in an alkaline zincate solution. A solution of potassium zinc salt (ZnO:
6.9%, KOH: 50.0%, H ₂ O: 43.1%). Untreated plates form a black film (zinc formation) with a rapid reaction. Since a barrier layer is being produced in the anodized plate, the zincate solution requires a longer time for this reaction. For comparison: anodized in sulfuric acid to oxide weight 3.0
An aluminum plate having an oxide weight of about 1.0 g/m ² shows blackening after about 30 seconds; a plate anodized in phosphoric acid and having an oxide weight of about 1.0 g/m ² requires about 2 minutes for the reaction. In tests with electrolytically treated plates using polyvinylphosphonic acid as electrolyte, significantly longer reaction times are universally achieved as long as the treatment is carried out without extremely low concentrations or operating conditions. Whereas the zincate test for anodized coatings according to the state of the art gives a clearly discernible transition point, for example up to about 1 minute, for the products according to the invention there is no discernible transition point, especially with increasing reaction time. shown to be more difficult. The tin chloride () test described below is not only faster, but also provides transition points that are easier to identify, especially when observations are made under a magnifying glass. However, long reaction times require some experience if results are to be correctly judged with two reagents. US Pat. No. 3,902,976 describes the use of tin chloride solution for this purpose. Visible hydrogen evolution is shown at the transition point with subsequent formation of black spots. From representative samples tested with zincate and tin chloride () it is obtained that the tin chloride () test is approximately four times faster. Aluminum conventionally anodized with sulfuric and/or phosphoric acid as electrolyte is used in construction because of its excellent weather resistance. The tin chloride () test on such materials usually lasts about 4 to 10 seconds, whereas the test time on aluminum plates according to the invention is used
It takes about 15 seconds for a 0.1% electrolyte solution and more than 200 seconds for a 5% electrolyte solution. It is assumed that the coating thickness is correlated with corrosion resistance, which is a crucial property of anodized coatings provided for the protection and decoration of metals. Due to its establishment, “organic metal oxide (Organo metal oxide)”
The film weight of the oxide film, also known as ``Metallloxid-Komplex'', is approximately 82°C in an aqueous chromic acid/phosphoric acid standard solution (CrO ₃ 1.95%, H ₃ PO ₄ 3.41% - 85%).
It can be quantitatively measured by removing the membrane in 15 minutes. The adhesion properties of the coatings produced by the method according to the invention are much better than those produced by immersion treatment in hot solutions, such as those carried out in the state of the art following anodization. The aqueous 1.0N NaOH solution removes most of the coating applied by immersion and heating. In contrast, coatings applied electrolytically are not substantially removed, ie they are insoluble in the same or less aggressive reagents. An offset printing plate with an aluminum oxide coating applied electrolytically and before being coated with a photosensitive film is tested. The plates can be inked wet or dry, with the latter test being more rigorous (more problematic). After inking, rinse the plate under running water or spray with water and wipe gently. The ease and completeness of removal of printing ink is an indication of the hydrophilicity of the surface. Dry inking and post-drying in an oven at 100℃,
Printing ink can be completely rinsed off from plates produced according to the invention. Plates that have not been anodized or that have been anodized in a conventional manner and then immersed in a hot aqueous solution of polyvinylphosphonic acid exhibit "staining" even when aged under less severe conditions, which may be due to the original I couldn't get it back. In the inking test, plates with and without a photosensitive coating are aged for various times at various temperatures and then tested for retention of hydrophilicity. Plates with various photosensitive diazo coatings are tested for substantial photosensitivity, resolution, retention of background hydrophilicity and ease of development by aging. Finally, the offset plates, including the comparison plate, are set in the printing machine and the printing machine is operated. Differences were observed in surface abrasion, point shrinkage, ink reception misalignment relative to the grade wedge, speed and cleanliness of inking, and printing durability. In general, the plates electrodeposited according to the invention outperform plates according to the prior art in all cases within a wide range of concentrations, times, temperatures, voltages and current densities, the method parameters being relatively important. It was shown to be small. However, within the scope of the present invention, certain variables were shown to be more important than others, and certain parameters of those variables were critical to obtaining the best performance. The processes that occur over time in a typical electrodeposition test are described. In this case, for example, a 1% polyvinylphosphonic acid aqueous solution is used as an electrolyte at a temperature of 20 DEG C. and a direct current of 10 V. A cleaned and etched aluminum plate is used as the anode and a carbon rod as the cathode. Aluminum oxide first forms very rapidly and after a few seconds the coating weight exceeds 140 mg/ ^m2 ; 3
It reaches 250 mg/ ^m2 within seconds, and reaches 275 mg/m2 after 5 seconds.
It begins to level out at mg/m ² and the coating weight no longer increases substantially until after 300 seconds. During this time, the voltage is approximately constant. Although the strength of the current is not a top variable,
It is determined by other selected conditions, in particular by voltage and electrolyte concentration. Immediately after the start of electrolysis, the strength of the current begins to decrease. A self-limiting process curve is obtained in which an electrolytically provided barrier layer is formed, which layer probably consists of an organic oxidized metal complex;
and restrict subsequent current flow. This limitation is less severe than in the case of anodization with boric acid, where the maximum coating thickness is, for example, 13-16.10 ^-10 m/V. The tin chloride (SnCl ₂ ) test lasts up to 250 seconds with increasing film weight. The film weight increases rapidly until a reaction time of 150 seconds (corresponding to 630 seconds for the potassium zincate test), then remains constant until an electrolysis time of 250 seconds, after which it decreases slightly. At higher voltages the weight increase is greater. However, in this case, the tin chloride () test initially progresses with an increase in weight, but the weight gradually decreases. This explanation comes from examination with a transmission electron microscope, which shows that the surface at approximately 55,000x magnification is non-porous for the processing time up to the point of decrease in film weight in the tin chloride () test;
