DE1521016A1 - Process for the production of colored oxide coatings on aluminum or its alloys by anodic oxidation - Google Patents

Description

UcZ ₅ : C 512 (Yo / kä) 27. Deaentoer 1966

POS - 9775 - SUIllTOKO

SUMlTOKO OHKIulCAL COKPALIY, LTD., Osaka, Japan

"Process for the production of colored oxide coatings on aluminum or its alloys by anodicβ

Oxidation"

Priority; December 27, 1965, Japan, No. 81012 / 6i> October 15, 1966, Japan, No.; 67 973/66

The invention relates to a method for producing colored Oxide coatings on aluminum or its alloys by onodial oxidation with the help of a new aqueous, acidic BIeJr. troly ten.

It is known to produce oxy over and over by the anouisohe oxidation of aluminum or its alloys. The most frequently used ancestor uses al "ilejcxrülyt Schwereleuur". ttni ancestors is the sulfuric acid solution as well as hni

009834/1340 bad orjg «nal

mqnchkm an η »ankkomto * mufschk · ανκ α. <l MOmomkm. Lio ^ OLsem n, «? $>. n *.

a temperature around H & umtaiaper & tur vexwe & det, and therefore the electrolyte must be cooled. The oxide liquors obtained by these processes are usually colorless in the case of certain However, they can also be colored in alloys.

Recently a process for the production of hard öxydi & it higher AbriobBb0Btfeai £ ability known by uan

Aluminum is anodically oxidized at temperatures around ⁰ ° C in aqueous sulfuric acid solution. The Oxyti.ti.ber & U £ obtained by this process has not only an "external abrasion resistance" but is also metallic, rough, gray-tinged brown or dark brown in color. Due to this coloration, the anodized aluminum can be used in construction. To each the ßlektroXyttttftperatur at etv / a O ch to maintain ⁰ C, mUeeen the cost of the device vmu cl @ n ^ Mt ieh be significantly increased. It is therefore desirable to provide · ® ± n praktiaohereo and economical proceed "aux H" retellune gefürbt "r QxydUberfee *. This object is achieved by the invention.

Oegenetand r Krflnaune is a 7e?: Fftitr «& eur hearing position of colored OxydUberr.Ü ^ an / liicii ^ ium odor its through anodiyche Oxyd & tioa iv. tin ^, tarry, acidic lyte, which is determined by the fact that an electrolyte is yerwAdat, dor 1.5 ^ iB 40 6ew _w -j5 5ap5ithalindi »sulfonic acid @ and 0.1 to 3.0 6" w , ^ Contains sulfuric acid, and anodic oxidation at an initial temperature of 20 volts

ü ^f! 9 H ^: i 4 - '■■ "■ · l -

BATH ORIGINAL

ft & ch the erfindungsgemäSBen process ea let possible to achieve Oxydüberzü <ve excellent Abriebe- and weather resistance at an electrolyte temperature ranging ron Rauateitpera 'door'

The Maphthalindieulfonäura used in the xHectrolyte according to the invention includes all isomeric naphthalene, sulfonic acids or external mixtures. Preferred mixtures contain _s the 1,5-- "naphthalenedisulfonic as an essential Beatandteil. The aluminum alloys treated in the process according to the invention include every alloy "which forms thick oxide layers by anodic oxidation in an electrolyte" which removes sulfuric acid.

The colors of the age-old oxide coverings are slightly different of an Eleictrülyts within the aforementioned i ' setzuiifesbereicns unci durcii alloyun ^ eri, different

and aluminum alloys and various he Aj-.iO.iU * i «r ^v j. ^

varies who '

When using "e erfindungegeiaäee ·" electrolyte i "t d even at low leaperatur as hard" CxydUfc ** ¹ - "^" fe "> zuatüllen, as are obtained by known methods deo with wabei3.g" ν sulfuric Furthermore itanii. At an electrolyte temperature of about 15 to 5C ⁰ C, colored oxides with excellent abrasion and weather resistance are obtained

00983471340

⁰ G erfindungsge to oxydierent -The of anodically O; aäßse method is therefore economically and technologically more favorable because the anoüiöche oxidation can be carried out at a KLektrolytteiaperatur ira range of about 15 to 3O ⁰ C.

