Method for testing corrosion resistance of clad metal material and corrosion resistance testing device

Abstract

Disclosed is a corrosion resistance test method for a coated metal material and a corrosion resistance test device. The method includes: a preparation step (S1) of preparing a series circuit (3), a switching unit (5), and a voltage detection unit (6), the series circuit being formed by connecting a plurality of test units (2) in series, the test unit having an electrode (21) for applying electric current to a test target portion (E) of the coated metal material (1), the switching unit disconnecting the test unit from the series circuit and forming the series circuit in place of the test unit, and the voltage detection unit detecting the voltage of the test unit; an electric current application step (S2) of applying a constant voltage or a constant electric current to the series circuit by an electric current application unit provided on the series circuit, thereby causing corrosion of the coated metal material; and a circuit switching step (S4) of monitoring the voltage of the test unit by the voltage detection unit in the electric current application step, and disconnecting the test unit whose voltage exceeds a predetermined threshold from the series circuit.

Description

Technical Field

[0001] This disclosure relates to a method and apparatus for testing the corrosion resistance of coated metallic materials. Background Technology

[0002] To date, corrosion-promoting tests such as composite cycle tests and salt spray tests have been used as methods to evaluate coating performance. However, these corrosion-promoting tests are time-consuming, taking several months to evaluate, and are difficult to readily assess the composition of the coated steel sheet, the state of the coating under different baking conditions, and to quickly optimize coating conditions. Therefore, in the fields of material development, process management in coating plants, and quality management related to vehicle rust prevention, there is a need to establish a rapid and convenient quantitative evaluation method for assessing the corrosion resistance of coated steel sheets.

[0003] For example, Patent Document 1 discloses a method for measuring the size of a bulge formed on a surface-treated film of a metal-coated material, which is formed by depositing the surface-treated film on a metal substrate, as a corrosion resistance testing method. In this method, an aqueous material in contact with the bulge and an electrode in contact with the aqueous material are arranged, and the electrode is electrically connected to the metal substrate. A constant voltage is applied between the electrode and the metal substrate to measure the current flowing between them. Then, the degree of corrosion of the metal-coated material is measured based on the extent of bulge expansion.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6801805 Summary of the Invention

[0007] -The technical problem the invention aims to solve-

[0008] The method described above requires a considerable amount of time from preparation to measurement completion for a single test. Therefore, to improve testing efficiency, multiple test units can be connected in series with a single power supply, ensuring a constant current applied to each unit and allowing for simultaneous testing. However, blockages can sometimes occur at the test sites due to bubbles generated during the test and solid components in the test solution. If one test unit becomes blocked, current cannot flow to the other connected test units, making it difficult to conduct tests with high precision and stability.

[0009] Therefore, the purpose of this disclosure is to enable high-precision and high-efficiency testing when multiple test units are used simultaneously in corrosion resistance testing of coated metal materials.

[0010] - Technical solutions used to solve technical problems -

[0011] To address the aforementioned technical problems, one aspect of the corrosion resistance testing method for coated metal materials disclosed herein is a method for testing the corrosion resistance of coated metal materials formed by depositing a surface treatment film on a metal substrate. The method is characterized by comprising: a preparation step, which prepares a series circuit, a switching unit, and a voltage detection unit. The series circuit is a circuit formed by connecting multiple test units in series. Each test unit has an energizing part that energizes the test object portion of the coated metal material. The switching unit disconnects the test unit from the series circuit and replaces the test unit to form the series circuit. The voltage detection unit detects the voltage in the test unit. An energizing step involves applying a constant voltage or constant current to the series circuit through the energizing unit, thereby allowing corrosion of the coated metal material to occur. A circuit switching step involves monitoring the voltage of the test unit detected by the voltage detection unit during the energizing step, and disconnecting the test unit whose voltage exceeds a predetermined threshold from the series circuit.

[0012] According to this configuration, by connecting multiple test units in series with a single power supply, the voltage or current applied to each test unit can be kept constant, allowing multiple tests to be performed simultaneously. In tests that corrode coated metal materials by applying electricity, if blockage occurs at the test site due to bubbles generated during the test or solid components contained in the test solution, the voltage will rise, making it impossible to perform the test with high precision and efficiency. However, according to this configuration, even if the voltage or current applied to each test unit is constant, the voltage applied to each test unit will differ due to varying degrees of blockage. Therefore, by monitoring these blockages, it is possible to determine whether blockage has occurred. For example, in multiple test units, if the voltage of a test unit exceeds a specified value, it can be considered that a blockage has occurred at its test site. By switching the circuit, that test unit can be disconnected from the series circuit, thereby enabling multiple tests to be performed with high precision and efficiency without affecting other test units.

[0013] As one aspect of the corrosion resistance test method, it can also be configured to further include an energization check step, a test restart step, and a test time adjustment step. In the energization check step, the switching unit is controlled so that the test unit disconnected from the series circuit is connected to the series circuit and energized at predetermined time intervals. The voltage of the test unit detected by the voltage detection unit during energization is checked to see if it exceeds the predetermined threshold. In the test restart step, if the voltage of the test unit does not exceed the predetermined threshold during the energization check step, the test unit is connected to the series circuit again, and the corrosion of the coating metal material restarts. In the test time adjustment step, the test unit that has been energized for a predetermined time is disconnected from the series circuit to end the test. For the test unit whose corrosion of the coating metal material restarts through the test restart step, the energization time for the portion of time that was disconnected from the series circuit is supplemented.

[0014] Test units disconnected from series circuits due to blockages may sometimes see the blockages clear over time. According to this configuration, by reconnecting the disconnected test unit to the series circuit after a specified time interval and energizing it, it is possible to confirm whether the blockage has been cleared. If the voltage detected upon reconnection does not reach the specified value, the blockage is considered cleared, and the corrosion resistance test is restarted with the test unit connected to the series circuit. Conversely, if the voltage detected upon reconnection reaches the specified value, the blockage is considered not cleared, and the test unit is disconnected from the series circuit again, thereby further improving test efficiency. For test units that have been reconnected to the series circuit, the test continues to compensate for the energizing time lost during the disconnection, thus allowing for adjustment of the test time and preventing a decrease in test efficiency and accuracy.

