CORROSION RATE MEASUREMENT EQUIPMENT ACCORDING TO ATMOSPHERIC ENVIRONMENT AND SHIP WITH THE SAME

In corrosion rate measurement equipment according to an atmospheric environment according to the present invention, the length of a conductive pattern for temperature correction of a corrosion sensor is greater than the length of a conductive pattern for corrosion measurement, and the surface area of the conductive pattern for temperature correction of a corrosion sensor is less than the surface area of the conductive pattern for corrosion measurement so that a measured error of reference resistance measured values measured in the conductive pattern for temperature correction is minimized and thus the measured values measured in the conductive pattern for corrosion measurement can be more accurately corrected by using the reference resistance measured value and thus, corrosion rate can be more accurately measured.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2022-0108680, filed on Aug. 29, 2022, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

The present invention relates to corrosion rate measurement equipment according to an atmospheric environment and a ship with the same, and more particularly, to corrosion rate measurement equipment according to an atmospheric environment in which a measured error according to ambient temperature change is minimized so that reliability can be improved and monitoring can be remotely performed, and a ship with the same.

BACKGROUND ART

In general, since facilities are exposed to the risk of corrosion due to an ambient environment, the development of corrosion rate models for preventing damage due to corrosion has been briskly studied.

In the related art, a corrosion damage prediction model has been derived through a stochastic statistical method based on inspection data. However, when a corrosion state is directly measured, inspection costs are high and pieces of reference data are not sufficient.

In order to solve this problem, recently, a method of manually measuring corrosion rate by using an electrical resistance sensor made of metal has been used. However, a resistance value continues to change due to thermal expansion or thermal contraction of metal due to temperature change in the atmosphere. Thus, errors occur according to the temperature change of the atmosphere, not corrosion.

DISCLOSURE OF THE INVENTION

The present invention provides corrosion rate measurement equipment according to an atmospheric environment in which a measured error according to ambient temperature change is minimized so that reliability can be further improved, and a ship with the same.

According to an aspect of the present invention, there is provided corrosion rate measurement equipment according to an atmospheric environment, the corrosion rate measurement equipment including: a corrosion sensor comprising a substrate, a conductive pattern for corrosion measurement provided to be exposed to an ambient environment on the substrate and formed so that a thickness of the conductive pattern for corrosion measurement changes according to an ambient temperature and corrosion, and a conductive pattern for temperature correction of which surface is covered by a protective layer so that the conductive pattern for temperature correction is not exposed to the ambient environment on the substrate and of which thickness changes according to the ambient temperature; a power supply unit configured to supply power to the corrosion sensor; and a data processing unit configured to collect a corrosion resistance measured value of the conductive pattern for corrosion measurement and a reference resistance measured value of the conductive pattern for temperature correction, respectively, from an initial measurement point at each measurement point at set time intervals when power is supplied to the corrosion sensor, to calculate a temperature correction value according to the reference resistance measured value of the conductive pattern for temperature correction, to correct a measured value in the conductive pattern for corrosion measurement as the temperature correction value and then to derive a resistance change rate measured in the conductive pattern for corrosion measurement and to calculate corrosion rate according to the resistance change rate, wherein the conductive pattern for temperature correction may have a greater length than a length of the conductive pattern for corrosion measurement and a less surface area than a surface area of the conductive pattern for corrosion measurement so that the reference resistance measured value of the conductive pattern for temperature correction is set to be greater than the corrosion resistance measured value of the conductive pattern for corrosion measurement so as to reduce a relative measured error of the conductive pattern for temperature correction.

The conductive pattern for temperature correction and the conductive pattern for corrosion measurement may have same thicknesses.

The conductive pattern for temperature correction and the conductive pattern for corrosion measurement may be formed in a long band shape that is bent more than at least once, and a width of each of the conductive pattern for temperature correction and the conductive pattern for corrosion measurement may be formed uniformly in a longitudinal direction.