And no pattern appears, but then a satin finish appears, which is due to the arc. Ink samples confirm this phenomenon. Based on tests carried out at various voltages and times, it is hypothesized that a film on the metal surface, possibly consisting of an organic oxidized metal complex, acts as a capacitor.
Unless the breakdown strength limit is exceeded during electrolysis, no subsequent weight gain over time is obtained and the film does not rupture and remains constant over the tin chloride () test time. On the other hand, if the dielectric breakdown strength limit is exceeded, pits appear in the coating and the coating loses weight. The tin chloride () test time corresponds to the appearance of this pit. The dielectric breakdown is primarily a function of the voltage, with 70 V being the minimum potential at which dielectric breakdown occurs rapidly. However, assuming that it is extended for 250 seconds or more, a certain degree of dielectric breakdown is already observed at 30V in the above example. The threshold for the occurrence of a dielectric breakdown condition therefore depends on the method variables selected. Very good conditions for carrying out the process according to the invention and obtaining the corresponding products lie within this threshold value, which can be easily determined by known methods. When the aluminum oxide coatings produced according to the invention are examined using a transmission electron microscope at a magnification of at least 55,000 times, no porosity is shown on the product surface, whereas conventionally anodized aluminum oxides are already 5,000 times more porous. The magnification shows typical porosity. Furthermore, ESCA-test (Elektronen-Spektroskopie)
aluminum treated with polyvinylphosphonic acid exhibits a high phosphorous to aluminum ratio (P/Al) in a surface film that appears to consist of an organic metal oxide complex. For aluminum produced by conventional anodic oxidation, the P/Al ratio is extremely low even when phosphoric acid is used. Aluminum by conventional anodization, non-electrochemically post-treated by simple immersion in hydrothermal polyvinylphosphonic acid, has significantly smaller P/Al between
It has a ratio. ESCA results on aluminum treated with polyvinylphosphonic acid ranged from 1.10 to 2.54:1 (average
1.54) for immersion treatment in hot polyvinylphosphonic acid with a phosphorus to aluminum ratio of 0.6 to 0.9:
1 is shown. When using according to the invention binary or ternary acid mixtures consisting of polyhydric organic acids and inorganic acids, the values generally correspond at least to those of the non-electrolytic immersion process using polyvinylphosphonic acid, but up to 2:1. The value reached is obtained. A third analytical method uses the Auger Technik for measuring the thickness of films formed by electrochemical action on metal surfaces. The thickness of coatings with the same composition can be measured and compared for different electrochemical methods.
Since the voltages used in each method are known, the results can be expressed in terms of 10 ^-10 m/V. Typical barrier coatings produced using boric and tartaric acids have a thickness of 13.10 ^-10 m/V to 16.10 ^-10 m/V and are non-porous. Aluminum anodized in sulfuric or phosphoric acid by conventional methods has a
10 ⁻¹⁰ m/V, which is porous as determined by examination using a transmission electron microscope. Aluminum electrolytically treated in a 1% polyvinylphosphonic acid aqueous solution forms a non-porous film of 50 to 30·10 ^-10 m/V at a voltage of 10 to 30V. When using an aqueous electrolyte containing 100 g of phosphoric acid and 1% of polyvinylphosphonic acid, a value of 100.10 ^-10 m/V is obtained at a voltage of 25 V. It should be noted that the film forms very quickly and no longer thickens during subsequent electrolysis times. The product according to the invention is a non-porous coating and furthermore has a high phosphorus to aluminum ratio, at least when using phosphonic acid as electrolyte, which indicates that the insoluble coating likely to constitute the electrolytically applied coating is It is clear that electrolyte molecules are included together with the metal oxide in the organic metal oxide complex. In the above description and in the following examples, "%" is "% by weight" unless otherwise specified. Example 1 Several flat pieces of aluminum alloy 3003 with dimensions 17.75 cm x 19.0 cm x 0.05 cm were pretreated for electrolytic treatment. For this purpose, both sides were first treated with a commercially available aqueous-alkaline degreaser containing a surfactant. The degreased aluminum piece was then etched with a 1.0N NaOH aqueous solution at room temperature for 20 seconds. After etching, the aluminum pieces were thoroughly rinsed with water and immediately placed in an electrically insulated container filled with 1.0% aqueous polyvinylphosphonic acid (PVPS). Lead electrodes with dimensions corresponding to the dimensions of the aluminum plate were placed on both sides of the aluminum. The two electrodes are each 10 cm from the aluminum
It had an interval of A direct current power supply was used, with the aluminum connected as anode and the lead electrode as cathode. The bath temperature was maintained at 25°C and the DC voltage was 60V. Continue this process for 30 seconds, then remove the plate from the bath, rinse thoroughly and then wipe dry. SnCl ₂ - many drops of saturated solution are dropped on the surface,
SnCl ₂ reacts with aluminum as soon as it penetrates the electrochemically produced film. Scattered black specks of metallic tin mark the end of the test. On the surface prepared as described above, SnCl ₂ −
The test lasted 182 seconds. By removing the film using a chromic acid/phosphoric acid solution, an aluminum oxide film weight of 648 mg/m ² was measured. The hydrophilicity of the surface was tested by applying a stiff ink without using water. A dry applicator was used for this purpose. The plate, which was immediately dry inked and washed with water, was sufficiently clean. Other plates were aged at room temperature for 7 days, 50°C for 7 days, and 100°C for 1 hour. After aging, the plates were dry inked and rinsed. In all cases the ink could be completely rinsed off the plates. Finally, the plate was provided with a photosensitive coating containing a pigment, a polyvinyl formal binder and a diazonium condensation product according to US Pat. No. 3,867,147. After exposure with a negative and development with an aqueous-alcoholic developer, the background can be easily removed;
A clear image remained, which was shown to be of very good quality when observed with a magnifying glass. “Dirt”
There was no need to wet the plate with a fleshing agent to prevent it. Exposure was carried out using a 21-step Stauffer-step wedge, resulting in 6 fully covered steps after development with an aqueous-alcoholic developer. Examples 2 to 19 In the tests described in Example 1, the electrolytes listed in the table were used instead of polyvinylphosphonic acid, and the plates were subsequently processed. After production as in Example 1, the weight of the oxide film, the time in the SnCl ₂ -test and the response in the inking test were determined for each plate. The results are clear from the table, in which the evaluation in the inking test has the following meaning: C = perfectly clean after rinsing and suitable for use in offset printing, even in difficult printing cases T; = Lightly soiled or spotted S = Stains, unsuitable for offset printing CT = Result between C and T

