Rust removal method and rust removal device

Abstract

A test piece 100 is immersed in a rust removal liquid 50, the weight change of the test piece 100 immersed in the rust removal liquid 50 is successively measured, the slope of the weight decrease amount is calculated from the weight changes of the test piece 100, and when the slope of the weight decrease amount falls to or below a given level, the immersion is ended. When the immersion is ended, the weight of metal components or corrosion products in the test piece 100 before the immersion is obtained from the immersion time, the weight of the test piece 100, and the slope of the weight decrease amount.

Description

Rust Removal Method and Rust Removal Device

[0001] The present disclosure relates to a rust removal method and a rust removal device.

[0002] Removing corrosion products (rust removal) from a metal sample is a necessary operation for evaluating the amount of corrosion of the metal sample. In a rust removal method in which a metal sample is immersed in a rust removal solution for a predetermined time, the composition, immersion time, and temperature of the rust removal solution are selected and executed according to the material of the metal sample to be rust-removed (Non-Patent Document 1).

[0003] At this time, it is common to use the change in mass as an index for determining the end of rust removal. Specifically, after immersing the metal sample in the rust removal solution, it is taken out, washed with water, the moisture is wiped off, dried, and weighed in a state where the sample temperature has reached room temperature. By repeating this series of operations, the process of gradually decreasing the mass of the metal sample can be traced (Non-Patent Document 2).

[0004] When the sample mass is taken on the vertical axis and the immersion time is taken on the horizontal axis, and the sample mass at each time is plotted, a blank reduction straight line indicating the mass reduction due to the dissolution of the sample itself in the rust removal solution is obtained. It is possible to calculate the amount of corrosion from the intersection of this blank reduction straight line and the vertical axis (Non-Patent Document 3).

[0005] "Standard Metal Test Pieces for Evaluating the Corrosiveness of the Atmospheric Environment and Method for Measuring Their Corrosion Degree", Japanese Industrial Standard, JIS Z 2383:1998, (Annex A (Reference) Chemical Method for Removing Corrosion Products) Hayashi Naohiro, et al. 3, "Application of Composite Cycle Test to Corrosion Promotion Test", Research Report 2013, Aichi Institute of Industrial Science and Technology, pp. 20-23, (2.3 Removal of Corrosion Products) "Handbook of Atmospheric Exposure Tests", Japan Weathering Test Center, January 2007, Gold-17 to Gold-19, ([II] Metal Edition, "9. Supplementary Note")

[0006] In a rust removal method in which a metal sample is immersed in a rust removal solution for a predetermined time, it is necessary to repeat a series of operations such as immersion, washing, wiping off moisture, drying, and weighing, which requires manual work. Therefore, process management is complicated and causes variations in measurement accuracy.

[0007] This disclosure is made in view of the above, and aims to provide a rust removal method and apparatus that reduces the repetition of rust removal work and alleviates the effort involved.

[0008] A rust removal method according to one aspect of the present disclosure involves immersing an object to be rusted in a rust removal solution, sequentially measuring the weight change of the object immersed in the rust removal solution, calculating the slope of the weight loss from the weight change of the object, and ending the immersion when the slope of the weight loss satisfies predetermined conditions.

[0009] According to this disclosure, a rust removal method and apparatus can be provided that reduces the repetition of rust removal work and alleviates labor.

[0010] Figure 1 shows an example of the configuration of the rust removal system in this embodiment. Figure 2 shows an example of the change in the weight of a test piece when it is immersed in the rust removal solution. Figure 3 shows an example of the configuration of the rust removal device. Figure 4 is a flowchart showing an example of the processing flow of the rust removal device. Figure 5 is a graph showing an example of experimental results after rust removal of a test piece. Figure 6 shows an example of the hardware configuration of the rust removal device.

[0011] Embodiments of this disclosure will be described below with reference to the drawings.

[0012] Figure 1 shows an example of the configuration of the rust removal system 1 in this embodiment. The rust removal system 1 shown in the figure comprises a rust removal device 10 and an electronic balance 20, and sequentially measures the weight of the test piece 100 to be rusted while it is immersed in the rust removal liquid 50, and determines the timing to end the immersion based on the change in the slope of the weight loss.

[0013] In the example shown in Figure 1, a weight 30 is attached to the test piece 100 with a rope, the rope is passed through a pulley 40, and the weight 30 is placed on an electronic balance 20 to measure the weight of the test piece 100. The weight of the weight 30 is set to be greater than the weight of the test piece 100. When the test piece 100 is immersed in the rust-removing solution 50, the following equation holds true, so the weight of the test piece 100 can be determined by subtracting the reading of the electronic balance 20 (also called the value of the electronic balance 20 or measured value) from the weight of the weight 30, and then adding the buoyancy acting on the test piece 100.

