Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Treating process fluid by means other than agitation or...
Patent
1995-09-28
1998-02-10
Valentine, Donald R.
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Treating process fluid by means other than agitation or...
205101, 205134, 205137, 204212, 204237, 204238, 204273, 204276, 204232, 204240, C25D 500, C25D 1700, C25D 2106, C25D 2110
Patent
active
057165092
DESCRIPTION:
BRIEF SUMMARY
The invention described here concerns a process as well as a device for electrolytic surface coating of electrically conductive objects, in particular of metal workpieces, as well as a special application of said device.
Electrolytic surface coatings of metal objects have for a long time constituted part of the prior art; said technology is widely represented in the patent literature.
Recent, pertinent, published patent applications include EP-A 0 196 420, EP-A 0 387 750 as well as DE-A 34 29 890.
In EP-A 0 196 420 (publication date Oct. 8, 1986), a high-speed electrolysis cell for surface coating of strip product is taught. Said device includes a vertical electrolytic galvanization cell for the coating of steel strips, in which the strip is guided by an upper guide roller or flow roller to a lower guiding immersion roller and from there to an additional, upper guide roller or flow roller. In this process, the falling and rising section of the strip to be coated is bombarded in a gap between vertically disposed anodes by the electrolyte stream guided in the circuit at a high speed counter to the direction the strip is moving. In such an electrolysis cell, the circulation of greater amounts of electrolyte is obtained using the least possible pumping energy.
According to EP-A 0 387 750 (publication date Sep. 19, 1990), the electrolysis cell described therein is characterized by a plurality of current feeds and a plurality of electrolyte inlets or discharges. By means thereof, uniform electrolysis and coating are achieved.
And finally, the arrangement from DE-A 34 29 890 is used for the application of a copper layer on an intaglio cylinder in a galvanization bath, which has a copper-containing electrolyte and at least one anode made of copper. The anode may have the form of a plate provided with a plurality of perforations, specifically that of a perforated metal plate or metal mesh concentrically disposed around the printing cylinder. This arrangement enables the performance of the electrolysis with relatively low voltage and application of a uniform copper layer on the cathodically connected intaglio cylinder.
A common element of the three teachings mentioned is that they do not pay adequate attention to the design-based elimination of the anode sludge. The accomplishment of this object leads, however, as tests of the applicant have clearly shown, to a significantly improved quality of the electrically applied coating layer in terms of homogeneity, i.e., a homogenous, fine-crystalline microstructure as well as corrosion resistance.
The process according to the invention for electrolytic surface coating of the electrically conductive workpieces, in particular of metal workpieces, by means of a fluid electrolyte is characterized in the electrolysis region between the anode and the cathodically connected workpiece, whereby most of the electrolyte is conveyed at a high flow rate, possibly at a higher inlet pressure, through the space between the cathodically connected workpiece and the anode, and a smaller share thereof is conveyed at a lower flow rate upward to the rear of the anode away from the cathode, the electrolysis region, and electrolysis region between the anode and cathode, precipitated or separated from the electrolyte.
In the process mentioned, it is further relevant that the electrolyte is conveyed to the anode, passed through the anode, or removed by the anode, that most of the anode sludge formed during the electrolysis is removed from the flowing electrolyte.
Advantageously, the electrolyte is continuously monitored in the circuit with regard to the essential process parameters such as temperature, conversion, content, etc. and optimized, if need be.
During the process the cathodically connected workpiece is either stationary or is moved during the electrolytic surface coating, in particular rotated; the anode is either periodically replaced or the anode material is continuously added.
As mentioned, during this circuit through the overflow tank the anode sludge is separated or precipitated eith
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Ecograph AG
Valentine Donald R.
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