Method for evaluating wettability of solid surface

Abstract

Provided is a method whereby surface wetting characteristics of a solid with respect to an arbitrary liquid can be obtained more simply and quantitatively. In a method for evaluating wettability of a solid surface, two solids are arranged so that the surfaces to be evaluated of the solids face each other with a space therebetween, and at least the entirety of the lower ends of the two solids are present on the same plane to form a test material. Performing an immersion test in which the test material is immersed in an evaluation liquid such that the entire lower end of the test material is parallel to the surface of the evaluation liquid; the wettability height, which is the difference between the liquid level height of an evaluation liquid immersed in a gap between the two solids at an arbitrary immersion time and the surface height of the evaluation liquid, is measured, and this measured value is used as an evaluation value for the wettability of the solid surface with respect to the evaluation liquid.

Description

Technical Field

[0001] The present invention provides a method for evaluating the wettability of a solid surface, which can more simply and quantitatively evaluate the wettability of the solid surface with respect to various liquids in an atmosphere above an arbitrary liquid surface. Background Art

[0002] Typically, the wettability of a liquid and a solid is evaluated by contact angle. The contact angle refers to the angle between the tangent line made to the liquid and the solid surface at the contact point of the three phases of solid, liquid and gas, which includes the angle on the liquid side. In the determination of the contact angle of a liquid and a solid, for example, as shown in non-patent document 1, a static drop method is typically used. This method has a method for directly measuring the contact angle and a method for measuring the angle by image analysis by shooting the profile of the droplet. In fact, a method for evaluating the static wettability of a molten Zn-Al solution on various oxides by a static method is described in non-patent document 3.

[0003] Other wettability evaluation methods include those using the Meniscograph method. As described in Non-Patent Document 2, the Meniscograph method measures the temporal variation in the force acting on a sample while it is immersed in a liquid. Measuring the force at which the force acting on the sample reaches a certain level of stability (equilibrium wetting load) is effective in evaluating solderability, for example.

[0004] Patent Document 1 proposes a method for more simply evaluating the wettability of a solid by a liquid. Specifically, two solids to be evaluated are placed facing each other in a V-shape. When immersed in an evaluation liquid, the height of the solids rising from the liquid surface to the wall surface is measured. This measured value is used to evaluate the wettability of the solids by the liquid.

[0005] Prior art literature

[0006] Non-patent literature

[0007] Non-patent document 1: Ono Shu, "Surface Tension (Surface Tension)", Kyoritsu Publishing, 1980, p. 82

[0008] Non-Patent Document 2: Sadayuki Fujima, “Evaluation of Solder Wettability of Coated Films Using Meniscograph,” Surface Technology, Vol. 63, No. 11, 2012, p. 660

[0009] Non-Patent Document 3: Yunkyum Kim, “Wettability of MnxSiyOz by Liquid Zn-AlAlloys,” Metallurgical Materials Transactions B, 2010, Vol. 14B, p. 872

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 06-148056 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] Among the methods described in Non-Patent Document 1, there are two methods: one that directly measures the contact angle and one that measures the angle by photographing the droplet's profile and analyzing the image. However, the former, due to its subjective judgment, has accuracy issues, while the latter is complicated by its operation. Furthermore, this method suffers from the disadvantage that the larger the contact angle, the greater the measurement error. Furthermore, these methods assume that measurements are performed at room temperature, making them difficult to perform in hot, oxidizable melts.

[0014] In contrast, Non-Patent Document 3 evaluates the wettability of high-temperature molten zinc on arbitrary steel sheets by placing a stage for performing a droplet test in a chamber capable of high-temperature, reduction annealing. However, this evaluation method only evaluates the wettability of a minute amount of liquid on the steel sheet, and there are problems with the method being significantly different from the actual process of continuously immersing the steel sheet in liquid, such as in a hot-dip galvanizing line.