[0015] As one aspect of the corrosion resistance test method, it can also be configured such that: in the preparation step, a heating unit is further prepared to heat the test object part of the coated metal material; the energizing step involves applying a constant voltage or constant current to the series circuit while heating the test object part of the coated metal material to a specified temperature, thereby allowing the corrosion of the coated metal material to proceed; after a specified energizing time, the test unit is disconnected from the series circuit, and heating is stopped or the test object part is cooled down to end the test.

[0016] According to this configuration, by stopping the power supply to the test unit that has been evaluated, stopping the heating, or cooling the test object, it is possible to prevent the evaluation object from drying out or corroding further, thereby improving the test accuracy and preventing evaluation deviations when multiple test units are used for evaluation at the same time.

[0017] Alternatively, the test unit may have a container and an electrode, the container holding the water-containing material in contact with the surface treatment film, the electrode being in contact with the water-containing material contained in the container, and the energizing unit applying a constant DC voltage or constant current between the electrode and the metal substrate as the anode and cathode, respectively, thereby enabling the corrosion of the coated metal material.

[0018] It should be noted that in this specification, "the test object part of the metal-coated material" refers to the part of the metal-coated material that corresponds to the contact area between the water-containing material and the surface treatment film.

[0019] One aspect of the corrosion resistance testing apparatus for coated metal materials disclosed herein is a corrosion resistance testing apparatus for coated metal materials formed by setting a surface treatment film on a metal substrate. The apparatus is characterized by comprising a test unit, a series circuit, an energizing unit, a switching unit, a voltage detection unit, and a control device. The test unit has an energizing section for energizing the test area of ​​the coated metal material. The series circuit is a circuit formed by connecting multiple test units in series. The energizing unit is disposed on the series circuit. By applying a constant voltage or constant current to the series circuit, corrosion of the coated metal material is carried out. The switching unit disconnects the test unit from the series circuit and replaces the test unit to form the series circuit. The voltage detection unit detects the voltage in the test unit. The control device monitors the voltage of the test unit through the voltage detection unit and disconnects the test unit whose voltage exceeds a predetermined threshold from the series circuit through the switching unit.

[0020] According to this configuration, by connecting multiple test units in series with a single power supply, the voltage or current applied to each test unit can be kept constant, allowing multiple tests to be performed simultaneously. In tests that corrode coated metal materials by applying electricity, if blockage occurs at the test site due to bubbles generated during the test or solid components contained in the test solution, the voltage will rise, making it impossible to perform the test with high precision and efficiency. With this configuration, even if the voltage or current applied to each test unit is constant, the voltage applied to each test unit will differ depending on the degree of blockage. Therefore, by monitoring this, it is possible to determine whether blockage has occurred. For example, in multiple test units, when the voltage of a test unit exceeds a specified value, it can be considered that a blockage has occurred at its test site. A switching circuit can then disconnect that test unit from the series circuit, allowing multiple tests to be performed with high precision and efficiency without affecting other test units.

[0021] -The effects of the invention-

[0022] As described above, according to this disclosure, in corrosion resistance tests of coated metal materials, tests can be performed with high precision and efficiency when evaluating multiple test units simultaneously. Attached Figure Description

[0023] Figure 1 This is a simplified structural diagram illustrating one example of the corrosion resistance testing apparatus according to the first embodiment.

[0024] Figure 2 This is a diagram representing one example of a test unit.

[0025] Figure 3 This is a flowchart illustrating the corrosion resistance test method involved in the first embodiment.

[0026] Figure 4 This is a schematic diagram of the test subject area where a blockage caused by hydrogen gas has occurred.

[0027] Figure 5 This is a simplified structural diagram illustrating one example of the corrosion resistance testing apparatus according to the second embodiment.

[0028] Figure 6 This is a simplified structural diagram illustrating one example of the corrosion resistance testing apparatus according to the third embodiment.

[0029] Figure 7 This is a diagram illustrating another embodiment of the test unit.

[0030] - Symbol Explanation -

[0031] 1 – Coated metal material; 2 – Test unit; 3 – Series circuit; 4 – Power-on unit; 5 – Switching unit; 5A, 5B – Connectors (switching units); 5a~5c – Switching switches (switching units); 6 – Voltage detection unit; 7 – Control device; 9 – Aqueous material; 10 – Steel plate (metal substrate); 11 – Chemical conversion film; 12 – Electrophoretic coating (surface treatment film); 20 – Container; 21 – Electrode; 22 – Temperature sensor; 23 – Heater (heating unit); 32 – Bypass circuit; 100 – Corrosion resistance testing device; 201, 202, 203 – Test units; E – Test object location; S1 – Preparation step; S2 – Power-on step; S3 – Blockage judgment step; S4 – Circuit switching step; S5 – Power-on check step; S6 – Test restart step; S7 – Test time adjustment step. Detailed Implementation

[0032] The embodiments of this disclosure will now be described in detail based on the accompanying drawings. The descriptions of the preferred embodiments below are merely illustrative in nature and are not intended to limit this disclosure, its application, or its uses.

[0033] ≪Corrosion Resistance Testing Apparatus for Coated Metal Materials≫

[0034] (First Implementation)

[0035] Figure 1 This is a simplified structural diagram illustrating one example of the corrosion resistance testing apparatus according to the first embodiment. Figure 2 This represents one example of a test unit. For example... Figure 1 As shown, the corrosion resistance testing apparatus 100 of this embodiment is a corrosion resistance testing apparatus for a coated metal material 1 formed by providing a surface treatment film 12 on a metal substrate 10. It includes a test unit 2 for testing the coated metal material 1, a series circuit 3, an energizing unit 4, a switching unit 5, a voltage detection unit 6, and a control device 7. The corrosion resistance testing apparatus 100 of this embodiment is an apparatus for simultaneously performing multiple tests by applying a constant voltage or constant current to multiple test units 2, 2 through a single energizing unit 4.

