EP0244685B1 - Aqueous acid galvanic bath - Google Patents

Aqueous acid galvanic bath Download PDF

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Publication number
EP0244685B1
EP0244685B1 EP87105754A EP87105754A EP0244685B1 EP 0244685 B1 EP0244685 B1 EP 0244685B1 EP 87105754 A EP87105754 A EP 87105754A EP 87105754 A EP87105754 A EP 87105754A EP 0244685 B1 EP0244685 B1 EP 0244685B1
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Prior art keywords
zinc
formula
bath
baths
alkyl
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EP0244685A1 (en
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Norbert Dr. Greif
Chung-Ji Dr. Tschang
Klaus Glaser
Ekhard Dr. Winkler
Knut Dr. Oppenlaender
Christos Dr. Vamvakaris
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BASF SE
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BASF SE
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    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25DPROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00Electroplating: Baths therefor
    • C25D3/02Electroplating: Baths therefor from solutions
    • C25D3/22Electroplating: Baths therefor from solutions of zinc

Definitions

  • auxiliaries are, for example, conductive salts, which are used to improve the conductivity of the baths, and so-called brighteners, which give the zinc coatings on the metals an increased sheen.
  • the brighteners also make it possible to work at low current densities.
  • the brighteners which can be assigned to a wide variety of chemical substance classes, are often poorly or not at all soluble in water and especially in salt solutions, so that another group of auxiliaries, namely surfactants, is required to fine-tune the brighteners in the electroplating bath Bring distribution.
  • the surfactants act as emulsifiers for the brighteners and produce clear, transparent microemulsions from which a uniform deposition of the zinc on the substrates is made possible.
  • nonionic surfactants have hitherto been used as surfactants in galvanic zinc baths, cf. GB-PS 1 149 106. From US Pat. No. 3,787,296 it is also known to use sulfated alkylphenol alkoxylates as surfactants in galvanic zinc baths. The gloss and ductility of the deposited zinc layers are not always optimal when using these compounds.
  • EP-A-115 020 discloses the use of sulfated alkylphenol ethoxylates, the phenolic core of which still carries a sulfonic acid group, as a surfactant in aqueous acidic galvanic zinc baths. These surfactants are able to solubilize the other water-poorly soluble auxiliaries, such as brighteners, and produce high-gloss, uniform and ductile coatings. However, these surfactants are not optimally effective in ammonium salt-free baths, which are sought among other things for reasons of environmental compatibility.
  • the present invention is based on the object of providing surfactants for aqueous acidic galvanic baths for the electrolytic deposition of zinc, in particular ammonium salt-free zinc baths, from which zinc coatings with improved properties, in particular gloss and ductility, can be deposited on metals compared to the known acidic zinc baths .
  • the compounds of formula 1 are preferably used as a surfactant in aqueous, acidic, ammonium salt-free galvanic baths for the electrolytic deposition of zinc in the presence of brighteners.
  • the compounds of the formula I are known and differ from the surfactants which, according to EP-A-115 020, are used in aqueous acidic electroplating baths for the electrolytic deposition of zinc in the presence of brighteners by the partial or complete replacement of ethylene oxide units by propylene oxide and / or butylene oxide units. At least one ethylene oxide unit of the surfactants according to the EP regulation mentioned is replaced by a propylene oxide or butylene oxide unit.