[0015] The Meniscograph method described in Non-Patent Document 2 involves immersing a sample in a liquid, enabling wettability evaluation close to the actual process. This method requires measuring minute temporal changes in the force acting on the sample while immersed in the liquid. In addition to requiring high precision, similar to the aforementioned method, this method also requires high-precision load measurement equipment and skilled personnel.

[0016] In this regard, Patent Document 1 proposes a method for more easily evaluating the wettability of a solid to a liquid. Specifically, two solids to be evaluated are made relative to each other to form a V-shaped body, and the value of the height of the rise from the liquid surface to the wall surface when the solid is immersed in the evaluation liquid is measured, and the measured value is evaluated as the wettability of the solid to the liquid. However, in the numerical comparison described in Patent Document 1, only the evaluation object must be changed under the same conditions. Specifically, from the evaluation liquid, liquid temperature, test piece size, immersion speed, immersion depth, etc., only the conditions that are desired to be used as the object are changed, and a relative comparison is performed. Therefore, there is a problem that it is difficult to measure absolute parameters such as the wetting contact angle. In addition, due to the limitations of the evaluation method, it is difficult to measure the wettability of high-temperature melts such as molten metal plating.

[0017] An object of the present invention is to propose a method for evaluating the wettability of a solid surface with respect to a liquid with high accuracy and quantitatively without requiring a load measuring device.

[0018] Another object of the present invention is to propose a method for evaluating the wettability of a solid surface, which is capable of setting the conditions of the environmental atmosphere to which the solid surface is exposed on the surface of the evaluation liquid.

[0019] Methods used to solve problems

[0020] The present inventors conducted extensive research to address the aforementioned issues and discovered that by horizontally immersing a pair of solid bodies with evaluation surfaces facing each other at a predetermined distance in an evaluation liquid, the difference between the liquid level in the space between the solid bodies and the evaluation liquid level, i.e., the wettability of the solid surface with respect to the evaluation liquid, can be evaluated based on this measured value. This method enables highly accurate evaluation of the wettability of a solid surface with respect to a liquid, even without the use of a load measuring device.

[0021] It is particularly suitable for evaluating the wettability of solid surfaces to molten metals with high precision under controlled atmosphere conditions.

[0022] The present invention has been completed based on such findings, and the gist of the present invention is as follows.

[0023] [1] A method for evaluating the wettability of a solid surface, wherein two solids are arranged so that the surfaces to be evaluated of the solids are spaced apart and face each other and the lower ends of the two solids are entirely on the same plane to form a test material, and an immersion test is performed in which the test material is immersed in an evaluation liquid so that the lower ends of the test materials are entirely parallel to the surface of the evaluation liquid.

[0024] The difference between the liquid level of the evaluation liquid that penetrates into the gap between the two solid bodies and the height of the surface of the evaluation liquid, i.e., the wetted height, is measured at any immersion time.

[0025] This measured value is used as an evaluation value of the wettability of the solid surface with respect to the evaluation liquid.

[0026] [2] A method for evaluating the wettability of a solid surface according to [1], wherein the contact angle between the solid and the evaluation liquid is calculated based on the wetting height and the width of the gap between the solids, and the contact angle is used as an evaluation value of the wettability of the solid surface with respect to the evaluation liquid.

[0027] [3] The method for evaluating the wettability of a solid surface according to [1] or [2], wherein the width w of the gaps between the solids after the immersion test is measured. 试验后 , based on the gap width w 试验后 The gap width w between the solid before the immersion test 试验前 , the above-mentioned wetting height h is corrected according to the following formula (1), and the corrected wetting height h is 修正后 It is an evaluation value of the wettability of the solid surface with respect to the evaluation liquid.

[0028] h 修正后 =(h·w 试验后 ) / w 试验前 (1)

[0029] [4] The wettability evaluation method for a solid surface according to [3], wherein the corrected wetting height h 修正后 The gap width w between the solid and the solid after the immersion test 试验后 The contact angle between the solid and the evaluation liquid is calculated, and the contact angle is used as an evaluation value of the wettability of the solid surface with respect to the evaluation liquid.