[0036] <Clad Metal Materials>

[0037] like Figure 2 As shown, the coated metal material 1 that is the test object in the corrosion resistance test of this embodiment can be exemplified by a coated metal material on which a resin coating is provided on a metal substrate as a surface treatment film.

[0038] Metal substrates can be, for example, steel used in household appliances, building materials, and automotive parts, such as cold-rolled steel sheet (SPC), alloyed hot-dip galvanized steel sheet (GA), high-tensile steel sheet, or hot-stamped materials, or they can be lightweight alloy materials. Metal substrates can also be materials with a chemical conversion film (phosphate film (e.g., zinc phosphate film), chromate film, etc.) formed on their surface.

[0039] The resin coating is a resin coating formed using resin-based paints, preferably an electrophoretic coating. As for the coated metal material on which a resin coating is applied as a surface treatment film, it is well-suited for use as the test subject in this corrosion resistance test because it is prone to corrosion when an electric current is applied. Specifically, examples of resin coatings include cationic electrophoretic coatings (primer films) such as epoxy resins and acrylic resins.

[0040] The cladding material can also include two or more multilayer films as surface treatment films. Specifically, for example, when the surface treatment film is a resin coating, it can also be a multilayer coating with a top coating layered on an electrophoretic coating, or a multilayer coating with a middle coating and a top coating layered on an electrophoretic coating, etc.

[0041] In the following description, we will take the following coated metal material 1 as an example. The coated metal material 1 is formed by setting an electrophoretic coating 12 (resin coating) as a surface treatment film on a metal substrate. The metal substrate is obtained by forming a chemical conversion film 11 on the surface of a steel plate 10.

[0042] At the test site E of the metal-coated material 1, a scratch 13 is formed that penetrates the electrophoretic coating 12 and the chemical conversion film 11 and reaches the steel plate 10. It should be noted that the scratch 13 may or may not be formed. The scratch 13 can be artificially formed or naturally formed.

[0043] <Experimental Unit>

[0044] Test unit 2 is an apparatus used for corrosion resistance testing of coated metal materials. First, the principle of the corrosion resistance test in this embodiment will be explained.

[0045] In coated metal materials, including surface-treated films, corrosive agents such as salt water can penetrate the surface-treated film and reach the metal substrate, thus initiating corrosion. In other words, the corrosion process of coated metal materials can be divided into a pre-corrosion phase and a corrosion development phase. By separately determining the period before corrosion begins (corrosion inhibition period) and the rate of corrosion development (corrosion development rate), an evaluation can be performed.

[0046] It is known that metal corrosion typically occurs through the simultaneous occurrence of an anodic reaction (oxidation) and a cathodic reaction (reduction). In the anodic reaction, the metal in contact with water dissolves (ionizes), generating free electrons. In the cathodic reaction, dissolved oxygen and other substances in the water are converted into hydroxide ions (OH-) by these free electrons. － wait.

[0047] In this configuration, electrode 21 and steel plate 10 are used as the anode and cathode, respectively, and an electric current is applied between them. When the electrode 21 is used as the anode and the steel plate 10 is used as the cathode, if the water-containing material 9 that has penetrated into the surface treatment film reaches the steel plate 10, a cathodic reaction will occur at the contact between the water-containing material 9 and the steel plate 10. For example, when a voltage greater than or equal to the theoretical voltage for producing hydrogen by electrolysis of water (1.23V at a system temperature of 25°C) is applied, or when an electric current requiring such a voltage is applied, water electrolysis will also occur to produce hydrogen.

[0048] If a cathode reaction is carried out, then due to the generation of OH... － Therefore, the area around the contact point between the water-containing material and the metal substrate becomes an alkaline environment. This damages the substrate treatment layer (chemical conversion treatment layer) on the metal substrate surface, leading to a decrease in the adhesion of the surface treatment film (in the absence of substrate treatment, only the adhesion between the metal substrate and the surface treatment film decreases). Consequently, the surface treatment film will lift at the contact point, and bulges will form. In an alkaline environment, the reduced adhesion of the surface treatment film to the metal substrate will be further damaged by water electrolysis or H2O. ＋ The hydrogen gas generated by the reduction pushes the surface treatment film upwards, allowing the bulges to expand. This cathodic reaction, along with the formation and expansion of the bulges in the surface treatment film, accelerates the reproduction of the actual corrosion of the coated metal material. In other words, in this specification, "causing corrosion of the coated metal material" means "causing the formation and expansion of bulges in the surface treatment film." Therefore, for example, by observing the formation and expansion of bulges in the surface treatment film at the contact area, the degree of corrosion of the coated metal material can be measured.

[0049] Test unit 2 includes a container 20, an electrode 21, a temperature sensor 22, and a heating unit 23. The multiple test units 2 included in the corrosion resistance testing apparatus 100 of this embodiment have essentially the same structure, but the temperature and test time can be set separately for each test unit 2. In the multiple test units, the coating metal material 1 used as the test object can be the same or different.

[0050] Container 20 is placed on the electrophoretic coating 12 covered with metal material 1 through a seal (not shown) to prevent liquid leakage. The container 20 contains an aqueous material 9. The aqueous material 9, while contained within the container 20, is in contact with the surface of the electrophoretic coating 12 at the test site E. In other words, the container 20 holds the aqueous material 9 in contact with the electrophoretic coating 12 at the test site E.

[0051] The shape of container 20 is not particularly limited; it can be cylindrical, polygonal, or other cylindrical shapes. Container 20 can be made of resin materials such as acrylic resin, epoxy resin, or polyetheretherketone (PEEK), or ceramic, and is particularly preferred to be made of resin materials such as acrylic resin, epoxy resin, or PEEK. This ensures insulation between container 20 and the outside environment, and also allows for a lighter and lower-cost test unit 2.

