EP0492487B1 - Means of temporary protection of bare silver and copper surfaces against tarnishing and method of using it - Google Patents
Means of temporary protection of bare silver and copper surfaces against tarnishing and method of using it Download PDFInfo
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- EP0492487B1 EP0492487B1 EP91121903A EP91121903A EP0492487B1 EP 0492487 B1 EP0492487 B1 EP 0492487B1 EP 91121903 A EP91121903 A EP 91121903A EP 91121903 A EP91121903 A EP 91121903A EP 0492487 B1 EP0492487 B1 EP 0492487B1
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- Prior art keywords
- inhibitor
- silver
- water
- emulsion
- copper
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
- C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
- C23F11/10—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using organic inhibitors
- C23F11/16—Sulfur-containing compounds
- C23F11/161—Mercaptans
Definitions
- the invention is based on an agent for protecting bare silver surfaces against tarnishing, which contains, as a hydrophobic inhibitor, a long-chain aliphatic mercapto compound with at least 12 carbon atoms in the chain and water.
- Silverware and silver-plated parts tarnish in an atmosphere containing hydrogen sulfide and turn brown to black due to the formation of silver sulfide.
- an inorganic cover layer for example with rhodium or with silver chromate, which are applied by electrolytic processes.
- silver surfaces by means of transparent lacquers or waxes, which are applied by dipping, spraying or vapor deposition.
- a major disadvantage of these coatings is that they do change the external appearance of the silver, which is particularly disadvantageous for decorative objects. In applications in electrical engineering, especially in electrical contacts, such passivating coatings are not desirable because they greatly increase the electrical contact resistance.
- a transparent, colorless, ideally monomolecular protective layer remains on the silver surface, which at least adheres to the goods until they are processed further or reach the consumer.
- the disadvantage here is that the inhibitors are dissolved in halogenated hydrocarbons which are harmful to the environment.
- the inhibitors which in turn are long-chain aliphatic compounds with SH group, namely mercapto compounds with 12 to 25 carbon atoms, in organic solvents such as glycols and / or Solve glycol ethers with a total of 4 or 5 carbon atoms and treat the silver surfaces to be protected with this solution.
- organic solvents such as glycols and / or Solve glycol ethers with a total of 4 or 5 carbon atoms and treat the silver surfaces to be protected with this solution.
- Glycols and glycol ethers have the advantage of being less harmful to the environment than halogenated hydrocarbons.
- they have the disadvantage that they are flammable and that the vapors escaping from the treatment solution can form an explosive mixture, so that special precautions must be taken when working with such solutions.
- DE-OS 39 05 850 In order to counteract the development of flammable or explosive gas mixtures, it is already known from DE-OS 39 05 850 not to dry the treated surfaces by letting the solvent evaporate. Rather, the solvent is removed from the treated surfaces by rinsing with aqueous solvents or with warm water with detergents. In order to reduce the evaporation rates, it is also known from DE-OS 39 05 850 to add water to the solution of the inhibitor in glycol or glycol ether. The glycol and the glycol ether dissolve in the water and are thereby diluted. However, care is taken to ensure that with this dilution the solubility limit of the inhibitor in the glycol or glycol ether is not exceeded so that there is no clouding or precipitation. The addition of water reduces the dangerousness of the glycol or the glycol ether, but does not eliminate it.
- thiocarboxylic acids have been used as an additive to polishing pastes (DE-AS 1 279 428, claim 5).
- Another, particularly significant disadvantage of thiocarboxylic acids is that water can attach to their hydrophilic carboxyl group, which ultimately enables the hydrogen sulfide from which the silver surface is to be protected to attack the silver surface, so that there is no protective layer which is impermeable to hydrogen sulfide receives.
- the agent which is supposed to protect against tarnishing of the surface, should be applied as a film so uniform that the gloss of the surface is retained.
- a precious metal cleaning and polishing bath is known from CH-A-478 925, which contains long-chain thiols as tarnishing protection, which are brought into solution by a primary alcohol as solubilizer.
- a primary alcohol as solubilizer.
- an alkylaryl polyglycol ether can also be present as an emulsifier.
- a paste for cleaning and polishing tarnished silver is known, which among other things. contains a thiol and a non-ionic surfactant.
- the present invention has for its object to provide a means for the temporary protection of bare silver surfaces, also in the field of electrical engineering, in particular in the case of electrical contacts, which can be handled easily and safely, even in immersion baths, and is environmentally compatible.
- This object is achieved by an agent with the composition specified in claim 1.
- a particularly suitable method for using this agent is the subject of claim 5.
- Advantageous developments of the invention are the subject of the subclaims.
- the agent according to the invention contains, as organic inhibitor substance, a hydrophobic aliphatic thio compound with at least 12 carbon atoms in the chain from the group of thio alcohols and their esterification products without hydrophilic carboxyl groups, the thio alcohols being particularly preferred. However, they are not dissolved in an organic solvent, but used in the form of an aqueous emulsion.
- the emulsifier which is inevitably required to bring the selected inhibitors into an emulsion, is only incorporated in a negligible amount in the inhibitor film which forms on the silver surface which has been treated with the emulsion.
- the emulsifier can be easily washed off by rinsing with water, while the passivating film of the inhibitor substance remains on the treated silver surface.
- the silver surface is treated in the emulsion at a temperature which is above the melting point of the inhibitor substance.