A width of the conductive pattern for temperature correction may be less thana width of the conductive pattern for corrosion measurement.

The data processing unit may be configured to calculate the temperature correction value at each measurement point and to correct a corrosion resistance initial value measured in the conductive pattern for corrosion measurement at the initial measurement point by using the temperature correction value, and the resistance change rate may be calculated from the corrosion resistance initial value corrected as a temperature correction value calculated at a corresponding measurement point and a corrosion resistance measurement value measured at the corresponding measurement point.

The corrosion rate measurement equipment may further include a satellite communication unit configured to transmit the corrosion rate calculated by the data processing unit to a monitoring terminal that is preset through satellite communications.

The corrosion rate measurement equipment may further include a wireless communication unit configured to transmit the corrosion rate calculated by the data processing unit to a monitoring terminal that is preset through wireless communications.

The corrosion rate measurement equipment may further include a solar panel configured to collect solar energy, wherein the power supply unit may be configured to convert the solar energy collected by the solar panel into electrical energy, to perform charging and to supply power to the corrosion sensor.

The power supply unit may be configured to supply power to the corrosion sensor for a preset time.

The corrosion rate measurement equipment may further include: a case in which the data processing unit and the power supply unit are provided, and outside which the corrosion sensor is mounted; a temperature sensor installed outside the case and configured to measure temperature; and a humidity sensor installed outside the case and configured to measure humidity.

According to another aspect of the present invention, there is provided corrosion rate measurement equipment according to an atmospheric environment, the corrosion rate measurement equipment including: a case configured to be waterproof; a corrosion sensor mounted outside the case and including a substrate, a conductive pattern for corrosion measurement provided to be exposed to an ambient environment on the substrate and formed so that a thickness of the conductive pattern for corrosion measurement changes according to an ambient temperature and corrosion, and a conductive pattern for temperature correction of which surface is covered by a protective layer so that the conductive pattern for temperature correction is not exposed to the ambient environment on the substrate and of which thickness changes according to the ambient temperature; a solar panel mounted outside the case and configured to collect solar energy; a power supply unit provided inside the case and configured to convert solar energy collected by the solar panel into electrical energy, to perform charging and to supply power to the corrosion sensor; a data processing unit provided inside the case and configured to collect a corrosion resistance measured value of the conductive pattern for corrosion measurement and a reference resistance measured value of the conductive pattern for temperature correction, respectively, from an initial measurement point at each measurement point at set time intervals when power is supplied to the corrosion sensor, to calculate a temperature correction value according to the reference resistance measured value of the conductive pattern for temperature correction, to correct a measured value in the conductive pattern for corrosion measurement as the temperature correction value and then to derive a resistance change rate measured in the conductive pattern for corrosion measurement and to calculate corrosion rate according to the resistance change rate; and a satellite communication unit provided outside the case and configured to transmit corrosion rate calculated by the data processing unit to a monitoring terminal that is preset through satellite communications, wherein the conductive pattern for temperature correction may have a greater length than a length of the conductive pattern for corrosion measurement and a less surface area than a surface area of the conductive pattern for corrosion measurement so that the reference resistance measured value of the conductive pattern for temperature correction is set to be greater than the corrosion resistance measured value of the conductive pattern for corrosion measurement so as to reduce a relative measured error of the conductive pattern for temperature correction.