[0030] [5] A method for evaluating the wettability of a solid surface according to any one of [1], [2], [3] or [4], wherein the wetting extension rate of the solid-liquid interface is calculated based on the change in the liquid level height immersed in the voids between the solids when the immersion time in the immersion test is changed.

[0031] [6] The method for evaluating the wettability of a solid surface according to any one of [1], [2], [3], [4] or [5], wherein the atmosphere on the evaluation liquid surface during or before immersion in the immersion test is controlled.

[0032] [7] The method for evaluating the wettability of a solid surface according to [6], wherein the evaluation liquid is molten metal.

[0033] [8] The method for evaluating wettability of a solid surface according to [7], wherein the evaluation liquid is molten zinc.

[0034] Effects of the Invention

[0035] According to the present invention, the wettability of solid surfaces to liquids can be evaluated with high precision, without the need for load measurement equipment. Furthermore, the wetting extension rate at the solid-liquid interface can be calculated, allowing the ambient atmosphere to which the liquid surface being measured is exposed to be controlled. As a specific application, the wettability of solid surfaces to high-temperature liquids can be simply and quantitatively measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a diagram schematically showing the test material for evaluating surface wettability of the present invention.

[0037] Figure 2 This is a schematic cross-sectional view in a direction perpendicular to the evaluation surface when the test material for evaluating surface wettability of the present invention is immersed in an evaluation liquid.

[0038] Figure 3 This is a diagram illustrating the Meniscograph method described in Non-Patent Document 2.

[0039] Figure 4 This is a schematic diagram of wetting rise when the liquid surface is well wetted.

[0040] Figure 5 This is a top view of a solid test material for evaluating surface wettability that expands due to temperature increase.

[0041] Figure 6 yes Figure 5 A cross-sectional view along the line A-A'.

[0042] Figure 7 This is a top view of a solid test material for evaluating surface wettability that is dented by temperature increase.

[0043] Figure 8 yes Figure 7 A cross-sectional view along the line A-A'. DETAILED DESCRIPTION

[0044] exist Figure 1 and Figure 2 The method of the present invention is schematically shown in FIG. Figure 1 As shown, first, a spacer is sandwiched between two solid bodies, i.e., a pair of solid bodies, with their evaluation target surfaces facing each other. The two solid bodies are fixed in this state to produce a test material. The opposing solid bodies and the spacer are fixed as needed. The evaluation target surfaces may have curvature, but are preferably flat to improve measurement accuracy. Furthermore, planar plate-like members are suitable for the solid bodies.

[0045] There are no restrictions on the method for securing the two solid bodies, and welding, screw clamps, and the like can be used. The spacer can be made of the same material as the solid bodies, or, for internal visualization, a glass plate or the like can be used. To evaluate the wettability of a surface, the two solid bodies must be arranged so that at least the lower ends of the two solid bodies are entirely on the same plane. Next, the test material is immersed in the evaluation liquid so that its entire lower end is parallel to the surface of the evaluation liquid. The difference between the evaluation liquid surface and the immersion liquid height is measured, and this value is used as the wettability evaluation value.

[0046] The size of the solid is determined by the size of the test material that can be cut and the amount of evaluation liquid to be immersed. However, in order to measure the difference between the evaluation liquid level and the immersion liquid height, the height of the solid (in a direction perpendicular to the evaluation liquid level) is preferably 10 to 1000 mm. The height of the solid is more preferably 50 mm or more. The height of the solid is more preferably 200 mm or less. The width of the solid (equivalent to the distance between the spacers) is preferably 10 to 1000 mm. The width of the solid is more preferably 30 mm or more. The width of the solid is more preferably 150 mm or less.

[0047] To clarify the differences in immersion liquid height caused by differences in wettability, the gap width between solids is preferably 2 mm or less. More preferably, it is 1.5 mm or less. On the other hand, if the gap width is too narrow, the shape of the solid becomes significantly affected, potentially compromising accuracy. Therefore, the gap width is preferably 0.2 mm or greater.