- the inhibitor substance is particularly readily distributed evenly thin on the surface to be passivated.
- the subsequent rinsing of the surface is then carried out at a temperature below the melting point of the inhibitor substance, which has the advantage that it then adheres particularly firmly to the passivated surface.
- the agent according to the invention is easy to handle. It contains neither an environmentally hazardous nor a flammable solvent, but only water as the carrier substance of the emulsion.
- the sub-substances contained in the water, the inhibitor and the emulsifier, are biodegradable.
- the agent according to the invention is easy to use. It can be marketed as a concentrate of the inhibitor and the emulsifier and can be made ready for use by the user by stirring it into water. It can be applied by dipping or spraying.
- the goods to be treated are preferably immersed in the emulsion because the treatment times are then the shortest.
- conventional devices such as in electroplating technology can be used, with the difference that there is no need for electrodes and that there are no problems with the disposal of the baths and rinsing water.
- the agent according to the invention contains 2 to 20 g / l of the inhibitor.
- the emulsifier is contained in the agent in an amount of 2 to 20 g / l.
- an anionic or nonionic surfactant can be added to the agent.
- Cationic surfactants are unsuitable.
- inhibitors are selected which have at least 12 and preferably not more than 20 C atoms in the chain. With less than 12 carbon atoms, it is sometimes not possible to achieve a well-adhering protective coating, and in part there are strong odor nuisances. With more than 20 carbon atoms, the inhibitors become too solid in consistency and it becomes more difficult to produce a satisfactory emulsion.
- the inhibitors can be emulsified very finely and with long-term stability and can be applied to the surfaces to be protected in a thin but dense layer.
- Particularly suitable emulsifiers for this purpose are branched fatty alcohols having 9 to 20 carbon atoms, in particular having 10 to 15 carbon atoms, the branched fatty alcohols preferably being alkoxylated, in particular ethoxylated, with a degree of alkoxylation of 2 to 10.
- the passivating agent when adjusted to a pH of 1-10, better 1-8, preferably 2-4, the emulsifier can be washed out of the deposited inhibitor layer practically completely with water, which is important for reliable surface protection is.
- the emulsifier can be washed out of the deposited inhibitor layer practically completely with water, which is important for reliable surface protection is.
- less inhibitor is washed out, which increases the protective effect and the lubricating effect; however, stains can appear on the surface, which can disturb the appearance of decorative surfaces.
- Decorative surfaces are therefore preferably passivated with an agent whose pH is lower, preferably between 2 and 4, with sufficient inhibitor substance remaining even after washing out to form a tight protective layer. If the pH is above 10 there is a risk of the emulsion splitting.
- the agent according to the invention is also suitable for passivating surfaces made of copper and copper alloys.
- the water-emulsified inhibitor also absorbs very well on copper and copper-containing materials and protects the surface against the attack of sulfur compounds and against oxidation. The good solderability and the electrical properties are not impaired.
- Examples of baths with which opaque and well-adhering coatings can be achieved on surfaces of silver and copper materials 1. Dissolved in one liter of deionized water: 2 - 20 g Inhibitor: Octadecanethiol 2 - 20 g Emulsifier: Branched fatty alcohol ethoxide with 8 to 16 carbon atoms (C8 - C16) and a degree of ethoxylation of 2 to 10 0.00 - 1 g
- Surfactant Sodium lauryl ether phosphate pH 2 adjusted with a mineral acid Particularly suitable for silver and silver alloys. 2.
- These baths are preferably used in such a way that the parts to be passivated are immersed in the approx. 40 ° C to 50 ° C warm baths. After 2 to 3 minutes, the surface of the parts is even and dense with the inhibitor wetted. The parts are then rinsed with cold water and then dried, preferably with hot air.
- the effect of the tarnish protection layer on silver can be easily demonstrated with the help of a two percent sodium sulfide solution. Untreated silver parts tarnish immediately, treated parts remain bare over a longer period. The effect of the protective layer on copper was checked by passivating copper parts for several hours in a hydrogen sulfide atmosphere with 1 ppm H2S; the copper parts did not change color.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Preventing Corrosion Or Incrustation Of Metals (AREA)
Description
Die Erfindung geht aus von einem Mittel zum Schutz von blanken Silberoberflächen gegen Anlaufen, welches als hydrophoben Inhibitor eine langkettige aliphatische Mercaptoverbindung mit mindestens 12 C-Atomen in der Kette und Wasser enthält.The invention is based on an agent for protecting bare silver surfaces against tarnishing, which contains, as a hydrophobic inhibitor, a long-chain aliphatic mercapto compound with at least 12 carbon atoms in the chain and water.