According to another aspect of the present invention, there is provided a ship with corrosion rate measurement equipment according to an atmospheric environment, wherein the corrosion rate measurement equipment may include: a corrosion sensor including a substrate, a conductive pattern for corrosion measurement provided to be exposed to an ambient environment on the substrate and formed so that a thickness of the conductive pattern for corrosion measurement changes according to an ambient temperature and corrosion, and a conductive pattern for temperature correction of which surface is covered by a protective layer so that the conductive pattern for temperature correction is not exposed to the ambient environment on the substrate and of which thickness changes according to the ambient temperature; a power supply unit configured to supply power to the corrosion sensor; and a data processing unit configured to collect a corrosion resistance measured value of the conductive pattern for corrosion measurement and a reference resistance measured value of the conductive pattern for temperature correction, respectively, from an initial measurement point at each measurement point at set time intervals when power is supplied to the corrosion sensor, to calculate a temperature correction value according to the reference resistance measured value of the conductive pattern for temperature correction, to correct a measured value in the conductive pattern for corrosion measurement as the temperature correction value and then to derive a resistance change rate measured in the conductive pattern for corrosion measurement and to calculate corrosion rate according to the resistance change rate, and the conductive pattern for temperature correction has a greater length than a length of the conductive pattern for corrosion measurement and a less surface area than a surface area of the conductive pattern for corrosion measurement so that the reference resistance measured value of the conductive pattern for temperature correction is set to be greater than the corrosion resistance measured value of the conductive pattern for corrosion measurement so as to reduce a relative measured error of the conductive pattern for temperature correction.

The conductive pattern for temperature correction and the conductive pattern for corrosion measurement may have same thicknesses.

The conductive pattern for temperature correction and the conductive pattern for corrosion measurement may be formed in a long band shape that is bent more than at least once, and a width of each of the conductive pattern for temperature correction and the conductive pattern for corrosion measurement may be formed uniformly in a longitudinal direction.

A width of the conductive pattern for temperature correction may be less than a width of the conductive pattern for corrosion measurement.

The data processing unit may be configured to calculate the temperature correction value at each measurement point and to correct a corrosion resistance initial value measured in the conductive pattern for corrosion measurement at the initial measurement point by using the temperature correction value, and the resistance change rate may be calculated from the corrosion resistance initial value corrected as a temperature correction value calculated at a corresponding measurement point and a corrosion resistance measurement value measured at the corresponding measurement point.

The ship may further include a satellite communication unit configured to transmit the corrosion rate calculated by the data processing unit to a monitoring terminal that is preset through satellite communications.

The ship may further include a wireless communication unit configured to transmit the corrosion rate calculated by the data processing unit to a monitoring terminal that is preset through wireless communications.

The ship may further include a solar panel configured to collect solar energy, wherein the power supply unit may be configured to convert the solar energy collected by the solar panel into electrical energy, to perform charging and to supply power to the corrosion sensor.

The ship may further include: a case in which the data processing unit and the power supply unit are provided, and outside which the corrosion sensor is mounted; a temperature sensor installed outside the case and configured to measure temperature; and a humidity sensor installed outside the case and configured to measure humidity.

Effects of the Invention

In corrosion rate measurement equipment according to an atmospheric environment according to the present invention, the length of a conductive pattern for temperature correction of a corrosion sensor is greater than the length of a conductive pattern for corrosion measurement, and the surface area of the conductive pattern for temperature correction of a corrosion sensor is less than the surface area of the conductive pattern for corrosion measurement so that a measured error of reference resistance measured values measured in the conductive pattern for temperature correction is minimized and thus the measured values measured in the conductive pattern for corrosion measurement can be more accurately corrected by using the reference resistance measured value and thus, corrosion rate can be more accurately measured.

In addition, even when the corrosion rate measurement equipment is installed in a ship operating overseas or at sea, transmission and reception of data can be performed by using satellite communication so that remote monitoring can be performed without restrictions in the use environment or installation location.

In addition, the corrosion rate measurement equipment is configured to use a solar panel so that there is an advantage of continuously measuring the corrosion rate and transmitting data without supplying an external commercial power source.

DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.

FIG.1is a diagram schematically illustrating the configuration of corrosion rate measurement equipment according to an atmospheric environment, according to an embodiment of the present invention, andFIG.2is a control block diagram of corrosion rate measurement equipment according to an atmospheric environment, according to an embodiment of the present invention.