  • the substituent R 1 is a C 4 - to C 2 o -alkyl group.
  • Suitable Me are hydrogen, alkali metal or equivalents of an alkaline earth metal or zinc atom, preferably sodium and potassium.
  • the substituent R in formula I preferably has the meaning CH 3 -.
  • the alkoxylation of the phenol derivatives can also be carried out using a mixed gas of ethylene oxide and propylene oxide and, if appropriate, butylene oxide.
  • the compounds of formula I are obtained from the alkoxylated phenol derivatives by esterifying the alkoxylated products with sulfuric acid and optionally neutralizing them.
  • the compounds of the formula I must be water-soluble.
  • the surfactants of the formula I to be used according to the invention are present in the baths in an amount of 1 to 30, preferably 2 to 15 g / l.
  • the compounds of the formula I can optionally be used in a mixture with known surfactants which are usually used in electroplating baths, for example compounds such as pC 4 H 9 to C 12 H 25 alkylphenol ethoxylates with 10 to 30 ethylene oxide units or ⁇ - naphthol ethoxylates with 5 to 20 ethylene oxide units.
  • the additional surfactants that are considered, if they are used, are used in an amount of 1 to 15 g / l of the bath.
  • the zinc baths usually contain brighteners.
  • the brighteners used can be divided into so-called basic brighteners and top brighteners.
  • Polyethyleneimines or their derivatives, for example, are expedient as basic gloss agents.
  • the top brighteners are usually poorly or not at all soluble in the aqueous zinc bath. These include representatives of the most diverse classes of substances, in particular certain aromatic or heteroaromatic ketones, as are described, for example, in GB-PS 1 149 106 or JP-OS 74 89 637.
  • R 3 is an aromatic or heteroaromatic radical, preferably an optionally alkyl, halogen or nitro substituted phenyl or thienyl radical and R 4 is C 1 - to Cs-alkyl, or crude products containing these compounds.
  • This class of compounds includes representatives such as:
  • benzal acetone is preferred.
  • o-chlorobenzaldehyde can be used as a brightener alone or as a mixture with a compound of the formula II.
  • the zinc baths advantageously contain brighteners in a total amount of 1 to 10 g / l and the top brighteners in an amount of 0.1 to 2.0 g / l, preferably 0.1 to 1 g / l.
  • the baths have the usual compositions. They contain, for example, 50 to 150 g / l zinc chloride or the equivalent amount of zinc sulfate, 100 to 250 g / l potassium chloride (conductive salt), 15 to 25 g / l boric acid, 1 to 8 g / l sodium benzoate and optionally 1 to 4 g / l an agent to increase scatter, e.g. Naphthalenesulfonic acid-formaldehyde condensation products. 10 to 150 g / l ammonium chloride or sodium chloride can also be used as conductive salts.
  • the pH of the baths is usually 3 to 6. The pH is adjusted by adding acids to the bath, e.g. Sulfuric acid or hydrochloric acid.
  • metals mainly iron and steel, are galvanized in order to protect them against corrosion and at the same time to give them a high gloss.
  • Bath 1 is an ammonium salt-free bath according to the preferred embodiment of the invention, while bath 2 is an ammonium salt-containing bath.
  • bath 1 The pH of bath 1 is 4.8, bath 2 has a pH of 4.5.
  • the pH is adjusted with dilute hydrochloric acid.
  • the galvanizing of steel sheets for testing purposes takes place over 10 minutes by galvanizing in a Hull cell with 1 ampere at approx. 23 ° C.
  • the quality of the zinc coatings obtained and the composition of the surfactants contained in the baths are given in the following table.

