JPS6064242A - Corrosion judging device - Google Patents

Abstract

PURPOSE:To measure the transfer function of a corrosion reaction circuit network over a broad frequency range, by imparting electric charge to a sample in a corrosive liquid, measuring the polarized potential and current, performing the frequency analysis of the output, and obtaining the phase difference. CONSTITUTION:A sample metal piece 1, a reference electrode 2, and a counter electrode 4 are immersed in a corrosive liquid 4. Electric charge is imparted to the sample metal piece 1 from a charge imparting part 5 through the counter electrode 3. The current, which flows from the charge imparting part 5 to the metal piece 1, is detected by a current detecting part 7 and converted into a potential signal. The potential response of the metal piece is detected by a potential detecting part 6. Fourier transform of these signals is performed in a high speed Fourier transform part 8, the impedance at each frequency and the phase difference of the current and the potential are computed, and a transfer function is outputted.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a corrosion determination device, and more specifically, the present invention relates to a corrosion determination device, and more specifically, a current waveform and fast Fourier transform when a sample metal piece is subjected to active electrodeposition and an electric charge is applied to this electrode. The present invention relates to a corrosion determination device that determines corrosion by calculating the transfer function of this electrode from the response potential waveform of this electrode that has been subjected to.

[Technical background of the invention and its problems]

Examining the surface of metals where corrosion is progressing is necessary to know the nature and rate of corrosion. For this purpose, we replaced the conventional corrosion reaction system with an electrical equivalent circuit.
Efforts have been made to examine the transfer function of the circuit network.

To find the transfer function of the corrosion reaction system network.

It is necessary to apply electrical stimulation at a certain frequency to the corrosion reaction system and observe the response to this stimulation while sequentially changing the stimulation frequency. For this reason, it takes a great deal of time and effort to accurately determine the corrosion reaction system transfer function over a wide frequency range.

Therefore, in order to reduce the labor required to carry out this work, a fully automatic measuring device was devised, and although it is commercially available, it takes about 1 hour to measure one corrosion reaction system transfer function. The disadvantage is that it takes time to prepare.

Therefore, the measurement time has been shortened by determining only the term related to the corrosion rate of the corrosion reaction system network transfer function compared to the conventional measurement at a specific frequency of 2 or 3, which has been put into practical use. This has the disadvantage that it is not possible to determine the cause when an abnormal corrosion rate is observed.

As mentioned above, according to the conventional measurement method, obtaining a transfer function of the corrosion reaction yarn over a wide frequency range and shortening the number of points during measurement are contradictory conditions.

Therefore, it has been desired to develop a measuring device that can obtain a transfer function over a wide frequency range in a short time.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a corrosion determination device capable of determining the transfer function of a corrosion reaction circuit network over a wide frequency range in a short period of time.

[Summary of the Invention] The present invention provides a charged cloth part that applies an electric charge to a sample metal piece immersed in a corrosive liquid, and a potential detection part that detects a temporal change in the polarization potential of the sample metal piece in an open circuit state. Then, the 'i1f flow detection section detects the current flowing from the charge applying section to the sample metal piece and converts it into a voltage signal, and the outputs of the potential detection section and the current detection section are frequency-analyzed to determine the transfer function of the sample metal piece. A voltage pulse generator that is continuous at least at a part other than the rising part, or a current pulse generator that is continuous at a part other than the rising part, as a voltage applying part for a corrosion determination apparatus equipped with a high-speed 7-RIE conversion part. It is characterized by the use of a container.

In other words, in the present invention, the response of a circuit network to a stimulus signal containing volatile frequency components is measured once, and then the stimulus signal and response are separated into various frequencies by a total 7-lier transform, and each frequency is By calculating the impedance and the phase difference between the current and the potential, it becomes possible to obtain the same result in a single measurement as in multiple conventional measurements.

In general, a complex function F(
ω) includes frequency ω as its variable F(ω)=J”
f(t)(cos ωt-j sin ωt)dt-
(1) It becomes a function in the frequency domain, and its absolute value IF(ω)
1 is called the amplitude term and the father, and Arr (F(ω)) is called the phase shift term. Therefore, for the current and potential responses when a stimulus is applied to an arbitrary circuit network, the expression n of equation (1) is
By sequentially changing kω, the amplitude term and phase shift term of the current and potential at each frequency are calculated, and then the impedance is calculated from the ratio of the amplitude terms of the current and the potential, and the phase is calculated from the difference between the phase shift terms. The phase difference can be calculated, and as a result, a transfer function can be obtained.

