DE1496949A1 - Process for the electrolytic production of colored coatings on aluminum - Google Patents

Description

DR. ELISABETH JUNG AND DR. VOLKER VOSSIUS M0NCHEN2S. SI EC ES8TRA8SE 2 «. TELEPHONE S4C0C7 -TCLEORAMM-AOREeSEi INVENT / MONCHEN

B 906 / H / kä

1 1st SEP. 1968

OLIIi IUSSiBSOSi CHEMICAL COBfOBAXIOK Kew York / USA

"Process for the electrolytic production of colored Coatings on aluminum "

Priorities: February 15, 1965 / USA registration numbers: 432 814 and 432 889

The invention relates to a method for electrolytic production coherent colored coatings firmly attached to the substrate on aluminum objects, the Aluminum object in an electrolytic cell that contains a special, aqueous, acidic electrolyte, the anode forms. - "

Decorative or protective oxide coatings on aluminum have long been due to the anodic treatment of aluminum in electrolytes, which consist of dilute aqueous sulfuric acid, has been manufactured. These electrolysers are usually used at or near room temperature, and around that temperature

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to maintain, they must be cooled. The coatings produced in this way are usually relatively clear or colorless, but may be with some alloys they are also tinted by certain components or be colored. However, they are generally low Marked abrasion resistance.

Processes have been developed for producing anodic oxide coatings which have better abrasion resistance, the anodic treatment in aqueous sulfuric acid electrolytes at extremely low temperatures, i. approximately between -13 and -I ⁰ C, has been carried out. These methods have the disadvantage that they require expensive cooling devices in order to keep the oil temperatures below -18 ⁰ O. However, the coatings produced in this way not only have good abrasion resistance, but they are also colored in a manner suitable for numerous uses of aluminum, ie they are obtained in the desired dark shades, for example dark brown, etc.

It is therefore very desirable to develop a practical method by which the electrolytic route relatively Dark surface colors and good corrosion resistance are achieved.

Accordingly, it is an object of the present invention to be practical Process for the production of permanently bonded, colored coatings on aluminum objects To create anodic treatment, with the cover also

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good physical properties, such as corrosion resistance, Able to be peeled off and lightfast in color, also made possible it is the inventive method, a large number to produce various darker surface colors that are firmly bonded to the substrate.

Further objects and advantages of the invention are evident from the following Description.

The invention thus relates to a method for the electrolytic production of colored coatings on aluminum, which is why it is characterized that the aluminum is at a current density of

ρ
10 to 100 amps / 929 cm and a voltage of 10 to 90 volts is anodically oxidized in an aqueous solution consisting essentially of 0.1 to 1 fi sulfuric acid, 3 # to saturation amidosulfonic acid and, if desired, 0.1 to 10 pounds sulfophthalic acid, wherein the bath is maintained at a temperature between 10 and 90 ⁰ C.

It has been found that the inventive Surprisingly, a large number of lightfast, abrasion and corrosion resistant coatings with excellent physical properties can be produced, the shades of which range from light silver-gray to a series of brown and dark olive-green hues to pitch black.

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Ss is particularly iibarrsvsehend that very desirable darker hues obtained by the method erfindungsgeraässe a wide range, v / obei Surprisingly, the concentration of ^l imidosulfoüSöAjre and sulfophthalic acid in the electrolyte within wide Grrenidferl .verändert · veitö © ""jesbm;, while the range for the concentration of sulfuric acid is strictly limited

There is a further advantage of the method according to the invention in the low cost, whereby the process P is particularly favorable in terms of economy.

It has now been shown that the conditions of the invention Process for achieving the desired effect are important.

You concentration of sulfamic acid can be between 3 i "and the saturation value, it is preferably 5 Ms '15 * 36. · The Sehwefelsäurekonsentration is particularly critical and should be between 0.1 and 1 percent t '$, preferably from 0.25 to 0 .73 wt. $> Are held. If sulfophthalic acid is used, its concentration is between 0.1 and 10 %, preferably between 1 and 3 °

The bath temperature is kept at 10 to 9O ⁰ C, preferably at 15 to 30 ⁰ C.

The duration of treatment is not particularly critical, longer Treatments result in thicker coatings and darker shades,

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The treatment generally lasts for at least 1 minute preferably 1 to 150 minutes.

The aliasing level is anodically oxidized to a current density of 10 to 100 amps / 929 cm, preferably 15 to 30 amps / 929 cm and a voltage of 10 to 90 volts, preferably 25 to 70 volts.

