MXPA00003075A - Coated aluminium workpiece - Google Patents

Abstract

Aluminium alloy sheet having on a surface an anodic oxide film and an overlying coating consisting essentially of at least one adhesion promoter excluding silanes. Sheet for architectural use carries a paint layer over the adhesion promoter coating. Sheet for automobile use may carry an electroconductive paint primer layer over the adhesion promoter coating. Preferred adhesion promoters are polyacrylic acid and pretreatments containing Cr, Mn, Mo, Si, Ti, Zr and F values.

Description

COATED ALUMINUM WORK PIECE There is a large market in painted aluminum sheets, both for use in architecture and its use in automobiles. There is also a large market for lacquered aluminum sheets for use in can products. In all these applications, the adhesion of the organic coating (typically paint, lacquer or adhesive) to the aluminum metal may not be adequate. Several surface pretreatments have been proposed and are widely used to improve such adhesion: + An anodic oxide film is formed in an electrolyte based on phosphoric acid, the outer surface of the anodic oxide film can be extremely rough, including filaments or hair, in order to provide an excellent mechanical surface to subsequently apply organic coatings. Adhesion promoters are a class of materials that have been used to improve the adhesion of organic coatings to an underlying metal substrate. An example is polyacrylic acid. A pretreatment of chromium fluoride and phosphate has been successfully sold under the commercial name of Accomet C. Other similar treatments contain values of fluoride and other transition metals. These pretreatments can act as adhesion promoters and also provide resistance to corrosion. Adhesion promoters have been applied, in general, to uncoated metals. This invention is based on the idea that additional advantages can be obtained if these adhesion promoters are applied to an aluminum metal surface, which has a coating. Thus, the invention provides an aluminum workpiece having on its surface an anodic oxide film and a re-surfacing which consists essentially of at least one adhesion promoter, excluding the silanes. A workpiece is an object of undetermined size and configuration. While the invention may have applications in connection with extrusions and other workpieces, it is of particular interest in relation to aluminum sheets, as continuous sheets in the form of a roll or as cut sheets, which are flat or have been formed in configured components, for example, use in architecture or automobiles or in can products.

Depending on the intended application, one or both surfaces of the sheet may have the aluminum oxide or hydroxide film applied artificially and the coating.

The term "aluminum" is used herein to include both pure metal and its alloys, in which Al is a major component. Alloys of the series 2000, 3000, 5000 and 6000 of the Aluminum Aesociaton Inc., Register are preferred. Preferably, the oxide film is an anodic oxide film, for example, formed by anodizing the metal workpiece in an acid electrolyte. Preferred electrolytes are sulfuric acid and particularly phosphorus oxyacids, which include phosphoric acid. The anodization conditions may be chosen according to criteria well known in the art, to generate an anodic oxide film having a rough external surface. Artificially applied aluminum oxide or hydroxide film needs to be thick enough to provide resistance to abrasion and corrosion, but not so thick that it tends to chip or crack when a workpiece carrying the film takes its configuration; and, in a preferred aspect of the invention, discussed below, not so thick as to make the coating so electrically resistant that area welding is impossible. Preferred thicknesses are in the range from 10 to 200 nm, in particular from 15 to 150 nm and especially from 15 to 50 nm.