Referring toFIGS.1and2, corrosion rate measurement equipment according to an atmospheric environment, according to an embodiment of the present invention may be used to measure corrosion rate according to the atmospheric environment during domestic and foreign construction works, or to monitor corrosion rate according to the atmospheric environment during sea transportation of various equipment. Also, the corrosion rate measurement equipment may be installed on equipment or structures on land, or may also be installed underwater or on a ship.

The corrosion rate measurement equipment includes a case10, a corrosion sensor20, a power supply unit30, a data processing unit40, a communication unit50, a temperature sensor60, a humidity sensor70, a solar panel80, and a monitoring terminal90.

The case10constitutes the exterior and is formed to have a waterproof function to be installed on a ship or underwater or to be mounted on marine transportation facilities.

The power supply unit30, the data processing unit40, and the communication unit50and the like are provided inside the case10. The corrosion sensor20, the temperature sensor60, and the humidity sensor70are mounted outside the case10.

FIG.3is a plan view illustrating a conductive pattern for temperature correction and a conductive pattern for corrosion measurement of a corrosion sensor according to an embodiment of the present invention.

Referring toFIG.3, the corrosion sensor20includes a substrate20a, a conductive pattern21for corrosion measurement, and a conductive pattern22for temperature correction. Here, the case where the corrosion sensor20is a corrosion probe, will be described.

The substrate20ais formed in the form of a flat insulator. A thin film made of metal is deposited on the substrate20ato a predetermined thickness by using a vacuum deposition method or the like so that the conductive pattern21for corrosion measurement and the conductive pattern22for temperature correction can be formed. However, embodiments of the present invention are not limited thereto, and other substrates, such as using a thin plate, are also applicable.

The conductive pattern21for corrosion measurement is a conductive pattern, that is an electrode, which is formed on the substrate20a, is exposed to an ambient environment and is formed so that the thickness of the conductive pattern21for corrosion measurement changes according to not only the ambient temperature but also corrosion by the atmospheric environment.

The conductive pattern21for corrosion measurement is formed in a long band shape that is bent more than once and has a first width W1, a first length L1, and a first surface area A1, which are preset. The cross-section of the conductive pattern21for corrosion measurement is formed in a rectangle shape, for example. However, embodiments of the present invention are not limited thereto, and the cross-section of the conductive pattern21for corrosion measurement may be modified in various shapes. The first width W1and the thickness of the conductive pattern21for corrosion measurement are formed uniformly in a longitudinal direction. Also, the first width W1of the conductive pattern21for corrosion measurement is greater than a second width W2of the conductive patter22for temperature correction to be described below.

Two first resistance measurement terminals21aand one first power supply terminal21bare provided at an end of the conductive pattern21for corrosion measurement.

The conductive pattern22for temperature correction is a reference sensor for measuring a reference value for correcting the effect of ambient temperature with respect to a resistance value measured in the conductive pattern21for corrosion measurement. Thus, the surface of the conductive pattern22for temperature correction is covered by a protective layer20bnot to be exposed to the ambient environment, that is, corrosion. The protective layer20bis a layer formed by applying an insulating paint or the like onto the surface of the conductive pattern22for temperature correction.

The conductive pattern22for temperature correction is a conductive pattern, that is, an electrode which is formed on the substrate20ato be connected to the conductive pattern21for corrosion measurement so that the thickness of the conductive pattern22for temperature correction changes according to the ambient temperature.

Two second resistance measurement terminals22aand one second power supply terminal22bare provided at an end of the conductive pattern22for temperature correction.