Table Acid Comparative Example V1 Plates were prepared as in Example 1. In this example the electrolyte was phosphoric acid and was added in an amount of 75g/. I lowered the DC voltage to 30V because the current flow was too high at 60V DC voltage. Processing time has been extended from 30 seconds to 60 seconds. After treatment the plates were rinsed and wiped dry. The oxide weight on the plate was determined to be 871 mg/ ^m2 . The reaction time in the SnCl ₂ test was 8 seconds. “Dirty” on the plate when dry inking the surface
happened. Similarly, "stains" occurred on the plate of coating, exposing, developing and inking the photoresist film of Example 1. Comparative Example V2 A plate was prepared as in V1, but rinsed after removing the plate from the electrolytic bath and consisting of tap water containing 0.2% polyvinylphosphonic acid, 66
The difference was that they were immersed in a warm bath at ℃. After this treatment the plates were rinsed again and wiped dry. The weight of the oxide complex on the plate was 909 mg/m ² and the reaction time in the SnCl ₂ test was 10 seconds.
After dry inking the plate, the ink could not be completely removed; only a portion of the ink was removed slowly. After application of the photosensitive solution of Example 1 to the substrate, exposure, development and inking, the plate was found to be suitable for use only if the background was moistened before inking. Comparative Example V3 A plate was degreased and etched as described in Example 1. Instead of electrolytic treatment using an aqueous polyvinylphosphonic acid solution, the etched plate was immersed in a 0.2% aqueous polyvinylphosphonic acid bath, and the bath was maintained at a temperature of 66°C (non-electrolytic heating treatment). The plates were in the bath for 60 seconds, then removed, rinsed, and wiped dry. A direct reaction occurred in the SnCl ₂ test (i.e. within 1 second). Decoating the plate gave a coating weight of 37 mg/m ² .
The dry ink was relatively easy to wipe off from the freshly manufactured plate, but after aging (as described in Example 1) the inked surface became reasonably difficult to wipe clean. was recognized. After one week of storage, the surface showed a "stain" that could no longer be removed in the ink test. A plate was coated with the photosensitive film of Example 1, exposed, developed and inked. With wet inking, the background was perfect, and with dry inking, some printing ink remained on the background even after rinsing. Comparative Example V4 A plate was cleaned and etched as in Example 1. Continued immediately to 96% − H ₂ SO ₄ 150
g/ in an electrically insulated aqueous bath. The plate was connected as an anode and treated with a constant voltage of 18 V DC for 30 seconds, and the bath temperature was increased to 40 V.
It was kept at ℃. The plates thus treated were removed from the bath, rinsed thoroughly and wiped dry. The oxide film had a weight of 3213 mg/ ^m2 . The time to reaction in the SnCl ₂ test was 4
It was only a second. Dry inking on the newly manufactured surface will cause irreversible "stains" on the plate.
bring about. A negative-acting photoresist according to Example 1 was applied and the plate was then exposed, developed and inked. The background was smudged in both the wet and dry inked samples. Comparative Example V5 Prepared as in Comparative Example V4, except that in an additional step the plate was treated with a 0.2% polyvinylphosphonic acid aqueous solution at 66° C. for 60 seconds. This step was performed immediately after anodizing and rinsing the plates. After hot treatment with polyvinylphosphonic acid, the plates were rinsed and wiped dry. Inspection by the stripping test described in Example 1 revealed a coating weight of 3267 mg/m ² on this plate.
The time in the SnCl ₂ test is 6 seconds and therefore small. Printing ink can be removed relatively easily from freshly produced dry inked plates. Under the aging conditions described in Example 1
After 24 hours, the ink remained scattered. After 48 hours the surface was no longer serviceable, ie the ink could not be removed. When the negative-acting photosensitive film according to Example 1 was applied to a freshly prepared surface, a satisfactory image could be formed and developed. After aging as in Example 1 the background was always dirty. Comparative Example V6 A plate was cleaned and etched as in Example 1. _Na2O vs. _SiO2 in a container filled with water
The concentration of the aqueous solution of sodium silicate in the ratio of 2.5:1 is
It was added until it reached 7.0%. The solution was heated to approximately 82°C and held at this temperature. The plate was then immersed in this solution for 60 seconds, removed after 60 seconds, and immediately rinsed thoroughly. Following a water rinse, the plates were immersed in a 1% _-H3PO4 aqueous _solution for 30 seconds, then removed, rinsed with water, and wiped dry. The time in the SnCl ₂ test was 10 seconds and wet and dry inking of the freshly produced plates gave satisfactory results, i.e. all the ink could be easily removed. Plates aged at 50°C for 1 week and 100°C for 1 hour failed to withstand practical use in the dry ink test. Freshly produced example 1
Plates provided with a negative-acting coating solution such as 100% were acceptable after exposure, development, and inking. On the other hand, if the plate is first aged and then coated, or coated and then aged, the background is no longer suitable for practical use after 7 days at 50°C and 4 weeks at room temperature by dry inking. Ta. Comparative Example V7 A plate is manufactured in the same manner as Comparative Example V6, but
In this example the silicate treatment was carried out electrochemically rather than thermally. A plate immersed in hot sodium silicate solution was connected as an anode, a potential of 30 V DC was applied for 30 seconds, and then rinsed with water. Immediately thereafter, immersion treatment in a 3.0%-H ₃ PO ₄ aqueous solution was performed. The plate was rinsed again with water and wiped dry. The reaction time in the SnCl ₂ test increased to 46 seconds. When the freshly manufactured plate was dry inked, the ink could be easily removed. Plates aged at room temperature lost their hydrophilicity, which was shown as "staining" when the plates were subjected to a dry ink test after 8 weeks. Aging at 50° C. already led to “staining” of the dry-inked plates after 15 days. Although the freshly coated, developed and inked plate according to Example 1 was satisfactory according to its background, the coated plate was not suitable for offset printing after 18 weeks of storage at room temperature and 22 days at 50°C. It was deemed unusable. Comparative Example V8 plates were degreased and etched as in Example 1. Continue plate with 85% − H ₃ PO ₄ 75
Anodizing was carried out in an aqueous solution to which g/g was added, during which a voltage of 30 V DC was applied for 60 seconds. Immediately after anodizing, the surface was thoroughly rinsed and silicate treated at elevated temperature as in Comparative Example V6. All tests gave approximately the same results as the plate of Comparative Example V6 (simple silicate treatment at elevated temperature).
The reaction time in the SnCl ₂ test was 9 seconds, and the plates could not be put to practical use after dry inking after aging at 50° C. for 7 days or 100° C. for 1 hour. The plate coated with the photoresist film was unsuitable for practical use after 30 days of storage at room temperature and 7 days of storage at 50°C. The only identified advantage of anodizing before silicate treatment at elevated temperatures was higher press life in printing tests. Comparative Example V9 The plate was anodized as in Comparative Example V4,
It was then electrochemically silicate treated in a 7% aqueous sodium silicate solution heated to 82°C. direct current
A potential of 30V was applied for 60 seconds. The reaction time in the SnCl ₂ test was 55 seconds. Dry inking of the freshly manufactured plates gave a surface that could be quickly and easily rinsed clean. Plates aged at room temperature "stained" after 10 weeks during dry inlaying, and plates aged at 50°C became stained after 19 days. Example 1 on a freshly manufactured plate
After 19 weeks of storage at room temperature, the plates were rendered unsuitable for practical use, and storage at 50 °C led to a lack of quality after 22 days. In this case as well, the advantage of after-treatment of the anodized plates by electrosilicate treatment was smaller in terms of improved hydrophilicity than in terms of increased press life. Examples 20-23 A mixture of organic electrolytes with a total concentration of 1.0% was prepared, which mixture was used as electrolyte in the process according to the invention. Electrolysis was carried out on previously degreased, grained with abrasive suspension and etched aluminum plates using 30 V DC for 30 seconds at room temperature. The composition of the electrolyte, the weight of the oxide film, the reaction time with SnCl ₂ and the behavior in the dry inking test are listed below. Corrosion resistance and hydrophilicity were very good in all cases. Example 20 Electrolyte 1: Polyvinylphosphonic acid 0.5%, Electrolyte 2: Vinyl methyl ether/maleic acid copolymer (hydrolyzed) 0.5%, Film weight: 369 mg/
m ² , SnCl ₂ test: 117 seconds, ink test: C Example 21 Electrolyte 1: polystyrene sulfonic acid 0.25%, electrolyte 2: polyvinylphosphonic acid 0.75%, film weight: 410 mg/m ² , SnCl ₂ test: 110 seconds, ink Test: C Example 22 Electrolyte 1: Polybenzenesulfonic acid 0.75%, Electrolyte 2: Polyvinylphosphonic acid 0.25%, Film weight: 377 mg/m ² , SnCl ₂ test: 108 seconds, Ink test: C Example 23 Electrolyte 1: Polyacrylic Acid 0.75%, Electrolyte 2: Polyvinylphosphonic acid 0.25%, Film weight: 358mg/
