WO2002022913A2

WO2002022913A2 - Ternary tin zinc alloy, electroplating solutions and galvanic method for producing ternary tin zinc alloy coatings

Info

Publication number: WO2002022913A2
Application number: PCT/EP2001/009452
Authority: WO
Inventors: Klaus Leyendecker; Günter Wirth; Klaus Reissmüller; Steffen Dumke
Original assignee: Degussa Galvanotechnik Gmbh
Priority date: 2000-09-16
Filing date: 2001-08-16
Publication date: 2002-03-21
Also published as: CN1239751C; JP4817352B2; US20040091385A1; JP2004509229A; DE10045991A1; WO2002022913A3; HK1054576A1; EP1319093A2; CN1468327A; DE50114623D1; EP1319093B1

Abstract

The invention relates to ternary tin zinc alloy coatings 30 - 65 wt. % tin, 30 - 65 wt. % zinc and 0.1 - 15 wt . % metal from the following group as a third alloy component; iron, cobalt, nickel. Correspondingly, alloy coatings can be produced by means of electrolytic deposition from aqueous galvanic electroplating solutions which contain the components of the alloy in a dissolved form. The alloy coatings are characterised in that they have a particularly high resistance to corrosion and are particularly suitable as anti-corrosion protective coatings on iron-based materials.

Description

Ternary tin-zinc alloys, electroplating baths and electroplating processes for the production of ternary tin-zinc alloy layers

Description:

The invention relates to new ternary tin-zinc alloys of a certain composition which contain a metal from the group iron, cobalt, nickel as the third alloy component. The invention further relates to galvanic electrolyte baths and a galvanic method for producing such ternary tin-zinc alloy layers and their use as corrosion protection layers or decorative layers.

It is known that ferrous materials are coated with zinc and then passivated, for example by chromating (based on Cr ⁶⁺ ) or chromiting (based on Cr ³⁺ ), which is recognizable by a yellow, blue, black or olive-green coloration of the surface , can be protected against corrosion. With these measures, protection times for salt spray testing (DIN 50021-SS) from 200 to 600 hours can be achieved until red rust occurs {corrosion protection through coatings and coatings, D. Grimme and J. Krüger, Weka specialist publisher for technical managers, Augsburg) ,

Higher requirements, such as resistance to salt spray testing up to the first appearance of red rust of up to 1000 hours, can be met by coating with zinc alloys that contain nickel, cobalt or iron as an alloy component and then chromating. The proportion of the alloying elements can range from less than 1% by weight, for example 0.4-0.6% by weight of Fe in the ZnFe system, to 15% by weight, for example 12-15% by weight of Ni in the ZnNi system {Zinc Alloy Process: Properties and Applications in Technology, Dr. A. Jimenez, B. Kerle and H. Schmidt, Galvanotechnik 89 (1998) 4). U)> fo Cπ o Cπ CD Cπ ω t- ¹ O Hl -3 er M Φ CL DJ o Φ Φ o H- H- H- CO H Φ H- 0 iQ ιQ r. Ω CQ Hi Φ Hi er H- Φ? s; C CO N

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% By weight of a metal from the group consisting of iron, cobalt and nickel as the third alloy component.

The ternary tin-zinc alloys according to the invention preferably contain cobalt as the third alloy component.

Tin-zinc-cobalt alloys according to the invention preferably consist of 40 to 55% by weight of tin, 45 to 55% by weight of zinc and 0.1 to 5% by weight of cobalt. Tin-zinc-nickel alloys according to the invention preferably consist of 35 to 50% by weight of tin, 50 to 65% by weight of zinc and 0.1 to 5% by weight of nickel. Tin-zinc-iron alloys according to the invention preferably consist of 40 to 55% by weight of tin, 40 to 60% by weight of zinc and 1 to 8% by weight of iron.

The ternary tin-zinc alloys according to the invention can be produced by melt or powder metallurgy from the individual components.

Preferred, in particular with regard to typical applications, is their production by electroplating, namely by electrolytic deposition from aqueous electrolytic electrolyte baths which contain the alloy components in dissolved form. The ternary tin-zinc alloys can be deposited on substrates from alkaline, neutral or weakly acidic galvanic electrolyte baths. An alkaline electrolyte is understood here to mean an electrolyte with a pH greater than 10. A neutral electrolyte is an electrolyte with a pH of 6-10. A weakly acidic electrolyte is an electrolyte with a pH of 3-6.

The alloy components are added to the aqueous electrolyte bath in the form of their ionogenic compounds which are soluble in the respective medium. Tin is preferably used as a sulfate,

Chloride, sulfonate, oxalate or in the form of sodium or potassium stannate. Zinc is preferably added as a sulfate, chloride, hydroxide, sulfonate ^'or oxide. The

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A temperature of approximately 20-70 ° C. and a current density of approximately 0.1-5 A / dm ² can be regarded as a framework for the deposition of the ternary tin-zinc alloys from the electrolytes according to the invention, with deposition speeds of approximately 0. 05 - 1 μm / minute.