[0048] Next, we will describe the process of discovering the wettability evaluation method of the present invention. The usefulness of contact angle measurement as a wettability evaluation method is well known, but as mentioned above, contact angle measurement is not easy. Therefore, we focused on "capillary action" as a phenomenon that can be used to evaluate wettability. Capillary action is a physical phenomenon in which liquid inside a thin tubular object rises within the tube. The contact angle can be calculated using the following formula: the height h of the liquid surface inside the tube when the thin tubular object is immersed in the evaluation liquid.

[0049] h={2γcosθ / (ρgr)}×10 6 (2)

[0050] Here, h is the height of the liquid surface (mm), γ is the surface tension (N / m), θ is the contact angle (°), and ρ is the density of the evaluation liquid (kg / m 3 ), g: acceleration due to gravity (m / s 2 ), r: inner diameter of the capillary tube (mm).

[0051] However, the above-mentioned derivation of the liquid level height is limited to solids that can be formed into a tubular shape. Therefore, there is a problem that high-strength steel plates, which are difficult to form into a tubular shape, cannot be used as solids for evaluating wettability.

[0052] Therefore, whether it is possible to evaluate the above-mentioned liquid level by a simpler and more practical method has been studied intensively. As a result, it was found that even if Figure 1 The test material with a small distance between solids, that is, a small gap width, also exhibits the same "capillary phenomenon".

[0053] It should be noted that the high-strength steel sheet referred to herein refers to, for example, a steel sheet having the following steel composition: in terms of mass %, containing C: 0.0001% or more and 0.30% or less, Si: 0.001% or more and less than 2.0%, Mn: 0.01% or more and 3.5% or less, P: 0.02% or less, S: 0.01% or less, Al: 0.10% or less, N: 0.006% or less, and further containing Nb: 0.005% to 1%, Ti: 0.005% to 1%, V: 0.005% to 1%, Zr: 0.006% or less, as required. The steel sheet preferably contains at least one of the following: 0.005-1%, Cr: 0.005-20%, Ni: 0.005-10%, Co: 0.005-1%, Mo: 0.005-1%, W: 0.005-1%, Ca: 0.0001-0.01%, Mg: 0.0001-0.01%, REM: 0.0001-0.01%, Sn: 0.001-0.2%, Sb: 0.001-0.2%, and B: 0.0001-0.01%, with the balance being Fe and unavoidable impurities. The steel sheet preferably has a tensile strength TS of 270 MPa or higher.

[0054] The force balance when the test material is immersed is determined using the Meniscograph method described in Non-Patent Document 2 ( Figure 3 ), the following equation holds.

[0055] F = γ cos θ l × 10 -3 -Vρg×10 -9 (3)

[0056] Here, F: vertical force (N), γ: surface tension (N / m), θ: contact angle (°), l: perimeter of the solid being evaluated (mm), V: volume of the immersed part (mm 3 ), ρ: density of the evaluation liquid (kg / m 3 ), g: acceleration due to gravity (m / s 2 Based on this relational expression, the relationship between the liquid level height and the contact angle when the test material of the present invention is used will be described.

[0057] exist Figure 4 A schematic diagram of wetting rise when the liquid surface is well wetted is shown in FIG. Here, “wetting rise” refers to the phenomenon in which a liquid wets the surface of a void between solids and rises.

[0058] exist Figure 4In the method, the height of the immersion liquid surface from the evaluation liquid surface is set to h (mm), and the width of the gap is set to w (mm). It should be noted that in the present method in which two solids are arranged relative to each other, the height of the immersion liquid surface from the evaluation liquid surface h (mm) represents the difference between the height of the liquid surface immersed in the gap between the two solids and the height of the surface of the evaluation liquid. Hereinafter, the height of the immersion liquid surface from the evaluation liquid surface h is sometimes referred to as the wetting height. Here, when the liquid surface stops, the surface tension of the evaluation liquid generated by the wettability is balanced with the mass of the evaluation liquid in the gap, therefore,

[0059] γcosθ·l=Vρg×10 -6 (4).

