DE1446461A1 - Sealing bath for oxidized aluminum surfaces and process for its production - Google Patents

Description

PATENT ADVOCATE
I ». R. POSCi JEN

8 Case 2834. /]?

SeÄ / JT

Dr. Expi. J

Kaieer Aluminum ft Chemical Corporation, Kaiser Center, 300 Lakeside Drive, Oakland 12, California (V.St.A.)

Sealing bath for oxidized aluminum surfaces and processes for its production

Addendum to patent ...... (German patent application K 37 475)

Me present invention relates to methods and means for Sealing of the oxide coating that is artificially formed on the surfaces of aluminum objects and affects them especially the sealing of these oxide coatings when formed by the use of an electrolyte which is essentially consists of an aqueous solution of sulfosalicylic acid and a metal sulfate or sulfuric acid.

In general, these oxide coatings are usually made by placing the aluminum part in a suitable electrolyte and an electric current passes through the electrolyte with the aluminum part serving as an anode. By the resulting decomposition of the electrolyte releases oxygen, which chemically interacts with the aluminum and its Binds alloy components and forms a hard oxide layer on the surface of the aluminum part, a process

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known as "anodic oxidation". The Oxydschi eht is usually subjected to a treatment known as sealing to prevent loss of color when stained to prevent and to make them more stable and resistant in general to make against corrosion.

This sealing can be achieved in a number of different ways. One form of sealing the "coatings, especially when they are colored with an organic dye, is to bring the anodized aluminum parts into solutions containing substantial amounts of hydrolyzable metal salts * especially nickel acetate and / or cobalt acetate. In certain cases this produces Process an unattractive residue ^{known as "dirt 11} " which can be observed on finished articles or appears after light rubbing. This residue affects the appearance of the part and must be removed by suitable means such as polishing, which is troublesome and expensive and increases the price of the finished item.

Attempts have been made to prevent the formation of "dirt" * ¹ on sealed, colored aluminum miniatures by adding substantial amounts of a metal acetate *, a manganese sulfonate and a buffering agent such as boric acid to the sealing solution. This method

However, it also has, "definate drawbacks. First is the cost des # ehandlung8bade8 through the prices for its «bed parts and the relatively large amounts used of it be pretty high. Second, the treatment bath tends to be unstable and, after relatively short periods of use, to produce undesirable side effects. that the oxide layers exposed to it are not one develop good looking brownish shading. For these reasons, the service life of such a treatment bath is relatively short.

During a series of tests on anodically oxidized coatings, which are described in the pending patent application Method and Composition for treating Metal and Article Produced! Hereby ¹¹ by Deal et al., S «V« 857 562, filed on December 7, 1959, it was found that that the previously known sealing baths are not completely satisfactory for these coatings, since they do not produce a good-looking Schmitz in addition to the other laughing parts mentioned above.

In general, however, these coatings can be formed an electrolyte is used, d «r sulfoaalicyleäure and at least one compound selected from the group consisting of metal sulfates and sulfuric acid, as in the above-mentioned Patent application carried out. The electrolyte consists essentially of an aqueous solution of about 5 to 50 wt .- ^ C

BATH ORIGINAL

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Sulphosalic acid and at least one substance selected from metal sulphates and sulfuric acid in an amount not exceeding 15% by weight of sulfuric acid. Of the groups enumerated above, it is preferable to use sulfuric acid, and perrisulfate is a preferable metal sulfate. Even a small amount of metal sulphate or sulfuric acid acts according to the invention a favorable effect on the electrolyte, ie, an amount of metal sulphate or sulfuric acid is equivalent to o, l wt .- ^ sulfuric acid is low, _the: preferred ranges are 7 to 15 wt .- ^ SuIfosalieylsäure and an amount of metal sulphate or sulfuric acid, which corresponds to 0.1 to 4 wt .- ^ sulfuric acid.