As the corus exitration of the maphthalenedisulphonic acid decreases, the cell tension decreases and the color of the oxide corrosive obtained becomes lighter. On the other hand, the Konsentration of naphthalene disulfonic acid decreases »increases the Zellenspanriuno and the color of Oxydüberzuges is gradually darkens and from brown to dark brown to echwara to" Mvmx the concentration of iiaphthalindisulfoneäure less than l _f 5 Crew.- ¹ / m, it is difficult to to obtain a usable »uniformly colored oxide coating«.

If the sulfuric acid concentration is less than 0.1% by weight, it is also difficult to obtain a uniform colored oxide coating. At a sulfuric acid concentration of more than 3.0% by weight, the color of the oxide overcoat becomes lighter with increasing sulfuric acid concentration, and finally the oxide overlay becomes colorless, although the ionic tension drops. The preferred concentration range for the sulfuric acid is 0.3 to 1.5% by weight. When using an aqueous electrolyte containing 10 to 20% by weight of sulfuric acid and 5 to 25% by weight; aph thai indisulfern acid, the dissolution of the oxide coating is inhibited by the electrolyte during the electrolysis, so that it is possible to turn this electrolyte into anodic oxidation at high levels of oxygen . use. Of the

00983A / 1340

BAD ORiGiNAU

The oxide coating obtained, however, is colorless or only slightly colored, depending on the type of alloy used. When using the electrolyte according to the invention, the most favorable results can be achieved if an aluminum alloy is anodically oxidized at a current of 1 to 3 A / du. In a .tllektrolytte / üperatur to liaunite.aperatur, ie, about 2O ⁰ C, the cell voltage is 20 to 80 volts, when the anodic oxidation at a current density of 1.0-3 A / dm & durcn efiihrt is.

If in anodic oxidation the initial voltage is below 20 volts should be, get out the anotous oxidation lower current density or higher electrolyte temperature or the amount of sulfuric acid in the electrolyte needs to be increased. In all of these cases, however, there is no thick, hard and deeply colored oxide oversize can be obtained.

With a constant current density, the cell voltage gradually increases with increasing thickness of the oxide coating. ^ there are some cases where, depending on the type of aluminum used or the Aluminum alloy combustion is observed if the cell voltage during anodization is at the same current density has exceeded the value of 60 volts. The will fall into these Cell apannunj preferably kept at a lower value, so that υ no combustion occurs the anodic oxidation is initially carried out at a constant current density and then at a constant cell voltage, so none Combustion takes place. Dio julreciieinun ^ ucr burning can also durcii JÄrhönun *, uer KleKtrolytteu.pöratur be prevented.

009834/1340

BUILDING

The anodic oxidation can either with alternating current, with Gleic soda or direct current modulated with alternating current can be carried out. The duration of the treatment depends on the current density and the desired thickness of the oxide coating. Colored Oxide coatings with sufficient abrasion resistance can be used within from about 3 & to 60 minutes can be obtained. The thickness of the oxide coating is usually between 15 and 20 microns per A-h / tar.

The invention is illustrated by examples.

Example 1

A strantig prepared aluminum alloy 6351-Tc ("it 0.9?, Wt. S ^ Si, 0.70 wt. 5 * Mg, 0.39 wt etten in conventional manner by -Jntf and stains from lohiaut "liberated una then in an aqueous electrolyte which contains 9 parts by weight of 5 £ Naphtiialindisulfonsäure and 0.6 wt .- # Schwefolsäuro, at 25 ⁰ C and a current density of 2 a / anodizes for 60 minutes while the electrolyte is passed in. The cell voltage rises almost from 30 tons to 55 volts towards the end of the anodic oxidation straightening of a single-phase Weüh »el» tron ·.

The oxide oversug produced by this anodizing treatment became Resealed in simmering, desalinated water. The Oxydtlberiug It was of a genuine color, and its thickness was about 3 crowns.

009134/1340

BATH ORIGINAL Example 2

An aluminum alloy 6063-κ in For; a from extrusion, em, which contained 0.43 wt. SS Si, O _f 55 wt. 5ε Yig and 0.17 wt 1 broom rubbed to iteini & pretreated clothes and contained in an aqueous CLektrolyt, 9 ßew * "$ Haplrfchalindiaulfonsäxire and 0.6 wt« ~ # sulfuric acid, at 20 ° C and a current density of anfänglicnen

2
2.4 A / dia anodically oxidized «Within 37 minutes of the beginning of the treatment, the cell voltage rose gradually from 30 to 56 volts. Then the alloy is anodized at a constant voltage of 56 volts for 24 minutes. The current density was against

At the end of the anodizing, 1 _P 3 A / dm. The oxide coating produced by this treatment was resealed in a manner similar to that described in Example 1. The oxide over-eye was brown in color and its thickness was about 35 Fücron #

In the table below are further examples among various Anodizing conditions compiled · The color of the The oxide coatings obtained are also listed.