[0014] Weight of test specimen - Buoyancy = Weight of counterweight - Reading of electronic balance

[0015] The values ​​from the electronic balance 20 are transmitted sequentially to the rust removal device 10. The values ​​from the electronic balance 20 may also be recorded using a logger or the like. Buoyancy can be determined from the volume of the test piece 100 and the density of the rust removal solution 50. Alternatively, the weight of the test piece 100 may be measured before immersion in the rust removal solution 50, and buoyancy may be determined from this measurement, the value from the electronic balance 20 when the test piece 100 is immersed in the rust removal solution 50, and the weight of the counterweight 30. It is sufficient to know the change in weight of the test piece 100 while it is immersed in the rust removal solution 50, so it is not necessary to determine the buoyancy precisely.

[0016] By immersing the test piece 100 in the rust removal solution 50, the corrosion products formed on the test piece 100 dissolve, and the weight of the test piece 100 decreases. While the test piece 100 is immersed in the rust removal solution 50, not only the corrosion products but also a small amount of the metal components of the test piece 100 dissolve. In the phase where all the corrosion products have dissolved and only the metal components have dissolved, the weight loss becomes small, and the weight loss of the test piece 100 per unit time becomes constant. When the weight loss of the test piece 100 per unit time becomes constant, that is, when the change in the slope of the weight loss is below a certain level, the rust removal device 10 determines that the immersion operation is complete.

[0017] Figure 2 shows an example of the change in weight of a test specimen 100 when it is immersed in a rust-removing solution 50. Immediately after immersing the test specimen 100 in the rust-removing solution 50, the amount of mass loss is large as corrosion products are removed. As time passes and almost all of the corrosion products dissolve, only the metal components of the test specimen 100 dissolve, so the amount of mass loss decreases and the change in the slope of the mass loss disappears. Point A in Figure 2 is the weight of the test specimen 100 before rust removal. At point B, most of the corrosion products are removed. At point C, the change in the slope of the mass loss becomes below a certain level, so the immersion process is terminated. The straight line BC is the blank weight loss line, where the mass loss occurs because the test specimen 100 itself dissolves in the rust-removing solution 50. The intersection point D of the straight line BC with the vertical axis is the weight of the test specimen 100 after the corrosion products have been removed. The distance between A and D is the weight loss due to the dissolution of corrosion products. The distance between D and C' is the weight loss due to the dissolution of the metal components of the test specimen 100. C' is the vertical axis component of point C. After the immersion process, the test piece 100 is removed from the rust removal solution 50 and linearly dried. The weight of the test piece 100 is then measured, and the weight loss between points D and C is added to the measured weight to determine the weight of the metallic component of the test piece 100.

[0018] Note that the change in weight of the test piece 100 while it is immersed in the rust-removing solution 50 is affected by the change in buoyancy due to the change in volume, but for simplicity, the change in buoyancy is ignored. If the change in buoyancy is to be considered, the density of the corrosion products and the density of the rust-removing solution 50 may be determined in advance, and the decrease in volume of the test piece 100 and the decrease in buoyancy may be calculated from the weight decrease, and the measured values ​​may be corrected.

[0019] In the rust removal system 1 shown in Figure 1, the weight of the test piece 100 is measured using an electronic balance 20, a weight 30, and a pulley 40, but this is not the only method. It is sufficient to measure the weight change of the test piece 100 immersed in the rust removal solution 50. For example, the weight change of the test piece 100 may be measured using a load cell, a balance scale, or a force gauge.

[0020] Referring to Figure 3, an example of the configuration of the rust removal device 10 for determining the completion of the immersion process will be described. The rust removal device 10 shown in the figure comprises an input unit 11, a calculation unit 12, and a determination unit 13.

[0021] The input unit 11 sequentially inputs the measured values ​​from the electronic balance 20. The input unit 11 and the electronic balance 20 together may be referred to as the measurement unit.

[0022] The calculation unit 12 calculates the slope of the weight loss of the test piece 100 (weight loss per unit time) from the change in the measured value.

[0023] Furthermore, the calculation unit 12 may calculate the amount of corrosion of the test piece 100 after the determination unit 13 has determined that the immersion process is complete. For example, the calculation unit 12 may determine the weight of the corrosion products or metal components of the test piece 100 before immersion from the immersion time, the weight of the test piece 100 at the end of the immersion process, and the slope of the weight loss at the end of the immersion process.

[0024] The determination unit 13 determines that the immersion process is complete when the amount of weight loss has decreased and the change in the slope of the weight loss has stopped or fallen below a certain level.

[0025] The determination unit 13 may, in advance, calculate the chemical reaction between the metal components of the test piece 100 and the rust removal solution 50, derive the weight change (slope) per unit time when the metal components dissolve from the surface area of ​​the test piece 100, and determine that the immersion process is complete when the slope of the weight loss calculated by the calculation unit 12 is the same as the slope derived in advance, or when the difference is less than or equal to a certain level.

[0026] The rust removal system 1 may include a mechanism for lifting the test piece 100 out of the rust removal liquid 50, and when the determination unit 13 determines that the immersion work is complete, the test piece 100 may be lifted out of the rust removal liquid 50. For example, the rust removal system 1 may include a mechanism for raising and lowering a pulley 40, lowering the pulley 40 to immerse the test piece 100 in the rust removal liquid 50, and raising the pulley 40 to lift the test piece 100 out of the rust removal liquid 50 when the immersion work is complete.