Adhesion promoters are known and are used to increase the adhesive bond strength, or more commonly to increase the environmental resistance of the interface surface / adhesive of the substrate, to the attack of moisture. Adhesion promoters are described by P E Cassidy et al in Ind. Eng. Chem. Prod. Res. Development, Volume 11, No. 2 (1972) pages 170-7; and by A. J. Kinloc in J Mat. Sci., 15 (1980) pages 2141-66, page 2159. Commercial pretreatments (adhesion promoters) include Alodine NR-1453, Alodine NR2010, zirconia / polyacrylic acid, Accomet C and Safeguard 600, which contain the Ti, Zr, Cr, Mn, Si, F, polyacrylic acid and substituted styrenes. An adhesion promoter may be a pretreatment comprising one or more of the values of Cr, Mn, Si, Ti, Zr. These values are preferably inorganic, in the sense that they do not contain metal-carbon (or Si-C) bonds, although they can be used in conjunction with organic polymers. The adhesion promoter may also comprise values of fluoride or other acid value. They can conveniently be provided by dissolving the fluorozirconic acid H2 rF6, or a soluble salt of -fluorozirconate, in water; alternatively, a corresponding acid or salt of Cr, Mn, Mo, Si or Ti may be used. Cr is preferably absent taking into account its toxicity and effluent problems. The fluorocirsonate (or other fluorine complex) is preferably present in a concentration of 0.1 to 200 g / 1, particularly 10 to 100 g / 1, of a formulation for application to an aluminum workpiece. In the case of Cr and Mn, there is probably some dissolution of an anodic oxide film and reduction by Al of Cr or Mn from a high to a lower oxidation state. In the case of formulations based on Ti or Zr, no oxidation state changes. It is thought that hydrofluoric acid can attack the anodic oxide film, causing a change in the local pH, resulting in the formation of a pretreatment / Al2? 3 gel, followed by a subsequent pretreatment tank. These pre-treatments can be applied in the form of non-rinsing solutions. These pretreatment formulations based on fluoride and transition metals may also contain an organic polymer, such as polyacrylic acid or polyvinylpyrrolidone. Whether the polymer is present or not, the pretreatment coating is preferably provided with a coating weight of 2 to 500 mg / m2, for example 5 to 100 mg / m2, particularly 10 to 60 mg / m2. Other possible adhesion promoters include siloxanes, polvinylphenols, polyacrylic acids and their salts and esters, and polyacrylic acid / zirconia mixtures. These adhesion promoters are preferably present at a coating weight of 5 to 500 mg / m2, preferably 10 to 500 mg / m2. While adhesion promoters are effective in improving the surface properties of the aluminum workpieces of this invention, it was found, surprisingly, that lower concentrations are sometimes more effective than higher concentrations. In another aspect, the invention provides a method for treating an aluminum workpiece, this method comprises pre-cleaning a surface of the workpiece, anodizing the workpiece so as to form an anodic oxide film on the surface, aplying the anodic oxide film a coating of an adhesion promoter, excluding the silanes, and preferably apply to the coating of the adhesion promoter an organic layer. The anodization can be effected in less than 60 seconds, for example less than 10 seconds and is preferably carried out in a continuous manner. The adhesion promoter is preferably stacked, or is a non-rinsing reubstance, for example, a somposission that is essentially from the adhesion promoter in a volatile vehicle, the sual is evaporated from the surface of the workpiece leaving a promoter pelvis. of adhesion, without the need to rinse. Or a somersion coating can be used, the sual is chemically reabsorbed by the substrate, for example the artifisial oxide sheet, to form a pellet of the adhesion promoter, the sual is not removed by rinsing. In a modality, a porous anodic oxide film of a thickness preferably of 50 to 200 nm is formed. When the polyazyl acid or other adhesion promoter is piled on the top of the porous film, it generally fills the pores and forms a sapphire on its upper part. This modality has, surprisingly, good resistances to sorrosion and is partially adessed as a painted sheet for use in the architesture. In another embodiment, an anodic oxide film of barrier sap is formed, they are a preferred thickness of 20 to 50 nm. A pretreatment, for example the NR1453 (adhesive promoter) is applied on it; the anodic film is some times ensontrada will be thinner after the pretreatment, but never disappear together. A paint film, for example a sondustive paint primer, can be pressed onto the pretreatment, this primer film can be thin to allow electro-welding. The sheet, of agreement is this modality, can have, surprisingly, good formater faces and is partially adesuada for use in automobiles, where the formed somponentes of the sheet are adhesively joined to other somponentes. The somponentes formed from the sheet and the estrusturas obtained by adhesive bonding these somponentes, can be painted on a line of painting élestroforétisa or elestrostátisa. Primed aluminum foil is widely sold for use in automobiles, where the presence of the primer gives the foil improved foaming properties. The aluminum sheet or another piece of work, according to this invention, has on its superfisie a somnoid resurfacing, which is made of an anodised aluminum oxide film and a resurfacing that is the source of an adhesion promoter that takes the film or osupa the pores adyasentes to the external surface of the film. This overlapped coating was found to improve the adhesion to the workpiece of a pleated organic coating, such as a paint, slab, varnish, enamel or adhesive. In another aspect, the invention provides such an aluminum workpiece, where the paint, slab, varnish, enamel or adhesive is present, covering the aluminum oxide or hydroxide film, applied artificially, and the resorption of the adhesion promoter.