Silberwaren und versilberte Teile laufen in schwefelwasserstoffhaltiger Atmosphäre an und werden infolge der Bildung von Silbersulfid braun bis schwarz. Um ein Anlaufen zu verhindern, ist es bekannt, Silberoberflächen mit einer anorganischen Deckschicht, z.B. mit Rhodium oder mit Silberchromat, welche durch elektrolytische Verfahren aufgebracht werden, zu schützen. Es ist auch bekannt, Silberoberflächen durch Klarsichtlacke oder Wachse, welche durch Tauchen, Sprühen oder Bedampfen aufgebracht werden, zu schützen. Ein wesentlicher Nachteil dieser Überzüge ist, dass sie das äussere Erscheinungsbild des Silbers verändern, was insbesondere bei dekorativen Gegenständen von Nachteil ist. Bei Anwendungen in der Elektrotechnik, insbesondere bei elektrischen Kontakten, sind derartige passivierende Überzüge nicht erwünscht, weil sie den elektrischen Übergangswiderstand stark erhöhen. Ausserdem erschweren solche Passivierungsschichten das Weichlöten einer Silberoberfläche. Es sind deshalb auch Mittel bekannt, mit denen Silberoberflächen nur zeitweise vor einem Anlaufen geschützt werden, nämlich vom Zeitpunkt der Herstellung bis zum Zeitpunkt der Weiterverarbeitung bzw. der Inbenutzungnahme. So ist es aus der DE-OS 1 621 459 bekannt, langkettige aliphatische Verbindungen, die eine SH-Gruppe enthalten (Mercapto-Verbindungen), in flüchtigen organischen Lösungsmitteln, nämlich in Chlorkohlenwasserstoffen, zu lösen, mit der Lösung die zu schützenden Silberoberflächen zu behandeln und dann zu trocknen, indem man die Lösung ablaufen und die restliche, an die Oberfläche noch haftende Lösung verdampfen läßt. Bei hinreichend langkettigen aliphatischen Mercapto-Verbindungen als Inhibitoren verbleibt auf der Silberoberfläche eine transparente, farblose, im Idealfall monomolekulare Schutzschicht, welche zumindestens solange auf der Ware haftet, bis diese weiterverarbeitet wird oder zum Verbraucher gelangt. Nachteilig dabei ist, dass die Inhibitoren in halogenierten Kohlenwasserstoffen gelöst werden, welche umweltschädlich sind.Silverware and silver-plated parts tarnish in an atmosphere containing hydrogen sulfide and turn brown to black due to the formation of silver sulfide. In order to prevent tarnishing, it is known to protect silver surfaces with an inorganic cover layer, for example with rhodium or with silver chromate, which are applied by electrolytic processes. It is also known to protect silver surfaces by means of transparent lacquers or waxes, which are applied by dipping, spraying or vapor deposition. A major disadvantage of these coatings is that they do change the external appearance of the silver, which is particularly disadvantageous for decorative objects. In applications in electrical engineering, especially in electrical contacts, such passivating coatings are not desirable because they greatly increase the electrical contact resistance. In addition, such passivation layers make soft soldering of a silver surface difficult. For this reason, means are also known with which silver surfaces are only temporarily protected from tarnishing, namely from the time of manufacture to the time of further processing or use. It is known from DE-OS 1 621 459 to dissolve long-chain aliphatic compounds which contain an SH group (mercapto compounds) in volatile organic solvents, namely in chlorinated hydrocarbons, with the solution to treat the silver surfaces to be protected and then drying by draining the solution and allowing the remaining solution still adhering to the surface to evaporate. In the case of sufficiently long-chain aliphatic mercapto compounds as inhibitors, a transparent, colorless, ideally monomolecular protective layer remains on the silver surface, which at least adheres to the goods until they are processed further or reach the consumer. The disadvantage here is that the inhibitors are dissolved in halogenated hydrocarbons which are harmful to the environment.
Um halogenierte Kohlenwasserstoffe als Lösungsmittel zu vermeiden, ist es aus der DE-OS 39 05 850, bekannt, die Inhibitoren, bei welchen es sich wiederum um langkettige aliphatische Verbindungen mit SH-Gruppe handelt, nämlich um Mercaptoverbindungen mit 12 bis 25 C-Atomen, in organischen Lösemitteln wie Glykolen und/oder Glykoläthern mit insgesamt 4 oder 5 C-Atomen zu lösen und die zu schützenden Silberoberflächen mit dieser Lösung zu behandeln. Glykole und Glykoläther haben den Vorteil, weniger umweltschädlich zu sein als halogenierte Kohlenwasserstoffe. Sie haben jedoch den Nachteil, dass sie entflammbar sind und dass die aus der Behandlungslösung entweichenden Dämpfe ein explosives Gemisch bilden können, so dass bei dem Arbeiten mit solchen Lösungen besondere Vorsichtsmaßnahmen zu ergreifen sind. Um dem Entstehen von entflammbaren oder explosiven Gasgemischen entgegenzuwirken, ist es aus der DE-OS 39 05 850 bereits bekannt, die behandelten Oberflächen nicht dadurch zu trocknen, dass man das Lösungmittel verdampfen läßt. Vielmehr wird das Lösungsmittel von den behandelten Oberflächen durch Spülen mit wässrigen Lösungsmitteln oder mit warmem Wasser mit Detergentien entfernt. Um die Verdampfungsraten zu reduzieren, ist es aus der DE-OS 39 05 850 weiterhin bekannt, der Lösung des Inhibitors in Glykol oder Glykoläther Wasser zuzusetzen. Das Glykol und der Glykoläther lösen sich im Wasser und werden dadurch verdünnt. Es wird jedoch darauf geachtet, dass bei dieser Verdünnung die Löslichkeitsgrenze des Inhibitors im Glykol bzw. Glykoläther nicht überschritten wird, damit es nicht zu Trübungen oder Ausfällungen kommt. Durch den Wasserzusatz wird die Gefährlichkeit des Glykols bzw. des Glykoläthers zwar vermindert, aber nicht beseitigt.To avoid halogenated hydrocarbons as solvents, it is known from DE-OS 39 05 850, the inhibitors, which in turn are long-chain aliphatic compounds with SH group, namely mercapto compounds with 12 to 25 carbon atoms, in organic solvents such as glycols and / or Solve glycol ethers with a total of 4 or 5 carbon atoms and treat the silver surfaces to be protected with this solution. Glycols and glycol ethers have the advantage of being less harmful to the environment than halogenated hydrocarbons. However, they have the disadvantage that they are flammable and that the vapors escaping from the treatment solution can form an explosive mixture, so that special precautions must be taken when working with such solutions. In order to counteract the development of flammable or explosive gas mixtures, it is already known from DE-OS 39 05 850 not to dry the treated surfaces by letting the solvent evaporate. Rather, the solvent is removed from the treated surfaces by rinsing with aqueous solvents or with warm water with detergents. In order to reduce the evaporation rates, it is also known from DE-OS 39 05 850 to add water to the solution of the inhibitor in glycol or glycol ether. The glycol and the glycol ether dissolve in the water and are thereby diluted. However, care is taken to ensure that with this dilution the solubility limit of the inhibitor in the glycol or glycol ether is not exceeded so that there is no clouding or precipitation. The addition of water reduces the dangerousness of the glycol or the glycol ether, but does not eliminate it.