Description

Bei der elektrolytischen Abscheidung von Zink auf metallische Substrate aus wäßriger saurer Lösung benötigt man verschiedene Hilfsmittel, weil andernfalls die aus saurer Lösung entstehenden Zinküberzüge meistens matt und häufig auch unregelmäßig anfallen. Eine Gruppe solcher Hilfsmittel sind beispielsweise Leitsalze, die zur Verbesserung der Leitfähigkeit der Bäder eingesetzt werden sowie sogenannte Glanzbildner, die den Zinküberzügen auf den Metallen einen erhöhten Glanz verleihen. Die Glanzbildner erlauben es auch, bei geringen Stromdichten zu arbeiten. Die Glanzbildner, die den verschiedensten chemischen Stoffklassen zugeordnet werden können, sind häufig in Wasser und vor allem in Salzlösungen schwer oder überhaupt nicht löslich, so daß man eine weitere Gruppe von Hilfsmitteln, nämlich Tenside, benötigt, um die Glanzbildner im galvanischen Bad in eine feine Verteilung zu bringen. Die Tenside wirken als Emulgatoren für die Glanzbildner und ergeben klare, durchsichtige Mikroemulsionen, aus denen eine gleichmäßige Abscheidung des Zinks auf den Substraten ermöglicht wird.Various means are required for the electrolytic deposition of zinc on metallic substrates from aqueous acidic solution, because otherwise the zinc coatings resulting from acidic solution are usually matt and often also irregular. A group of such auxiliaries are, for example, conductive salts, which are used to improve the conductivity of the baths, and so-called brighteners, which give the zinc coatings on the metals an increased sheen. The brighteners also make it possible to work at low current densities. The brighteners, which can be assigned to a wide variety of chemical substance classes, are often poorly or not at all soluble in water and especially in salt solutions, so that another group of auxiliaries, namely surfactants, is required to fine-tune the brighteners in the electroplating bath Bring distribution. The surfactants act as emulsifiers for the brighteners and produce clear, transparent microemulsions from which a uniform deposition of the zinc on the substrates is made possible.

Als Tenside in galvanischen Zinkbädem sind bisher eine Reihe von nichtionischen Tensiden eingesetzt worden, vgl. GB-PS 1 149 106. Aus der US-PS 3 787 296 ist außerdem bekannt, sulfatierte Alkylphenolalkoxylate als Tenside in galvanischen Zinkbädem zu verwenden. Glanz und Duktilität der abgeschiedenen Zinkschichten sind bei Einsatz dieser Verbindungen nicht immer optimal.A number of nonionic surfactants have hitherto been used as surfactants in galvanic zinc baths, cf. GB-PS 1 149 106. From US Pat. No. 3,787,296 it is also known to use sulfated alkylphenol alkoxylates as surfactants in galvanic zinc baths. The gloss and ductility of the deposited zinc layers are not always optimal when using these compounds.

Aus der EP-A-115 020 ist die Verwendung von sulfatierten Alkylphenolethoxylaten, deren Phenolkem noch eine Sulfonsäuregruppe trägt, als Tensid in wäßrigen sauren galvanischen Zinkbädem bekannt. Diese Tenside vermögen die in Wasser schwer löslichen übrigen Hilfsmittel, wie Glanzbildner, gut zu solubilisieren und ergeben hochglänzende, gleichmäßige und duktile Überzüge. Diese Tenside sind jedoch in Ammoniumsalz-freien Bädern, die unter anderem aus Gründen der Umweltverträglichkeit angestrebt werden, nicht optimal wirksam.EP-A-115 020 discloses the use of sulfated alkylphenol ethoxylates, the phenolic core of which still carries a sulfonic acid group, as a surfactant in aqueous acidic galvanic zinc baths. These surfactants are able to solubilize the other water-poorly soluble auxiliaries, such as brighteners, and produce high-gloss, uniform and ductile coatings. However, these surfactants are not optimally effective in ammonium salt-free baths, which are sought among other things for reasons of environmental compatibility.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, Tenside für wäßrige saure galvanische Bäder zur elektrolytischen Abscheidung von Zink zur Verfügung zu stellen, insbesondere Ammoniumsalzfreie Zinkbäder, aus denen gegenüber den bekannten sauren Zinkbädem Zinküberzüge mit verbesserten Eigenschaften, insbesondere Glanz und Duktilität, auf Metallen abgeschieden werden können.The present invention is based on the object of providing surfactants for aqueous acidic galvanic baths for the electrolytic deposition of zinc, in particular ammonium salt-free zinc baths, from which zinc coatings with improved properties, in particular gloss and ductility, can be deposited on metals compared to the known acidic zinc baths .

