SE430175B - PROCEDURE FOR CLEANING ANODIZING LAYERS ON ALUMINUM OR ALUMINUM OF ALUMINUM WITH SURFUL FLUOROUS WATER SOLUTIONS - Google Patents

Description

780p5bf35-0 talking appearance and becomes mottled and streaked. To prevent further destruction and improve the appearance must such surfaces with certain intervals are cleaned. How often cleaning must be performed depends on where the object is located and the degree of soiling ..

For cleaning and care of anodized aluminum, which was used for building purposes, neutral cleaning solutions are recommended, for example, aqueous solutions of surfactants or organic solvents. with these, however, only light and loosely adhering dirt, which affects the appearance, is removed., The cleaning effect is not sufficient for the removal of strong soils or refresh or renewal of partially corroded layers. When Therefore, it is recommended that the surface is stripped with fine-grained polish so that the dirt is removed with the corrosion product and part of the layer. Such a cleaning is admittedly effective but laborious and time consuming and thereby very expensive.

There is thus a need for a simplified working method as well makes it possible to dispose of heavier soils and corrosion ions from anodizing layers on aluminum or alloys hence without requiring any significant mechanical action. Attempt However, solving this problem has encountered considerable difficulties.

Common alkaline cleaners, the type used for treatment aluminum, have not proved useful even when containing inhibitors against attack on aluminum, as a rapid disturbance of the alumina layer occurs. Even numerous attempts to using common acidic cleaners has not brought to it either desired and required activity as most acids for an unfavorable dissolution of the oxide layer, or also entails the acidic solution only an insufficient removing effect on the adhesive adhesions and coatings. Of the inorganic the acids, hydrofluoric acid has been found to be particularly disadvantageous. Already at the concentration of 0.1% HF, a strong detrimental effect of Organic acids, such as tartaric acid, citric acid or oxalic acid acid, which in some cases has also been discussed for cleaning anodized aluminum, although hardly attacks the oxide layer but has shown insufficient cleaning effect.i Such as acidic, unobtrusive cleaning short-chain phosphorus components have also been proposed. acid esters. Without the help of mechanical measures, however, removes even such agents only slightly adhering soils.

According to the invention, it has been found that an effective and 7805435-0 3 trouble-free cleaning of anodizing layers on aluminum or aluminum minium alloys can be produced in an advantageous manner if one on the surface applies an aqueous solution, sml contains 0.1 to 10% by weight acid fluorocomplex compound of elements belonging to group III and / or IV of the Periodic Table and at least 0.1% by weight of an i the solution is soluble and stable surfactant and has a pH value within the range 0.8 to 3, at ambient temperature in the form of a thin film and after a short exposure time, rinse with water.

The concentration of use of the fluorocomplex compound in solution the degree depends on the degree of corrosion of the anodizing layer, the species of present contamination and the application technique. When applying of the solution, for example by brushing, more dilute solutions can be used. use, for example, for light wiping with the solution. Generally has a fluorine complex compound content of 4 to 6% by weight ( calculated as free acid) proved to be suitable. It should be borne in mind that the action solution does not contain any free hydrofluoric acid because also small amounts thereof would lead to enhanced attack of the solution on the alumina layer.

As a fluorine complex compound of elements belonging to group III or IV of the periodic table, one can e.g. use fluoroborates, aluminates, silicates, titanates or zirconates such as acids or salts and individually or in admixture for the preparation of Preferably, a treatment solution containing complex fluorosilicon.

The treatment solution should have a pH value within the range of 0.8 to 3. When preparing the solution, one can therefore start from the dilute acids, possibly by partial neutralization with alkaline agents reach the desired pH or bring the corresponding salt in solution and then with inorganic acids bring the solution to the required pH. In the latter case, one can_ suitably sulfuric acid is used. An essential component of treatment solution is also the surfactant.

This must be soluble and stable in the solution. You can use ionic, nonionic or cationic agents. Particularly suitable have, for example, non-ionic products of alkyl or alkylaryl poly- glycol ethers with a content of at least 15 ethylene oxide groups were found be. The content of surfactant in the solution must be at least 0.1% by weight. percent to ensure good wetting and penetration of the fluorocomplex compound in the treated surface. In general, is it is advisable not to use the surfactant in an amount less than the fluorine complex association. vàosass-o D D 4 The cleaning solutions are applied at ambient temperature on the anodized surface in the form of a thin film. This can be achieved for example by spraying but preferably by brushing, hand drying or hand washing. Generally adjusted the application of the solution in such a way that one applies to the surface per m2 not more than 1 liter and preferably not more than 300 ml of solution with use of a maximum exposure time of 5 minutes.