m ² , SnCl ₂ test: 134 seconds, ink test: C C = completely rinseable, suitable for difficult offset printing. Comparative Example V10 A small piece of aluminum 3003 was degreased as in Example 1. The surface was mechanically roughened by the combined abrasive action of a quartz suspension and a rotating nylon brush. After roughening, the aluminum was thoroughly washed to remove all quartz particles, and the aluminum, which was still wet after washing with water, was heated to 65°C, 0.2
%-polyvinylphosphonic acid aqueous solution. The treatment time was 60 seconds, then the aluminum was washed with water and dried. In this sample, the film weight was 37mg/
^m2 was confirmed. The reaction time when applying SnCl ₂ was 6 seconds. On freshly produced plates, a dry inking test suggests a hydrophilic surface, since the ink was removed by gentle rubbing. Plates aged for 7 days at room temperature were partially stained by dry inking and were completely stained after 10 days of aging in the same test. When the substrate was coated with a negatively acting photoresist and aged at various times and temperatures as described in Example 1, the background was rendered unsuitable for practical use because the background became irreversibly ``stained.'' This is because it had Example 24 The plates were prepared as in Comparative Example V10, except that the plates were electrochemically treated in a 1% aqueous polyvinylphosphonic acid solution at room temperature with 30 V DC for 30 seconds, and then the plates were rinsed and wiped dry. I processed it like this. The reaction time in the SnCl ₂ test was 122 seconds. According to the chromic acid/phosphoric acid method, a coating weight of 395 mg/m ² was measured. A dry inking test carried out as in Example 1 gave very good results. Similarly, as described in Example 1,
Apply a negative photoresist film, then expose to light,
When developed and inked, a plate was obtained which at the same time had good image adhesion and high resolution and had a perfectly clean background. Example 25 Aluminum alloy 1100 was substituted for alloy 3003 and the method of Example 24 was repeated exactly. _SnCl2
The same results were obtained for reaction time, film weight, dry inking test, aging and coating test in the tests. Improvements were observed in all properties when compared with the sample of Comparative Example V10. Example 26 and Comparative Example V11 A small piece of aluminum alloy 3003 was degreased and dried. The plates were then mechanically roughened using a rotating brush (wire brush) with steel bristles in a dry process. After roughening, the plate was etched for surface activation, rinsed, and exposed to direct current for 30 seconds.
Electrolysis was carried out at a potential of 30V. Continued rinsing and wiping dry. The electrolytically produced surface resisted applied _SnCl2 for 127 seconds. The electrolytically produced film had a weight of 415 mg/m ² .
The aging method described in Example 1 was applied before dry inking and it was shown that the surface had good hydrophilicity, which remained unchanged over time. When a negatively acting photosensitive coating material (as described in Example 1) is applied, it is applied non-electrolytically (0.2% aqueous solution, 65 °C,
Advances were made in improved resolution, developer resistance, and image adhesion relative to the processed comparative samples (60 seconds). Moreover, the background was significantly more hydrophilic than in the comparison sample. Example 27 and Comparative Example V12 Degreased aluminum alloy 1100 plates were electrochemically roughened in hydrochloric acid and rinsed with water. The plate was then immediately placed in a 0.1% aqueous polyvinylphosphonic acid solution and heated at 30 V DC at room temperature.
Electrolytic treatment was carried out for 30 seconds at a potential of . After treatment the plates were rinsed and wiped dry. The generated surface is
Shows resistance of 103 seconds in SnCl ₂ test and film weight
It had 396mg/ ^m2 . Just manufactured,
The ink could be rinsed off the dry inked plate. For the aged dry inking tests described in Example 1, the surfaces produced on the electrochemically roughened substrates were satisfactory in all cases. Improvements were obtained over substrates that had been electrochemically roughened and treated in a warm aqueous solution of polyvinylphosphonic acid even when followed by a negatively acting photosensitive coating as in Example 1. This is because the adhesion and developer resistance were better. Example 28 and Comparative Example V13 A small piece of aluminum alloy 1100 was etched,
And the surface was roughened electrochemically. The plates were then rinsed and placed in an aqueous bath containing 150 g/H ₂ SO ₄ (96%). Aluminum was anodized by applying a DC potential of 18 V and treating for 60 seconds. The plate was then thoroughly rinsed with water and placed in a bath containing a 1% aqueous polyvinylphosphonic acid solution;
A potential of 30 V DC was applied for 30 seconds at room temperature. This surface was compared to a plate similarly prepared, but only non-electrolytically warm treated in an aqueous polyvinylphosphonic acid solution (0.2%, 65° C., 60 seconds). The comparison plate has a coating weight of 2876mg/ ^m2 and
SnCl ₂ had a resistance of 8 seconds. The test plate electrolytically treated with aqueous polyvinylphosphonic acid solution had a coating weight of 2919 mg/m ² and SnCl ₂
It had an increased resistance of 114 seconds. Two freshly produced plates were shown to be suitable for practical use during dry inking. However, the comparison plate lost its hydrophilicity within a short time (less than 4 days at room temperature, 1 day at 50°C and 30 seconds at 100°C). A plate coated with a photosensitive film according to Example 1 and electrolytically treated in an aqueous polyvinylphosphonic acid solution showed better image adhesion and better developer resistance than the comparison plate. Examples 29-31 and Comparative Example V14 Test plates of aluminum alloys 1100, 3003 and A-19 were roughened by hand using a quartz suspension and a nylon brush in a wet method and in an aqueous polyvinylphosphonic acid solution according to Example 24. electrolytically treated.
The plates were then coated with a negative-acting coating solution according to Example 1, exposed, developed and finished for printing and run to the limit on a sheet-fed printing press. Under certain conditions of use (wear coefficient 2.5), a plate made of alloy A-19 achieved a printing capacity of 45,000 copies before image collapse, a plate made of alloy 3003 achieved a printing capacity of 36,000 copies, and a plate made of alloy 1100 achieved a printing capacity of 45,000 copies. The printing power is
29,000 copies were sold. A comparative plate made of alloy 3003, heated non-electrolytically in an aqueous polyvinylphosphonic acid solution according to comparative example V10 and otherwise treated similarly to the test plate described above,
It has already become unusable in some areas. Examples 32-35 and Comparative Examples V15-V18 A number of plates were electrolytically finished as described in Example 24 for use as substrates for various photosensitive coating solutions. As a comparative sample, a plate was prepared according to comparative example V10, which was treated non-electrolytically in a warm aqueous polyvinylphosphonic acid solution. Coating 1
(Example 32) was a dimeric photopolymerizable film described in US Pat. No. 2,670,286. Coating 2 (Example 33) was a diazo compound-free photocrosslinkable film based on a radically polymerizable polyfunctional acrylic resin as known from US Pat. No. 3,615,435. Coating 3 (Example 34) was a diazo compound-free photopolymerizable film according to US Pat. No. 4,161,588. Coating 4 (Example 35) is a positively acting membrane based on diazonaphthol sulfoester; such a membrane is described in US Pat. No. 3,046,118. Coatings 1, 2 and 3 were applied both to the comparison plates (comparative examples V15 to V17) and to the plates treated according to the invention, and were applied with a metal halide lamp under a negative original in a conventional copying frame. exposed. This plate is developed and inked using the developer solution proposed in the respective US patent specification according to its photosensitive coating;
and compared. The lines on the comparison plate have an overall lower intensity than the corresponding lines on the test plate, the number of wedges exposed in all cases being 2 with a step wedge (21 steps - Schutaufer wedge). There weren't many. In the comparison plate, the highlights disappeared, whereas in the electrolytically treated plate, all the highlights were obtained, and on top of that, the background in the comparison plate was smeared.
All plates electrolytically treated with aqueous polyvinylphosphonic acid solution had a clear background. The positive coating described above was applied to the test plate and the comparative plate (Comparative Example V18). Underneath the positive copy manuscript, after development in a conventional alkaline developer, it was exposed with a 21-step Schutaufer wedge so that two fully exposed steps were visible. The comparison plate had 2 fully exposed stages and 10 blurred stages. The electrochemically treated plate with aqueous polyvinylphosphonic acid solution had 2 fully exposed steps and 14 blurred steps. The highlights disappeared on the comparison plate, whereas they remained on the test plate. Examples 36-44 and Comparative Examples V19-V20 The method of Example 24 was repeated, but the aqueous polyvinylphosphonic acid solution had a concentration of 0.01% and the tests were carried out at room temperature. Work was carried out at DC voltages S, 30 and 90 V with treatment times of 10, 60 and 300 seconds, respectively. A SnCl ₂ test was carried out and the film weight of the oxide film on the surface was measured using standard methods. The corresponding data are listed in Table 3.

