Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Depositing predominantly alloy coating
Patent
1992-05-29
1995-08-22
Valentine, Donald R.
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Depositing predominantly alloy coating
205253, 205299, C25D 332, C25D 336, C25D 338
Patent
active
054437148
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for acidic electrolytical deposition of lead layers and predominantly lead-containing layers onto surfaces using an electrolyte containing lead salts and acids, in particular alkanesulfonic acid, borofluoric acid or silicofluoric acid. Furthermore, the present invention relates to an electrolyte for performing the process and the use of surfactants in acidic lead electrolytes.
Processes for acidic electrolytical deposition of lead layers and predominantly lead-containing layers are known in prior art. In these processes, only lead fluorosilicate, lead fluoroborate and lead perchlorate electrolyte have been gaining special significance. To these lead electrolytes are added organic materials, e.g., gelatin, glue, peptones, phenolsulfonic acid, and waste sulfite liquor to obtain fine-grained, smooth precipitates.
Among these known electrolytes, the lead perchlorate electrolyte, in particular, is said to have special merits:
1. good solubility.,
2. high electrical conductivity,
3. good chemical stability,
4. a 100% anodic and cathodic current efficiency,
5. smooth, dense coatings, and
6. no polarization phenomenons.
In spite of these obvious advantages, the lead perchlorate electrolyte could not gain acceptance in practice. Drawbacks of this electrolyte result, in particular, from the dangerousness of perchlorate.
From U.S. Pat. No. 2,525,942, acidic lead electrolytes on the basis of the alkanesulfonate are known. The drawback of the electrolytes mentioned therein is that lead deposited therefrom forms an amorphous, non-dense, porous layer of lead. Furthermore, this electrolyte permits deposition only in a very narrow range of current density.
U.S. Pat. No. 4,701,244 discloses an electrolytical bath for the deposition of tin and lead in the presence of excess (lower alkylsulfonic acid or acid salt containing the following admixtures: additives such as benzalacetone, benzaldehydes and aromatic pyridines, surface-active substances such as betaines, alkylene oxide, polymeres, imidazolinium compounds, and quaternary ammonium salts, and formaldehyde. No disclosure is made whatsoever concerning the combination of non-ionic surfactants and cationic or amphoteric surfactants in an electrolyte for the deposition of lead layers and predominantly lead-containing layers.
It is object of the present invention to provide a process for acidic electrolytical deposition of lead layers and predominantly lead-containing layers onto surfaces, the merits of which resembling those of electrolysis using lead perchlorate without having the extraordinary dangerousness of same process.
Now, this problem is solved in surprisingly simple fashion by a process wherein the electrolyte, in addition to lead salts and acids, particularly alkanesulfonic acid, borofluoric acid or silicofluoric acid, contains non-ionic surfactants and/or cationic or amphoteric surfactants.
Using the process according to the invention, it is now possible to obtain smooth, dense and finely crystalline lead deposits even on basis materials having gross deformations. Moreover, in the process according to the invention, polarization phenomenons of previously used electrolytes are reduced both in the anode and cathode reactions. At the same time, better anode solubility is achieved. It is of particular advantage that applicable cathodic current densities are higher. Thus, it is possible to operate using substantially lower electrolyte lead content. As a consequence, the rinsing water lead contamination is lower as well. Thus, on the whole, waste management of both lead-containing electrolyte and rinsing water is substantially simplified.
Hence, subject matter of the present invention is a process for acidic electrolytical deposition of lead layers and predominantly lead-containing layers onto surfaces using an electrolyte containing lead salts and acids, in particular alkanesulfonic acid, borofluoric acid or silicofluoric acid, characterized in that non-ionic surfactants and cationic or amphoteric surfactants are added to the
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Knaak Eberhard
Schmidt Karl-Jurgen
Blasberg Oberflachentechnik GmbH
Valentine Donald R.
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