The electrolysis bath can of course also have various, additional known ingredients, e.g. metal sulfates, added to achieve special results or special Reinforce properties.

If necessary, some sulphophthalic acid can also be used v / earth, s.B. 4-sulfophthalic acid or 5-sulf © isophthalic acid, where 4-sulfophthalic acid is preferred "

Each of the anodic oxidation treatment, the aluminum article can be desired failing a common sealing treatment in hot water, e.g. by immersion in boiling water or water heated almost to boiling point.

The method according to the invention is for "every alienation against" stand suitable, i.e. for highly cleaned aluminum, aluminum in various degrees of trade and aluminum-based alloys »

The type of cathode for the electrolytic ropes is not especially Jcritisoh · Practically are cathodes made of lead or stainless steel uses "909882 /" / "P

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The invention is illustrated in more detail by the following examples. The characteristics of the constituents are given in wt. #.

Example 3.

This example explains the multitude of colors in a number of alloys by the process according to the invention can receive / earth »

There v / ground different Altnaisiiuialegierungea anodically oxidized "wherein at specified current densities and voltages is changed duration * used electrolyte is an aqueous" the etv / a 0.25 # sulfuric acid, about 3 ^C J> Amidosulf acid and about 2 $ 4 ~ Contains sulphophthalic acid. Bas bath! Had a temperature of 25 ⁰ C held one verv / ends a lead cathode. The voltage is increased to the maximum voltage with constant current density and then kept constant until the end of the anodic treatment. The electrolyte is shaken while introducing air.

The results are shown in Table I below.

BATH ORIGINAL 909 8 8211416

iOabsXXe X- Current density at
maximum
Tension "
Amp / 929 on. Brown
schv / arz • öÄBäss a.oSflsieJ? -
lenrjj & seicfestmg a " Maxima * - ·
Xe Time,
There- 24
■ 24 ' Gray
dark gray 6061-26
It 50
65 20 '
40 24
'24 bronze 3003
Il 50
65 20th
40 '. 24 yellow
dark yellow 5052 40 30th 24
24 tan
© liv 6063-Ϊ5
It 50
60 20th
40 24
24 1100
η 50
60 30th
45 Example Z

This example explains the abrasion resistance of the inventively treated Rehearse.

JThe is. In the same way as in Example 1, probes are tested for their resistance to abrasion by sanding the side with a fine sandblasting gel, so that each probe can penetrate the anodic oversugation in 10 places necessary. The total time sum see penetration of the points is then dureh dia thickness of the coating in 0 _r 0254 mm divided _r where one obtains a measured value mm with the unit seo / 0.0254. The higher this value, the greater the resistance to abrasion.

The values are given in the following table.

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Alloy type treatment. . Abrasion resistance,

. - sec / 0 «0254» am

1100 30 min. Anodically treat with

165 g / 1 U ₂ SO ^ -IZ ASP *) 25

30 min. Anodically treat with

165 g / l E ₂ SO ₄ -Z * ASP *). 32

30 min. Anodically treat with

8 i> sulfamic acid plus

$ 0.25 HoSO _A plus

2 # 4-SttXfoghthalic acid-24 ASP · 81 ·.

*) ASP »Amp / 929 '

Example 3

This example explains the production of improved darker shades obtained by the method according to the invention.

• *

compared to the anodic treatment with an aqueous bath that contains only sulfuric acid or that contains sulfuric acid and sulfamic acid.

You aluminum alloy 1100 is made in the same way as in Example 1 anodically oxidized, the treatment conditions as well the compositions of the aqueous electrolyte are shown in FIG following table «, ·.

The hues obtained are reported as photovolt readings, with generally darker hues replaced by lower ones Readings are shown in photovolt, i.e. the lower Reading in photovolt corresponds to a lower reflectivity and therefore a «darker party, ■

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The results given in Table III below show; that darker by the inventive process colors he will hold ^-1.