Die Aufgabe wird erfindungsgemäß gelöst durch ein wäßriges saures galvanisches Bad zur elektrolytischen Abscheidung von Zink, wobei das Bad als wesentliche Hilfsmittel Leitsalze, Glanzbildner und Tenside enthält, wenn das Bad Tenside einer Verbindung der Formel

Figure imgb0001

  • enthält, in der
  • R - CH3-, CH3-CH2-
  • x,z = 0 bis 49,
  • y =1 bis 25,
  • x+y+z = 3 bis 50,
  • R1 = C4- bis C20-Alkyl,
  • R2 = H, C4- bis C20-Alkyl und
  • Me = H, Alkalimetallatom oder ein Äquivalent eines Erdalkalimetall- oder Zinkatoms
  • bedeuten. Vorzugsweise steht der Substituent R2 in Formel für Wasserstoff.
The object is achieved according to the invention by an aqueous acidic galvanic bath for the electrolytic deposition of zinc, the bath containing conductive salts, brightening agents and surfactants as essential auxiliaries if the bath contains surfactants of a compound of the formula
Figure imgb0001
  • contains in the
  • R - CH 3 -, CH 3 -CH 2 -
  • x, z = 0 to 49,
  • y = 1 to 25,
  • x + y + z = 3 to 50,
  • R 1 = C 4 to C 20 alkyl,
  • R 2 = H, C 4 - to C 20 alkyl and
  • Me = H, alkali metal atom or an equivalent of an alkaline earth metal or zinc atom
  • mean. The substituent R2 in the formula is preferably hydrogen.

Die Verbindungen der Formel 1 werden vorzugsweise als Tensid in wäßrigen, sauren, Ammoniumsalz- freien galvanischen Bädern zur elektrolytischen Abscheidung von Zink in Gegenwart von Glanzbildnem verwendet. Die Verbindungen der Formel I sind bekannt und unterscheiden sich von den Tensiden, die gemäß der EP-A-115 020 in wäßrigen sauren galvanischen Bädern zur elektrolytischen Abscheidung von Zink in Gegenwart von Glanzbildnem eingesetzt werden, durch den partiellen oder vollständigen Ersatz von Ethylenoxid-Einheiten durch Propylenoxid- und/oder Butylenoxid-Einheiten. Mindestens eine Ethylenoxid-Einheit der Tenside gemäß der genannten EP-Anmeidung ist durch eine Propylenoxid- oder Butylenoxid-Einheit ersetzt. In den Verbindungen der oben angegebenen Formel I bedeutet der Substituent R2 vorzugsweise Wasserstoff, die Zahl der gesamten Alkylenoxid-Einheiten, d.h. die Summe aus x+y+z = 3 bis 50, vorzugsweise 6 bis 25, y steht für Zahlen von 1 bis 25, vorzugsweise 3 bis 15, x und z können Werte von 0 bis 49 annehmen. Der Substituent R1 ist eine C4- bis C2o- Alkylgruppe. Als Me kommen Wasserstoff, Alkalimetall oder Äquivalente eines Erdalkalimetalls oder Zinkatoms in Betracht, vorzugsweise Natrium und Kalium. Der Substituent R in Formel I hat vorzugsweise die Bedeutung CH3-.The compounds of formula 1 are preferably used as a surfactant in aqueous, acidic, ammonium salt-free galvanic baths for the electrolytic deposition of zinc in the presence of brighteners. The compounds of the formula I are known and differ from the surfactants which, according to EP-A-115 020, are used in aqueous acidic electroplating baths for the electrolytic deposition of zinc in the presence of brighteners by the partial or complete replacement of ethylene oxide units by propylene oxide and / or butylene oxide units. At least one ethylene oxide unit of the surfactants according to the EP regulation mentioned is replaced by a propylene oxide or butylene oxide unit. In the compounds of the formula I given above, the substituent R 2 preferably denotes hydrogen, the number of the total alkylene oxide units, ie the sum of x + y + z = 3 to 50, preferably 6 to 25, y represents numbers from 1 to 25, preferably 3 to 15, x and z can assume values from 0 to 49. The substituent R 1 is a C 4 - to C 2 o -alkyl group. Suitable Me are hydrogen, alkali metal or equivalents of an alkaline earth metal or zinc atom, preferably sodium and potassium. The substituent R in formula I preferably has the meaning CH 3 -.