Aus der DE-AS 1 279 428 ist es bereits bekannt, Silberwaren zum Schutz gegen Schwefelanlauf mit Hilfe von aliphatischen Thiokarbonsäuren zu schützen, welche in wässriger Emulsion angewendet werden und auf der Silberoberfläche besser haften sollen. Die wässrige Emulsion benötigt keinen Emulgator, weil die Thiokarbonsäuren eine hydrophile Carboxylgruppe haben, durch die sie teilweise sogar wasserlöslich sind. Wässrige Emulsionen von Thiokarbonsäuren haben aber nur eine geringe Standzeit und ihre Handhabung ist schwierig. Sie haben deshalb für die Tauchbehandlung oder Sprühbehandlung von Silberwaren, keinen Eingang in die Praxis gefunden, vielmehr wurden die Thiokarbonsäuren als Zusatz zu Polierpasten verwendet (DE-AS 1 279 428, Anspruch 5). Ein weiterer, besonders wesentlicher Nachteil der Thiokarbonsäuren besteht darin, dass sich an ihre hydrophile Carboxylgruppe Wasser anlagern kann, welches dem Schwefelwasserstoff, vor welchem die Silberoberfläche geschützt werden soll, letztlich den Angriff auf die Silberoberfläche doch ermöglicht, so dass man keine gegenüber Schwefelwasserstoff dichte Schutzschicht erhält. Auf dekorative Silberwaren soll das Mittel, das vor dem Anlaufen der Oberfläche schützen soll, als so gleichmässiger Film aufziehen, dass der Glanz der Oberfläche erhalten bleibt. Mit einer wässrigen Emulsion von Thiokarbonsäuren ist das kaum möglich, denn dazu genügt es nicht, den Überschuß der Emulsion von der Oberfläche ablaufen zu lassen, vielmehr müßte man die Oberfläche mit Wasser spülen; dabei würde aber ein erheblicher Teil der Thiokarbonsäure wieder abgespült, weil sie hydrophile Gruppen hat.From DE-AS 1 279 428 it is already known to protect silverware to protect against sulfur tarnishing with the aid of aliphatic thiocarboxylic acids, which are used in an aqueous emulsion and are said to adhere better to the silver surface. The aqueous emulsion does not require an emulsifier because the thiocarboxylic acids have a hydrophilic carboxyl group, which makes them partially water-soluble. Aqueous emulsions of thiocarboxylic acids have only a short shelf life and are difficult to handle. They have therefore found no entry into practice for the dip treatment or spray treatment of silverware, rather the thiocarboxylic acids have been used as an additive to polishing pastes (DE-AS 1 279 428, claim 5). Another, particularly significant disadvantage of thiocarboxylic acids is that water can attach to their hydrophilic carboxyl group, which ultimately enables the hydrogen sulfide from which the silver surface is to be protected to attack the silver surface, so that there is no protective layer which is impermeable to hydrogen sulfide receives. On decorative silverware, the agent, which is supposed to protect against tarnishing of the surface, should be applied as a film so uniform that the gloss of the surface is retained. This is hardly possible with an aqueous emulsion of thiocarboxylic acids, because it is not enough to remove the excess of the emulsion from the Letting the surface run off, rather one would have to rinse the surface with water; however, a considerable part of the thiocarboxylic acid would be rinsed off again because it has hydrophilic groups.
Aus der CH-A-478 925 ist ein Edelmetallreinigungs- und Polierbad bekannt, welches als Anlaufschutz langkettige Thiole enthält, die durch einen primären Alkohol als Lösungsvermittler in Lösung gebracht werden. In Kombination mit einer waschaktiven Substanz kann auch ein Alkylarylpolyglykoläther als Emulgator vorhanden sein.A precious metal cleaning and polishing bath is known from CH-A-478 925, which contains long-chain thiols as tarnishing protection, which are brought into solution by a primary alcohol as solubilizer. In combination with a detergent substance, an alkylaryl polyglycol ether can also be present as an emulsifier.