[Table] The plates produced according to the conditions of Table 3 were each tested for hydrophilicity by dry inking according to the method of Example 1, and by aging and subsequent dry inking, and the plates produced according to Comparative Examples V3 and V5. Compared to comparison plates (V19 and V20). In all cases the ink from the plates according to Examples 36 to 44 could be rinsed completely, whereas the comparative plates either could not be rinsed completely clean or had to be scraped off to remove the ink. Ta. The results show that the oxide film produced by the method of the present invention has a film weight of
Even if it is only 0.016mg/ ^m2 (10 seconds, 5V),
Shows excellent hydrophilicity. Although not listed in Table 3, 0.008 generated in 1 second with 5V DC
The mg/m ² coating had similarly good hydrophilicity in the same test. Good corrosion resistance cannot be simultaneously achieved at slightly lower electrolyte concentrations. Examples 45-53 Processed according to the method of Examples 36-44, but with the electrolyte concentration increased to 0.1%. The results are listed in the table. It is clear from the table that at this concentration longer electrolysis times or higher voltages result in increased corrosion resistance.
All coatings showed a high degree of hydrophilicity in the dry inking and aging tests compared to the comparative plates of Comparative Examples V19 and V20 as well as Examples 36-44.

[Table] Examples 54-82 The method of Examples 36-44 was repeated, but the electrolyte concentration was
Increased to 1.0%. Plate on it DC voltage 30
and electrolytically treated at 60V for 20, 40 and 80 seconds.
The results are listed in Table 5 for each treatment time (film weight and reaction time in the SnCl ₂ test). Plates processed at 20, 40, and 80 seconds were used as substrates for printing tests.