An alkaline electrolyte according to the invention can have the following typical frame composition:

10 - 50 g / 1 tin as sulfate, chloride, sodium or potassium stannate

1 - 10 g / 1 zinc as sulfate, chloride, hydroxide or oxide

0.1 - 10 g / 1 cobalt, nickel or iron as sulfate,

1 - 20 g / 1 potassium or sodium hydroxide

10 - 200 g / 1 complexing agent

0.1 - 10 g / 1 wetting agent

0.1 - 5 g / 1 brightener

The alloy is electrodeposited at temperatures between 40 - 70 ° C at current densities of 1 - 5 A / dm ² with deposition speeds of 0.15 - 0.3 μm / minute. Graphite or platinum-plated titanium can be used as anodes.

Organic acids and their salts, phosphonic acids, phosphonates, gluconates, glucoheptonic acids, glucoheptonates and ethylenediaminetetraacetic acid can be used as complexing agents. Resistant surfactants, polyhydric alcohols and betaines can be used as wetting agents and brighteners in the corresponding media. The alloy composition of the layer can be varied by changing the ratio of the individual components in the bath. Thus an increase in the hydroxide content causes a reduction in the tin content and a corresponding increase in the other two metals in the layer. A

Increasing the amount of complexing agent causes a reduction in the zinc content and an increase in the proportion of tin in the layer. These changes have practically no effect on the third alloy metal.

A neutral electrolyte according to the invention can have the following typical frame composition:

10 - 40 g / 1 tin as sulfate, sodium or potassium stanate

0.5 - 10 g / 1 zinc as sulfate, chloride, hydroxide or oxide

0.1 - 10 g / 1 cobalt, nickel or iron as sulfate,

Chloride, hydroxide or oxide

50-200 g / 1 tetrasodium pyrophosphate

1 - 20 g / 1 potassium or sodium hydroxide

10 - 200 g / 1 complexing agent

0.1 - 10 g / 1 wetting agent

0.1 - 5 g / 1 brightener

The alloy is electroplated at temperatures between 40 - 70 ° C at current densities of 0.5 - 3 A / dm ² with deposition speeds of 0.05 - 0.3 μm / minute. Graphite or platinized titanium can be used as anodes. The use of soluble anodes is also possible. The ratio of the alloy composition can be varied by varying the coating parameters.

A weakly acidic electrolyte according to the invention can have the following typical frame composition:

1 - 10 g / 1 tin as sulfate or chloride

1 - 10 g / 1 zinc as sulfate, chloride, hydroxide or oxide

1 - 20 g / 1 cobalt, nickel or iron as sulfate, chloride, hydroxide or carbonate

5-200 g / 1 carboxylic acid salt

5 - 50 g / 1 buffer substance

1 - 30 g / 1 sodium chloride

1 - 20 g / 1 wetting agent

0.1 - 5 g / 1 brightener

The alloy is electroplated at temperatures between 20 - 70 ° C at current densities of 0.5 - 5 A / dm ² with deposition speeds of 0.1 - 1 μm / minute. Graphite or platinized titanium can be used as anodes. The use of soluble anodes is also possible. Boric acid, for example, can be used as the buffer substance.

The ratio of the alloy composition can be adjusted by changing the coating parameters (amount of components, working parameters). For example, an increase in the current density causes an increase in the proportion of alloys in zinc and nickel, cobalt or iron and a decrease in the proportion of tin. The variation of the temperature in the specified range only results in insignificant changes in the alloy composition of the layer. The ternary tin-zinc alloys according to the invention have very advantageous material properties, on the basis of which they can be used in different ways both as an independent material and in particular in the form of coatings on substrates.

In general, the ternary tin-zinc alloys have a particularly high level of corrosion resistance, which is most pronounced in the SnZnNi and SnZnCo systems. These alloys are therefore particularly suitable as corrosion protection layers on ferrous materials. The corresponding galvanic electrolytes can therefore preferably be used to produce corrosion protection layers on ferrous materials. In this way, coated iron sheets in combination with the usual passivation by chromating or chromitizing easily achieve a resistance to the appearance of red rust of over 3000 hours.

Further advantageous properties can be controlled by the choice of the respective third alloy element. The properties of the ternary tin-zinc alloy layers according to the invention can be optimized depending on the choice of the third alloy element. Table 1 provides an overview of the preferred third alloy element when either good corrosion resistance, hardness, abrasion or solderability are desired.

Table 1

Among the three alloy systems, the SnZnFe and SnZnCo alloy layers achieve the highest hardness values. The greatest abrasion resistance is shown by SnZnNi layers. Such alloy layers can therefore advantageously be used as wear protection layers in the event of mechanical stress. SnZnFe and SnZnCo layers can be soldered particularly well and are therefore particularly suitable in electronics as solderable layers and as contact surfaces. Table 2 shows the corresponding data for selected alloy systems.