It has been found that these oxidized aluminum surfaces can be produced at a much lower cost and without the formation of "Dirt" or discoloration of the finished product can be effectively sealed by placing the finished product in one Sealing bath is immersed, the relatively small and precisely defined amounts of a compound, such as Mckel acetate, which supplies metal ions, and a substance such as a lignosulfonate, contains. In fact, according to the invention, less than 4 g of the total additives are used per liter of bath and preferably about once to five times as much lignosulfonate as metal ion source. The bath should also be at a pH between 4 and 6.

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In the following example, commercially available aluminum alloys used as indicated in the following color I. Of course these are only examples since other alloys can also be used.

Table 1

J ''h>'■ * "■' ——————

alloy j. gi JL Je * Ou j> Ifa * Mg * Zn jL Ji * Cr

5052 0.10 0.20 0.009 0.02 2.44 0.05 0.003 0.20

6061, -f & 0.68 0.32 0.24 0.03 0.93 0.05 0.01 0.23

6O63 *! E5 0.32 0.26 0.01 0.01 0.50 0.00 0.01 0.00

6351-55 0.94 0.17 0.00 0.56 0.57 0.03 0.03 0.01

In Table I the remainder of the substances in each palette is aluminum. The alloys 5052 and 6061-T6 were, while alloys 6Ο63-Ϊ5 and 6351-T5 were ΐοπα of plates having a thickness of lmm (0.04 ^s) in the form of Preßstüoken. These alloys were electrolytically anodized as follows.

1. They were in an alkaline detergent inhibitor with a concentration uad purified 65 g / l for 5 minutes at 71 ⁰ C (160 ⁰ P). An example of a suitable alkaline cleaning agent consists of 40 g / l sodium carbonate, 20 g / l sodium phosphate, 5 g / l sodium metasilicate, the remainder being water.

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2. Rinsed in cold water.

3. Etched for five minutes at 71 ⁰ C (16O ⁰ F) with 5 wt .- # Lger sodium hydroxide solution *

4. Rinsed in cold water.

5. Two minutes at room temperature in 30 wt% nitric acid submerged.

6. Rinsed in cold water.

7 * At 24 Amp./929 em (24 Amp./sq..ft) at a temperature tone 25 + I ⁰ C in a bath of the following composition, electrolytically anodized:

5-sulfosalic acid 95 * 9 g / l Sulfuric acid 6.7 g / l.

Alloys Kr. 6061 and 6351 were rated at 24 amps / 929 cm (24 Amp./sq..ft) anodized until the voltage between anode and cathode reached 65V. Over this point the anodic oxidation continued at 65 volts. The total time of the anodic Oxidation was 40 minutes. With the alloys 5052 and 6063 the anodic oxidation at 24 amps / 929 cm (24 Amp./sq.ft) continued until the voltage between the anode and cathode reached 60Y. At this point the anodic became Oxidation continued at 60V. The total time for the anodic oxidation lasted 45 minutes.

8. Rinsed carefully in cold water.

9. The anodized plates 5052 and 6O61-T6 were then Cut into 3 x 4 "(7.62 χ 10.16 cm) coupons. The anodically oxidized pressed pieces made of 6O63-T5 and 6351-15 were cut into 4 "long coupons.

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10. Sealed in a sealing bath as indicated below.

11. Its exit from the sealing tank with warm water sprayed and air dried.

At process step 10, above, the sealing baths had the following compositions and were used under the following " .

example 1

fl & elft * «*« * 0.5 g / l

latriualigninsulphonate 1.0 g / l

Best waeeer

temperature 99 ⁰ C (210 ⁰ F)

pH 4.9

Time 20 minutes.

They were too. Temperatures of 95 ^° C. (203 ^° P) with times of 15 minutes and a pH of 5 * 0 were used.