【table】

TABLE All plates listed in Table 5 as well as Examples 36-44 were shown to be highly hydrophilic in dry inking and aging tests. Examples 83-91 Processed according to the method of Examples 36-44, the electrolyte concentration being 5.0%. The results are listed in Table 6.

TABLE All plates in Table 6 were highly hydrophilic in the dry inking and aging tests. Examples 92-100 Processed according to the method of Examples 36-44, but with an electrolyte concentration of 1.0%. The results are listed in Table 7.

TABLE All plates in Table 7 were highly hydrophilic in the dry inking and aging tests. Examples 101-109 The method of Examples 36-44 was repeated but the electrolyte concentration was 30%.
was used. The results are listed in Table 8.

Table: All plates in Table 8 were highly hydrophilic in the dry inking and aging tests. Examples 110-120 were processed according to the method of Examples 36-44 (1.0% aqueous polyvinylphosphonic acid solution), at a temperature of 10
It was warm at ℃. The results are listed in Table 9.

TABLE All plates in Table 9 were highly hydrophilic in the dry inking and aging tests. Examples 121-131 Treated according to the method of Examples 36-44, but at a temperature of 40℃
It was hot.

【table】

Table: All plates in Table 10 were highly hydrophilic in the dry inking and aging tests. Examples 132-143 and Comparative Examples V21-V23 Printing tests were carried out on some of the plates finished in the above examples (with the photosensitive coating of Example 1). In all cases, the commercially available "Dablgren" - "Solna" with dampening device - sheet-fed printing presses with a pH of 3.9 to
Worked using dampening solution 4.0. Place a thick support plate under the plate and factor the normal wear rate
2.4 Printing was carried out using printing ink with strong abrasive properties, and commercially available paper was used. Table 11 shows the point at which point reduction and shift in ink acceptance relative to the step wedge began, not the point at which the plate became unusable.