The conductive pattern22for temperature correction is formed in a long band shape that is bent more than once, and has a greater length than the length of the conductive pattern21for corrosion measurement and has a less surface area than the surface area of the conductive pattern21for corrosion measurement. That is, the conductive pattern22for temperature correction is formed to have the second width W2that is set to be less than the first width W, to have a second length L2that is set to be greater than the first length L1and to have a second surface area A2that is set to be greater than the first surface area A1. The thickness and the second width W2of the conductive pattern22for temperature correction are formed uniformly in the longitudinal direction. The cross-section of the conductive pattern for temperature correction is formed in a rectangle shape, for example. However, embodiments of the present invention are not limited thereto, and the cross-section of the conductive pattern22for temperature correction may be modified in various shapes.

The relationship between a resistance value R measured by the corrosion sensor20, the length of a conductive pattern, and the surface area of the conductive pattern is given by the equation 1.

where μ is a coefficient, L is the length of the conductive pattern, and A is the surface area of the conductive pattern.

In the present invention, the conductive pattern22for temperature correction has a greater length L than the length of the conductive pattern21for corrosion measurement and a less surface area A than the surface area of the conductive pattern21for corrosion measurement, so that a reference resistance measured value R2measured in the conductive pattern22for temperature correction is set to be relatively greater than a corrosion resistance measured value R1measured in the conductive pattern21for corrosion measurement. As the reference resistance measured value R2measured in the conductive pattern22for temperature correction increases, a relative measured error of the reference resistance measured value R2decreases, so that temperature correction of the corrosion resistance measured value R1of the conductive pattern21for corrosion measurement can be more accurately performed. Here, the relative measured error is also referred to as a relative error and means a value obtained by dividing a difference between a true value and a measured value by the true value.

The following Table 1 shows comparison of the relative measured error according to the size of the reference resistance measured value R2of the conductive pattern22for temperature correction.

Referring to Table 1, when a reference resistance initial value R2iof the conductive pattern22for temperature correction increases three times from 0.015 to 0.045, the relative measured error decreases about 66% from 0.033 to 0.011. Here, a case where measurement resolution is 0.001Ω, will be described, and thus, the reference resistance measured value R2is a value rounded to 4 decimal places from a true value R2T.

As described above, as the reference resistance initial value R2iof the conductive pattern22for temperature correction increases, the relative measured error decreases.

Thus, the conductive pattern22for temperature correction is set to have a greater length L than the length of the conductive pattern21for corrosion measurement and to have a less surface area A than the surface area of the conductive pattern21for corrosion measurement so that the relative measurement of the reference resistance measured value R2measured in the conductive pattern for temperature correction can be minimized. When the relative measured error of the reference resistance measured value R2is minimized, the accuracy of a corrosion resistance initial value R1ito be described below and to be corrected by using the reference resistance measured value R2can be improved.

The power supply unit30is a power supply unit for supplying power to the corrosion sensor20. The power supply unit30is connected to the solar panel80for collecting solar energy, includes a battery for converting solar energy collected by the solar panel80into electrical energy and charging, and supplies power to the corrosion sensor20from the battery. The power supply unit30may supply power to the corrosion sensor20at preset time intervals and may also supply power continuously to the corrosion sensor20for a preset time.

The data processing unit40may include a data logger (not shown) that supplies power from the power supply unit30and collects a resistance value of the corrosion sensor20, and a data calculation unit (not shown) that calculates a temperature correction value, a corrosion resistance correction value and corrosion rate to be described below according to the measured resistance value. Both the data logger (not shown) and the data calculation unit (not shown) may be provided inside the case10, and only the data logger (not shown) may be provided inside the case10, and the data calculation unit (not shown) may be provided in a preset server (not shown) communicatively connected to the data logger (not shown).

The data processing unit40calculates a temperature correction value according to the reference resistance measured value R2measured in the conductive pattern22for temperature correction and corrects the corrosion resistance initial value R1imeasured in the conductive pattern21for corrosion measurement by using the temperature correction value to calculate a resistance change rate according to corrosion from the corrosion resistance initial value R1i. Also, the data processing unit40calculates corrosion rate by using the corrosion resistance initial value R1i. An algorithm for calculating the temperature correction value and calculating corrosion rate from the corrected corrosion resistance initial value R1iis previously built in the data processing unit40.

