Method for electrodeposition of bronzes

Abstract

A method for electrodeposition of bronzes, with which the substrate to be coated is plated in an acid electrolyte that contains at least tin and copper ions, an alkylsulfonic acid and a wetting agent, and the preparation of such an electrolyte.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation-in-part from U.S. app. Ser. No. ______ entitled METHOD FOR ELECTRODEPOSITION OF BRONZES filed Apr. 11, 2005, the entire disclosure of which is explicitly incorporated by reference.FIELD OF THE INVENTION [0002] This invention concerns a method for electrodeposition of bronzes, with which the substrate to be coated is plated in an acid electrolyte that contains at least tin and copper ions, an alkylsulfonic acid and a wetting agent, and the preparation of such an electrolyte. BACKGROUND OF THE INVENTION [0003] Methods for deposition of tin and tin alloys on the basis of various types of electrolytes are known from the prior art and are already widely used in practice. Methods for deposition of tin and / or tin alloys from cyanide electrolytes are very common. Such electrolytes, however, are highly toxic, which makes their use problematic from the environmental standpoint, so that for some years there has b...

AI Technical Summary

Benefits of technology

[0017] The additional or alternative use of one or more anionic and / or aliphatic nonionic wetting agent that is known from the prior art is also optionally possible, provided these wetting agents support or even enhance the advantageous effects of the aromatic nonionic wetting agent. In this regard polyethylene glycols and / or anionic surfactants are preferably added to the electrolyte as anionic and / or aliphatic nonionic wetting agents. Additional exemplary aliphatic nonionic wetting agents include aliphatic fatty alcohol ethoxylates.

[0018] It has also been discovered that substituted dithioglycols act advantageously as wetting agents and brighteners. Therefore, certain embodiments of the invention include substituted dithioglycols, such as, for example, those selected from the group consisting of:

[0023] (6) 4,10-dioxa-7-thiatridecane-2,12-diol represented by HO—CH (CH3)CH2 —OCH2CH2 —SCH2CH2—OCH2CH (CH3)—OH,

[0024] (7) Thiodiglycerin represented by HOCH2CH (OH) CH2—S—CH2CH (OH) CH2OH,

[0025] (8) Thiobis(triglycerin) represented by H—(OCH2CH (OH) CH2)3—S—(CH2CH (OH) CH2O)—H,

[0026] (9) 2,2′-thiodibutanolbis(octaethyleneglycolpentaglycerol) ether represented by H—(OCH2CH (OH) CH2)—(OCH2CH2) 8—OC4H8—SC4H8—O—(CH2CH2O)8—(CH2CH (OH)CH2O)—H,

Problems solved by technology

Such electrolytes, however, are highly toxic, which makes their use problematic from the environmental standpoint, so that for some years there has been a push to develop cyanide-free electrolytes, for example electrolytes based on pyrophosphates or oxalates, which operate in a pH region of 5-9.

However, such methods have both economic and technical disadvantages, of which the relatively slow deposition rates may be mentioned here.

However, such methods have their limits in the deposition of tin-copper alloys with high copper contents, such as the so-called “true” bronzes, which have a copper content of at least 10%.

However, in this form tin can no longer be electrolytically deposited in an acid and thus is withdrawn from the process, which leads to uneven deposition of the two metals and to a decrease of the deposition rate.

In addition, oxidation to tetravalent tin leads to increased sludge formation, which can prevent stable operation and long lifetime of the acid electrolyte.

Moreover, because of such contaminated of a firmly bonding and pore-free coating is no longer guaranteed.

Because of such technical process disadvantages, there is currently no large area of use for electrolytically deposited bronze coatings. occasionally bronze coatings are used in the jewelry industry as a substitute for expensive silver or allergy-triggering nickel.

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