【table】

Table: Comparative Examples V21, V22 and V23 are commercially successful comparative plates. The plates according to the invention outperformed the best comparison plate (V23) in 7 cases with respect to stability against point shrinkage and in 4 cases with respect to ink acceptance deviation against step wedges. The plates according to the invention outperformed the medium-quality comparison plate (V22) in 9 cases in terms of stability against spot shrinkage and in 7 cases in terms of ink acceptance deviation against step wedges. Compared to the worst comparison plate (V21), the plates according to the invention were better in 12 cases in terms of stability against point shrinkage and in 12 cases in terms of ink reception deviation against the step wedge. Example 144 An anodized film was formed in a 1% aqueous solution of vinyl methyl ether/maleic acid copolymer by a method similar to Example 1. under a transmission electron microscope
When inspecting the insulating oxide film at 55,000 magnification, a flat surface with no visible porosity was obtained. Example 145 and Comparative Example V24 Flat specimens made of aluminum alloy 3003 having dimensions 18.3 cm x 17.8 cm x 0.03 cm were prepared for electrolytic treatment as described in Example 1. After etching (10-15 seconds) the samples were washed with water and dried in a stream of air. The sample was fixed to a conductive rail and suspended in an insulating tank at a distance of about 20 cm from two lead plates. The bath contained an aqueous solution containing 50 g/H ₂ SO ₄ , 50 g/H ₃ PO ₄ and 0.5% polyvinylphosphonic acid (PVPS). Aluminum wool was connected as an anode and a lead electrode was connected as a cathode using a DC power source. The bath has an ambient temperature of 22°C during the test.
The temperature was ±2℃. Current is pre-regulated DC voltage
10V was switched on and the electrolytic treatment lasted 60 seconds. The current strength initially increased to 5A, dropped very rapidly to 1-2A, and remained at this level during the treatment. The connection was disconnected, the plate was removed from the bath, rinsed with water, and finally wiped dry. The aluminum oxide coating on the surface had a weight of 108 mg/m ² . The weight was determined by weighing before and after stripping with a chromic acid/phosphonic acid solution. To test the hydrophilicity of the surface, a highly abrasive printing ink was applied without water using a dry applicator. When the ink was dry applied and washed off with water, the plates were significantly cleaner than conventionally produced plates. The test time until the transition point when several drops of potassium zincate solution are dropped on the surface is
It took 35-40 seconds. In contrast, H ₂ SO ₄
This test was 25-30 seconds for plates that were anodized in the medium and treated non-electrolytically in a warm aqueous polyvinylphosphonic acid solution. Finally, the plate was coated with a photosensitive solution according to US Pat. No. 3,867,147, containing pigment, polyvinyl formal binder and diazonium condensation product. After exposure under a negative original and development with an aqueous-alcoholic developer, the background was clean and clear image lines were present within the exposure area. twenty one
Water-based
After development with an alcoholic developer, exposure was carried out so that the 6th stage was completely blackened. When examining the insulating aluminum oxide film with a transmission electron microscope at 55,000x magnification,
A smooth plane with no visible porosity was shown. Comparative Example V25 A plate was prepared as in Example 145, but the aqueous electrolyte contained phosphonic acid in an amount of 75 g/min and no polybasic organic acids. After treatment at 30 V DC for 60 seconds, a plate with an oxide weight of 871 mg/m ² was obtained. The transition point for the potassium zincate test occurred after about 2 minutes, and the dry inking resulted in very dirty plates. Photoresist coating and exposure according to Example 145;
Development and inking with an aqueous-alcoholic developer resulted in a dirty plate. Comparative Example V26 A plate was manufactured as in Comparative Example V25.
Rinse the plate after removal from the anodizing bath and immerse for 30 seconds in an aqueous bath at 65°C containing 0.2% PVPS, following this treatment rinse the plate,
I wiped it dry. The oxide weight of the plate is
It was 909mg/ ^m2 . The transition point in the potassium zincate test occurred after about 2 minutes and the printing ink was difficult to remove after dry inking of the plate and some areas were smeared. When this substrate was coated with a photosensitive solution according to Example 145, exposed, developed and inked, it was shown that the plate was only suitable for practical use if it was sufficiently moistened before inking. Example 146 A plate was degreased and etched as in Example 145. etched plate
H ₂ SO ₄ 63g/, H ₃ PO ₄ 37g/ and PVPS1
% in an aqueous bath containing . Electrolysis at 15V for 30 seconds (initially 10A, reduced to 1-2A within 5 seconds) resulted in an aluminum oxide film with a weight of 500mg/ ^m2 , potassium zincate test lasted 42 seconds, and the dry inked sample I was able to clean it quite well with a dampening applicator. A sample coated with a photoresist film according to Example 145 could be developed successfully with an aqueous-alcoholic developer. Transmission electron microscopy examination of the insulating aluminum oxide film showed a smooth surface without pores. Example 147 Plates were degreased and etched as in Example 145. etched plate
It was immersed in a water bath containing 23 g H ₃ PO ₄ / and 0.25% PVPS. After electrolytic treatment at 30 V DC for 60 seconds, an aluminum oxide film with a weight of 198 mg/m ² was obtained. Transmission electron microscopy examination of the insulating aluminum oxide film showed a nearly patternless surface with some rips. Example 148 A plate was degreased and etched as in Example 145. The sample was mixed with 23g of H ₃ PO ₄ / and
Electrolytically treated in an aqueous solution containing 0.6% PVPS,
At this time, this treatment was continued for 60 seconds at 20 V DC, and an aluminum oxide film of 101 mg/m ² was obtained. A time of 250 seconds was recorded for this sample in the potassium zincate test. After dry inking, the plate can be cleaned fairly easily with a wet applicator, and samples coated with a photosensitive film as in Example 145 are easily developed in an aqueous-alcoholic developer following exposure with a negative. Can be done. under a transmission electron microscope
At 55,000 magnification, the insulation coating showed a smooth, uniform surface with no visible porosity. Example 149 A plate was degreased and etched as in Example 145. Sample H ₂ SO ₄ 75g/,
Electrolytic treatment at 15 V DC for 60 seconds in an aqueous bath containing 25 g of H ₃ PO ₄ and 0.5% of PVPS resulted in the formation of an aluminum oxide film of 500 mg/m ² . The transition point occurred after 30-35 seconds in the potassium zincate test.
Dry inked plates can be easily cleaned by rubbing vigorously with a damp cotton applicator. Plates photosensitively coated according to Example 151, exposed, and developed with an aqueous-alcoholic developer were fairly clean and free of "smudge" but had limited shelf life. Examination with a transmission electron microscope at 55,000x magnification showed the beginnings of porosity. Example 150 A sample was prepared and electrolytically treated as in Example 145, but the electrolysis was carried out at 25 V DC for 60 seconds (the current strength was initially 25 A, rapidly dropping to 2 A,
Thereafter it remained constant throughout the treatment. ) The aluminum oxide coating had a weight of 522 mg/m ² . This plate was comparable to the plate of Example 145 in its behavior in printing techniques. Example 151 A sample was prepared according to Example 150 and electrolytically treated,
The processing time was 120 seconds. The aluminum oxide coating had a weight of 1085 mg/m ² . This plate was comparable in printing behavior to the plate of Example 145. Example 152 A plate was degreased and etched according to Example 145. H ₃ PO ₄ 100g/plate with DC 16V
and electrolytically treated within 60 seconds in an aqueous bath containing 1% PVPS, an aluminum oxide film of 113 mg/m ² was formed, and the transition point in the potassium zincate test was reached at 90 seconds. After dry inking, the plate was very easily cleaned by rinsing it with water and wiping it gently with a cotton applicator. Plates coated with the diazonium material described in Example 146 could be developed cleanly and satisfactorily in an aqueous-alcoholic developer after exposure. Example 153 A plate was manufactured as in Example 146, in which the electrolysis voltage was 5 V DC. The finished plate was comparable in print-technical behavior to the plate of Example 146. Example 154 A plate was prepared as in Example 146. The temperature of electrolysis was 40°C. The finished plate was comparable in print-technical behavior to the plate of Example 146.