Verbindungen der Formel I werden beispielsweise dadurch erhalten, daß man das zugrundeliegende Phenol mit Ethylenoxid zur Reaktion bringt, wobei an 1 Mol Phenol x Mol Ethylenoxid angelagert werden. Dieses Reaktionsprodukt wird danach mit Propylenoxid und/oder Butylenoxid umgesetzt Pro Mol Phenol lagert man y Mol Propylenoxid oder Butylenoxid oder eine Mischung aus Propylenoxid und Butylenoxid an das Additionsprodukt an. An dieses Additionsprodukt kann noch weiteres Ethylenoxid angelagert werden. Bezogen auf 1 Mol des eingesetzten Phenols kommen in diesem Fall z Mol Ethylenoxid. Die Bedeutung von x, y und z ist oben angegeben. Für den Fall, daß z gleich 0 bedeutet, liegen alkoxylierte Phenolderivate vor, bei denen die Alkoxylierung zunächst mit Ethylenoxid und anschließend mit Propylenoxid vorgenommen wurde. Für den Fall, daß x gleich 0 bedeutet, wurde die Alkoxylierung der den Verbindungen der Formel I zugrundeliegenden Phenole zunächst mit Propylenoxid und/oder Butylenoxid und anschließend mit Ethylenoxid vorgenommen, wobei in diesem Fall z mindestens 1 ist. Besonders wirksame Tenside für den Einsatz in wäßrigen sauren galvanischen Bädern zur elektrolytischen Abscheidung von Zink erhält man, wenn man die den Verbindungen der Formel 1 zugrundeliegenden Phenolderivate 3 bis 15 Mol Propylenoxid und 3 bis 15 Mol Ethylenoxid pro Mol Phenol umsetzt. Das Phenolderivat kann dabei entweder zuerst mit Ethylenoxid und anschließend mit Propylenoxid zur Reaktion gebracht werden. In diesem Fall ist in Formel I x = 3 bis 15 und y = 3 bis 15. Das Phenolderivat kann aber auch zunächst mit Propylenoxid und danach mit Ethylenoxid in den vorstehend angegebenen bevorzugten Molverhältnissen umgesetzt werden. Dann bedeuten in Formel y und z = 3 bis 15 und x = 0. Die Alkoxylierung der Phenolderivate kann auch mit einem Mischgas aus Ethylenoxid und Propylenoxid sowie gegebenenfalls Butylenoxid vorgenommen werden. Die Verbindungen der Formel I werden aus den alkoxylierten Phenolderivaten erhalten, indem man die alkoxylierten Produkte mit Schwefelsäure verestert und gegebenenfalls neutralisiert. Die Verbindungen der Formel I müssen wasserlöslich sein. Sie können allein oder in Mischung verwendet werden. Die erfindungsgemäß zu verwendenden Tenside der Formel I sind in den Bädern in einer Menge von 1 bis 30, vorzugsweise 2 bis 15 g/l enthalten. Die Verbindungen der Formel I können gegebenenfalls in Mischung mit bekannten, üblicherweise in galvanischen Bädern verwendeten Tensiden eingesetzt werden, z.B. Verbindungen wie p-C4H9- bis C12H25- Alkylphenolethoxylaten mit 10 bis 30 Ethylenoxid-Einheiten oder ß-Naphtholethoxylaten mit 5 bis 20 Ethylenoxid-Einheiten. Die zusätzlich in Betracht kommenden Tenside werden, sofern sie mitverwendet werden, in einer Menge von 1 bis 15 g/l des Bades eingesetzt.Compounds of the formula I are obtained, for example, by reacting the underlying phenol with ethylene oxide, with 1 mol of phenol x mol of ethylene oxide being added. This reaction product is then reacted with propylene oxide and / or butylene oxide. Per mole of phenol, y moles of propylene oxide or butylene oxide or a mixture of propylene oxide and butylene oxide are added to the addition product. Further ethylene oxide can also be added to this addition product. In this case, based on 1 mole of the phenol used, there are z moles of ethylene oxide. The meaning of x, y and z is given above. In the event that z is 0, there are alkoxylated phenol derivatives in which the alkoxylation was carried out first with ethylene oxide and then with propylene oxide. In the event that x is 0, the alkoxylation of the phenols on which the compounds of the formula I are based was first carried out with propylene oxide and / or butylene oxide and then with ethylene oxide, in which case z is at least 1. Particularly effective surfactants for use in aqueous acidic galvanic baths for the electrolytic deposition of zinc are obtained if the phenol derivatives on which the compounds of formula 1 are based are reacted with 3 to 15 moles of propylene oxide and 3 to 15 moles of ethylene oxide per mole of phenol. The phenol derivative can either be reacted first with ethylene oxide and then with propylene oxide. In this case, in formula I x = 3 to 15 and y = 3 to 15. However, the phenol derivative can also be reacted first with propylene oxide and then with ethylene oxide in the preferred molar ratios given above. Then in formula y and z = 3 to 15 and x = 0. The alkoxylation of the phenol derivatives can also be carried out using a mixed gas of ethylene oxide and propylene oxide and, if appropriate, butylene oxide. The compounds of formula I are obtained from the alkoxylated phenol derivatives by esterifying the alkoxylated products with sulfuric acid and optionally neutralizing them. The compounds of the formula I must be water-soluble. They can be used alone or in a mixture. The surfactants of the formula I to be used according to the invention are present in the baths in an amount of 1 to 30, preferably 2 to 15 g / l. The compounds of the formula I can optionally be used in a mixture with known surfactants which are usually used in electroplating baths, for example compounds such as pC 4 H 9 to C 12 H 25 alkylphenol ethoxylates with 10 to 30 ethylene oxide units or β- naphthol ethoxylates with 5 to 20 ethylene oxide units. The additional surfactants that are considered, if they are used, are used in an amount of 1 to 15 g / l of the bath.