[0052] The aqueous material 9 contains water and a supporting electrolyte, and functions as a conductive material. The aqueous material 9 may also be a mud-like substance containing clay minerals. In the case where the aqueous material 9 contains clay minerals, ions and water in the aqueous material 9 can easily penetrate into the electrophoretic coating 12 during the energizing step S2 described later.

[0053] The supporting electrolyte is a salt, which is a substance used to impart sufficient conductivity to the aqueous material 9. Specifically, for example, at least one salt selected from sodium chloride, sodium sulfate, calcium chloride, calcium phosphate, potassium chloride, potassium nitrate, potassium bitartrate, and magnesium sulfate can be used as the supporting electrolyte. It is particularly preferred to use at least one salt selected from sodium chloride, sodium sulfate, and calcium chloride as the supporting electrolyte. The content of the supporting electrolyte in the aqueous material 9 is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, and particularly preferably 5% by mass or more and 10% by mass or less.

[0054] Clay minerals are used to make the aqueous material 9 into a mud-like state and to promote the movement of ions into the electrophoretic coating 12 and the penetration of water into the electrophoretic coating 12, thereby promoting corrosion in the electro-coating step S2. Layered silicate minerals or zeolites can be used as clay minerals, for example. Layered silicate minerals can be selected from at least one of kaolinite, montmorillonite, sericite, illite, glauconite, chlorite, and talc, with kaolinite being particularly preferred. The content of clay minerals in the aqueous material is preferably 1% by mass or more and 70% by mass or less, more preferably 10% by mass or more and 50% by mass or less, and particularly preferably 20% by mass or more and 30% by mass or less. It should be noted that by making the aqueous material 9 into a mud-like state, the aqueous material 9 can be placed on the surface of the electrophoretic coating 12 even when the electrophoretic coating 12 is not horizontal.

[0055] The aqueous material 9 may also contain additives other than water, supporting electrolytes, and clay minerals. Specifically, examples of such additives include organic solvents such as acetone, ethanol, toluene, and methanol, as well as substances that improve the wettability of the coating film. These organic solvents and substances can also promote the penetration of water into the electrophoretic coating film 12. These organic solvents and substances can be added to the aqueous material 9 instead of clay minerals. When the aqueous material 9 contains organic solvents, the volume ratio of the organic solvent to water is preferably 5% or more and 60% or less. This volume ratio is more preferably 10% or more and 40% or less, and even more preferably 20% or more and 30% or less.

[0056] Electrode 21 and steel plate 10 are the energized parts in test unit 2 that conduct electricity to the test object. Electrode 21 is arranged at a distance from the electrophoretic coating 12 covering the metal material 1. Aqueous material 9 is arranged between the electrophoretic coating 12 and the electrode 21, and the aqueous material 9 is in contact with the electrophoretic coating 12 and the electrode 21. Specifically, electrode 21 is configured such that at least its front end is embedded in the aqueous material 9 and in contact with the aqueous material 9.

[0057] Electrode 21 can be any electrode commonly used in electrochemical measurements, specifically, for example, a carbon electrode, a platinum electrode, etc.

[0058] The shape of electrode 21 can be any shape commonly used in electrochemical measurements, such as rod or plate. For example, a porous electrode with at least one hole at the front end can also be used as electrode 21. For example, if a porous electrode with a ring-shaped front end is used, it is sufficient to arrange the porous electrode so that the ring is approximately parallel to the electrophoretic coating 12. Alternatively, a mesh electrode can also be used as the porous electrode, and the mesh electrode can be arranged so that it is approximately parallel to the electrophoretic coating 12 while being embedded in the aqueous material 9.

[0059] A temperature sensor 22 is inserted into the container 20 to detect the temperature of the water-containing material 9. Specifically, the temperature sensor 22 may be, for example, a thermocouple, a fiber optic thermometer, or an infrared thermometer. In the corrosion resistance test according to this embodiment, the temperature of the water-containing material 9, especially the temperature of the water-containing material 9 near the electrophoretic coating 12, is crucial. By accurately detecting the temperature of the water-containing material 9 near the electrophoretic coating 12 using the temperature sensor 22, the reliability of the corrosion resistance test is improved.

[0060] Heating unit 23 is provided for heating and temperature regulation of the water-containing material 9 and the cladding metal material 1. Heating unit 23 is, for example, located on the side of the steel plate 10 of the cladding metal material 1; specifically, it is a heater such as a heating plate or a Peltier element. Heater 23 is electrically or wirelessly connected to the control device 7 (described later) and is controlled by the control device 7. Under the control of the control device 7, different temperatures and heating times can be set for each test unit 2, for example.

[0061] By appropriately heating and temperature-regulating the water-containing material 9 and the coating metal material 1 using heater 23, the movement of ions into the electrophoretic coating 12 and the penetration of water into the electrophoretic coating 12 can be promoted, thereby effectively carrying out corrosion. This allows for shorter and more reliable corrosion resistance tests. Since the temperatures of the water-containing material 9 and the coating metal material 1 can be kept constant throughout the desired test time, highly reliable corrosion resistance tests can be performed under specified temperature conditions.

[0062] Heater 23 is not limited to, for example Figure 2 The heater 23 can be positioned on the side of the steel plate 10, for example, it can be positioned around the periphery of the container 20 to cover the container 20, or it can be positioned on the electrophoretic coating 12 of the metal material 1 covering the outside of the container 20. Specifically, it can be, for example, a rubber heater, a thin film heater, etc. In addition, the heater 23 is not limited to such... Figure 1 The heater designed for each test unit 2 can also be used to heat and regulate the temperature of multiple coated metal materials 1 using a single heater.