Claims (1)

[Scope of Claims] 1. At least one plate-shaped, sheet-shaped or band-shaped material made of aluminum or aluminum alloy
A method for anodizing in an aqueous electrolyte containing a polybasic organic acid, wherein the polybasic organic acid has at least 5 acid functional groups and a phosphonic acid, a sulfonic acid or a carboxylic acid. A method characterized by belonging to a group. 2. The method according to claim 1, wherein the aqueous electrolyte contains 0.05 to 30% by weight of polybasic acid. 3. The aqueous electrolyte contains at least 0.5% by weight of polybasic acid.
The method according to claim 1 or 2, comprising: 4 Anodic oxidation using a voltage of 1 to 30 V and a current density of 1
0.08~5 at ~5A/ ^dm2 and temperature -2℃~60℃
4. A method according to any one of claims 1 to 3, which is carried out for a minute. 5 Anodization using a voltage of at least 5 V and a current density of 1.3 to 4.3 A/ ^dm2 and 0.16 to 0.16 at 10 °C to 35 °C
Claims 1 to 3, executed for 1 minute.
The method described in any one of the preceding paragraphs. 6. The method according to any one of claims 1 to 5, wherein the at least one polybasic organic acid is a phosphonic acid. 7 Polybasic organic acids such as polybenzenephosphonic acid, hydrolyzed copolymers of methyl vinyl ether and maleic anhydride, copolymers of methyl vinyl ether and maleic acid, polyvinyl sulfonic acid, polystyrene sulfonic acid, alginic acid, poly-n-butyl-benzene Sulfonic acid, poly-diisopropyl-benzenesulfonic acid, polyvinylphosphonic acid, poly-diisopropyl-naphthalene disulfonic acid, poly-2-ethyl-hexanephosphonic acid, poly-decyl-benzenesulfonic acid, polyacrylic acid, polymethacrylic acid, Using ethylenediamine-pentaacetic acid, polynaphthalene sulfonic acid, or a mixture of two or more of these organic acids,
A method according to any one of claims 1 to 5. 8. The method of any one of claims 1 to 8, wherein the at least one polybasic organic acid is polyvinylphosphonic acid. 9 At least one plate, sheet or strip material made of aluminum or aluminum alloy
A method for anodizing in an aqueous electrolyte containing polybasic organic acids of species, wherein the polybasic organic acids have at least 5 acid functional groups and are of the group of phosphonic acids, sulfonic acids or carboxylic acids. belongs to the class,
and characterized in that the aqueous electrolyte additionally contains an inorganic acid from the group of phosphoric acid, phosphorous acid and mixtures of phosphoric acid and sulfuric acid or phosphorous acid,
Method. 10. The method according to claim 9, wherein the aqueous electrolyte contains 0.05 to 30% by weight of polybasic acid. 11 Claim 9 or 1, wherein the aqueous electrolyte contains at least 0.5% by weight of polybasic acid
The method described in item 0. 12 The aqueous electrolyte contains 10 to 200 g/inorganic acid,
A method according to any one of claims 9 to 11. 13 Anodic oxidation using a voltage of 5 to 40 V and a current density
0.08~ at 0.2~6A/ ^dm2 and temperature -2℃~60℃
Claims 9 to 1, carried out for 5 minutes.
The method described in any one of items up to item 2. 14. The method of any one of claims 9 to 13, wherein the at least one polybasic organic acid is a phosphonic acid. 15 Polybasic organic acids such as polybenzenephosphonic acid, hydrolyzed copolymers of methyl vinyl ether and maleic anhydride, copolymers of methyl vinyl ether and maleic acid, polyvinyl sulfonic acid, polystyrene sulfonic acid, alginic acid, poly-n-butyl-benzene Sulfonic acid, poly-diisopropyl-benzenesulfonic acid, polyvinylphosphonic acid, poly-diisopropyl-naphthalene disulfonic acid, poly-2-ethyl-hexanephosphonic acid, poly-decyl-benzenesulfonic acid, polyacrylic acid, polymethacrylic acid, 14. The method according to any one of claims 9 to 13, wherein ethylenediamine-pentaacetic acid, polynaphthalene sulfonic acid, or a mixture of two or more of these organic acids is used. 16. The method of any one of claims 1 to 15, wherein the at least one polybasic organic acid is polyvinylphosphonic acid. 17 A method for anodizing a plate, sheet or strip material made of aluminum or an aluminum alloy in an aqueous electrolyte containing at least one polybasic organic acid, wherein the polybasic organic acid contains at least 5 polybasic organic acids. in an aqueous sulfuric acid solution as an electrolyte prior to anodization in an electrolyte having acid functional groups and belonging to the group of phosphonic acids, sulfonic acids or carboxylic acids and containing polybasic organic acids. A method, characterized in that anodizing is carried out at 18. The method according to claim 17, wherein the aqueous electrolyte contains 0.05 to 30% by weight of polybasic acid. 19 Claim 17 or 18, wherein the aqueous electrolyte contains at least 0.5% by weight of polybasic acid
The method described in section. 20 Anodization using a voltage of 1 to 30 V with a current density of 1 to 5 A/ ^dm2 and a temperature of -2°C to 60°C of 0.08 to
20. A method according to any one of claims 17 to 19, which is carried out for 5 minutes. 21 Anodization using a voltage of at least 5 V and a current density of 1.3 to 4.3 A/ ^dm2 and 0.16 at 10 °C to 35 °C
21. The method of any one of claims 17 to 20, wherein the method is carried out for ~1 minute. 22 Claims 17 to 21, wherein the at least one polybasic organic acid is a phosphonic acid.
The method described in any one of the preceding paragraphs. 23 Polybasic organic acids such as polybenzenephosphonic acid, hydrolyzed copolymers of methyl vinyl ether and maleic anhydride, copolymers of methyl vinyl ether and maleic acid, polyvinylphosphonic acid, polystyrene sulfonic acid, alginic acid, poly-n-butyl-benzene Sulfonic acid, poly-diisopropyl-benzenesulfonic acid, polyvinylsulfonic acid, poly-diisopropyl-naphthalene disulfonic acid, poly-2-ethyl-hexanephosphonic acid, poly-decyl-benzenesulfonic acid, polyacrylic acid, polymethacrylic acid, 22. The method according to any one of claims 17 to 21, wherein ethylenediamine-pentaacetic acid, polynaphthalene sulfonic acid, or a mixture of two or more of these organic acids is used. 24. The method of any one of claims 17 to 23, wherein the at least one polybasic organic acid is polyvinylphosphonic acid.