Aus der FR-A-1 347 705 ist eine Paste zum Reinigen und Polieren von angelaufenem Silber bekannt, welches u.a. ein Thiol und ein nicht-ionisches Tensid enthält.From FR-A-1 347 705 a paste for cleaning and polishing tarnished silver is known, which among other things. contains a thiol and a non-ionic surfactant.
Der vorliegenden Erfindung liegt die Aufgabe zugrunde, ein Mittel zum zeitweiligen Schutz von blanken Silberoberflächen, auch im Bereich der Elektrotechnik, insbesondere bei elektrischen Kontakten anzugeben, welches bequem und gefahrlos gehandhabt werden kann, auch in Tauchbädern, und umweltverträglich ist. Diese Aufgabe wird gelöst durch ein Mittel mit der im Anspruch 1 angegebenen Zusammensetzung. Ein besonders geeignetes Verfahren zum Anwenden dieses Mittels ist Gegenstand des Anspruchs 5. Vorteilhafte Weiterbildungen der Erfindung sind Gegenstand der Unteransprüche.The present invention has for its object to provide a means for the temporary protection of bare silver surfaces, also in the field of electrical engineering, in particular in the case of electrical contacts, which can be handled easily and safely, even in immersion baths, and is environmentally compatible. This object is achieved by an agent with the composition specified in claim 1. A particularly suitable method for using this agent is the subject of claim 5. Advantageous developments of the invention are the subject of the subclaims.
Das erfindungsgemässe Mittel enthält als organische Inhibitor-Substanz eine hydrophobe aliphatische Thioverbindung mit wenigstens 12 C-Atomen in der Kette aus der Gruppe der Thioalkohole und deren Veresterungsprodukten ohne hydrophile Carboxylgruppen, wobei die Thioalkohole besonders bevorzugt sind. Sie werden aber nicht in einem organischen Lösungsmittel gelöst, sondern in Form einer wässrigen Emulsion angewendet. Überraschenderweise hat es sich gezeigt, dass man mit diesen hydrophoben Verbindungen auch dann hauchdünne, aber dichte und dadurch zuverlässig passivierende Deckschichten auf Silberoberflächen oder Silberlegierungsoberflächen bilden kann, wenn die Inhibitor-Substanzen nicht in organischer Lösung angewendet werden, sondern in Form einer wässrigen Emulsion, obwohl sie in der Emulsion in Form von wesentlich größeren Teilchen vorliegen als in einer echten Lösung.The agent according to the invention contains, as organic inhibitor substance, a hydrophobic aliphatic thio compound with at least 12 carbon atoms in the chain from the group of thio alcohols and their esterification products without hydrophilic carboxyl groups, the thio alcohols being particularly preferred. However, they are not dissolved in an organic solvent, but used in the form of an aqueous emulsion. Surprisingly, it has been shown that with these hydrophobic compounds , wafer-thin, but dense and therefore reliably passivating cover layers can also be formed on silver surfaces or silver alloy surfaces if the inhibitor substances are not used in organic solution, but in the form of an aqueous emulsion, although they are present in the emulsion in the form of much larger particles than in a real solution.
Insbesondere hat sich gezeigt, dass der Emulgator, den man zwangsläufig benötigt, um die ausgewählten Inhibitoren in eine Emulsion zu bringen, nur in vernachlässigbarer Menge in den Inhibitor-Film eingelagert wird, der sich auf der Silberoberfläche bildet, die mit der Emulsion behandelt wurde. Nach dem Behandeln der Silberoberfläche mit der Emulsion kann der Emulgator leicht durch Spülen mit Wasser abgewaschen werden, während der passivierende Film aus der Inhibitor-Substanz auf der behandelten Silberoberfläche verbleibt.In particular, it has been shown that the emulsifier, which is inevitably required to bring the selected inhibitors into an emulsion, is only incorporated in a negligible amount in the inhibitor film which forms on the silver surface which has been treated with the emulsion. After treating the silver surface with the emulsion, the emulsifier can be easily washed off by rinsing with water, while the passivating film of the inhibitor substance remains on the treated silver surface.
Die Silberoberfläche wird in der Emulsion bei einer Temperatur behandelt, die oberhalb des Schmelzpunktes der Inhibitor-Substanz liegt. In diesem Fall verteilt sich die Inhibitor-Substanz nämlich besonders bereitwillig gleichmässig dünn auf der zu passivierenden Oberfläche. Das anschließende Spülen der Oberfläche führt man dann bei einer Temperatur unterhalb des Schmelzpunktes der Inhibitor-Substanz durch, was den Vorteil hat, dass diese dann besonders fest auf der passivierten Oberfläche haftet.The silver surface is treated in the emulsion at a temperature which is above the melting point of the inhibitor substance. In this case, the inhibitor substance is particularly readily distributed evenly thin on the surface to be passivated. The subsequent rinsing of the surface is then carried out at a temperature below the melting point of the inhibitor substance, which has the advantage that it then adheres particularly firmly to the passivated surface.