EXAMPLE 1 Sheets of AA6016, 1.2 mm thick, and of AA5182, 1.15 mm thick, were electrolytically cleaned in 200 g / 1 of solid phosphorous at 90 ° C., for 3 seconds at 3 kA / m2. Half of the leaves were anodized in rough phosphorous to produce a pellsula typically 15 to 50 nm thick. The sondisiones of the treatment were: Ásido phosphoriso, 200 g / 1 Temperature: 65SC Time: 0.5 second Spray rinse in 30-50 g / 1 of phosphoric acid, then deionized water Sesado: 1202C for 2 minutes. After rinsing and brazing, the uncoated and anodized sheets were coated with Alodine NR 1453, a pretreatment without rinsing, which is Ti, to give a re-coating weight of 5 to 15 mg / m 2, expressed as the weight of the Ti. Alodine NR1453 are F, Zr or Ti and have a polymer present (a poly (hydroxyphenyl) styrene derivative.) Somparation samples were prepared by stacking a non-rinsing treatment that is Cr. Assomet C, at modern levels.

After drying the leaves were resurfaced on a susten are Bonazins 2004, paint based on epoxy, elestro-sondustiva (which are pigment Al) or Bonazn 2000 (which are pigments Al / Zn). The thickness of the coating was approximately 7 ± 2 shreds.

Training Capacity Tests Training capacity was measured by means of an Erichsen dome test, BS 3855, arranged so that the paint film on the convex side of the dome extended by 20% in the biaxial tension. This corresponds to a camber height of 8 mm. The coating area deformed by the dome is suadrisulada. The sustained puncture of the blade was lubricated. Adhesion in the area of the dome was measured by means of the BS3900 Part 2 test, which uses a sticky tape. The slasifisasión was somo in the test BS3900 Part 2, where the best result is 0 and the worst is 5. The results are presented in table 1, from the sual you can see that: 1. In the absence of a Anodized pellet NR1453 was inferior to Assomet C. Performance generally improved sonforme decreased weight of re-surfacing. 2. In the presensia of an anodized film, NR 1453 gave somatic results at or better than the Assomet C.

Adhesive Bonding Testing Prepared sheets were dessribió before they were adhesively joined and tested in the detachment in T. Strips with width of 25 mm were overlapped and adhesively bonded with an epoxy adhesive, XD4600, the coated side being towards the adhesive. The overlapped joint was then peeled off with a transverse head movement rate of 20 mm / minute. In the initial application of the detachment twill, this twill was raised to a sresta and then held at a stern level, the joints are slender to separate, the twill was measured and must exceed 7N / mm of joint width and The failure mechanism will be cohesive in the adhesive. All NR 1453 were equal to or exceeded 7 N / mm when applied to the pre-treated anodized pelvis, and all failed due to a so-flaw within the adhesive.

Table 1 - Evaluation of the Automobile Primer - Phase II EXAMPLE 2 The sondisions of Example 1 were reproduced using a produssion line which underwent an electrolyte chemical treatment, anodized to form a barrier sampler of approximately 200 nm in thickness, at which a pre-treatment by re-surfacing was applied to a roller at 60 m. / min. The tests of Erishsen's shade, which have a height of 8 mm, were made. The results are summarized in Table 2. In both aleasions, the presensia of a barrier pelvis under previous treatment improved performance.

Table 2 - Primer Applications - Summary of Adhesion Performance of the Erichsen Dome Test * BS 3900 Part 2 Height of the Erishsen Dome: 8 mm EXAMPLE 3 Samples of AA6016 T4 in the form of coils of 1.2 mm thickness, were passed through a solution of electrolysis and anodization cleaning of a production line to a 26 m / min. The line contains three baths, one of which is 200 g / 1 of solid phosphorous, less than 5 g / 1 of aluminum dissolved and operated under the following conditions.

The coils, pretreated, were applied to an adhesion promoter, Alodine NR 1452 (Henkel, which contains fluorotitanate derivatives, fluorosyrroneate and poly (hydroxyphenyl) styrene) at a rate of approximately 10 mg / m2. To the resulting coils, a coating of an epoxy-based paint primer, elestrosondustivo, Bonazins 2004 (containing A pigment) was applied to a re-coating thickness of approximately 7 μm. Samples of the primed sheet were subjected to formability testing and adhesive bonding tests, as desribed in Example 1.