For all of the alloys mentioned in Table 1, the anodized surfaces of the specimens were completely sealed, as evidenced by their resistance to staining by dyes or inks. There was no "dirt ^w formation observed on the surface of the finished objects or brownish discoloration. The bathroom was continu- for the treatment of anodically oxidized aluminum articles

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nuierlieh eighing for a period of two $ ^v used -.und .-, was full: effective. In addition, its cost is much less than that of the previously conventional crucible baths described above which used kick 1 acetate, cobalt acetate, calcium lignosulfonate, and boric acid. , .......

Example 2

Siekel acetate 0.5 g / l

Affirmation of affiliation 1.0 g / l

Eest haters.

This bath proved to be as fully effective as that of the first example *

example 3

Mekelae acetate 0.2 g / l

HatrluBSiligiiinSuifönat 1.0 g / l

Äest Wäasef ¹ .

Di «see lad also gave · With the alloys from Table I satisfactory results.

fäse # r. BATH ORIGINAL

This bad gafc bad · results.

example tfiokelaoetat 5 1.0 g / 1 Water lignin sulfonate 5.0 g / 1 rest Water.

This bath gave 8Ch.leeh.te results.

These and other tests have shown that the content of block acetate in the Tor bath can preferably fluctuate between 0.3 to 0.6 g / l, but that it must not exceed 0.8 g / l, since otherwise "Sohmutz" formation will occur can. Also, solder never fall below 0.02 g / L if it is to keep its effectiveness. The content of lignosulphonate in the bath can preferably vary between 0.5 to 2.0 g / l, but should never exceed 3.0 g / l, since otherwise the finished object can develop a brownish discoloration. It should never fall below 0.1 g / l in order to remain effective in ^{preventing N} dirt ^{R formation.}

In order to obtain the results described with the small amounts of kickel acetate and lignin sulfonate salt as indicated above, it is essential to keep the pH of the solution between 4 and 6, preferably at or close to 5. An additional buffer, such as boric acid, is not necessary.

~ ¹⁰ ~ BATH

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For the Tosten successes, the temperature of the bath between 85 ° C and 100 ⁰ C (185 and 212 ⁰ P) ", a target, and the oxidized AIuminiuBgegenstände aollen the bath for periods of 10 to 30 Hinuten exposed" a.

In practice, the additives of the bath according to the invention are used as a dry mixture consisting of kickel acetate and a lignin sulfonate in a ratio of approximately 1: 1 to 1: 5 Admitted, stored and shipped, and can use this mixture be dissolved in water in such amounts that a solution is obtained which contains less than 4 g of the mixture per liter of water.

Substances other than lignosulfonate can of course be used in the present invention if they are in function in the same way, and therefore the invention is not limited to these compounds in this regard. In In the description and in the claims, the term "aluminum" denotes high-purity, technically pure aluminum Aluminum and aluminum-based alloys containing at least 50 grains of aluminum.

Claims

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Claims (1)

