JPS5940237B2 - Strip radial cell plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial cell plating method for strip.

A strip that is in contact with the outer periphery of the energizing rotating drum and runs synchronously with its rotation is energized between the strip and an anode, which is separated by a radial energizing gap and into which a plating solution is introduced, through the plating solution. The strip plating method using so-called radial cells is advantageous in processing only one side of the strip under high-speed threading.
A number of methods have been proposed for its effective implementation.

Generally, when applying this type of plating method, when attempting to thicken the plating film by rotating the current-carrying rotating drum at low speed, the allowable current density tends to decrease and may exceed its allowable limit. If an electrolytic cell is operated at too high a current density, it will cause burns, or coarsening of the crystals of the plated metal. We must increase the number of installations. In the example of electrogalvanizing, 6Of
l/m2 or more, unless multiple electrolytic cells are used, low current density and slow operation conditions are forced, which is less efficient in terms of efficiency than high efficiency operation when high current density and high speed threading is performed. The disadvantage is significant.

Therefore, this invention proposes the results of research developed for the purpose of increasing the allowable current density under low-speed operation during sheet plating using a radial cell.

This invention provides plating between a strip that is in contact with the outer periphery of a rotating energizing drum and runs synchronously with its rotation, and an anode that is separated by a radial energizing gap and into which a plating liquid is introduced. During the treatment, each current-carrying gap of the strip is provided with a fluid supply system that includes the current-carrying gap as part of a separate and independent plating liquid circulation path to direct a renewal flow of plating liquid. This is a radial cell plating method for strips, and by making both renewal flows in the opposite direction to the running of the strip, it is possible to bring about a particularly remarkable increase in allowable current density. 60 in galvanized example
When performing radial cell plating at a line speed as low as 25 m/- or less, such as when a thick plating film of f1/M2 or more is required, the allowable current density can be greatly accumulated. By increasing the number of cells, it is possible to eliminate the use of multiple cells without deteriorating the plating conditions and dramatically improve the plating processing efficiency. The efficiency gains extend not only to low line speed conditions, but also to general high line speed conditions.

Now, FIG. 1 shows an example of a radial cell suitable for applying the present invention, in which 1 is a rotating drum for energizing, 2 is a strip that is wound around half the circumference of the drum and runs along the arrow; 3 is a line tank, and 4 is an anode attached to the bottom of the line tank. A gap 9 is formed. This current-carrying gap 9 is separated by a partition wall w at the front and rear of the inlet side down path Pd and the outlet side up path Pu, and each current-carrying gap 9, 9 of both paths is separated from each other by a partition wall w.
', a pair of liquid supply systems each including the energized gap 9 or 9' as part of a separate and independent circulation path for the plating liquid, for example by means of a pump from the circulation tanks T, T'. guide. The partition wall w is made of vinyl chloride, hard rubber, etc. that is not affected by the plating solution, and a slight gap is left between it and the strip 3 to avoid undesired contact.

Each circulation route is connected to a pipe P1 connected to the circulation tanks T and T7.
-P2jP3-P4) Each energizing gap 99f! A spray nozzle or a slit-like nozzle can be connected to both ends of the strip 2 to form a branch manifold, and a spray nozzle or a slit-like nozzle can be connected to the energized gears 9 and 9' to produce a uniform flow across the width of the strip 2. Alternatively, a horizontal impeller or the like may be used.

As plating liquid, ZnC222OO9/1, NH4Cj
A chloride bath with a composition of 3009/l and a pH of 3.5 and a liquid temperature of 55°C was used, a soluble electrode containing zinc as the main component was used as the anode 4, and the circulating plating solution in each energizing gap 9, g2 was used. The flow velocity was set to 0.5 m/Sec, and this was maintained constant according to the measurement result by the hot wire anemometer, and the direction of the circulating flow of the simmering liquid in the down path Pd and up path Pu was determined to be the allowable current density. We investigated the effect on Example 5 of the results when the line speed is 25w'n is as shown in the following Table 1. In the above table, the down path Pd and the up path Pu are countercurrent, that is, the renewal flow is in the opposite direction to the running of strip 2. Since a significant increase in allowable current density was observed in this case, tests were conducted under similar conditions with various line speeds and the results shown in FIG. 2 were obtained.

Here, the relationship between the line speed and the allowable current density in the case of using a radial cell in which the above-mentioned soluble anode 4 is simply immersed and held in a plating bath to allow natural circulation accompanying the running of the strip 2 is shown in the second section. As shown by the dotted line in the figure for comparison, both are relatively comparable, but this is especially true when forced circulation in the opposite direction to the running of strip 2 is applied to both the down path Pd and the up path Pu. Therefore, it is possible to obtain a sufficiently high allowable current density even at 25 inches or less, which was the conventional limit line speed, and maintain high operating efficiency with a thickness of 609/M2 or more without adding a radial cell. It was possible to carry out the experiment at high current densities.

Furthermore, as shown in Fig. 3, which shows the effect on the allowable current density when the renewal flow rate of the circulating plating solution is increased or decreased, if the renewal flow rate is increased to 1.0 m/Sec, It is clear that the allowable current density can be increased.
In addition to the above, it is clear from Table 1 above that the allowable current density tends to increase sharply in each case where at least one of the down path Pd and up path Pu is a forward flow. For example, Pu; forward flow, P
d; It is obvious that they can be combined in a counter-flow or forward-flow adaptation, and therefore each circulation path is equipped with piping that includes a switching valve that can reverse the direction of flow to adapt to various usage conditions. can be done.

Although the above description has been made by taking as an example the case of galvanizing treatment using a chloride bath, the present invention can also be applied to radial cell sheet plating of tin, chromium, manganese, nickel, or the like.

In this way, the present invention is particularly effective in the range of line speeds for sheet plating using radial cells, particularly at 25 m/111. The current density can be increased even under thick coating conditions at low line speeds of about n or less,
It is advantageous for its efficient operation.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the radial cell plating procedure according to the present invention, Fig. 2 is a graph comparing the effect of this invention with the conventional method regarding the relationship between line speed and allowable current density, and Fig. 3 is a graph showing the relationship between cyclic update flow rate and allowable current density. 1... Rotating drum for energizing, 2... Strip, 3... Line tank, 4...
Anode, Pd... Down pass, Pu...
... Up pass, 9... Energizing gap, P1 ~
P4...Piping, w...Partition.

Claims (1)

[Scope of Claims] 1. A strip that is in contact with the outer periphery of a rotating energizing drum and runs synchronously with its rotation, and an anode that is separated by a radial energizing gap and into which plating liquid is introduced. When plating is performed using a radial cell that conducts electricity through the plating liquid, the energization gap is isolated from the front and back for the inlet down pass and the outlet up pass of the strip, and each pass is energized. A method of radial cell plate-through plating of strips, which comprises introducing a renewal flow of plating liquid into the gaps by having a liquid supply system including the energized gaps as part of each individual and independent plating liquid circulation path. 2. The strip plating method according to claim 1, wherein the renewal flow in both the energizing gaps of the inlet down pass and the outlet up pass of the strip is in the opposite direction to the running of the strip.