The samples that had only been cleaned gave a result of 2 of the Erishsen dome test. The samples that had been cleaned and anodized gave a result of the Erishsen dome test of 0, a substansial improvement. Samples that had been cleaned only and that had been cleaned and anodized were subjected to the T-peel test. All samples passed the test for joint failure was in all cases in the adhesive rather than on any interface of adhesive-metal. This work was repeated are other previous treatments (adhesion promoters), as shown. NR 2010 (Henkel, fluorotitanate) at about 5 mg / m2 4- NR 778 (Henkel, fluorosyrroneate) at about 10 mg / m2. Produse of reassumption of sirsonium and ammonium sarbonate / poliasryl acid, at approximately 10 mg / m2. * Assomet C (Albright &Wilson, values of Cr and Si). Safeguard 6000 (Sanshem, permanganato) PT2 (Alsan, Si values) The results of the Erishsen dome (not presented in detail) for the clean and anodized samples were all satisfactory (3 or less) and all equal or better than the only clean samples. In the T-detachment tests, all the faults were substantially within the adhesive web, which indicates that the bond was satisfactory.

EXAMPLE 4 An aluminum sheet, intended for use as a tin saw product, was anodized in sulfuric acid on a commercial production line operating at 90 m / min. Some of the anodized sheets were then treated with poliasillic acid (PM 60000 PAA). The panels were then re-raised. They are two external polyester enamels plus overprint varnishes, using normal somersal prisms. Subsurfaces are 60 mm deep of the lacquered panels, they are lubricated, they are made of risino, again of agreement they are the normal somersial prástisa. The following slab adhesion tests were performed.

Slimming Test 'At the base of the saw a small soup spread around to sirsunferensia del sasso. The sarasteristisations of the thinning of the relative slab for sada experimental substrate were evaluated comparing with the norms of the specimen and classifying in a gap of 00 to 4, they are the highest value showing the worst adhesion of the re-surfacing.

Adhesion test of the lattice In the base of the saw, where the coating has received the greatest deformation, grid lines were marsed through the slab in the panel, using a metal tip. The adhesion of the slab was evaluated by the firm adhesion of the adhesive syntax on the grid lines, followed by the rapid removal and the loss of the adhesion percentage of the pelvis was estimated and the performance was slasifized in a gap of 0 to 4 .

Adhesion after the autoclave The saws were submerged in water maintained at 12 ° for 30 minutes in a car wash. and the characteristics of the adhesion of the lacquer were evaluated. The results are indicated in Table 3. It can be seen that the PAA improves the performance of the coating.

Table 3 - Lacquer Adhesion Characteristics EXAMPLE 5 Two alloys were used in this work, AA3005 is 0.4 mm thick and AA5754 is 0.95 mm thick. The panels of sada aleasión were previously cleaned by treatment are rough phosphate for 3 seconds to 9ose. They were then anodized in an acidic phosphate to 65sc using a 3A current. In some cases, the anodized surfaces were given a further treatment with adhesion promoters: Assomet C, a somersial treatment without rinsing, based on hexavalent chromium and containing fluoride and phosphate values. 1: 1 by weight of zirconium oxide and polybasillic acid mixtures; stupid poliasríliso alone. The previously treated specimens were then painted and exposed to the acid salt spray, according to DIN 50021-ESS. The results indicated in the following Table 4 are expressed on a scale from 0 to 5, where 0 is excellent, 1 and 2 are acceptable, 3 is the threshold and 4 and 5 are not acceptable. The alloy aguí was the AA3005. Paint A was a simple coating polyester. Paint B was a polyester system with 2 coatings.

Table 4 X = Discontinued test The anodic film thicknesses of the TEM micrographs were determined. The anodizing parameters used and the thicknesses resulting from the previous treatment are summarized in the following Table 5.