30th
30th There.
Min. Table III Readings in
Photovolt Deletion
Type treatment 55
50 1100 treat anodically with
165 g / l H ₂ S0 ₄ ~ 12 ASl? *)
treat anodically with
165 g / l HoSO ,, - 24 ASS ¹ *)

30 min. Anodically treat with

10 i> sulfamic acid plus

0.25 f * H ₂ S0 ₄ ~ 24 ASP »), 20

30 min ο anodic, treat with. 8 i> amido sulfonic acid plus 2 i> 4-sulfophthalic acid and 0.25 ^ H ₂ SO ₄ -24 ASP *) 15

*> ASP β Amp / 929 cm ²

Example 4 -

The following example explains the great diversity of Shades of color. Which, in the case of a number of alloys according to a Further execution forms of the process according to the invention are obtained can be. '.

Various aluminum alloys are anodically oxidized, v / o at fixed current densities and voltages the duration of the treatment is changed. An aqueous Lo * 3ung is used as an electrolyte, composed mainly of about 0.25 ^ sulfuric acid and about 10 ^p /> sulfamic acid * Dae vird bath. kept at a temperature of 25 ^° C. You use your lead

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cathode. The voltage is at constant current density * to increased to maximum tension and then to completion the anodic treatment kept constant. ' The lead electrolyte is shaken while air is introduced.

The results are summarized in the following Table IV:

gabeile IV

Aluminum maximum time ₉ current density at alloy voltage, min · maximum

V voltage, «" - Amp./929 öm

colour

6061 55
70 20th
40 24
24 . Brown
black 3003 65
'70: 20th
• · 40 24
- 24th gray ■
dark gray 5005 65
75 • 30
. ·· 45 · 24
24 Gray
gray-green 5457,. 50 30th 24 brownish
green 5052 50 • 30 24 bronze 2024 50 30th 12th bluish gray 1100 65 30 * 24 • .dark olive
green

Example 5

. The following example explains the surprising effect that is caused by a change in the concentration of Sohw @ £ elsic acid. . ,

The aluminum alloy 6061-S6 is according to Example 4 in a

2 '
Current density of 24 Amp / 929 ca anodically oxidized. This requires

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a tension of about 40 yoIt at the beginning of the procedure until the Maximum of about 50 volts after about 10 minutes Minutes you keep the voltage at about 50 volts and leave the Current sink. ...

Eb aqueous electrolytes are used, which are different Have concentrations of sulfuric acid and sulfamic acid. The color shades obtained are given as readings in Ihotovolt, v / o for darker shades again as in Example 3 lower readings in photovolt are displayed corresponding to a lower deflectivity

The results show that darker shades are obtained by the process according to the invention. The results are given in Table V:. ^: ,. ·· ■■ ·. .,

Tabolle V

electrolyte - 0 jfc H ₂ SO ₄ Readings in
Photovolt 165 g / Idter H ₂ SO,
$ 5> Amidosulf oneaure - - 0.25 & H ₂ SO ₄
- 0.50 # H ₂ SO ₄
- 0.75-5 H ₂ SO ₄
τ 2.0 $ H ₂ SO ₄ 53
37 Il
η - 0 SS HpSO. . 20th
15th
15th
38 10 j6 amidosulfonic acid .40 • 0.50 J6 H ₂ SO ₄ 18th - 0.75 S ^ H ₂ SO ₄ 20. ·. ti - 2.0 36 H ₂ SO ₄ 23 N . 37

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Port setting Table V - 0 ia H, Readings in
Phot0volt electrolyte - 0.25 S . . · 40 · 15 # sulfamic acid - 0.50 5 22nd • 0 - 0.75 5 21 Il -2.0? 27 η ^ι 44 IJ > ^S0 4 I H ₂ SO ₄ 4 "H ₂ SO ₄ δ H ₂ SO ₄ i H ₂ SO ₄

Example 6 .. ·· '-. ·

This example again shows how critical the conditions are of the method according to the invention.

Various aluminum alloys are made according to Example 5 anodically oxidized at a current density of 12 Amp / 929 οία, wherein aqueous electrolytes (1) with a content of 10 56 Amidosulfonic acid and 0.5 ^ sulfuric acid and (2) can only be used with a content of 165 g / liter sulfuric acid

The results are summarized in Table VI below, which also includes the alloy used, the voltage, treatment time and the photovolt readings for the respective Indicating electrolytes. Saraus clearly shows that the darker shades are obtained by the method according to the invention will.

