SU1684651A1 - Method and device for quality control of coatings - Google Patents

Abstract

The invention relates to electrochemical analysis methods and can be used to determine the thickness and composition of electroplating. The purpose of the invention is to provide local analysis, increase its accuracy and express bones in determining the thickness and composition of coatings — achieved by electrochemical polarization of a small portion of the coating in a pressure cell containing an additional electrochemically inert working electrode. Electrochemical dissolution of the coating layer, deposition of electrolysis products on an additional working electrode and dissolution of the newly formed sediment are performed consistently and continuously, simultaneously registering the amount of electricity at different stages, then calculating the composition of the coating in the third stage of the continuous process, and the first stage is its thickness taking into account the correction for the coating density. 2 sec. f-ly, 2 ill. sl C

Description

This invention relates to electrochemical analysis methods and can be used to determine the thickness and composition of electroplated coatings with alloys.

The purpose of the invention is to provide local analysis, increasing its accuracy and expressness in determining the thickness and composition of coatings with alloys.

Fig, 1 shows the presser cell used to implement the method, the cut; 2 shows the polarization characteristic of a continuous electrochemical process recorded during the implementation of the proposed method.

The cell presser (figure 1) consists of a glassy carbon hollow body 1. having a rubber nozzle 2 at the bottom with a calibrated orifice 3. For introducing, withdrawing, mixing the electrolyte in the cell volume and purging the electrolyte with an inert gas, the presser cell has two nozzles 4, 5. Through the holes in the cell body, an auxiliary electrode 6 and an additional working electrochemically inert electrode 7 are introduced into its volume.

The method and apparatus for its implementation were implemented as follows in the quality control of the coating of the metal base with the alloy.

Example. To determine the thickness and composition of the test coating, a pressure cell is installed on it (Figure 1), bounding the surface area

00 4 About SL

the area to be electrochemically dissolving, the area of the contact hole 3 of the rubber nozzle 2. Connect the cell to the circuit diagram of the polenograph or potentiostat. At the same time, the cell case 1 (as a reference electrode), auxiliary electrode 7, a dedicated surface area of the coating 8 (as a working electrode) are included in the potentiation circuit. The cell is filled with electrolyte through the pipe 4 by creating a reduced pressure in the pipe 5.

After that, the three third electrochemical stages of the method with simultaneous registration of the polarization curve (Fig. 2) are sequentially and continuously conducted.

In the first stage, the coating is dissolved, for example, under the conditions of a potentiodynamic dissolution with a polarization rate of 6 mV / s to form a maximum on the polarization curve, which corresponds to the complete dissolution of the coating. At the same time, the parameters of the polarization curve are recorded, for example, the amount of electricity O.Pokr.

Then, the second stage of the process is carried out, for which at the moment of maximum formation on the polarization curve, the potentiostat potentiometer is automatically switched. At the same time, the cell case 1 (as a reference electrode), the additional electrochemically inert electrode 6 and the auxiliary electrode 7 are included in the potentiation circuit. At the same time, a constant voltage is applied to the additional electrode 6 (for a tin-bismuth alloy, the voltage is-1.0 V ), which is maintained for a certain period of time, ensuring the constancy of the amount of electricity passed through the cell He, and, consequently, the contingency released on the additional electrode of the sediment. The deposition of electrolysis products occurs with stirring and deaeration of the solution with an inert gas.

In the third stage of the process, the newly formed sediment is dissolved in a linear sweep of the voltage from the value corresponding to the voltage of the second stage. In this case, separate maxima of the anodic current of the coating components are recorded on the polarization curve. At the same time, the quantity of O. electricity is recorded. According to the ratio of the polarization curve parameters, the composition of the coating is calculated in the third stage of the process, taking into account

100

1 + K

About ME 2 Q ME 1

where Q ME 1 - the percentage of the first component in the coating-alloy;

K is an empirical constant, which is found using a standard solution of this alloy.

The application of the method allows to reduce the time to determine the quality of the coating by combining the control operations of measuring the thickness and composition by at least two times; to increase the accuracy of determining the thickness of coatings on alloys by introducing an amendment to the alloy composition by.

Claims (2)

1. A method for determining the quality of coatings with alloys, including galvanic deposition of the metal of the coating from the electrolyte, followed by electrosolution of the deposited metal to determine the thickness of the coating by the coulometric method, characterized in that, in order to ensure locality of the analysis, increase its accuracy and expressivity, local dissolution of the analyzed coatings followed by deposition of the dissolved metal coatings on an electrochemically inert electrode, at each stage of electrochemistry Skog process measured elapsed electrical quantity, wherein the quantity of electricity expended in the dissolution of the coating, the coating thickness was determined, and the quantity of electricity expended in dissolution of the precipitated metal coating, the coating composition is determined. 2. A device for determining the quality of coatings containing an electrochemical cell with an auxiliary platinum electrode, a reference electrode made in the form of a glass-carbon cell body, an elastic gasket limiting the holes in the cell body, which serve to contact the electrolyte with the analyzed surface, which is the working electrode, and two branch pipes for inlet and outlet of inert gas mixing the electrolyte, characterized in that it additionally contains an inert glassy carbon electrode. figl 10n, Ail Stadion SupersiN 1nA fae. 2