JPH0428896A - Continuous electroplating method - Google Patents

Abstract

PURPOSE:To prevent plating metal from being stuck on an electricity conductive roll by specifying both the contact wire pressure of the electricity conductive roll and steel strip and the concn. of Fe<3+> in a plating soln. in a continuous electroplating method wherein a horizontal plating cell is utilized to electroplate steel strip. CONSTITUTION:The contact wire pressure of an electricity conductive roll and steel strip is controlled by the pushing force of the backup rolls 4 shown in a figure 1. This contact wire pressure of the roll and steel strip is regulated to 20-120kg/cm<2>. When the concn. of Fe<3+> in a plating liquid is increased, electrocorrosion on the surface of the electricity conductive roll proceeds. Accord ingly, it is necessary that the concn. of Fe<3+> is regulated to <=0.6g/l. Fe<3+> is present at about 1g/l in the plating liquid by elution from steel strip but the concn. of Fe<3+> is controlled by treating this plating liquid by ion exchange resin. On the other hand, when the concn. of Fe<3+> is reduced, this concn. is lowered by dissolving velocity of plating metal in the case of replenishing this plating metal into the plating liquid. Since plating can not be continuously performed, it is necessary that the concn. of Fe<3+> is regulated to >=0.2g/l.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electroplating method that prevents deposition of plating metal on a current-carrying roll during electroplating of a steel strip and produces a product free of dents.

(Prior art) Horizontal electroplating equipment has advantages such as lower voltage loss (and lower strength of the current-carrying roll) than vertical electroplating equipment, and has been used for galvanizing etc. for a long time. 6 Figure 1 is a schematic diagram of a horizontal electroplating equipment generally used for galvanizing steel strips.A horizontal electroplating equipment has multiple electrolytic cells arranged in sequence. , each electrolytic cell is provided with a pair of anode electrodes corresponding to the upper and lower sides of the steel strip.A current-carrying roll 2 and a backup roll 4 are installed near the various entry and exit sides, where the steel strip is 1 is negatively charged and undergoes an electrolytic reaction in the plating solution 3,
Plating is performed on the surface of the steel strip 1. In an electroplating apparatus having such a structure, the current-carrying roll 2 and the plating solution 3 come into direct contact, so that the plating metal is deposited and adheres to the current-carrying roll 2. When metal adheres to the energizing roll 2, it gets caught between the energizing roll 2 and the steel strip 1, causing scratches on the surface of the steel strip and resulting in product defects. Furthermore, the electrical contact between the energizing roll and the steel strip 1 becomes incomplete, and energization is partially obstructed, making uniform plating impossible.

Therefore, it is essential to prevent or remove the plating metal from adhering to the current-carrying roll 2.

For this purpose, the following methods have been conventionally used. Figure 2 shows the energizing roll 2 in the darkness between the energizing roll 2 and the anode electrode 5.
A reverse electrolytic electrode 6 is attached adjacent to the rotating rolling roll 2, and a reverse electrolytic voltage is applied to electrolytically peel off the plated metal attached to the current carrying roll 2. A method of pressing the material 7 to remove plated metal adhering to the energizing roll 2, and furthermore, a method of detecting plating metal adhesion to the energizing roll is disclosed in JP-A-1-14708.
There is one shown in Publication No. 9.

(Problems to be Solved by the Invention) The method using reverse electrolysis described above performs 713R electrolysis between the current-carrying roll and the reverse electrolysis electrode installed close to it.
If metal af* is partially attached to the energizing roll, the part of the energizing roll to which the plating metal is not attached will be electrolyzed directly, which will cause impurity metal ions to be mixed into the plating solution. The roll life is shortened because the roll is electrolytically eroded. On the other hand, in the case of removing plated metal adhering to the energizing cable by pressing an abrasive, the removed plated metal mixes into the plating solution and causes scratches. Moreover, it also causes scratches on the surface of the current-carrying roll, shortening the life of the roll. Further, the example shown in Japanese Unexamined Patent Publication No. 1-147089 merely detects the adhesion of plated metal to the current-carrying roll, and is not a means for preventing the adhesion of plated metal itself.

As can be seen from the above description, adhesion of plated metal to the current-carrying roll causes problems once it occurs, so it must be prevented. Under such circumstances, the present invention provides an electroplating method that prevents plating metal from adhering to a current-carrying roll.