Table 2

In addition to these functionally shaped areas of application, the ternary tin-zinc alloys according to the invention can also be used as decorative end layers. Depending on the choice of the third alloy element, the three alloy systems have interesting and appealing colors in the blue range. example 1

An alkaline electrolyte for the deposition of an alloy consisting of 45% by weight Sn, 52% by weight Zn and 3% by weight cobalt has the following composition:

30 g / 1 tin as sodium stannate

2.4 g / 1 zinc as zinc oxide

1 g / 1 cobalt as cobalt sulfate

8 g / 1 potassium hydroxide

50 g / 1 sodium citrate

100 ml / l sodium phosphonate

2.5 ml / 1 anionic surfactant

1 g / 1 butynediol

A pH of 11 is established. The above-mentioned layer composition can be achieved with this electrolyte at a temperature of 60 ° C. and current densities of 1-2 A / dm ² . In this case, about 0.2 μm alloy layer is built up per minute. The density of the alloy layer is 7.27 g / cm ³ .

A coating of iron sheets with this alloy in a thickness of 8 μm with chromating (based on Cr ⁶⁺ ) showed the following resistance in the salt spray test according to DIN 50021 ~ SS:

White rust first appears in the period 1800 - 3000 hours.

The test was terminated after 3000 hours since no red rust had occurred up to 3000 hours. Example 2

A neutral electrolyte for the deposition of an alloy consisting of 48% by weight Sn, 49% by weight Zn and 3% by weight cobalt has the following composition:

25 g / 1 tin as tin sulfate

2.4 g / 1 zinc as zinc oxide

1 g / 1 cobalt as cobalt sulfate

130 g / 1 tetrasodium pyrophosphate

2.5 ml / 1 anionic surfactant

1 g / 1 butynediol

A pH of 8.5 is established. The above-mentioned layer composition can be achieved with this electrolyte at a temperature of 60 ° C. and current densities of 0.5-1 A / dm ² . A 0.15 μm layer is built up per minute. The density of the alloy layer is 7.27 g / cm ³ .

Example 3

A weakly acidic electrolyte for the deposition of an alloy consisting of 49.2% by weight of Sn, 50.5% by weight of Zn and 0.3% by weight of nickel has the following composition:

5 g / 1 tin as tin sulfate

6.8 g / 1 zinc as zinc sulfate

12 g / 1 nickel as nickel sulfate

80 g / 1 sodium citrate

25 g / 1 boric acid 10 ml / 1 anionic surfactant

1 ml / 1 beta naphthol ethoxylate

A pH of 4.5 is established. The above-mentioned layer composition can be achieved with this electrolyte at a temperature of 40 ° C. and current densities of 1.5 A / dm ² . In this case, about 0.4 μm alloy layer is built up per minute. The density of the alloy layer is 7.2 g / cm ³ .

Example 4

A weakly acidic electrolyte for the deposition of an alloy consisting of 52% by weight of Sn, 44% by weight of Zn and 4% by weight of iron has the following composition:

5 g / 1 tin as tin sulfate

6.8 g / 1 zinc as zinc sulfate

10 g / 1 iron as iron sulfate

80 g / 1 sodium citrate

25 g / 1 boric acid

10 ml / 1 anionic surfactant

1 ml / 1 beta naphthol ethoxylate

A pH of 4.4 is established. The above-mentioned layer composition can be achieved with this electrolyte at a temperature of 40 ° C. and current densities of 1.5 A / dm ² . In this case, about 0.4 μm alloy layer is built up per minute. The density of the alloy layer is 7.25 g / cm ³ .

Claims

1. Ternary tin-zinc alloys, characterized in that they consist of 30 to 65 wt.% Tin, 30 to 65 wt.% Zinc and 0.1 to 15 wt.% Of a metal from the group iron, cobalt, nickel third alloy component exist.

2. Ternary tin-zinc alloys according to claim 1, characterized in that they consist of 40 to 55% by weight of tin, 45 to 55% by weight of zinc and 1 to 5% by weight of cobalt.

3. Ternary tin-zinc alloys according to claim 1, characterized in that they consist of 35 to 50% by weight of tin, 50 to 65% by weight of zinc and 0.1 to 5% by weight of nickel.

4. Ternary tin-zinc alloys according to claim 1, characterized in that they consist of 40 to 55% by weight of tin, 40 to 60% by weight of zinc and 1 to 8% by weight of iron.

5. Alkaline, neutral or weakly acidic electrolytic electrolytic baths, containing the alloy components in dissolved form and optionally other customary additives and auxiliaries, for the galvanic production of alloy layers from ternary tin-zinc alloys according to claims 1 to 4.

6. A method for producing alloy layers from ternary tin-zinc alloys according to claims 1 to 4, characterized in that they are made of an alkaline, neutral or. weakly acidic electrolytic electrolytic bath, containing the alloy components in dissolved form and, if appropriate, other customary additives and auxiliaries, electrolytically deposits.

7. Use of electroplated alloy layers made of ternary tin-zinc alloys according to claims 1 to 4 as corrosion protection layers.

8. Use of electroplated alloy layers made of ternary tin-zinc alloys according to claims 1 to 4 with a subsequent passivation as corrosion protection layers on ferrous materials.

9. Use of electroplated alloy layers made of ternary tin-zinc alloys according to claims 1 to 4 as solderable layers.

10. Use of electroplated alloy layers made of ternary tin-zinc alloys according to claims 1 to 4 as decorative end layers.