Das erfindungsgemässe Mittel ist problemlos in der Handhabung. Es enthält weder ein umweltgefährdendes noch ein brennbares Lösungsmittel, sondern als Trägersubstanz der Emulsion lediglich Wasser. Die im Wasser enthaltenen Sub-Substanzen, der Inhibitor und der Emulgator, sind biologisch abbaubar.The agent according to the invention is easy to handle. It contains neither an environmentally hazardous nor a flammable solvent, but only water as the carrier substance of the emulsion. The sub-substances contained in the water, the inhibitor and the emulsifier, are biodegradable.
Das erfindungsgemässe Mittel ist leicht anzuwenden. Es kann als Konzentrat aus dem Inhibitor und dem Emulgator in den Handel gebracht und vom Anwender durch Einrühren in Wasser gebrauchsfertig gemacht werden. Es kann durch Tauchen oder Sprühen angewendet werden. Vorzugsweise taucht man die zu behandelnde Ware in die Emulsion ein, weil dann die Behandlungszeiten am kürzesten sind. Für das Behandeln der Ware durch Eintauchen in die Emulsion, Spülen und Trocknen können herkömmliche Einrichtungen wie in der galvanischen Beschichtungstechnik eingesetzt werden mit dem Unterschied, dass die Ausrüstung mit Elektroden entfällt und dass keine Probleme mit der Entsorgung der Bäder und Spülwässer bestehen.The agent according to the invention is easy to use. It can be marketed as a concentrate of the inhibitor and the emulsifier and can be made ready for use by the user by stirring it into water. It can be applied by dipping or spraying. The goods to be treated are preferably immersed in the emulsion because the treatment times are then the shortest. For the treatment of the goods by immersion in the emulsion, rinsing and drying, conventional devices such as in electroplating technology can be used, with the difference that there is no need for electrodes and that there are no problems with the disposal of the baths and rinsing water.
Das erfindungsgemässe Mittel enthält 2 bis 20 g/l des Inhibitors.The agent according to the invention contains 2 to 20 g / l of the inhibitor.
Der Emulgator ist in dem Mittel in einer Menge von 2 bis 20 g/l enthalten.The emulsifier is contained in the agent in an amount of 2 to 20 g / l.
Zur Unterstützung der Benetzung können dem Mittel bis zu 2 g/l, vorzugsweise 0,05 bis 1 g/l eines anionischen oder nicht-ionischen Tensids zugesetzt werden. Kationische Tenside sind ungeeignet.To assist wetting, up to 2 g / l, preferably 0.05 to 1 g / l, of an anionic or nonionic surfactant can be added to the agent. Cationic surfactants are unsuitable.
Erfindungsgemäss werden solche Inhibitoren ausgewählt, die mindestens 12 und vorzugsweise nicht mehr als 20 C-Atome in der Kette haben. Bei weniger als 12 C-Atomen ist teils kein gut haftender Schutzüberzug erzielbar, teils treten starke Geruchsbelästigungen auf. Bei mehr als 20 C-Atomen werden die Inhibitoren in ihrer Konsistenz zu fest und es wird schwieriger, eine befriedigende Emulsion herzustellen.According to the invention, inhibitors are selected which have at least 12 and preferably not more than 20 C atoms in the chain. With less than 12 carbon atoms, it is sometimes not possible to achieve a well-adhering protective coating, and in part there are strong odor nuisances. With more than 20 carbon atoms, the inhibitors become too solid in consistency and it becomes more difficult to produce a satisfactory emulsion.
Es hat sich gezeigt, dass sich die Inhibitoren sehr fein und langzeitstabil emulgieren lassen und in dünner, aber dichter Schicht auf die zu schützenden Oberflächen aufziehen. Als Emulgatoren eignen sich dafür besonders verzweigte Fettalkohole mit 9 bis 20 C-Atomen, insbesondere mit 10 bis 15 C-Atomen, wobei die verzweigten Fettalkohole vorzugsweise alkoxyliert, insbesondere ethoxyliert, sind mit einem Alkoxylierungsgrad von 2 bis 10.It has been shown that the inhibitors can be emulsified very finely and with long-term stability and can be applied to the surfaces to be protected in a thin but dense layer. Particularly suitable emulsifiers for this purpose are branched fatty alcohols having 9 to 20 carbon atoms, in particular having 10 to 15 carbon atoms, the branched fatty alcohols preferably being alkoxylated, in particular ethoxylated, with a degree of alkoxylation of 2 to 10.
Überraschenderweise hat sich gezeigt, dass bei Einstellung des Passivierungsmittels auf einen pH-Wert von 1-10, besser 1-8, vorzugsweise 2-4, der Emulgator aus der abgeschiedenen Inhibitorschicht praktisch vollständig mit Wasser ausgewaschen werden kann, was für einen zuverlässigen Oberflächenschutz wichtig ist. Bei hohem pH-Wert wird weniger Inhibitor ausgewaschen, wodurch die Schutzwirkung und die Schmierwirkung verstärkt werden; allerdings können dabei Flecken auf der Oberfläche auftreten, die das Aussehen von dekorativen Oberflächen stören. Dekorative Oberflächen werden deshalb vorzugsweise mit einem Mittel passiviert, dessen pH-Wert niedriger liegt, vorzugsweise zwischen 2 und 4, wobei auch dann nach dem Auswaschen genügend Inhibitorsubstanz zurückbleibt, um eine dichte Schutzschicht zu bilden. Bei einem pH-Wert über 10 besteht die Gefahr einer Spaltung der Emulsion.Surprisingly, it has been shown that when the passivating agent is adjusted to a pH of 1-10, better 1-8, preferably 2-4, the emulsifier can be washed out of the deposited inhibitor layer practically completely with water, which is important for reliable surface protection is. At high pH, less inhibitor is washed out, which increases the protective effect and the lubricating effect; however, stains can appear on the surface, which can disturb the appearance of decorative surfaces. Decorative surfaces are therefore preferably passivated with an agent whose pH is lower, preferably between 2 and 4, with sufficient inhibitor substance remaining even after washing out to form a tight protective layer. If the pH is above 10 there is a risk of the emulsion splitting.