[0063] <Series Circuit>

[0064] The series circuit 3 includes wiring 31, multiple test units 2 arranged on wiring 31, and energizing units 4. Wiring 31 connects the multiple test units 2 and energizing units 4 in series to form the series circuit 3. Wiring 31 includes wiring 31a connected to the electrodes 21 (energizing parts) of the test units 2 and wiring 31b connected to the steel plate 10 (energizing parts). Known wiring can be appropriately used as wiring 31.

[0065] <Power-on Unit>

[0066] The energizing unit 4 is connected to the electrode 21 and the steel plate 10 via wiring 31 and is disposed on the series circuit 3. The energizing unit 4 functions as a power source that energizes the electrode 21 and the steel plate 10, i.e., applies voltage and / or current. It should be noted that, as described later, in the energizing step S2, the energizing unit 4 uses the electrode 21 and the steel plate 10 as the anode and cathode, respectively, and applies a constant DC current, a constant DC voltage, or a constant current between them. Specifically, for example, a potentiostat / galvanostat capable of controlling the application of voltage / current can be used as the energizing unit 4. The energizing unit 4 is electrically or wirelessly connected to the control device 7 (described later) and is controlled by the control device 7. The energizing information, such as the current value, voltage value, and energizing time applied to the series circuit 3 by the energizing unit 4, is sent to the control device 7 and stored in the storage unit 72.

[0067] <Switching Unit>

[0068] Switching unit 5 is connected to wiring 32a, which forms a bypass circuit 32 for test unit 2. Switching unit 5 disconnects test unit 2 from series circuit 3 and replaces test unit 2 with bypass circuit 32 to form a series circuit. Switching unit 5 is, for example, a current control element composed of a FET. Switching unit 5 controls the current supplied to wiring 31a or wiring 32a based on the voltage detected by voltage detection unit 6 (described later) and a preset voltage value. For example, when the voltage of test unit 2 reaches or exceeds a predetermined value, the current flows to bypass circuit 32 through switching unit 5. Since bypass circuit 32 forms a series circuit, test unit 2 is disconnected from series circuit 3. Switching unit 5 is electrically or wirelessly connected to control device 7 (described later), and is controlled by control device 7. Through switching unit 5, energizing information such as the energizing time of test unit 2 in series circuit 3 is sent to control device 7 and stored in storage unit 72.

[0069] <Voltage Detection Unit>

[0070] A voltage detection unit 6 is provided relative to each test unit 2 and detects the voltage of the test unit 2 when it is energized. The voltage detection unit 6 is, for example, a resistor. The voltage detection unit 6 is electrically or wirelessly connected to the control device 7 (described later) and outputs the voltage value to the control device 7. Information such as the voltage of the test unit 2 detected by the voltage detection unit 6 is sent to the control device 7 and stored in the storage unit 72.

[0071] For example, if there is no blockage in the test unit, the voltage of test unit 2 detected by voltage detection unit 6 is 3-4V. If the voltage change of test unit 2 detected by voltage detection unit 6 is 10-100V, it can be determined that a blockage has occurred in the test unit.

[0072] <Control Device>

[0073] The control device 7 is, for example, a device based on a known microcomputer. The control device 7 includes a control unit 71, a storage unit 72, and an arithmetic unit 73. The control device 7 also includes, for example, an input unit 74 composed of a keyboard, and an output unit 75 composed of a display, etc. The control device 7 is electrically or wirelessly connected to the temperature sensor 22, heater 23, power-on unit 4, switching unit 5, and voltage detection unit 6. The control device 7 controls the temperature sensor 22, power-on unit 4, switching unit 5, etc., based on various pre-defined arithmetic programs. Based on the information output from the temperature sensor 22, power-on unit 4, switching unit 5, voltage detection unit 6, etc., it performs various calculations and judgments. Based on the calculation results and judgment results, it controls the temperature adjustment and on / off of the heater 23, the on / off of the power-on unit 4, the voltage / current values ​​applied to the series circuit by the power-on unit, and the circuit switching performed by the switching unit 5, etc.

[0074] The storage unit 72 is composed of RAM (Random Access Memory) and ROM (Read Only Memory), storing various data and processing programs. The arithmetic unit 73 performs various arithmetic operations based on the information stored in the storage unit 72, information input via the input unit 74, and information obtained from various recording media via the reading unit. The control unit 71 outputs control signals to the controlled object based on the data stored in the storage unit 72 and the results of the arithmetic operations 73, performing various control functions.

[0075] The storage unit 72 stores the voltage value of the test unit 2 when it becomes blocked as a threshold. The calculation unit 73 determines whether the voltage of the test unit 2 input from the voltage detection unit 6 is above the threshold. When the voltage of the test unit 2 input from the voltage detection unit 6 is above the threshold, it can be determined that a blockage has occurred in the test unit. When a voltage above the threshold is detected, the control unit 71 controls the switching unit 5 to form a series circuit in the bypass circuit 32 and disconnects the test unit 2 from the series circuit 3.

[0076] For example, in the storage unit 72, as a control program after disconnecting the test unit 2 from the series circuit, a control program can also be stored to connect the test unit 2, which has been disconnected from the series circuit 3, to the series circuit 3 at predetermined time intervals to energize it. According to such a control program, the control unit 71 controls the switching unit 5 to connect the test unit, which has been disconnected from the series circuit, to the series circuit at predetermined time intervals to energize it. The predetermined time interval is, for example, every 1 to 10 minutes. If the voltage of the test unit does not exceed a predetermined threshold, the control unit 71 keeps the test unit 2 connected to the series circuit 3, causing the corrosion of the coated metal material 1 to restart.

[0077] For example, the storage unit 72 can also store test programs that set test time, test temperature, etc., for each test unit. Based on such test programs, the control unit 71 adjusts the temperature of the heater 23 and controls its on / off state for each test unit, as well as controls the switching unit 5. Based on the test program, the control unit 71 disconnects the test unit from the series circuit after the specified energizing time has elapsed, thus ending the test. Based on the test program, the control unit 71 controls the heater 23 to stop heating or cool the test object area for test units that have elapsed the specified energizing time, thus ending the test.