[0060] Will Figure 1 When the length between the spacers in is assumed to be L (mm), the above formula can be transformed as follows. In this case, the length L between the spacers is set to be sufficiently larger than the gap width w.

[0061] γcosθ·(2L)=(w·h·L)ρg×10 -6 (5)

[0062] cosθ=(whρg×10 -6 ) / (2γ) (6)

[0063] θ=arccos{(whρg×10 -6 ) / (2γ)} (7)

[0064] That is, it is known that if this method is used, the contact angle θ can be derived by measuring the wetting height h at any plate width, and the wettability can be quantitatively evaluated. In addition, if this method is used, the wetting height h between two solids can be measured, and the measured value can be used as the evaluation value of the wettability of the solid surface for the evaluation liquid. In addition, according to this method, the wettability of the solid surface for the liquid can be evaluated with high precision even without using a load measuring device. It should be noted that in the evaluation of the wettability using the method of the present invention, by unifying the immersion time of the solid to a specific time, the wettability between different samples can be relatively compared and evaluated. In addition, the immersion time at this time can be changed according to the purpose.

[0065] In addition, the evaluation device used in the wettability evaluation method of the present invention is as follows Figure 1 It is very simple as shown. By placing the evaluation device in a sealed device that can control the environmental atmosphere and selecting device materials that can be used in the environmental atmosphere, the wettability of solid surfaces to liquids in high temperature environments and corrosive environments can be evaluated with high precision.

[0066] Generally, it is not easy to enable load measuring equipment to be used in high temperature environments and corrosive environments. Here, high temperature refers to a temperature of 100°C or higher and 2000°C or lower. In this method, since the wettability can be measured even when the evaluation liquid is at a high temperature, it is suitable for evaluating the wettability of a solid surface with respect to a molten metal. In particular, in the case of using a high-temperature melt as the evaluation liquid for metal plating, which requires high-precision evaluation of the wettability of a solid surface with respect to a liquid from an industrial point of view, the temperature of the evaluation liquid is mostly 100°C or higher and 700°C or lower. The wettability evaluation method of the present invention is particularly suitable for evaluating the wettability of a solid surface using molten zinc, which has a melting point of mostly 400°C or higher, as the evaluation liquid in the plating treatment of metals.

[0067] It should be noted that when two solids are identical, the derived contact angle represents the wettability of the solid. However, when the solids are two different materials, the derived contact angle is the average of the different contact angles of the two solids. Here, the wetting height h is as follows.

[0068] h={γ(cosθ 固体1 +cosθ 固体2 ) / (ρgr)}×10 6 (8)

[0069] Therefore, by using the wettability evaluation method of the present invention, it is also possible to measure the contact angle of an evaluation liquid in a structure obtained by combining two solids composed of different materials.

[0070] Furthermore, in the wettability evaluation method of the present invention, since the immersion can be performed in a sealed apparatus with a controlled atmosphere, the wettability of a solid surface with respect to liquids under various environmental atmospheres can be evaluated with high precision. For example, in the case of hot-dip galvanizing, representative atmospheric factors include hydrogen concentration, oxygen concentration, carbon monoxide concentration, carbon dioxide concentration, and dew point, an indicator of water vapor concentration. The effects of gas atmospheres that control these factors on wettability can also be evaluated.

[0071] As the inert gas for the remainder of the atmosphere that controls the above-mentioned elements, nitrogen, argon, helium, etc. can be cited. In particular, the present invention has the following characteristics: it is possible to cause a chemical reaction such as an oxidation reaction between the atmospheric gas and the solid in a closed device in which the atmosphere is controlled, thereby coating a part or all of the solid surface with the reaction product generated by the above reaction, and it is possible to evaluate the wettability of the solid surface to the liquid in this state. For example, a sample made of a steel plate is kept in a gas atmosphere controlled to a specified atmosphere for a specified time to oxidize the surface of the steel plate, and the sample coated with oxide is immersed in a high-temperature molten metal for plating without contact with the outside air, thereby evaluating the wettability of the oxide-coated steel plate with the plating solution. That is, in the present invention, it is possible to evaluate the wettability of a liquid with a solid coated with a reaction product at a certain coverage rate.