Unerwartet hat es sich ferner gezeigt, dass das erfindungsgemässe Mittel darüberhinaus geeignet ist, Oberflächen aus Kupfer und Kupferlegierungen zu passivieren. Entsprechendes gilt damit auch für Bimetallteile aus einem Silberwerkstoff einerseits und einem Kupferwerkstoff andererseits, z.B. für Bimetall-Kontaktniete. Der in Wasser emulgierte Inhibitor zieht auch auf Kupfer und kupferhaltige Werkstoffe sehr gut auf und schützt die Oberfläche vor dem Angriff von Schwefelverbindungen und vor Oxidation. Die gute Lötbarkeit und die elektrischen Eigenschaften werden dadurch nicht verschlechtert.It has also been shown, unexpectedly, that the agent according to the invention is also suitable for passivating surfaces made of copper and copper alloys. The same applies accordingly to bimetal parts made of a silver material on the one hand and a copper material on the other hand, for example for bimetal contact rivets. The water-emulsified inhibitor also absorbs very well on copper and copper-containing materials and protects the surface against the attack of sulfur compounds and against oxidation. The good solderability and the electrical properties are not impaired.
Beispiele von Bädern, mit denen sich deckende und gut haftende Überzüge auf Oberflächen von Silber- und Kupferwerkstoffen erzielen lassen:
1. In einem Liter deionisiertem Wasser gelöst:
Besonders geeignet für Silber und Silberlegierungen.
2. In einem Liter deionisiertem Wasser gelöst:
Besonders für Teile aus Kupfer oder Kupferlegierungen geeignet.
Examples of baths with which opaque and well-adhering coatings can be achieved on surfaces of silver and copper materials:
1. Dissolved in one liter of deionized water:
Particularly suitable for silver and silver alloys.
2. Dissolved in one liter of deionized water:
Particularly suitable for parts made of copper or copper alloys.
Die Anwendung dieser Bäder geschieht vorzugsweise so, dass die zu passivierenden Teile in die ca. 40°C bis 50°C warmen Bäder getaucht werden. Nach 2 bis 3 Minuten ist die Oberfläche der Teile gleichmässig und dicht mit dem Inhibitor benetzt. Die Teile werden anschließend mit kaltem Wasser gespült und dann getrocknet, vorzugsweise mit Heißluft.These baths are preferably used in such a way that the parts to be passivated are immersed in the approx. 40 ° C to 50 ° C warm baths. After 2 to 3 minutes, the surface of the parts is even and dense with the inhibitor wetted. The parts are then rinsed with cold water and then dried, preferably with hot air.
Die Wirkung der Anlaufschutzschicht auf Silber läßt sich mit Hilfe einer zweiprozentigen Natriumsulfidlösung gut nachweisen. Unbehandelte Silberteile laufen sofort an, behandelte Teile bleiben über einen längeren Zeitraum blank. Die Wirkung der Schutzschicht auf Kupfer wurde überprüft, indem passivierte Kupferteile für mehrere Stunden in einer Schwefelwasserstoffatmosphäre mit 1 ppm H₂S ausgelagert wurden; die Kupferteile verfärbten sich dabei nicht.The effect of the tarnish protection layer on silver can be easily demonstrated with the help of a two percent sodium sulfide solution. Untreated silver parts tarnish immediately, treated parts remain bare over a longer period. The effect of the protective layer on copper was checked by passivating copper parts for several hours in a hydrogen sulfide atmosphere with 1 ppm H₂S; the copper parts did not change color.
Claims (7)
- Means for temporarily protecting bare silver surfaces and silver alloy surfaces against tarnishing, which, as a hydrophobic inhibitor, contains a long-chained aliphatic thio-compound with at least one SH group and at least 12 C atoms in the chain from the thio-alcohol group and whose ester products contain water and one water-soluble emulsifier, with the aid of which the inhibitor is emulsified in the water and its pH-value adjusted to between 1 and 10, characterised in that it contains2 to 20 g/l of inhibitor,2 to 20 g/l of emulsifier,0 to 2 g/l of an anionic or non-ionic surfactant,the remainder being water, and that the emulsifer is selected from the group of the branched, alkoxylated - preferably ethoxylated - fatty alcohols with 4 to 20 C atoms and an alkoxylation level of 2 to 10.
- Means as claimed in claim 1, characterised in that it is adjusted to a pH-value smaller than 7, preferably within the range of 2 to 4.
- Means as claimed in claim 1, characterised in that it contains 0.05 to 1 g/l of the surfactant.
- Means as claimed in one of the previous claims, characterised in that it contains no inhibitors with more than 20 C atoms in the chain.