Munich, the 8th time in 1963 / f <Deuteoh ^ Pa tentanaeldun " 1448481 * 4 «945 VXb / 48d Kaieer Aluainu «4 Chemical Corp. 1. TereiegelunAebad for anodiech oxidized «, colored · Aliuiinlu» - Xluchtn. as a result, d-ιύ daa bath in the weekly "in #" rmürif · Lüeun "from 0.02 to 0,,, -yi liicktlacetat and 0.1 fei _L v 3, C, /. a · lignin: *; Ifonate ”and that“ i has a yS-Jert ”like 4 and 6. 2. TeJWlieetlurigebad nucn Annpiruoh 1, characterized in that ea for anodically oxidized, colored aluminum surfaces, * Eiid that were eu «t in elite electrolytes, the ia -i »e» »ntHohen au« a wSi ^ rlgen T.-aun ^ by CuIfο alicyl-B .ufi and iainueut na ein.-Überetanz, aua ^ eselects aue 4 * t »ll-sulphates and; sulfuric acid, beeteth. I "Ter" ie "eluflÄ" bud nuoh Anapiraoh I _{9 identified} by it, IiI dia Bad Ü weetntichen au · a wätirl ^ tn L.; tu * Ä «on 0.3 bit 0.6 fi / 1 Nioktlaootat and 0.5 ti * 2.0 f / 1 eiaü Ligttia- • ulfoiut * »commits to a pH value of about 5 n * t. 4 · T »reieeelttn« tbad according to Aneyraen 1, d «d« rok k «nns« i «hA * t» the JU watntiiohett in * a wäOri «en Töeun« tone 0.3 0.6 M / i KleJceXaeetat umd 0.5 «1« 2.0 & / 1 a «Lifftiniulfon t * tau · 1ηβ« pH-f * rt divides tmiefätor 5 and d * I In * for I * "temperature a" l * "h" A oa "e approximately 85 ⁰ O bÜ 10O ⁰ O ei" Z12 ° f) H & AVMll im B ^ rIeW * g «teltÜI« 1H. BATH ORIGINAL gfc; YES _* 5. Sealing bath me claim 1, characterized! the dna bath in the weekly from an aqueous heating of about 0.5 g / l Hiekel acetate and about 1.0 g / l sodium and has a pH of around 5 6. Ver & iegelungsUad according to claim 1, characterized «that the bath essentially an aqueous color of Hickel acetate and a lignosulfonate in total amounts of less than 4 £ / 1 and in a miners ratio in the range of un ^ ef: hr 1 si bie 1 : 5 iöt. 7 · Process for sealing fashionably oxidized, colored alveolar surfaces, characterized in that the object is immersed in a bath containing essentially an aqueous solution of 0.02 bic ,, · g / l nickel acetate and 0 , 1 bio 3.0 g / 1 cB Liiiiiiiitiulfcnatei ^ and that is aged on a pH value between 4 and 6 i. 8. Method including sealing of oxidized fluid surfaces according to claim 7, characterized in that the object is dewed in a bath which is generally open. en auo einer WÜL-rii'en lößun; of ί ·; 5 bie 0.6 fc / 1 ϊ-ickelacetiit and 5 to ² Toe g / 'l a "ignineulf onatee" exists, and the pH on oinen ^h ert of ingefiihr ¹ J is maintained. 9 · Method for sealing oxidized aluminum flasks according to Snapruch 7, characterized in that the -e ^ was immersed in a bud for a time of about 50 minutes 90 9 80 ^ / 105 6 ^{BATHROOM 0RiaiNAL} is because »consists essentially of an aqueous solution of 0.3 to 0.6 e / 1 nickel acetate and 0.5 to 2.0 g / l sodium 1igninaulfonate and that at a pH of about 5 and on The temperature is kept around 85 ° C and 100 ° G (185 ° P and λΊ2 ° Ρ). 10. Method for sealing oxidized aluminum surfaces according to claim 7 »daduroh characterized daw the object is immersed for a time of about 20 minutes in a bath, which consists essentially of an aqueous solution of about 0.5 g / l of hickel acetate and approximately 1.0 g / l of sodium li (~ nlnaulphonate and which has a pH value of un- /and ' _ drive 5 at a temperature of about 99 C (210?) salary η -.vird 11 · Mixture for the animal treatment of a Hadeo sum Sealing of anodically oxidized, colored αluainium surfaces, characterized in that the bid is produced by the fact that the ae f'lschun ,? in hay at the tight of less than 4.0 ₍ x / \ to .8 it is given and that the '! iochung essentially consists of IjI bia 1i5 consists 12 ·,.! Ischun ^ for making a ß * des zu sealing Oxidized air foils according to claim 11, characterized in that the bath is produced in that it Mix in seed quantities of less than 4.0 g / l xu water BATH ORIGINAL 90980Λ / 105ß is given and that the mixture is essentially ·]! the end Nickelaoe + at unri Hatriusli & ninsulfonat in the ratio im Range from un * ref "her 1i1 to 1t5 consists. 009804/10