The communication unit50includes at least one of a satellite communication unit that transmits corrosion rate calculated by the data processing unit40to the monitoring terminal90that is preset through satellite communications using a satellite antenna51, and a wireless communication unit that transmits the corrosion rate to the monitoring terminal90through wireless communications.

The temperature sensor60is installed outside the case10and measures the temperature of the ambient environment. The temperature measured by the temperature sensor60is referred when data is generated by calculating the corrosion rate by using the data processing unit40.

The humidity sensor70is installed outside the case10and measures the humidity of the ambient environment. The humidity measured by the humidity sensor70is referred when data is generated by calculating the corrosion rate by using the data processing unit40.

An operating method of corrosion rate measurement equipment according to an atmospheric environment having the above-described configuration according to the present invention will be described below.

The power supply unit30converts solar energy collected by the solar panel into electrical energy and charges in the battery. Thus, the power supply unit30does not need to receive the supply of electricity from the outside, and self-power generation of the power supply unit30is possible by using the solar panel80. Thus, the power supply unit30is continuously operable even overseas, during sea transportation, or in remote areas.

The power supply unit30supplies power to the corrosion sensor20and the data processing unit40at preset time intervals.

When power is supplied to the corrosion sensor20, the corrosion resistance initial value R1iof the conductive pattern21for corrosion measurement and the reference resistance initial value R2iof the conductive pattern22for temperature correction are respectively measured and stored in the data processing unit40.

In addition, for each of a plurality of measurement points set at set time intervals from an initial measurement point, the corrosion resistance measured value R1of the conductive pattern21for corrosion measurement is measured, and the reference resistance measured value R2of the conductive pattern22for temperature correction is measured.

The data processing unit40calculates a temperature correction value C by using the reference resistance initial value R2imeasured in the conductive pattern22for temperature correction at the initial measurement point and the reference resistance measured value R2measured at a corresponding measurement point at which a set time has elapsed from the initial measurement point.

Equation 2 is an equation in which the temperature correction value C is calculated at the corresponding measurement point.

where R2is a reference resistance measured value measured in the conductive pattern22for temperature correction, and R2iis a reference resistance initial value of the conductive pattern22for temperature correction.

Because the reference resistance measured value R2measured at each measurement point is reflected on the temperature correction value C, the temperature correction value C is calculated as a different value for each measurement point.

When the temperature correction value C is calculated, the data processing unit40corrects the corrosion resistance initial value R1by using the calculated temperature correction value C.

Because the corrosion resistance initial value R1iis a measured value affected by both temperature and corrosion, the corrosion resistance initial value R1iis corrected by using the temperature correction value C. That is, when the temperature correction value C is reflected on the corrosion resistance initial value R1i, the corrosion resistance correction value RCaffected by only corrosion without being affected by temperature is calculated.

Equation 3 is an equation in which the corrosion resistance correction value RCis calculated.

The corrosion resistance correction value RCis a value obtained by correcting the corrosion resistance initial value R1imeasured in the conductive pattern21for corrosion measurement at the initial measurement point.

Here, because the reference resistance measured value R2measured at a corresponding measurement point is reflected on the temperature correction value C, the effect of temperature at the measurement point is reflected on the corrosion resistance correction value RC, and the corrosion resistance correction value RCis corrected as a different value for each measurement point.

For example, the temperature correction value C is calculated by using the reference resistance measured value R2measured in the conductive pattern22for temperature correction at a second measurement point in which a set time has elapsed from the initial measurement point. The corrosion resistance correction value RCis calculated by correcting the corrosion resistance initial value R1imeasured at the initial measurement point by using the calculated temperature correction value C, and a resistance change rate of the calculated corrosion resistance correction value RCand the corrosion resistance measured value R2measured at the second measurement point can be calculated.