[0027] Referring to the flowchart in Figure 4, an example of the processing flow of the rust removal device 10 will be explained. After immersing the test piece 100 in the rust removal liquid 50, the rust removal device 10 performs the process shown in Figure 4.

[0028] In step S11, the input unit 11 sequentially measures the weight of the test piece 100 at predetermined timings.

[0029] In step S12, the calculation unit 12 calculates the slope of the weight loss from the weight change of the test piece 100.

[0030] In step S13, the determination unit 13 determines whether the change in the slope of the weight loss amount has fallen below a certain level. For example, the determination unit 13 determines whether the difference between the slope of the weight loss amount calculated in step S12 and the slope of the weight loss amount at the time of the previous measurement is below a certain level.

[0031] If the change in the slope of the weight loss is not below a certain level, the rust removal device 10 returns to step S11 and measures the weight of the test piece 100.

[0032] If the change in the slope of the weight loss is below a certain level, in step S14, the determination unit 13 determines that the immersion of the test piece 100 is complete. The rust removal device 10 may notify the operator that the immersion is complete, or it may remove the test piece 100 from the rust removal liquid 50.

[0033] In step S15, the calculation unit 12 calculates the amount of corrosion of the test piece 100 from the intercept of the blank loss line.

[0034] Figure 5 shows an example of the experimental results after rust removal from test piece 100.

[0035] The weight of test piece 100 before rust removal was 258g. After immersing test piece 100 in rust removal solution 50, the weight of test piece 100 was measured every 4 minutes. After 20 minutes, the change in the slope of the weight loss of test piece 100 fell below a certain level, so test piece 100 was removed from the rust removal solution 50. At this time, the weight of test piece 100 was 256.6g. The intercept of the blank loss line was calculated from the weight of test piece 100 after 20 minutes and the slope of the weight loss, and it was found to be 257g. Therefore, the weight of the metal component of test piece 100 is 257g, and the weight of the corrosion products of test piece 100 is 1g.

[0036] As described above, the rust removal method of this embodiment involves immersing a test piece 100 in a rust removal solution 50, sequentially measuring the weight change of the test piece 100 immersed in the rust removal solution 50, calculating the slope of the weight loss from the weight change of the test piece 100, and ending the immersion when the change in the slope of the weight loss falls below a certain level. This eliminates the need to repeat the processes of immersion, washing, wiping off moisture, drying, and weighing in the rust removal process, thereby reducing the effort required for rust removal.

[0037] When immersion is complete, the amount of corrosion of the metal sample can be automatically and accurately measured by determining the weight of the corrosion products or metal components of the test piece 100 before immersion from the slope between the immersion time, the weight of the test piece 100, and the weight loss.

[0038] The rust removal device 10 described above can utilize, for example, a general-purpose computer system as shown in Figure 6, which includes a central processing unit (CPU) 901, memory 902, storage 903, communication device 904, input device 905, and output device 906. In this computer system, the rust removal device 10 is realized when the CPU 901 executes a predetermined program loaded onto the memory 902. This program can be recorded on a computer-readable non-temporary recording medium such as a magnetic disk, optical disk, or semiconductor memory, or it can be distributed via a network.

[0039] 1 Rust removal system 10 Rust removal device 11 Input unit 12 Calculation unit 13 Judgment unit 20 Electronic balance 30 Weight 40 Pulley 50 Rust removal liquid 100 Test piece

Claims

1. A rust removal method comprising: immersing an object to be rusted in a rust removal solution; sequentially measuring the weight change of the object immersed in the rust removal solution; calculating the slope of the weight loss from the weight change of the object; and ending the immersion when the slope of the weight loss satisfies predetermined conditions.

2. A rust removal method according to claim 1, wherein immersion is terminated when the change in the slope of the weight loss falls below a certain level.

3. A rust removal method according to claim 1, comprising: determining the weight change per unit time when only the metal component of the object to be rusted dissolves based on the chemical reaction between the metal component of the object to be rusted and the rust removal liquid and the surface area of ​​the object to be rusted; and terminating the immersion when the difference between the slope of the calculated weight loss and the weight change per unit time falls below a certain level.

4. A rust removal method according to claim 1, comprising: calculating the buoyancy acting on the object to be rusted from the amount of weight loss when the object to be rusted is immersed in the rust removal liquid, the density of the corrosion products of the object to be rusted, and the density of the rust removal liquid, and correcting the measurement result with the buoyancy.

5. A rust removal method according to any one of claims 1 to 4, wherein the weight of the corrosion products or metal components of the object to be rusted before immersion is determined from the immersion time, the weight of the object to be rusted, and the slope of the weight loss.

6. A rust removal device for determining when immersion of an object to be rusted in a rust removal solution is complete, comprising: a measuring unit that sequentially measures the weight change of the object to be rusted while it is immersed in the rust removal solution; a calculation unit that calculates the slope of the weight loss from the weight change of the object to be rusted; and a determination unit that determines that immersion is complete when the slope of the weight loss satisfies predetermined conditions.

7. A rust removal device according to claim 6, wherein the weight of the corrosion products or metal components of the object to be rusted before immersion is determined from the immersion time, the weight of the object to be rusted, and the slope of the weight loss.

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