PL152644B1 - Bath for zinc coating of aluminium and aluminium alloys,especially before galvanizing with metals - Google Patents

Description

REPUBLIC POLAND PATENT DESCRIPTION 152 644 Additional patent to patent no. --- Int. Cl. ⁵ C23C 18/46 Reported: 87 12 14 / P. 269453 / Priority, - OFFICE PATENT Application announced: 89 06 26 RP Patent description published: 1991 07 31

Creators of the invention: Piotr Toms9i, Danuta Koźmińska, Janusz Hołownia

Authorized by the patent: Institute of Precision Mechanics,

Warsaw Poland/

BATH FOR BREATHING SURFACES OF ALUMINUM AND ALUMINUM ALLOYS, ESPECIALLY BEFORE APPLICATION OF GALVANIC METAL COATINGS

The subject of the invention is a bath for galvanizing aluminum and aluminum alloy surfaces, in particular before applying electroplated metal coatings.

The basic problem to be solved in the case of electroplating metal coatings on aluminum is ensuring good adhesion of the metal layer to the substrate. The strong tendency of aluminum to passively pass the surface on contact with oxygen in the air or solutions containing oxygen atoms causes the presence of a thin oxide film on the surface. The oxide vat formed in the natural atmosphere on the aluminum surface has a thickness of about 10 m and it effectively weakens the adhesion of metal coatings deposited with a galvanic method on the aluminum surface.

In order to remove the passive oxide layer and increase the adhesion of the applied metal coatings, electroless chemical galvanization in alkaline solutions or electroless chemical tinning or anodic oxidation in phosphoric acid solutions are used to form a thin porous and electrically conductive oxide layer.

Due to the lowest cost and ease of the process, electroless chemical galvanizing in alkaline solutions is most often used.

The chemical galvanizing process takes place in an alkaline solution containing 100-500 g / dm of sodium hydroxide and 10-100 g / dm of zinc in the form of sodium zincate. In such a solution, the aluminum surface is etched, the oxide layer is removed and a thin layer of zinc is formed on the surface by chemical reduction, protecting the surface against re-oxidation. After galvanizing, aluminum objects are subject to subsequent surface treatment operations to produce appropriate protective, decorative or technical coatings. The most common coatings are nickel, chrome, silver or multi-layer Cu-Ni and Cu-Ni-Cr.

To ensure sufficient adhesion of metal coatings, the zinc layer must be even, have a proper structure and thickness. The use of a sodium zincate solution does not provide the desired quality of the zinc films.

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152 644

For example, it is known from British patents Nos. 1,338,975 and 1007252 or United States Patent Nos. 2,142,564 to use in a new zinc solution additives such as Fe, Ni, Cu and complexing compounds, most often cyanides in order to improve the quality of the produced zinc films. These solutions bring a slight improvement in the efficiency of the trimming operation and increase the adhesion of metal coatings applied to aluminum.

The known baths do not fulfill their function in the treatment of a wide variety of technical aluminum alloys, especially casting alloys, for which it is still difficult to obtain sufficient adhesion of electroplated metal coatings.

The aim of the invention is to develop an improved method of chemical zinc coating of the aluminum surface. The aim is to develop citation baths with greater efficiency and reliability. *

The essence of the present invention is the use of a new group of additives in zincide solutions, which have a particularly beneficial effect on the structure of the produced zinc layer and cause high adhesion of metal coatings even in the case of difficult-to-process Al alloys with a high content of alloying additives, such as silicon, magnesium, copper and others. These additives are compounds of the alSanolololamiz type.

A bath for galvanizing aluminum and aluminum alloy surfaces, especially before applying electroplating metal coatings, containing zinc cations in the amount of 5 to 200 g / 1 and iron cations in the amount of 0 to 100 g / 1 or copper cations in the amount of 0 to 100 g / 1 1 or nickel cations in an amount from 0 to 100 g / 1 or cobalt cations in an amount from 0 to 100 g / 1 or a mixture of above-mentioned cations and further containing sodium hydroxide in an amount from 50 to 800 g / 1 and sodium citrate in an amount from 0 to 100 g / 1 or sodium tartrate in an amount from 0 to 100 g / 1 or sodium edetate in an amount from 0 to 100 g / 1 or sodium gluconate in an amount from 0 to 100 g / 1 or sodium laurinate in an amount from 0 to 100 g / 1 or sodium cyanide in an amount from 0 to 100 g / 1 or a mixture of the above-mentioned low-low compounds, according to the essence of the invention, is characterized by the fact that it contains an alcicololyamysis of the general formula in which x is a natural number from to 7, from 0.01 to 100 g / 1.

The developed bath enables the production of zinc coatings on the aluminum surface with very good adhesion to the substrate and ensuring high adhesion of protective decorative or technical coatings applied to the zinc. An additional effect is the possibility of direct application to galvanized coatings of shiny nickel without the need to use additional copper interlayers from a cyanide bath or mto ^ e ^ o.

It is obvious that potassium salts can be used in the bath instead of the sodium salts of the compounds mentioned.