Die Zinkbäder enthalten üblicherweise Glanzbildner. Die verwendeten Glanzbildner können eingeteilt werden in sog. Grundglanzbildner und Spitzenglanzbildner. Als Grundglanzbildner sind zweckmäßig beispielsweise Polyethylenimine oder deren Derivate. Die Spitzenglanzbildner sind in der Regel im wäßrigen Zinkbad schlecht oder überhaupt nicht löslich. Hierzu gehören Vertreter der verschiedensten Stoffklassen, insbesondere bestimmte aromatische oder heteroaromatische Ketone, wie sie beispielsweise in der GB-PS 1 149 106 oder der JP-OS 74 89 637 beschrieben sind.The zinc baths usually contain brighteners. The brighteners used can be divided into so-called basic brighteners and top brighteners. Polyethyleneimines or their derivatives, for example, are expedient as basic gloss agents. The top brighteners are usually poorly or not at all soluble in the aqueous zinc bath. These include representatives of the most diverse classes of substances, in particular certain aromatic or heteroaromatic ketones, as are described, for example, in GB-PS 1 149 106 or JP-OS 74 89 637.

Es sind dies zum Beispiel die Verbindungen der Formel II

Figure imgb0002
in der R3 einen aromatischen oder heteroaromatischen Rest, vorzugsweise einen gegebenenfalls alkyl-, halogen- oder nitrosubstituierten Phenyl- oder Thienylrest bedeutet und R4 für C1- bis Cs-Alkyl stehen, oder diese Verbindungen enthaltende Rohprodukte.These are, for example, the compounds of the formula II
Figure imgb0002
in which R 3 is an aromatic or heteroaromatic radical, preferably an optionally alkyl, halogen or nitro substituted phenyl or thienyl radical and R 4 is C 1 - to Cs-alkyl, or crude products containing these compounds.