- Method of stabilising bare silver and silver alloy surfaces or copper and copper alloy surfaces with an emulsion of a composition as set out in claims 1 to 4, characterised in that the surfaces are treated with the emulsion at a temperature above the melting point of the inhibitor, and that the surfaces are thereafter rinsed at a temperature below the melting point of the inhibitor.
- Method as claimed in claim 5, characterised in that the surfaces are rinsed with water.
- Method as claimed in claim 5 or 6, characterised in that the rinsed surfaces are dried with hot air.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19904041596 DE4041596A1 (en) | 1990-12-22 | 1990-12-22 | Compsn. for protecting silver@ surfaces against tarnishing |
DE4041596 | 1990-12-22 | ||
DE4124955 | 1991-07-27 | ||
DE4124955 | 1991-07-27 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0492487A1 EP0492487A1 (en) | 1992-07-01 |
EP0492487B1 true EP0492487B1 (en) | 1996-03-20 |
Family
ID=25899756
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP91121903A Expired - Lifetime EP0492487B1 (en) | 1990-12-22 | 1991-12-20 | Means of temporary protection of bare silver and copper surfaces against tarnishing and method of using it |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0492487B1 (en) |
DE (1) | DE59107581D1 (en) |
ES (1) | ES2086471T3 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102005047843A1 (en) * | 2005-10-05 | 2007-04-12 | OTB Oberflächentechnik in Berlin GmbH & Co. | Passivating and lubricating agents for gold, silver and copper surfaces and methods of use |
CN104032289A (en) * | 2013-08-23 | 2014-09-10 | 珠海罗西尼表业有限公司 | Method for corrosion resistance and tarnishing resistance treatment of gold and its alloy surface |
WO2021028440A1 (en) | 2019-08-13 | 2021-02-18 | Saint-Gobain Glass France | Reducing the corrosion of silver wires on a glass substrate |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE4333127A1 (en) * | 1993-09-29 | 1995-03-30 | Basf Ag | Process for protecting solderable copper and copper alloy surfaces from corrosion |
US7524535B2 (en) * | 2004-02-25 | 2009-04-28 | Posco | Method of protecting metals from corrosion using thiol compounds |
GB2412666B (en) * | 2004-03-30 | 2008-10-08 | Paul Gilbert Cole | Water-based metal treatment composition |
US7883738B2 (en) | 2007-04-18 | 2011-02-08 | Enthone Inc. | Metallic surface enhancement |
US10017863B2 (en) | 2007-06-21 | 2018-07-10 | Joseph A. Abys | Corrosion protection of bronzes |
TWI453301B (en) | 2007-11-08 | 2014-09-21 | Enthone | Self assembled molecules on immersion silver coatings |
IT1398698B1 (en) | 2010-02-24 | 2013-03-08 | Mesa S A S Di Malimpensa Simona E Davide E C | METHOD FOR THE PROTECTION OF SILVER SURFACES AND ITS UNDERSTANDING ALLOYS. |
CN108315739B (en) * | 2018-02-10 | 2019-03-22 | 深圳市祥盛兴科技有限公司 | A kind of chemical polishing solution and surface with chemical polishing technology |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1347705A (en) * | 1961-09-28 | 1964-01-04 | Minnesota Mining & Mfg | Composition preventing tarnishing of copper-based surfaces |
DE1282414B (en) * | 1963-12-18 | 1968-11-07 | Wmf Wuerttemberg Metallwaren | Agent for protecting silver goods by passivating their surface using organic thio compounds |
US3398003A (en) * | 1965-04-26 | 1968-08-20 | Verle C. Smith | Silver polish-tarnish retarder containing a dialkyl disulfide having from 8 to 20 carbon atoms in each alkyl radical |
DE1546119A1 (en) * | 1965-11-04 | 1970-03-12 | Becker Hans Delu Fab | Precious metal cleaning and polishing bath with tarnish protection |
DE3905850A1 (en) * | 1989-02-24 | 1990-08-30 | Blasberg Oberflaechentech | Method of protecting untreated silver surfaces |
-
1991
- 1991-12-20 DE DE59107581T patent/DE59107581D1/en not_active Expired - Lifetime
- 1991-12-20 ES ES91121903T patent/ES2086471T3/en not_active Expired - Lifetime
- 1991-12-20 EP EP91121903A patent/EP0492487B1/en not_active Expired - Lifetime
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102005047843A1 (en) * | 2005-10-05 | 2007-04-12 | OTB Oberflächentechnik in Berlin GmbH & Co. | Passivating and lubricating agents for gold, silver and copper surfaces and methods of use |
CN104032289A (en) * | 2013-08-23 | 2014-09-10 | 珠海罗西尼表业有限公司 | Method for corrosion resistance and tarnishing resistance treatment of gold and its alloy surface |
CN104032289B (en) * | 2013-08-23 | 2015-02-25 | 珠海罗西尼表业有限公司 | Method for corrosion resistance and tarnishing resistance treatment of gold and its alloy surface |
WO2021028440A1 (en) | 2019-08-13 | 2021-02-18 | Saint-Gobain Glass France | Reducing the corrosion of silver wires on a glass substrate |
Also Published As
Publication number | Publication date |
---|---|
EP0492487A1 (en) | 1992-07-01 |
ES2086471T3 (en) | 1996-07-01 |
DE59107581D1 (en) | 1996-04-25 |
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