[0072] Continuously performing the chemical reaction and wettability evaluation within the chamber offers the advantage of preventing changes in the reaction product's crystal structure caused by cooling to room temperature, changes in adhesion, and oxidation caused by contact with the outside air, enabling highly accurate wettability evaluation. Furthermore, this evaluation allows understanding the impact of the gas atmosphere composition on the wettability of the solid with respect to the evaluation liquid. Therefore, in the present invention, it is preferred to control at least one of the following: the temperature, hydrogen concentration, oxygen concentration, carbon monoxide concentration, carbon dioxide concentration, and dew point of the atmosphere at the time of immersion of the solid in the evaluation liquid or at the evaluation liquid surface before immersion.

[0073] In addition, this method does not require forming the test material into, for example, a cylindrical shape, and is therefore suitable for evaluating the wettability of difficult-to-form materials such as high-strength steel sheets.

[0074] Furthermore, when using a small amount of evaluation liquid, the chemical composition of the evaluation liquid may change due to reaction between the evaluation liquid and the solid surface, or the temperature of the evaluation liquid may change significantly due to the influence of the solid's temperature. On the other hand, the wettability evaluation method of the present invention allows the wettability of a solid surface to be evaluated by immersing the sample in the evaluation liquid. Specifically, immersion in the evaluation liquid minimizes changes in the composition and temperature of the evaluation liquid to negligible levels, enabling high-precision wettability measurements even when changes in the composition and temperature of the evaluation liquid are minimal.

[0075] For example, when a molten zinc bath is used as the evaluation liquid and a steel sheet is used as the solid, the Al in the hot-dip galvanizing bath, which serves as the evaluation liquid, reacts with trace amounts of oxides present on the surface of the solid steel sheet, reducing the oxides. Therefore, if a small amount of droplets is used as the evaluation liquid, the Al in the droplets is consumed more, the Al in the droplets disappears, and there is a possibility that the reduction of the oxides on the surface of the steel sheet becomes insufficient. Furthermore, when the temperature of the droplets differs from the temperature of the steel sheet after the addition of the small amount of droplets, the smaller the droplet volume, the greater the temperature change after the droplet is added. This results in different results from the case where the sample is immersed in the evaluation liquid, as in the present invention, in terms of chemical composition and temperature. On the other hand, according to the wettability evaluation method of the present invention, since the sample is immersed in the evaluation liquid, changes in the composition and temperature of the evaluation liquid can be reduced to a negligible level, making it possible to accurately evaluate the wettability of the solid surface to the evaluation liquid while minimizing changes in the composition and temperature of the evaluation liquid.

[0076] In the wettability evaluation method of the present invention, it is preferable to appropriately set the volume of the evaluation liquid as a liquid according to the production method assumed for evaluating wettability.

[0077] From the perspective of reducing the influence of composition changes and temperature changes of the evaluation liquid, the solid evaluation area is 2 (Every 2mm on both sides 2 ), the volume of the evaluation liquid as a liquid is preferably set to 0.8mm 3 More preferably, it is 1.2 mm 3 above.

[0078] In addition, when evaluating the wettability of the present invention, the immersion depth of the solid in the evaluation liquid is preferably less than 60 mm. In the present invention, since the wettability is calculated by the difference between the height of the evaluation liquid wetting rise and the bath liquid surface, the calculation result of the wettability is not affected by the immersion depth of the solid. However, by setting the immersion depth of the solid in the evaluation liquid to less than 60 mm, the elements consumed in the reaction between the solid / evaluation liquid are immediately replenished from the evaluation liquid immersion part at the lower end of the solid, thereby suppressing the change in the component composition of the evaluation liquid in the gap between the immersed solids. From the viewpoint of suppressing the change in the component composition caused by the chemical reaction between the solid and the evaluation liquid, the immersion depth of the solid in the evaluation liquid is more preferably less than 50 mm. In addition, from the viewpoint of fully replenishing the consumed elements in the evaluation liquid, the volume of the evaluation liquid as a liquid is further preferably set to 50 mm per 1 mm on one side of the solid area. 2 (Every 2mm on both sides 2 ) is 5mm 3 above.