009834/1340

3ei »
game Electrolyte, wt
(Rest water) Alvuainiun-
ocier Al-
[alloy
description
after
aluminum
Association Alloy composites setuiiti ed Fe Mn Cr Cu 0.55 0.17 - . " 0.23 shape troa-
ichtfi,
A / dm ^ required
liche
tension
V älelctro-
lyttejap.
⁰ C Time,
min colour
the 3 Jiapjatnalindi-
sulfonic acid 30
H ₂ SO ₄ 1.8 1100 Si Usual impurities 0.94 0.17 0.33 - sheet 2.0 20-30 15-20 60 Oxyd- c
about- I ^s
eye 4th HaphtnaliEii-
sulfonic acid «? lo
H ₂ SO ₄ 1.2 6063 - I ₅ 0.43 0.70 Ot 39 O ₈ 48 - strand
) ress-
Linge 2.0 20-30 20th 60 yellow-
lightly-
silver - <
ι Jfaphtnalindi-
sulionic acid 15
H ₂ SO ₄ 1.9 6061 - ϊ ₄ 0.63 Il η η - sheet 3.0 25-60 15-20 60 <
( 6th Saphtiialindi-
sulfonic acid 9
H ₂ SO ₄ 0.6 6351 - T ₅ 0.93 Strand*
) res8 "
Linge 1.0 3C-45 20th 60 Brown i Sapphthallzuii-
eulfonic acid 9
H ₂ SO ₄ o _t 6 η η ti 1.5 30-55 20th 60 dark
Brown black

8AD ORiGiNAL

! • rteetsung you page 8

δ ■ Bapathalindi-
sulfonic acid 9
H ₂ So ₄ 0.6 6351 - T ₅ 0.95 0.70 0.39 0.48 - β » - - - strand
press
ling « 2.0 30-70 20 40 heavy 9 - do - Al-Legie
tion 0.96 0.67 0.17 - 0.24 η 2.0 28-70 20 6C Brown .0 - do - 0.42 0.62 0.16 - - - N 1.8 30-55 20 60 η t
ι a Ma-nhthalindl- 6351 - X ₅ 0.93 0.70 0.39 0.48 0.24 m 1.5 · 30-56 25 60 .2 TOlfonsltaT * 4.5 Al-Legi -
down 0.96 0.67 0.16
t - M. 1.0 · 35-56 25 60 black H ₂ SO ₄ 0.5 Brown Vaph thai 1 tv3 ■ »-
• uJLf onic acid 1.5 H ₂ SO ₄ 0> l

They anodic oxidation was carried out at constant current density,

until the cell voltage reached 56 volts, and then continued at a constant 56 volts.

cn κ:

Claims (3)

1. Process for the production of colored Dxydüberü ^ en Aluminum or its alloys by anodic oxidation in an aqueous electrolyte, which draws "j k e η η" that an electrolyte is used which contains 1.5 to 40 wt. Contains sulfuric acid, and at an initial cell tension of at least 20 volts works. 2. The method according to claim!, Characterized in that g e k ε η η ~ draws »that the anodic oxidation with an aqueous ι Electrolyte containing 5 to 20% waphthalenedisulphoic acid and 0.3 - Contains 15% by weight of sulfuric acid, with a current of ο
1 to 3 A / dm and at an electrolyte temperature / on about 15 to 30 ⁰ C is carried out. 3. The method according to claim 1 and 2, characterized dadursh, that the anodic oxidation initially occurs at a constant current density of 1 to 3 A / dm and thereafter is carried out at constant voltage. 4 electrolyte for the anodisic oxidation of aluminum and seir; Alloys consisting of an aqueous solution containing 1.5 to 40% by weight of naphthalene disulphonic acid and 0.1 to 3.0% by weight of sulfur contains acid. 009834 / 13AO BATH ORIGINAL