Diese Verbindungsklasse umfaßt Vertreter wie:

Figure imgb0003
Figure imgb0004
This class of compounds includes representatives such as:
Figure imgb0003
Figure imgb0004

Davon ist das Benzalaceton bevorzugt. Darüber hinaus kann als Glanzbildner o-Chlorbenzaldehyd allein oder in Mischung mit einer Verbindung der Formel II verwendet werden.Of these, benzal acetone is preferred. In addition, o-chlorobenzaldehyde can be used as a brightener alone or as a mixture with a compound of the formula II.

Die Zinkbäder enthalten Glanzbildner zweckmäßig in einer Gesamtmenge von 1 bis 10 g/l und die Spitzenglanzbildner in einer Menge von 0,1 bis 2,0 g/l, vorzugsweise 0,1 bis 1 g/l.The zinc baths advantageously contain brighteners in a total amount of 1 to 10 g / l and the top brighteners in an amount of 0.1 to 2.0 g / l, preferably 0.1 to 1 g / l.

Im übrigen weisen die Bäder die üblichen Zusammensetzungen auf. Sie enthalten beispielsweise 50 bis 150 g/l Zinkchlorid oder die äquivalente Menge Zinksulfat, 100 bis 250 g/l Kaliumchlorid (Leitsalz), 15 bis 25 g/l Borsäure, 1 bis 8 g/l Natriumbenzoat und gegebenenfalls 1 bis 4 g/l eines Agens zur Erhöhung der Streuung, z.B. Naphthalinsulfonsäure-Formaldehyd-Kondensationsprodukte. Als Leitsalze können auch 10 bis 150 g/l Ammoniumchlorid oder Natriumchlorid verwendet werden. Der pH-Wert der Bäder liegt in der Regel bei 3 bis 6. Die Einstellung des pH-Wertes erfolgt durch Zugabe von Säuren zum Bad, z.B. Schwefelsäure oder Salzsäure.Otherwise, the baths have the usual compositions. They contain, for example, 50 to 150 g / l zinc chloride or the equivalent amount of zinc sulfate, 100 to 250 g / l potassium chloride (conductive salt), 15 to 25 g / l boric acid, 1 to 8 g / l sodium benzoate and optionally 1 to 4 g / l an agent to increase scatter, e.g. Naphthalenesulfonic acid-formaldehyde condensation products. 10 to 150 g / l ammonium chloride or sodium chloride can also be used as conductive salts. The pH of the baths is usually 3 to 6. The pH is adjusted by adding acids to the bath, e.g. Sulfuric acid or hydrochloric acid.

In den beschriebenen Bädern werden Metalle, hauptsächlich Eisen und Stahl galvanisiert, um sie gegen Korrosion zu schützen und ihnen gleichzeitig einen hohen Glanz zu verleihen.In the baths described, metals, mainly iron and steel, are galvanized in order to protect them against corrosion and at the same time to give them a high gloss.

Besonders vorteilhafte Ergebnisse werden erhalten, wenn man die Verbindungen der Formel I als Tensid in wäßrigen, sauren, Ammoniumsalz-freien galvanischen Bädern zur elektrolytischen Abscheidung von Zink verwendet. Die erfindungsgemäßen Bäder liefem über den gesamten technisch in Betracht kommenden Stromdichtenbereich hochglänzende und duktile Zinküberzüge mit einer gegenüber dem Stand der Technik verbesserten Qualität.Particularly advantageous results are obtained if the compounds of the formula I are used as surfactants in aqueous, acidic, ammonium salt-free galvanic baths for the electrodeposition of zinc. The baths according to the invention ran high-gloss and ductile zinc coatings with an improved quality compared to the prior art over the entire current density range that is considered technically.

BeispieleExamples

Die Wirksamkeit von Tensiden der Formel in galvanischen Bädern zur elektrolytischen Abscheidung von Zink in Gegenwart von Glanzbildnem wird anhand von zwei verschiedenen Bädern demonstriert. Bad 1 ist ein Ammoniumsalz-freies Bad gemäß der bevorzugten Ausführungsform der Erfindung während das Bad 2 ein Ammoniumsalz-haltiges Bad ist.