[0079] In addition, unlike the conventional method based on measurement at room temperature, such as Patent Document 1, this evaluation method is particularly useful for evaluating high-temperature molten metals, etc., where there is a concern about the shape change of the solid accompanying heating and cooling. By measuring the width w of the gap between the solids before and after the immersion test, the gap width w between the solids is obtained. 试验前 and w 试验后 By correcting the wetting height based on the following calculation formula, wettability can be evaluated with higher accuracy.

[0080] h 修正后 =(h·w 试验后 ) / w 试验前 (1)

[0081] Here, when the solid undergoes shape change, it also includes the case where the solid bends or warps and changes into an irregular shape. In such a case, the gap width w between the solids after the immersion test is calculated. 试验后 It is defined as the distance between the solids at the center of the spacers in the impregnated part of the distance between the solids after the immersion test. In addition, the wetted height h after the test is defined as the difference between the liquid level height on the center line of the liquid level in the vertical direction between the spacers in the impregnated part and the surface height of the evaluation liquid. Furthermore, the corrected wetted height h can also be used to calculate the difference between the liquid level height and the surface height of the evaluation liquid. 修正后 , the gap width w between solids before the test 试验前 Substitute the distance L between the spacers into equation (7) to obtain the corrected estimated wetting contact angle θ 修正后 .

[0082] Furthermore, according to the method of the present invention, not only is the wetting contact angle derived for a specific immersion time, but by intentionally changing the immersion time, the wetting extension rate of the solid-liquid interface of two or more test materials with different immersion times, that is, the time change of the wetting contact angle, can be calculated from the change in the liquid level height in the gap between the two solids immersed in the test materials.

[0083] In addition, when the evaluation liquid level moves up and down with the passage of immersion time, it is necessary to measure the height of the evaluation liquid level together with the height of the liquid level in the infiltrated space.

[0084] The method for calculating the wetting and spreading speed is not particularly specified, but it can be estimated as follows based on the difference between the immersion times of 1 s and 5 s at which the change in the wetting height is greatest, for example.

[0085] (Estimated wetting contact angle θ 1s 修正后 - Estimated wetting contact angle θ 5s 修正后 ) / 4s

[0086] Here, “the estimated wetting contact angle θ 1s 修正后" refers to the corrected estimated wetting contact angle at 1s immersion time. The corrected estimated wetting contact angle is the calculated contact angle using the measured wetting height h and the gap width w between the solids before and after the immersion test. 试验前 and w 试验后 Substituting into formula (1) and calculating the corrected wetting height h 修正后 , the angle estimated according to formula (7).

[0087] Example

[0088] Molten zinc containing 0.2% by mass of Al at 460°C was used as the evaluation liquid, and a pure iron plate was used as the solid. Furthermore, a solid SiO2 or MnO film was formed on the pure iron plate using PVD with an average thickness of 1 μm. As a spacer, a SUS304 plate was used. As the test material, two solids of the same shape were used, and after drilling holes through the solid and the spacer, they were fixed with bolts and screws. Figure 1 The test material shown was first recrystallized and annealed at 700°C, then cooled to 460°C. The entire evaluation apparatus was placed in a sealed chamber with a controlled atmosphere of 10% H₂, the remainder N₂, and unavoidable impurities above the molten zinc bath to prevent oxidation of the molten zinc bath and the solid. In this state, the test material was immersed in the molten zinc bath for 1 to 60 seconds. After immersion, the spacer portion of the test material was cut with a microcutter. The height of the molten zinc wetting rise was visually measured, and the difference from the bath surface was calculated as the wetted height. The wetted height was measured at the centerline of the immersed portion of the solid, farthest from the spacer, perpendicular to the liquid surface.