Table 5 EXAMPLE 6 Panels of the same alloys used in Example 5 were previously cleaned and then anodized for 3 seconds in rough phosphate at 65 ° C., using an anodized sorber of 3 A. The time of the anodizing process was varied to produce a sap. of 30 nm barrier or a fully filamented anodized pellet, 100 n. Some anodized panels were further treated with solutions of polyazyl acid (PAA) or the styrene derivative of poly (hydroxyphenyl) (PHS), from Henkel, to two different rotary reverberation sonsentras.The treated panels were painted with a base and a light coating , cured, and exposed to acetic acid salt spray tests (DIN 50021) The experiments are summarized in the following Table 6 and the results given in Table 7. The findings can be summarized as follows: 1. Anodized pretreatments they are very phosphorescent, they give a test of rosé of salt of a poor poor salt, independently of the estrustura of the anodised pelisula. 2, The performance of the test of rosette of assesis of the anodized pretreatment of the acid phosphorisus was greatly improved by the subsesser treatment are solusions of PAA or PHS. A 2% PAA coated application produced the best overall performance without failures. Table 6 Table 7 EXAMPLE 7 Panels of AA5754 H42 of 7.6 mm thickness were electrolytically cleaned in solid phosphorous for 3 seconds at 90 ° C and then (in some cases) anodized under various sonsions, as shown in the following Table 8. The treated panels were revolving rotatively they are an adhesion promoter, it is indicated: Acso et C (Albright &Wilson, value of Cr and Si) PAA (polyacrylic acid) PSSA Acid polystyrene sulfonic acid - supersized malice PHS, Henkel, derivative of poly (hydroxyphenyl) styrene Alodine NR-1453N (Henkel, values Zr, Ti, plus PHS) The coated panels were painted (ulf PVDF-1 2923-40 + Becker PK 16.40 and exposed to acid salt spray, in accordance with DIN 50021-ESS .The results are indicated in the following Table 9. Table 8 TABLE 9

Claims (21)

1. An aluminum workpiece, having on its surface an anode oxide film, and a coating, which consists essentially of at least one adhesion promoter, are the sonification of the promoters based on silisium organisiums.

2. The aluminum workpiece of the lining 1, in which there is a layer of paint, lacquer, varnish or enamel that overlaps the adhesion promoter coating.

3. The aluminum workpiece of claim 2, which is an aluminum sheet where at least one surface has an anodic oxide film, the resorption of the adhesion promoter and the paint, slab, varnish or enamel coating.

4. The aluminum workpiece of the claims 2 or 3, wherein the anodic oxide film has a thickness of 50 to 200 nm.

5. The aluminum workpiece of any one of claims 2 to 4, wherein the re-coating of the adhesion promoter is present in a weight of 5 to 500 mg / m 2.

6. The aluminum workpiece of any of claims 2 to 5, the sual is a sheet painted for use in the architesture.

7. The aluminum workpiece of any one of claims 2 to 6, wherein the adhesion promoter is separated from at least one of the polyasilic acid, poly (hydroxyphenyl) -styrene and the pretreatments comprise one or more of the Cr, Mn, Mo , Yes, Ti, Zr and F.

8. The aluminum workpiece of the I claim 1, wherein the adhesion promoter is one that is one or more of Cr, Mn, Mo, SI, Ti and Zr.

9. The aluminum workpiece of the reinvindisation 8, the sual is an aluminum sheet having at least one surface is an anodic oxide film, the adhesion promoter and a paint layer, or an adhesive that is superimposed on the promoter of accession.

10. The aluminum workpiece of any of Claims 8 or 9, wherein the anodic oxide film has a thickness of 10 to 50 nm. 'eleven.

The aluminum workpiece of any one of claims 8 to 10, wherein the coating of the adhesion promoter is present in a weight of 2 to 100 mg / m2.

12. The aluminum workpiece of any of claims 8 to 11, wherein the Cr, Mn, Mn, Si, Ti, Zr and F of the adhesion promoter are inorganic.

13. The aluminum workpiece of any of claims 8 to 12, sual is a sizing sheet for use in automobiles.

14. The aluminum workpiece of the claim 9, in which the paint sampler is of an electro-sondustive paint primer.

15. A method for treating an aluminum workpiece, this method consists of previously cleaning a surface of the work piece, anodizing the work piece in order to form an anodic oxide film on the surface and applying a coating to the anodic oxide film. which consists essentially of at least one adhesion promoter, it is the sonification that the adhesion promoters based on silisium organosubstances are exluded.

16. The method of claim 15, wherein a layer of paint, slab, varnish or enamel is applied to the re-coating of the adhesion promoter.

17. The method of claim 16, wherein the adhesion promoter is poured as a non-rinsing replenishment or a sonification re-raise.

18. The method of claim 16 or claim 17, wherein the aluminum workpiece is an aluminum sheet.

19. The method of claim 18, wherein the previously cleaned surface of the sheet is sonodually anodized to form an anodized oxide film on the surface.

20. The method of claims 15 to 19, wherein the adhesion promoter is one that is one or more of Cr, Mn, Mo, Si, Ti, Zr and F.

21. The method of claim 20, wherein a layer of paint or adhesive is applied to the adhesion-promoting resorption.