[0078] For a test unit that is disconnected from the series circuit during a blockage and restarts the test in the series circuit after the blockage is cleared, the calculation unit 73 calculates the test time required to restart the test based on a pre-defined test time and the time of disconnection from the series circuit. Then, the control unit 71 controls the power-on unit 4 and the switching unit 5 to be powered on to make up for the amount of power-on time required to compensate for the time the test unit was disconnected from the series circuit.

[0079] The calculation unit 73 can also calculate the degree of corrosion based on at least one of the time-dependent changes in current value, voltage value, and resistance value generated between the electrode 21 and the steel plate 10 due to the application of a constant DC current, a constant DC voltage, or a constant current by the energizing unit 4.

[0080] <Test Methods for Corrosion Resistance of Coated Metal Materials>

[0081] Figure 3 This is a flowchart illustrating the corrosion resistance test method involved in this embodiment. Hereinafter, refer to... Figure 3 The corrosion resistance test method involved in this embodiment will be described.

[0082] like Figure 3As shown, this corrosion resistance test method includes preparation step S1, power-on step S2, blockage judgment step S3, circuit switching step S4, power-on check step S5, test restart step S6, and test time adjustment step S7. Each step is explained below.

[0083] Preparation Steps

[0084] In preparation step S1, the following are prepared: a series circuit 3 including multiple test units 2, each test unit 2 having an energizing part (electrode 21 and steel plate 10) for energizing the test object part covered with metal material 1; a bypass circuit 32 including a switching unit 5; and a voltage detection unit 6 for detecting the voltage in the test unit 2.

[0085] The cladding metal material 1 is preferably a cladding metal material 1 having a scratch 13 that penetrates the electrophoretic coating 12 and the chemical conversion coating 11 to reach the steel plate 10. The scratch 13 may not be formed on the cladding metal material 1, but it is preferred to have it for the following reasons: If a scratch 13 exists that penetrates the electrophoretic coating 12 and the chemical conversion coating 11 to reach the steel plate 10, then when the scratch 13 comes into contact with the water-containing material 9, the water-containing material 9 will penetrate into the scratch 13 and thus come into contact with the steel plate 10 exposed at the scratch 13. Therefore, by forming the scratch 13, the following state in the corrosion process of the cladding metal material 1 described above can be simulated and reproduced: the state where the process before corrosion has ended, i.e., the state at the end of the corrosion inhibition period.

[0086] Regarding test unit 2, for example, firstly, preferably surrounding the scratch 13, a container 20 is placed on the surface of the electrophoretic coating 12 of the test piece covered with metal material 1, separated by a sealing material, and the aqueous material 9 is filled into the container 20. Then, the aqueous material 9 is brought into contact with the surface of the electrophoretic coating 12, preferably with the scratch 13. Then, the electrode 21 connected to the wiring 31a is immersed in the aqueous material 9. Wiring 31b is connected to the steel plate 10. Multiple such test units are prepared, and the wiring 31a, 31b are connected to other test units 2 or energized units 4. Thus, the electrodes 21 and steel plates 10 in multiple test units 2 are electrically connected to the energized units 4 through a series circuit 3. A bypass circuit 32 and a voltage detection unit 6 are provided for each test unit 2.

[0087] Power-on steps

[0088] The energizing step S2 is a step in which a constant voltage or constant current is applied to the series circuit 3 by the energizing unit 4, thereby causing corrosion of the coated metal material 1 in multiple test units 2. In the energizing step S2, a constant DC voltage or constant current is preferably applied. Each test unit 2 is energized, for example, by using the electrode 21 and the steel plate 10 as the anode and cathode, respectively, thereby causing corrosion of the steel plate 10. In the energizing step S2, the voltage of the energized test unit 2 is continuously detected by the voltage detection unit 6 and monitored by the control device 7.

[0089] When current is applied with electrode 21 as the anode and steel plate 10 as the cathode, such as Figure 2 As shown, a cathodic reaction is performed at the contact point between the water-containing material 9 and the steel plate 10, preferably at the exposed portion 13A of the steel plate 10 at the scratch 13. Furthermore, depending on the energizing conditions, water electrolysis also occurs to produce hydrogen gas. That is, for example, when a voltage greater than or equal to the theoretical voltage required to produce hydrogen gas through water electrolysis (1.23V at a system temperature of 25°C) is applied, or when an energizing condition requiring such a voltage is applied, water electrolysis will also occur to produce hydrogen gas.

[0090] like Figure 4 As shown, bulging occurs in the electrophoretic coating 12 during the cathodic reaction. Furthermore, hydrogen gas promotes the bulging of the electrophoretic coating 12.

[0091] The cathodic reaction and the expansion of bulges on the electrophoretic coating 12, preferably occurring around the scratch 13, accelerate the reproduction of the actual corrosion of the coating metal 1. In other words, the expansion of bulges on the electrophoretic coating 12 is a simulation of the corrosion process of the coating metal 1.

[0092] The constant voltage or constant current applied in the energizing step S2 is preferably 0.05V or higher, more preferably 0.1V or higher. If the constant voltage or constant current is less than the lower limit, the current value will be too small, and the measurement error may increase.

[0093] In the energizing step S2, the control unit 71 preferably heats and regulates the temperature of the coating metal material 1 and / or the water-containing material 9. The temperature of the coating metal material 1 and / or the water-containing material 9 is preferably 30°C or higher and 100°C or lower, more preferably 50°C or higher and 100°C or lower, and particularly preferably 50°C or higher and 80°C or lower.

[0094] like Figure 4As shown, when hydrogen gas covers the surface of the electrophoretic coating 12 and causes blockage at the test site E, current cannot flow through the test site E. Blockage at the test site E can sometimes also occur due to solid components contained in the aqueous material 9.

