SU1242546A1 - Method of measuring cathode area in electroplating bath - Google Patents

Description

The invention relates to electrical equipment and can be used to measure the area of parts made of electrically conductive materials.

The aim of the invention is to provide a measurement of the effective area of the cathode in the drum and bell type baths and to increase the measurement accuracy between the anode and the cathode.

FIG. 1 shows a block diagram of the device implementing the proposed method in FIG. 2, an electrolytic bath replacement circuit for high frequency currents (a) and a time diagram of the voltage on the additional bath electrode (P),

A device that implements the proposed method (FIG. 1) contains a galvanic bath 1, anode 2 immersed in an electrolyte, a cathode 3, an additional electrode 4, a generator 5 of different rectangular current pulses of stable amplitude and frequency, a measuring unit 6 and a computational device 7,

In FIG. 2 Ace E, K, respectively, an anode, an additional electrode, a cathode; IP is the current through the bath, Cd, C is the capacitance of the electrical double layer anode-electrolyte and cathode-electrolyte, respectively; R. R. is the resistance of the electrolyte layer between the anode and additional electrode and between the cathode and additional electrodeJ and is the voltage between the cathode and additional electrode j and ,, and - voltage at the time of the front and rear current fronts through the bath.

The method is carried out as follows.

With the aid of generator 5., a current is passed through the electrolyte between the anode 2 and the cathode 3, which is a continuous sequence of different polarity pulses of stable amplitude and frequency, and the frequency of this pulse sequence is chosen not lower than a few hundred hertz. This current causes the anode-cathode voltage drop in the gap. A part of this voltage is removed with the help of an additional electrode 4 and is fed to the measuring unit 6. According to the bath replacement circuit (FIG.), The voltage between the cathode and the additional electric

by the electrode during each half-wave of current through the bath is (fig, 2.5)

U (t) I, R, + I, -,

where t is the current time, starting with

the moment of the current pulse,

At the moment of the leading edge of the current pulse U,, and at the moment of the trailing edge

(t |),, R, + IO | s; .

where T is the period of the pulse current through the electrolyte,

In measuring unit 6, the signal from generator 5 measures the voltage between the cathode 3 and, an additional electrode 6 at the moments of the leading and trailing edges of the current pulse through the bath, and the difference between these values,

The differential voltage is inversely proportional to the cathode-electrolyte capacitance and, consequently, the cathode area.

i.-i, 1, 2c;

from the output of the measuring unit 6, the differential voltage is fed to the input of the computing unit 7, by means of which the value opposite to the input voltage difference is determined. The output of the unit 7 is a value proportional to the measured area of the parts.

The frequency of the current pulses through the bath is chosen so high that there are no electrochemical reactions on the electrodes. For most of the known and practical electrolytes

it is 500-800 Hz. In general, the frequency at which electrochemical reactions cease depends on the composition of the electrolyte and the mobility of the ions. From the top side, the pulse frequency

The constraints are limited by the presence of parasitic capacitances and equipment inductances and the resolution of the measuring apparatus. The highest frequency can be 10-15 kHz.

The amplitude, or more precisely the magnitude of the current pulses, is chosen so that the current density on the surface

electrodes (anode and cathode) did not exceed the amount of fyu for this electrolyte. The current density is in the range of 0.5-1 A / dm. Therefore, the current through the bath must be (0.5-1) -S, where S is the area smaller of the electrodes (anode or cathode).

The proposed method, in contrast to the known methods, makes it possible to increase the accuracy of measuring the cathode surface by eliminating the error associated with the occurrence of electrochemical reactions at the electrodes. This is achieved by the fact that

By cutting the nponycKajraT bath, the impulse current is of such a frequency that the electrochemical reactions at the electrodes are stopped.

The use of a pulsed current of stable magnitude makes it possible to obtain a voltage increment on the additional electrode that is inversely proportional to the measured cathode surface and is independent of the resistance of the electrolyte. This makes it possible to determine the magnitude of the surface of the parts, not only on the suspensions, but also inside the drums or bells.

but

FIG. 2

Claims (1)

METHOD FOR MEASURING THE CATHODE AREA IN A GALVANIC BATH, which includes installing parts together with an auxiliary electrode, characterized in that, in order to measure the effective area of the cathode in the drum and bell baths and to increase the measurement accuracy between the anode and cathode, a rectangular pulse current is passed forms of stable amplitude with a frequency of 500-800 Hz, measure the voltage between the cathode and the auxiliary electrode at the time of the leading and trailing edges of the current pulse through the galv nical bath, find the difference between these values and the cathode area is calculated as a value inversely proportional to the voltage difference. figure 1