The bath according to the invention is shown in the embodiment.

Example I. A bath with the following composition was prepared:

- zinc cations converted to ZnO 12 g / 1

- sodium hydroxide 50 g / 1

- alkazolololi8mine of the general formula

3+

W ₂ - / - CH ₂ -CH ₂ -NH- / _x -CH ₂ -CH ₂ -NH ₂ where x = 2

- ion ^{Y of} iron ^F e ³ +

- nickel ions ^N and ² +

- sodium edetate

- sodium gluconate

- sodium cyanide

Example II. A bath with the following composition was prepared:

- zinc cations, converted to ZnO

- sodium hydroxide

- alkazolopolappina of the general formula

104 g / 1 450 g / 1

NH ₂ - / - ^^ H ₂ -CH ₂ - ^^ - / _x -CH ₂ -CH ₂ -NH ₂ , where x * 3 - iron ions Fe ^ ⁺ g / 1 g / 1 22 g / 1 g / 1 0.6 g / 1 g / 1 25 g / 1

152 644

Ο 1

- copper ions Cu 5 g / 1

- sodium citrate 2 g / 1

- sodium tartrate 45 g / 1

Example III · A bath with the following composition was prepared:

- zinc cations, based on ZnO 230 g / 1

- sodium hydroxide 800 g / 1

- · elkaoooopoiaamina with the general formula

NS ₂ - ^ / - C ^ H ₂ -CH ₂ -N ^ - // _x -CH ₂ -CH ₂ -NH _2> where x = 0 80 g / 1

- ion ^of copper Cu® 1 ^{g / 1}

- sodium gluconate 0.4 g / 1

Example IV. A bath with the following composition was prepared:

- zinc cations, calculated as ZnO '5 g / 1

- sodium hydroxide 62 g / 1

an alkanol polyamine of the general formula

NH4 / cH2 -C1-NH-N -C1 -C2 -N2, where x = 7 0.2 g / 1

- ions than the ^class of ^N ± 1 ^6-2+

- sodium edetate 224 gH

Example V A bath with the following composition was prepared:

- zinc cations, calculated as ZnO 120 g / 1

- sodium hydroxide 500 g / 1

- an alkanol polyamine of the formula

NH2 "/ cCH ₂ -CH ₂ -NH / -C 1 -C 2 -N 2, where x is 5 g / 1

- copper cations Cu * 11 g / 1

- cation ^{y of} nickel ^N and ² * 1 g / ¹

- sodium cyanide 11 g / l

Example V ^ · A bath with the following composition was prepared:

- zinc cations, calculated as ZnO 180 g / 1

- sodium hydroxide 630 g / 1

- an alkanol polyamine of the formula

ΝΗ ₂ - / ΟΗ ₂ -ΟΗ ₂ -ΝΗ / χ-ΟΗ ₂ -ΟΗ ₂ -ΝΗ ₂ , where x 3 66 g / 1

- iron cation ^y Fe ² *

- cations n and ^k lu Ki. ² *

- sodium citrate 0.3 g / 1

- sodium tartrate 25 g / 1

- sodium gluconate 2 g / J

- sodium laurate 6 g / 1

- sodium cyanide 1 g / 1

Example VII · A bath was developed with the following composition:

- zinc cations, converted to ZnO 90 g / 1

- sodium hydroxide 280 g / 1

- an alkanol polyamine of the formula

NH ₂ - / CH ₂ -CH ₂ -MH / _x -CH ₂ -CH ₂ -NH ₂ where * w _y is 1 15 _g / 1 * cations that ^ for Fe ^ * 14 g ^{/ 1} pi

- copper ^y cation Cu 1 ^{g / 1}

- ^k ation nickel Kl · ^{y 2} * 20 ^g / ¹

- ^k ation kobartu ^y Co ² * 6 gA

- sodium citrate 100 g / 1

- sodium tartrate 12 g / 1

Example d VIII. A bath was developed with the following composition:

- zinc cations, converted into ZnO 25 g / 1

- sodium hydroxide 50 g / 1

- an alkanol polyamine of the formula

M ^ -z / C ^ - ^ - NH ^ -C ^ -CH ^ N ^, where x is 4 0.04 g / 1

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- iron cations Fe ^ ⁺ 3 g / 1

2+

- copper cations Cu 12 g / 1

- ^{y k} ation nickel Ni ²⁺ B5 ^{g / 1}

- sodium citrate 40 g / 1

- sodium edetate 60 g / 1

- sodium laurate 6 g / 1

Example IX · A bath with the following composition was developed:

- zinc cations, converted to ZnO. 40 g / 1

- sodium hydroxide 78 g / 1

- an alkanol polyamine of the formula

NH ₂ - / CH ₂ -CH ₂ -NH / _x -CH ₂ -CH ₂ -NH ₂ where x is 0 23 g / 1

- ^k ation ^of copper Cu ²⁺ * 1 ^g / l

- ^{y k} ation nickel Ni ² '0.1 ^g / 1

- cation ^y kobaMu Co ² 7 ^g / 1

- sodium tartrate 80 g / 1

- sodium edetate 2 g / 1

- sodium laurate 12 g / 1

- aodic cyanide 0.5 g / 1

Example X · A bath with the following composition was prepared:

- zinc cations, converted into ZnO 200 g / 1

- sodium hydroxide 700 g / 1

- ilkinrlrprliamine of the formula

N1 -C1 -C1 -NH1 -C1 -C1 -N2, where x is 56 g / 1

- cation ^{y of} cobalt Co ² + 3 ^g / 1

- sodium citrate 28 g / 1

- sodium tartrate 8 g / 1

- sodium edetate 8 g / 1

- sodium gluconate 8 g / 1

Example d X! · A bath with the following composition was prepared:

- zinc cations, calculated as ZnO 80 g / 1

- sodium hydroxide 130 g / 1

- an alkanol polyamine of the formula

NH-CC ^ -C ^ -NH / ^ J ^ -Nra, in the circle x is 5 14 g / 1

- cation ^y n and ^kl u ^N i * + 4 ^g / l

- sodium tartrate 80 g / 1

- sodium gluconate 12 g / 1

Example XII. A bath with the following composition was prepared:

- zinc cations, converted into ZnO 64 g / 1

- sodium hydroxide 180 g / 1

- an alkanol polyamine of the formula

NH ₂ - / CH ₂ -CH ₂ -NI / _x -CH ₂ -CH ₂ -NH ₂ where x is 1 1.3 _g / 1

- ^{k Y of} iron ation e ^ ^{P +} 1 ^g / 1

- copper cations Cu + 6 g / 1

- ^{y k} ation nickel and ^{N 2 of} 1 ^g / ^l

p.

- cation ^y kobslk Co 4 ^g / l

- sodium citrate 18 g / 1

- mating tartrate 11 g / 1

- sodium edetate 11 g / 1

- sodium gluconate 22 g / 1

- sodium laurate 6 g / 1

- sodium cyanide 44 g / 1

152 644 nickel sulphate boric acid nickel chloride saccharin process paramters

Example XIII. Aluminum sheet made of the PA4 alloy was galvanized in a solution with the following composition / content of components in g / l /:

NaOH 500

ZnO 80

PaCl ₃ 1 sodium potassium tartrate 15 Etyeenddiamine 10

Process parameters: time 2 minutes, temperature 20 ° C.

Then the sheet was electrolytically nickel plated in a Watts type bath with the following composition / g / 1 /:

250.

current voltage 2.5 V current density 4 A / dm ² time 30 min.

temperature 50 ° C

Example XIV. Cast aluminum from the AG5 alloy was galvanized in a solution with the following composition / content of components in g / l /:

NaOH 250

ZnO 50

NiS04.7H ₂ 0 10

CuSO4 5 sodium laurate 40 dueylene triamine 20

Process parameters: time 3 minutes, temperature 2O ° C.

Then the casting was electroplated in a bath with the composition given in Example 1. Nickel plating process parameters: current voltage 4 V

A / dm ² min. 50 ° C

Adhesion of the nickel coating, the current density time temperature method tested

The thickness of the nickel coating was 25 µm. the temperature shock was very good.

Example XV. Cast aluminum from AK11 alloy was quoted in a solution with the following composition / content of components in g / l /:

NaOH 200

ZnO 55

CuSO4 10 sodium citrate 35 triethyl 45

Process parameters: time 4 min, temperature 15 ° C.

Then the casting was electroplated in a solution with the composition given in Example 1.

V

A / dm ^by 45 min.

60 ^o C.

Adhesion of the nickel coating, method tested

Process parameters: voltage current time temperature

The thickness of the nickel coating was 30 µm. incisions was very good.

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Claims (1)

Patent claim Keel for galvanizing aluminum and aluminum alloy surfaces, especially before applying electroplating metal coatings, containing zinc cations in the amount of 5 to 200 g / 1 and iron cations in the amount of 0 to 100 g / 1 or copper cations in the amount of 0 to 100 g / 1 or nickel cations in an amount from 0 to 100 g / 1 or cobalt cations in an amount from 0 to 100 g / 1 or a mixture of the above-mentioned cations and further containing sodium hydroxide in an amount from 50 to 800 g / 1 and sodium citrate in an amount from 0 to 100 g / 1 or 0 to 100 g / 1 sodium tartrate or 0 to 100 g / 1 sodium edetate or 0 to 100 g / 1 sodium gluconate or 0 to 100 g / 1 sodium laurate 100 g / 1 or sodium cyanide in an amount from 0 to 100 g / 1 or a mixture of the abovementioned compounds, characterized in that it contains an alkanol polyamine of the general formula Ν ^ -ΑΟΙ ^ -Ο ^ -ΝΗ - / ^ - 0 ^ - in which x is a natural number from 0 to 7, in an amount from 0.01 to 100 g / 1. Department of Publishing of the UP RP. Circulation 100 copies Price: PLN 3,000