Thus, in the present invention, a plurality of corrosion resistance measured values R1measured at each measurement point are not corrected, and the corrosion resistance initial value R1iis corrected by using the temperature correction value C calculated at the measurement point. Correcting the initial corrosion resistance value R1iat the initial measurement point does not change the corrosion resistance measured values at each measurement point, so that data accuracy can be improved. In addition, compared to changing the corrosion resistance measured values R1at each measurement point, a resistance change rate with respect to corrosion can be more accurately calculated.

The data processing unit40may calculate a change rate of the corrosion resistance correction value RCand the corrosion resistance measured value R1measured at the corresponding measurement point, and may calculate a thickness loss and a corrosion rate from the change rate.

The data processing unit40transmits data including the calculated corrosion rate, the temperature measured by the temperature sensor60, and humidity measured by the humidity sensor70to the monitoring terminal90through the communication unit50.

In the present embodiment, a case where the communication unit50transmits data through satellite communications, will be described. Thus, data can be remotely transmitted/received not only in Korea but also anywhere in the world.

When the communication unit50fails to transmit data, the communication unit50is configured to transmit data again after a preset time so that unnecessary power consumption can be minimized.

Meanwhile, in the present embodiment, the conductive pattern22for temperature correction has a greater length L than the length of the conductive pattern21for corrosion measurement and a less surface area A than the surface area of the conductive pattern21for corrosion measurement, so that the reference resistance measured value R2measured in the conductive pattern22for temperature correction is set to be relatively greater than the corrosion resistance measured value R1measured in the conductive pattern21for corrosion measurement. As the reference resistance measured value R2measured in the conductive pattern22for temperature correction increases, a relative measured error decreases. Thus, temperature correction of the corrosion resistance measured value R1of the conductive pattern21for corrosion measurement can be more accurately performed.

Table 2 below shows comparison of an error according to a true value and a measured value in two cases where corrosion resistance initial values R1iof the conductive pattern21for corrosion measurement are the same and reference resistance initial values of the conductive pattern22for temperature correction are different from each other.

Here, (RC)mis a corrosion resistance value obtained by correcting the corrosion resistance measured value R1by using the reference resistance measured value R2that is a measured value of the conductive pattern22for temperature correction, (RC)Tis a corrosion resistance correction value obtained by correcting the corrosion resistance measured value R1by using a true value of the conductive pattern22for temperature correction, A is a ratio of the corrosion resistance correction value (RC)mobtained as a measured value with respect to the corrosion resistance initial value R1i, and B is a ratio of the corrosion resistance correction value (RC)Tobtained as a true value with respect to the corrosion resistance initial value R1i, and an error represents a difference between the corrosion resistance correction value (RC)mcorrected as a measured value and the corrosion resistance correction value (RC)Tcorrected as a true value.

Referring to Table 2, when the reference resistance initial value R1iof the conductive pattern22for temperature correction is large, the difference between the corrosion resistance correction value (RC)mcorrected as a measured value and the corrosion resistance correction value (RC)Tcorrected as a true value decreases. That is, when the reference resistance initial value R1iof the conductive pattern22for temperature correction is large, an error between the true value and the measured value can be reduced.

Thus, in the present invention, the conductive pattern22for temperature correction has a greater length L than the length of the conductive pattern21for corrosion measurement and a less surface area A than the surface area of the conductive pattern21for corrosion measurement so that the reference resistance measured value R2measured in the conductive pattern22for temperature correction is set to be relatively greater than the corrosion resistance measured value R1measured in the conductive pattern21for corrosion measurement and thus a measured error of the conductive pattern22for temperature correction can be minimized. The measured error of the reference resistance measured value R2measured in the conductive pattern22for temperature correction is minimized so that the corrosion resistance measured value R1measured in the conductive pattern for corrosion measurement can be more accurately corrected by using the reference resistance measured value R2and thus, corrosion rate can be more accurately measured.