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labölle VI Min Maximum Readings in Aluminum- time used, 20th Tension,
V Photovolt alloy electrolyte 45 50 23 6061-26 ' 1 20th • 70 8th » 1 45 14.5 52 It 2 20th 14.5 45 η 2 40 50 27 3002 1 20th 65 11 1 40 14.5 48 ti 2 20th 14.5 40 il 2 40 50 27 5005 1 20th 60 19th Il 1 40 14.5 47 I) 2 5α 14.5 44 H 2 45 50 20th 1100 1 30th 60 15th IJ 1 45 14.5 41 (I. . 2 30th 14.5 40 il 2 45 40 ■ 37 5052 1 3Q 60 19th 11 1 45 14.5
t & et .50
M f * H
t * 2 14.5 45 Ii 2

Example 7

Two samples of aluminum alloy 6061 are processed under the conditions specified in labeile IV for alloy 6061 anodically colored. As in Example IV, the shades turn brown bsw. get black «

These samples are then sown for 2500 hours of exposure to ultraviolet light. During the 2500 hours, both samples still have their brown or black Parba.

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Example 8

This example explains the abrasion resistance of one Embodiment of the process according to the invention anodically "treated Rehearse,,

The samples anodically treated in the same way as in Example 4 are tested for their abrasion resistance by grinding the surface of the sample with a fine sandblast. The time is determined which is necessary for every rehearsal to penetrate the anadic exercise in ten places. The total time aun. Penetration in 10 places is then divided by the thickness of the coating in 0.0254 mm, whereby a measured value is obtained with the unit sec / 0.0254 μά , the higher this value, the greater the abrasion resistance »

The values are given in the following table.

Table TII

Alloy treatment abrasion resistance

6c6l-0) 6 anodically treat for 1 hour with

165 g / l H ₂ SO, -12 ASl? *) 28 see /. 0.0254 mm

Treat anodically for 1 hour with

165 g / l H ₂ S0 ₄ ^ 24 ASl? *) 42 see / 0.0254 mm

1 hour anodic treatment with.

10 ^ araido sulfonic acid "ilus _m / _Ω 0.25 $ H ₂ SO ₄ -24 ASP *) ^{91 se0 /} °»

3003 anodically treat for 1 hour

165 g / l H ₂ SÖ ₄ ~ 12 ASP ») 27 sea / 0.0254 mm

Treat anodically for 1 hour with

165 g / l H ₂ S0 ₄ ~ 24 ASP *} 35 s @ ö / 0.0254 mm

1 hour anodically treat with

10 $ Amidosulf onsäui * © plus

0.25 ■ # K ^ SO ₄ - «» 24 ASF ^ J 73 aae / 0.0254 am

*) ASS ¹ * Amp / 929 oat ² 90 9882 / 1'4 1 6.

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Claims (9)

Claims Ι »Process for the electrolytic production of colored coatings on aluminum, characterized in that the aluminum is anodically oxidized at a current density of 10 to 100 amps / 929 cm and a voltage of 10 to 90 volts in an aqueous solution consisting essentially of O ₁ I to 1 f * sulfuric acid, and desired trap consists of 3 0.1 $> to saturation Amidosuifonsäure to 10 # SuIfophthalsäure, wherein the bath at a temperature between 10 and 9O ⁰ C. 2. The method according to claim 1, characterized in that g e k e η η · ~ Not that the electrolyte has 5 to 15 # amidosulfonic acid contains. 3. The method according to claim 1, characterized in that g e k e η η zeiohnet, that the electrolyte is 0.25 to 0.75 # Sohwdfel * contains acid. 4e method according to claim 1, since you raw characterized that the electrolyte contains 1 to 3 % Su If oph thai acid. The method of claim 5 x 1-4 »dadurchgek β η η ε ei without t that the bath is maintained at a temperature of 15 to 30 ⁰ C. 909882/1416 ' New documents (a-i U96949 6. The method according to claim 1 to 5 *, characterized in that the current density 15 to, 30 Amp / 929 cm and the voltage is 25 to 70 volts ". 7. The method according to claim 1 and 4 »thereby g e k e η η - ζ € i oh. η et that the electrolyte contains 4-8ulf © phthalic acid 8. The method according to claim 1 to I ₉ characterized ge k eanz eich η et that the aluminum is anodically oxidized for 1 to 150 minutes. 9. Electrolyte for carrying out the method according to claim 1 to 8, 'seke η η ζ e ± Q h ® t äureh a content of 0 _v 1 to 1 # »sulfuric acid, of 3 ⁰ A Ms ^ ur saturation amidosulfonic acid and optionally O ₉ 1 "to 10" S sulf © phthalic acid. BATH ORIGINAL .909882 / 1416 '