[0095] Blockage Judgment Steps

[0096] In the blockage determination step S3, the control device 7 determines whether a blockage has occurred at the test target location E of the test unit 2. Specifically, for example, the storage unit 72 stores a predetermined threshold as the voltage value when a blockage occurs in the test unit 2, and the calculation unit 73 determines whether the voltage of the test unit 2 detected by the voltage detection unit 6 exceeds the threshold. If the voltage of the test unit 2 input from the voltage detection unit 6 exceeds the threshold (step S3: Yes), the calculation unit 73 determines that a blockage has occurred in the test unit 2, and the control unit 71 executes the circuit switching step S4. If the voltage of the test unit 2 input from the voltage detection unit 6 is below the threshold (step S3: No), the calculation unit 73 determines that no blockage has occurred in the test unit 2, and the control unit 71 continues the power-on step S2.

[0097] For example, in the blockage determination step S3, the voltage at which the test unit 2 is determined not to be blocked is 3 to 4V, and the threshold voltage at which the blockage is determined is, for example, 10 to 100V. If this threshold is set too high, it may cause damage to parts other than the test object; therefore, 20 to 40V is more preferable.

[0098] Circuit switching steps

[0099] Circuit switching step S4 is a step in which the test unit 2, which is determined to be blocked, is disconnected from the series circuit, while other test units continue to be powered by the series circuit. The control unit 71 controls the switching unit 5 to use the bypass circuit 32 to replace the blocked test unit 2 to form a series circuit, thereby disconnecting the test unit 2 from the series circuit 3.

[0100] Power-on inspection steps

[0101] The power-on check step S5 is a step to check whether the blockage has been eliminated by connecting the test unit, which has been disconnected from the series circuit, to the series circuit at predetermined time intervals and energizing it. The predetermined time interval is, for example, every few minutes, specifically, every 1 to 10 minutes. The storage unit 72 stores a predetermined threshold as the voltage value when the test unit 2 experiences a blockage. Based on this threshold, the calculation unit 73 determines in the power-on check step S5 whether the voltage of the test unit 2 detected by the voltage detection unit 6 exceeds the threshold.

[0102] If the voltage input from the voltage detection unit 6 to the test unit 2 exceeds the threshold (step S5: Yes), the arithmetic unit 73 determines that the blockage in the test unit 2 has not been eliminated, and the control unit 71 controls the switching unit 5 to disconnect the test unit 2 from the series circuit 3. Then, for the test unit disconnected from the series circuit, the test unit is connected to the series circuit at predetermined time intervals, and the power-on check step S5 is repeated until it is determined that the blockage has been eliminated.

[0103] ≪Trial Restart Procedure≫

[0104] If the voltage input from the voltage detection unit 6 to the test unit 2 is below the threshold (step S5: No), the calculation unit 73 determines that the blockage in the test unit 2 has been eliminated. When it is determined that the blockage has been eliminated, the control unit 71, in the test restart step S6, connects the test unit 2 back to the series circuit 3, so that the corrosion of the coating metal material 1 can restart.

[0105] ≪Test Time Adjustment Steps≫

[0106] The test time adjustment step S7 is a step to supplement the energizing time for the portion of time that was disconnected from the series circuit 3 for test unit 2, where the corrosion of the coated metal material has restarted through the test restart step S6. In test time adjustment step S7, the control unit 71 disconnects the test unit from the series circuit after the predetermined energizing time has elapsed to end the test. For test units where the predetermined energizing time has elapsed, the control unit 71 stops the heater 23. In test time adjustment step S7, the control unit 71 energizes the test unit where the corrosion of the coated metal material has restarted through the test restart step S6, and the energizing time is the portion of time that was disconnected from the series circuit, thereby satisfying the set test time. It should be noted that the test time for the corrosion resistance test can be set to, for example, 0.05 hours or more and 24 hours or less, preferably 0.1 hours or more and 10 hours or less, and more preferably 0.1 hours or more and 5 hours or less.

[0107] According to the corrosion resistance testing apparatus and method described above, by connecting multiple test units 2 in series with a single energized unit 4, the voltage applied to each test unit 2 can be kept constant, and multiple tests can be performed simultaneously. In tests that corrode coated metal materials by applying current, blockages can sometimes occur at the test site due to bubbles generated during the test or solid components contained in the test solution. If a blockage occurs in one test unit 2, current flow is difficult, affecting other test units 2 and hindering high-precision and efficient testing. However, according to this configuration, when the voltage of a test unit 2 exceeds a specified value, it can be considered that a blockage has occurred at its test site. By switching the circuit, the test unit is disconnected from the series circuit 3, thereby enabling high-precision and efficient testing without affecting other test units.

[0108] For test unit 2, which is disconnected from the series circuit due to blockage, after a specified time, test unit 2 is reconnected to the series circuit and energized to confirm whether the blockage has been eliminated. If the voltage does not reach the specified value, the blockage is considered eliminated and the test restarts, thereby further improving test efficiency. For test units that restart the test, the test continues to make up for the energizing time during the period of disconnection from the series circuit, thereby adjusting the test time and preventing a decrease in test efficiency and accuracy.

[0109] The following describes other embodiments involved in this disclosure in detail. It should be noted that in the description of these embodiments, the same symbols are used for the parts that are the same as those in the first embodiment, and detailed descriptions are omitted.

[0110] (Second Implementation)

[0111] Figure 5 This is a simplified structural diagram illustrating an example of the corrosion resistance testing apparatus according to the second embodiment. The structure of the switching unit in the second embodiment differs from that in the first embodiment. In the first embodiment, the switching unit 5 is a current control element composed of a FET or the like, which is connected to wiring 32a forming the bypass circuit 32 for the test unit 2, but the switching unit is not limited to this configuration.