An example of the equipment configuration for performing this work on a corrosion reaction system is shown in the first example.
As shown in the figure. A sample metal piece 1 is an object to be measured whose corrosion is to be detected, and four electrical connections are made using a reference electrode 2, a counter electrode 3, and a corrosive liquid 4. A charge is applied to this sample metal piece from the charge applying section 5 through the counter electrode. At this time, the current flowing from the charge applying section 5 to the sample metal piece 1 is detected by the current detecting section 7 and converted into a potential signal. Also, trial 3:) Metal piece 109's 6th response (d is used more sparingly by the potential detection unit 61).

A continuous voltage pulse is applied from the charge applying unit 5 to the sample metal piece 1 except for at least the rising portion, and the potential response is measured. The fast Fourier transform section 8 performs Fourier transform on these signals, calculates the impedance and phase difference of the sample metal piece 1 at various frequencies, and transmits them.
Output as iA number.

[Embodiments of the invention]

Embodiment 1 In order to output a current pulse having a discontinuous point only in the rising part as shown in FIG.
Hit Haina') -O force') 7ter 9, H &)
M.I.O.

An example of a circuit configuration using a 0-bit D/A converter 11 and a voltage-current converter 12 is shown. In this configuration, when switch 14 is pressed, control circuit 13 operates and 12-bit binary counter 9 starts counting. RjlJM 10 outputs 10-bit digital output according to the output of 12-pin binary counter 9.
0 pits) Send the voltage E to the D/A converter 11 E=exp(-x)-exp(-X/2)-=(2) Shown by formula (2) let In equation (2), x is the output value of [)MIQ. The voltage-current converter 12 converts the output of the D/A converter 11 into a current value as shown by equation (2) and applies it to the sample metal piece l.

This circuit configuration is equivalent to the equivalent circuit shown in Figure 3 (9.4μ
The results of measuring F=9.65Ω) are shown in FIG. 4 as a Nyquist diagram. The semicircle indicated by the broken line in the figure is the calculated value calculated from the equivalent circuit in FIG. The time required to perform this measurement was 6 seconds from the start of the measurement to the end of the Fourier transformation. Furthermore, when the same measurement as this measurement was performed using a conventional Solartron 125o model, it required about 1 hour.

Embodiment 2 FIG. 5 shows an example of a circuit configuration using a voltage pulse generator that uses a part of a sine wave and has no discontinuous points as the charge applying section 5. As shown in Fig. 6, the voltage pulse has a minimum value of 0 (V) and a maximum value of E [
:V:], and is a pulse with no discontinuity.

Figure 7 shows the results of measurements made on a three-coat coated steel for automobiles using this circuit configuration. 341 measured by this method
Ω and 0.25 NF and 710 Ω and 2.0 μF are appropriate values when considering the values of the coating film and corrosion under the coating, respectively, and the present invention is applicable to actual corrosion systems. I understand.

〔Effect of the invention〕

According to the present invention, it has become possible to quickly and easily measure the transfer function of a corrosion reaction system over a wide frequency range, and it has become possible to easily carry out corrosion monitoring by measuring the transfer function in an industrial setting.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a circuit configuration showing the basic configuration of the present invention, FIG. 2 is a diagram showing an example of the circuit configuration of the device of the present invention, and FIG. 3 is a diagram showing an equivalent circuit as a measurement target in Example 1. , FIG. 4 is a Nyquist diagram obtained in Example 1, and FIG. 5 is a diagram showing the circuit configuration of the device of the present invention. FIG. 6 is a diagram showing a voltage pulse used as a charge imparting pulse in Example 2, and FIG. 7 is a Nyquist diagram obtained in Example 2. 1... Sample metal piece, 2... Reference electrode, 3. Counter electrode, 4
- Corrosive liquid, 5 charge imparting section, 6... potential detection section. 7. Current detection section, 8. Fast Fourier transform device. 9...12-bit binary counter, 10...
・・ROM, 11-10 bit D/A converter, 12
Voltage-current converter, 13. Control circuit, 14. Switch, 15. Buffer amplifier for current amplification.

Claims (1)

[Claims] A charge applying part applies an electric charge to a sample metal piece immersed in a corrosive liquid, a potential detection part detects a time change in the polarization potential of this sample metal piece in an open circuit state, and a charge applying part applies an electric charge to a sample metal piece. The present invention is equipped with a current detection section that detects the current flowing through the sample tube and converts it into a voltage signal, and a fast Fourier transform section that performs frequency analysis on the outputs of the potential detection section and the current detection section and calculates the transfer function of the sample tube piece. A corrosion determining device characterized in that a voltage or current pulse generator that is continuous at least at a portion other than a rising edge portion thereof is used as a charge applying portion.