(Means for solving the problem) 1 of the present invention! This means that in a continuous electroplating method in which a horizontal plating cell is used in a sulfuric acid-based electroplating bath to electroplate a steel strip, the contact line pressure between the current-carrying roll and the steel strip is set at 20 to 12
0kg/c chain, Fe3+ concentration in plating solution 0.2~
0.6. This is a continuous electroplating method characterized by the following: /l.

(effect) The operation of the present invention will be described below.

Conventionally, in order to prevent the plating metal from depositing on the current-carrying roll and to reduce the contact resistance between the current-carrying roll and the steel strip, the contact line pressure between the current-carrying roll and the steel strip was set as high as possible within the allowable range of equipment specifications. A method has been taken to do so. However, when the contact linear pressure is increased, linear concavities occur along the circumferential direction of the current-carrying roll surface at the ends of the steel strip, and the contact resistance between the current-carrying roll and the steel strip locally decreases in the concave portions. The plated metal will adhere to that part. Therefore, in order to prevent dents, the upper limit of the contact line pressure between the current-carrying roll and the steel strip should be 120
It is necessary to make it kg/c so. On the other hand, if the contact line pressure between the aIE roll and the steel strip is too low, the contact resistance between the energized roll and the steel strip will increase, and the plating metal will be deposited more heavily on the energized roll, so the lower limit of the contact line pressure should be set at 20 kg/e. It is necessary to rub 1.

The contact line pressure between the energized roll and the steel strip described here is based on the pressing force of the back 7 tube roll 4 shown in diagram vJ1! 8!
can do. The contact line pressure between the back-up roll and the steel strip can be expressed by the following equation.

Contact linear pressure (kg/cm) = Backup roll pressing force (
kg) ÷ Steel strip width (cl!1) The above-mentioned effects are facilitated by the flat surface of the electrifying roll, but the surface of the energizing roll is generally affected by contact with a plating solution with a low pH. Electrolytic corrosion progresses and it is difficult to maintain flatness.

Electrolytic corrosion on the surface of the current-carrying roll progresses as the Fe3+ concentration in the plating solution increases, so it is necessary to reduce Fe'711 degrees to 0.6 g/or less. The Fe'+ concentration can be controlled by treating the plating solution with an ion exchange resin to determine if 3g/I@+ is present.On the other hand, if the Fe3'r concentration is low, the Fe'+ concentration can be controlled by treating the plating solution with an ion exchange resin. When replenishing plating metal, the dissolution rate decreases, making it impossible to continue plating continuously, so the Fe'+ concentration must be 0.2 g/I or more.

(Example) Energizing roll body Ni-Cr-Fe alloy plating solution
Zinc sulfate 300g/Soda sulfate 100g/pH 1.4 Temperature 50°C Current density 150A /+Je2 Under conditions of 300g of zinc sulfate/100g of soda sulfate/+Je2, the contact line pressure between the energized roll and the steel strip and the Fe'" concentration in the plating solution were varied to improve the The state of plating metal precipitation on the steel strip and the occurrence of suppression in the steel strip were visually inspected.The results are shown in Table 1.

Table 1 ■: ■: Status of plating metal deposition on energized roll 0: None 62 Partially present Yes (Effects of the Invention) The present invention is an excellent invention that can prevent the deposition of plating metal on the current-carrying roll when performing electroplating, and can manufacture products without suppression.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a general horizontal electroplating device, Figure 2 is a schematic diagram of a horizontal electroplating device equipped with a reverse electrolytic electrode, and Figure 3 is a diagram showing an outline of a horizontal electroplating device equipped with a reverse electrolytic electrode. It is a figure which shows an example. DESCRIPTION OF SYMBOLS 1... Steel strip, 2... Current roll, 3... Plating solution, 4... Backup roll, 5... Anode electrode, 6
... Reverse electrolytic electrode, 7... Abrasive material.

Claims (1)

[Claims] (1) Using a horizontal plating cell in a sulfuric acid-based electroplating bath,
In the continuous electroplating method of electroplating a steel strip, the contact line pressure between the current-carrying roll and the steel strip is set at 20 to 120 kg/cm.
, the Fe^3^+ concentration in the plating solution is 0.2-0.6g.
A continuous electroplating method characterized by: /l.