After a short period of action of the solution, then rinse with water. The duration of the impact is not particularly critical. meaning but should generally not exceed 5 minutes as is already very active in a short time. 7 It is surprising that it is possible in the manner indicated to quickly and efficiently clean even soiled and corroded anodizing layers without any measurable attack on the anodizing the sering layer enters. This effect could in no way lead expected because it has previously been proposed to use, for example, silicon hydrofluoric acid to remove oxide layers before welding or use of hydrolyzable fluoride salts for blank pickling of aluminum nium. It must therefore be assumed that such substances would not be suitable for the purpose according to the invention.

The process according to the invention is described in more detail with the following working examples.

Example 1 - An aqueous solution containing 5% by weight of sodium silicon fluoride was adjusted with sulfuric acid to a pH of 1.5 and then added to the solution 10% by weight of nonylphenol polyglycol ether with 15 ethyl lenoxide groups. The solution was applied at ambient temperature of anodized aluminum sheets (layer thickness 20-26 μm), were allowed to act for 5 minutes and rinsed with water. The plates were dried with compressed air.

Samples taken before and after treatment were prepared emetallurgical abrasion tests and the thickness of the oxide layer were unmeasured.

No difference could be established between the treated and non- treated layers.

Example 2 For comparison, to the solution given in Example 1 was added .a 0.2% hydrofluoric acid (as HF). After the same treatment was the oxide layer partially destroyed down to the substrate metal.

Example 3 To demonstrate the operation of the solution for corroded anodic 5 i vsosass - o surfaces were subjected to anodized test plates for 10 days corrosion according to ESS DIN 50021 (spraying with 5% sodium chloride solution with the addition of 0.5% glacial acetic acid). The layers were then covered with white blooms and stripes. During raster electron microscopy roscope it could be determined that the corrosion products formed a thin layer, under which the anodizing layer was intact.

The corroded surfaces were then treated on it in examples in the manner indicated. The corrosion products were removed on a peacefully. The anodizing layer was not attacked. äëš fl l fi i _ A sodium silicofluoride solution of that given in Example 1 the kind, which was adjusted with sulfuric acid to a pH of 4, gave a completely unsatisfactory cleaning effect on the corroded anodize the surfaces. Negative results were also obtained with different surfactants solutions which did not contain any complex fluoride. That's why necessary to remove the adhering white blooms by a laborious grinding process.

Example 5 Experiments similar to those given in Examples 1 and 3 were performed using other fluorocomplex acids in question, respectively. salts thereof and with other acidic solutions, such as sulfur acid, hydrochloric acid, amidosulfonic acid, citric acid, for comparison. In addition- cases showed the acidic solutions, which contained fluorine complexes compounds, clear benefits both in terms of cleaning effect and in terms of gentle effect on the anodized surface.

Claims (7)

vsøsass-0 PATENTKRAV il. Process for cleaning anodizing layers on aluminum or aluminum alloys used for building purposes with acidic fluorine-containing aqueous solutions, characterized in that a thin film of an aqueous solution containing 0, is applied to the surface at ambient temperature. 1 to 10% by weight and preferably 4 to 6% by weight of acid fluorine complex compound of elements belonging to group III and / or IV of the periodic table and at least 0% by weight of soluble and stable surfactant in the solution, the solution having a pH value within the range of 0.8 - 3, and after a short exposure time, rinse with water. 2. A method according to claim 1, characterized in that the solution applied to the surface is free of free hydrofluoric acid. 3. A process according to claim 1 or 2, characterized in that the acidic treatment solution is prepared using complex fluorine compounds of boron, aluminum, silicon, titanium or zirconium or mixtures of such compounds. 4. A process according to any one of claims 1-3, characterized in that an acidic treatment solution containing complex fluorine compound of silicon is used. Process according to one of Claims 1 to 4, characterized in that the aqueous treatment solution is adjusted to the required pH value by dissolving a fluorocomplex acid, optionally by partially neutralizing it with alkaline agents or by acidification of solutions of corresponding salts with inorganic acids, preferably sulfuric acid. VSÛEI-: ZS-O Process according to one of Claims 1 to 5, characterized in that a maximum of 1 liter and preferably 300 ml of the aqueous solution per m2 is used on the surface for a maximum exposure time of 5 minutes. A method according to any one of claims 1 to 6, characterized in that the application of the solution to the surface is effected by brushing, rolling or by a hand washing method.