SU787494A1 - Method of measuring current density distribution over long-sized article surface - Google Patents

Description

(54) METHOD FOR DETERMINING THE CURRENT DENSITY DISTRIBUTION ON A SURFACE OF A LONG-DIMENSIONAL PRODUCT

I

The invention relates to the electrochemical treatment of metals and can be used to study the distribution of current density on a long product in an electrolytic cell.

The current density affects the surface quality during electrochemical processing (etching, polishing, coating deposition).

The more evenly current is distributed over the treated surface, the more uniform the metal removal (during electrochemical polishing and etching) and the more uniform the thickness of the deposited metal during electrodeposition of coatings.

The known method allows the determination of the average value of the current density on the whole treated surface 1.

However, it is only possible to control the electrochemical processes by determining the current density at each elementary segment of a long product.

A known method for determining the current density distribution on the surface of a long article is by immersing a cell in an electrolytic bath, applying a voltage to the electrodes and registering an electrical parameter in the circuit of article 2.

In the determination, an error occurs associated with the use of a contact method for measuring the potential by means of a platinum electrode, in contact with the product through an electrolyte.

The purpose of the invention is to improve the accuracy of determining the current density in the elementary area of a long product and to improve the method of determining

10 as a result of the elimination of the contact measurement of the potential difference between the current lead and the platinum sliding contact.

This goal is achieved by measuring the current strength with a device 5 connected directly to the circuit of the workpiece in place of its rupture when the product moves through the electrolytic cell.

FIG. 1 and 2 shows a diagram of the proposed device; in fig. 3 - electrical circuit of the device.

A lengthy object can be such products as wire, microlenta, ivy.

The device comprises a sensor 1, an electrolytic bath 2 with electrodes 3 and a gap 4, a partition 5, plates 6, a rewinding mechanism 7.

The product (Fig. 1) is filled into the bath with electrodes 3 through the slots 4, corresponding to the product profile, the sensor 1 is connected to the rupture of the product. The product length is counted from the partition 5 separating the anode and cathode zones.

The fixing of the product in the sensor 1 (Fig. 2) is carried out with the help of elastic pressure plates 6, which are made as a sensor from an insulating material and prevent the electrolyte from flowing inside the sensor. The ends of the product are connected to the terminals of the ammeter with lead wires. The sensor is immersed in the electrolyte at half the height.

The product is pulled through the bath by means of a rewinding mechanism 7, and at the same time the sensor moves along the entire bath and the stationary ammeter measures the current flowing through the product in each elementary section of length 3. The current is supplied bipolarly by means of electrodes 3 (Fig 1 and 3) (anode and cathode).

FIG. 3, the direction of current movement is indicated by arrows, using the following notation:

NEP is the resistance of the electrode column;

RHJA is the resistance of the product area;

In is the current value in the partition; Bc ,, Ij, U is the current flowing in the product at the elementary part of its length; dGh, D1x, A1x-current, going to flow

electrochemical reactions. There is no need for grounding the ends of the product, since outside the bath the current is zero.

The presence of the sensor does not distort the electric field between the two electrodes, one of which is the product with a bipolar current supply. This is due to the fact that the sensor is moved parallel to the power lines of the field, which are perpendicular to the surface of the electrodes.

The measurement error is determined only with the accuracy of the measuring instrument-ammeter and is 0.5%. The resistance of the lead wires is 0.004 ohm-cm, which is practically zero.

The use of the proposed method for determining the current density in the elementary area of a lengthy product allows; to improve the accuracy of determining the current density at the elementary part of the product, since the current is measured by the device connected directly to the chain of a long product; to improve the method of determination as a result of the elimination of the contact measurement operation of the potential difference between the current lead and the sliding

platinum contact.

The proposed method can be used when studying in laboratory conditions the distribution of current density on long items. Knowledge of the nature of the current density distribution along the length allows one to determine the optimum shape of the electrodes for the industrial baths by electrochemical treatment in order to ensure a uniform current density distribution along the length of the long product to improve the quality of the treatment.

Claims (2)

1. Yampolsky Ya. M., Ilina V. A. Short reference book electroplating. L., 1972. 2. USSR author's certificate number 467950, cl. C 25 D 21/12, 1973. IG