[0112] like Figure 5As shown, the switching unit can also be switching switches 5a, 5b, and 5c. Switches 5a and 5b are installed on the wiring 31a and 31b before and after each test unit 201 and 202, and switch 5c is installed in the bypass circuit 32. Each switching switch 5a to 5c switches between an on position that connects the wiring before and after the test unit 2 in series and an off position that disconnects the test unit 2 from the series circuit 3. Each switching switch 5a to 5c is electrically or wirelessly connected to the control device 7, and the control device 7 controls the switching between the on and off positions.

[0113] exist Figure 5 In the test unit 201 on the left, switches 5a and 5b are in the ON position, and switch 5c of the bypass circuit is in the OFF position, so test unit 201 is connected to the series circuit 3; in the test unit 202 on the right, switches 5a and 5b are in the OFF position, and switch 5c of the bypass circuit is in the ON position, so test unit 202 is disconnected from the series circuit 3.

[0114] (Third implementation method)

[0115] Figure 6 This is a simplified structural diagram illustrating an example of the corrosion resistance testing apparatus according to the third embodiment. The structure of the switching unit in the third embodiment differs from that in the previous embodiment. Figure 6 As shown, the switching unit can also be a disconnecting unit such as connectors 5A and 5B, which are installed on the wiring 31a and 31b before and after each test unit 201 and 202 and physically disconnect the test units 201 and 202 from the series circuit. Each connector 5A and 5B can also be electrically or wirelessly connected to the control device 7, and the switching is controlled by the control device 7. Figure 6 The image shows the test unit 202 on the right side in a state where the connection between connectors 5A and 5B has been released and it has been removed from the series circuit.

[0116] (Other implementations of the test unit)

[0117] Figure 7 This is a simplified diagram illustrating one example of another implementation of the test unit. For example... Figure 7 As shown, each test unit 203 can also be housed within the housing 203a. This embodiment includes a connector 203b on the housing 203a, creating a structure that allows for easy connection and separation of multiple test units. The connector 203b enables the electrical connection of multiple test units in a longitudinal or transverse arrangement, thereby achieving a more compact test setup and improved operability.

[0118] As a means of eliminating blockages in a test unit that has become clogged, one can not only wait for time to pass, but also implement measures such as swapping the anode and cathode, applying vibration to the cladding metal material, or stirring the water-containing material. Furthermore, even in the absence of blockages, when implementing blockage elimination (blockage prevention) measures during testing, the test unit can be disconnected from the DC circuit, or the connections of various instruments can be severed.

[0119] -Industry Applicability-

[0120] This disclosure is extremely useful because it enables further reduction of test time and measurement error in corrosion resistance tests of coated metal materials.

Claims

1. A method for testing the corrosion resistance of a coated metal material, wherein the coated metal material is formed by depositing a surface treatment film on a metal substrate, characterized in that... The corrosion resistance test method for the cladding metal material includes: Preparation steps include preparing a series circuit, a switching unit, and a voltage detection unit. The series circuit is a circuit formed by connecting multiple test units in series. The test unit has a energizing part that energizes the test object part covered with metal material. The switching unit disconnects the test unit from the series circuit and replaces the test unit to form the series circuit. The voltage detection unit detects the voltage in the test unit. The energizing step involves applying a constant voltage or constant current to the series circuit via an energizing unit disposed on the series circuit, thereby allowing the corrosion of the cladding metal material to proceed; and In the circuit switching step, during the power-on step, the voltage of the test unit detected by the voltage detection unit is monitored, and the test unit whose voltage exceeds a predetermined threshold is disconnected from the series circuit.

2. The corrosion resistance test method for coated metal materials according to claim 1, characterized in that, The corrosion resistance test method for the cladding metal material includes: The power-on check step involves controlling the switching unit to connect the test unit, which is disconnected from the series circuit, to the series circuit at predetermined time intervals and power it on. The voltage of the test unit detected by the voltage detection unit during power-on is checked to see if it exceeds the predetermined threshold. The test restart step involves, during the power-on check step, ensuring that the voltage of the test unit does not exceed the specified threshold, allowing the test unit to remain connected to the series circuit and restarting the corrosion of the cladding metal material; and The test time adjustment step involves disconnecting the test unit from the series circuit after a specified energizing time to end the test. For test units where the corrosion of the coated metal material restarts through the test restart step, the energizing time equal to the time spent disconnected from the series circuit is supplemented.

3. The corrosion resistance test method for coated metal materials according to claim 2, characterized in that, In the preparation step, a heating unit is further prepared to heat the test object portion coated with the metal material. The energizing step involves heating the test area of ​​the coated metal material to a predetermined temperature while applying a constant voltage or constant current to the series circuit, thereby allowing the corrosion of the coated metal material to proceed. After the specified energizing time, the test unit is disconnected from the series circuit, and heating is stopped or the test object is cooled down to end the test.

4. The corrosion resistance test method for coated metallic materials according to any one of claims 1 to 3, characterized in that, The test unit has a container and electrodes. The container holds an aqueous material in contact with the surface-treated film, and the electrodes are in contact with the aqueous material contained in the container. The energizing unit enables the corrosion of the coated metal material by applying a constant DC voltage or current between the electrode and the metal substrate, respectively, as the anode and cathode.

5. A corrosion resistance testing apparatus for a coated metal material, wherein the coated metal material is formed by depositing a surface treatment film on a metal substrate, characterized in that... The corrosion resistance testing device for the clad metal material includes a testing unit, a series circuit, a power supply unit, a switching unit, a voltage detection unit, and a control device. The test unit has an energizing part that supplies electricity to the test object part covered with metal material. The series circuit is a circuit formed by connecting multiple test units in series. The energizing unit is disposed on the series circuit, and by applying a constant voltage or constant current to the series circuit, the corrosion of the coated metal material is carried out. The switching unit disconnects the test unit from the series circuit and replaces the test unit to form the series circuit. The voltage detection unit detects the voltage in the test unit. The control device monitors the voltage of the test unit through the voltage detection unit, and disconnects the test unit whose voltage exceeds a predetermined threshold from the series circuit through the switching unit.

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