Figure imgb0005
The effectiveness of surfactants of the formula in galvanic baths for the electrolytic deposition of zinc in the presence of gloss agents is demonstrated using two different baths. Bath 1 is an ammonium salt-free bath according to the preferred embodiment of the invention, while bath 2 is an ammonium salt-containing bath.
Figure imgb0005

Der pH-Wert des Bads 1 beträgt 4,8, das Bad 2 hat einen pH-Wert von 4,5. Die Einstellung des pH-Wertes erfolgt jeweils mit verdünnter Salzsäure. Die Verzinkung von Stahlblechen zu Prüfzwecken erfolgt während 10 Minuten, indem man in einer Hull-Zelle mit 1 Ampere bei ca. 23°C galvanisiert. Die Qualität der dabei erhaltenen Zinküberzüge sowie die Zusammensetzung der jeweils in den Bädern enthaltenen Tenside ist in der folgenden Tabelle angegeben.

Figure imgb0006
The pH of bath 1 is 4.8, bath 2 has a pH of 4.5. The pH is adjusted with dilute hydrochloric acid. The galvanizing of steel sheets for testing purposes takes place over 10 minutes by galvanizing in a Hull cell with 1 ampere at approx. 23 ° C. The quality of the zinc coatings obtained and the composition of the surfactants contained in the baths are given in the following table.
Figure imgb0006

Claims (5)

1. An aqueous acid electroplating bath for the electrolytic deposition of zinc containing as essential assistants a conducting salt, a brightener and a surfactant, wherein the surfactant is a compound of the formula
Figure imgb0010
where
R is CHa- or CH3―CH2―,
x and z are each from 0 to 49,
y is from 1 to 25,
x+y+zis from 3 to 50,
R1 is C4- to C2o-alkyl,
R2 is H or C4-to C2o-alkyl and
Me is H, an alkali metal atom or one equivalent of an alkaline earth metal or zinc atom.
2. A bath as claimed in claim 1, wherein the surfactant used has the formula I where R2 is H.
3. A bath as claimed in claims 1 and 2, wherein the surfactant used has the formula I where R is CH3 and x,y and z = from 3 to 15 with either x or z being 0.
4. A bath as claimed in claims 1 to 3, wherein the brightener used is a compound of the formula
Figure imgb0011
where R3 is aryl or hetaryl and R4 is C1- to Ce-alkyl, or o-chlorobenzaldehyde.
5. The use of a compound of the formula
Figure imgb0012
where
R is CHa-or CH3―CH2-,
x and z are each from 0 to 49,
y is from 1 to 25,
x+y+z is from 3 to 50,
R1 is C4- to C20-alkyl,
R2 is H or C4- to C20-alkyl and
Me is H, an alkali metal atom or one equivalent of an alkaline earth metal or zinc atom, as a surfactant in an aqueous acid electroplating bath for the electrolytic deposition of zinc in the presence of a brightener and in the absence of any ammonium salt.
EP87105754A 1986-04-24 1987-04-18 Aqueous acid galvanic bath Expired EP0244685B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19863613874 DE3613874A1 (en) 1986-04-24 1986-04-24 AQUEOUS ACID GALVANIC BATH
DE3613874 1986-04-24

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EP0244685A1 EP0244685A1 (en) 1987-11-11
EP0244685B1 true EP0244685B1 (en) 1989-07-26

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EP (1) EP0244685B1 (en)
DE (2) DE3613874A1 (en)

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4270990A (en) * 1979-06-07 1981-06-02 Minnesota Mining And Manufacturing Company Acidic electroplating baths with novel surfactants
DE3248503A1 (en) * 1982-12-29 1984-07-05 Basf Ag, 6700 Ludwigshafen ACID GALVANIC ZINC BATH

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EP0244685A1 (en) 1987-11-11
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