[0089] Wetting height corresponds to immersion Figure 4 The difference h between the height of the liquid level in the gap and the height of the surface of the evaluation liquid is calculated. At this time, if the wetting height is lower than the bath surface, the wetting height is calculated as a negative value.

[0090] The gap width between two solid bodies of the test material was set to 0.2 mm to 1.2 mm, and the gap width after the immersion test and the gap width between solid bodies at the center between the spacers were also measured.

[0091] like Figure 5 As shown in Table 1, when the shape of the solid changes with heating and cooling, the wetted height is corrected using equation (1).

[0092]

[0093] In Table 1, the results for an immersion time of 1 second correspond to the results of the initial wetting evaluation. The estimated wetting contact angle corresponds to the result calculated from the gap width and the wetted height. The calculation used the surface tension γ of molten zinc at 460°C: 0.77 N / m, and the zinc density ρ: 6.570 g / cm 3 , Gravitational acceleration g: 9.8 m / s 2 .

[0094] Observations of the initial wettability of each solid revealed that pure iron exhibited excellent wettability, but that solids depositing SiO₂ and MnO exhibited poor wettability, leading to an estimated increased contact angle. Regarding the wettability of molten zinc on these oxides, Non-Patent Document 3, for example, reports that the static wetting contact angle of molten zinc on SiO₂ and MnO is approximately 120°. However, contact angle measurements using the method used in this study revealed that the contact angle assumed in the actual process is even larger than that reported in Non-Patent Document 3.

[0095] Furthermore, when the immersion time was set to 5 seconds or longer, the wetting height increased in pure iron and in the solid film forming MnO. This is because, in a system where an alloy reaction occurs between molten zinc and pure iron, the iron-zinc alloy reaction proceeds over time, causing an increase in the wetting height (wetting spread). Therefore, the contact angle calculated from this wetting height corresponds to a value that includes wetting spread during the initial wetting phase and is reported only as a reference value.

[0096] On the other hand, in the solid formed with SiO2, almost no change in the wetted height due to immersion time was observed, suggesting that the reaction rate of the iron-zinc alloy on the solid formed with SiO2 was much slower than that on the other two solids.

[0097] There is no particular method for estimating the wetting and spreading speed, but here, the estimation is made as follows based on the difference between the immersion times of 1 s and 5 s, at which the change in the wetting height is greatest.

[0098] Wetting extension speed = (estimated wetting contact angle θ 1s 修正后 - Estimated wetting contact angle θ 5s 修正后 ) / 4s (9)

[0099] As described above, using the present invention, not only can the wettability of a solid surface for any liquid be obtained more simply and numerically, it is also possible to perform a quantitative comparative evaluation of the wetting spread behavior. Furthermore, when the shape of a solid changes with heating and cooling, the wettability of the solid surface can be obtained more simply and numerically by correcting the surface height of the evaluation liquid based on the change in the width of the gaps between the solids. Furthermore, the wettability of a solid surface for liquids under specific ambient atmospheres can be measured. In particular, the present invention can evaluate the wettability of a solid surface for a plating bath liquid under conditions assumed to be the actual operation of hot-dip galvanizing, which is widely used in industry.

[0100] Explanation of symbols

[0101] 1 solid

[0102] 2 spacers

[0103] 3 Gap Width

[0104] 4 Evaluation liquid

[0105] 5 Immerse in liquid

[0106] 6Evaluate the liquid level

[0107] F vertical force

[0108] γ surface tension

[0109] The perimeter of the solid

[0110] V is the volume of the immersed part

[0111] θ contact angle

[0112] h is the height of the immersion liquid from the evaluation liquid surface

[0113] wGap width

[0114] h 修正后 Corrected wetting height

[0115] w 试验前 Gap width before immersion test

[0116] w 试验后 Gap width after immersion test

Claims

1. A method for evaluating the wettability of a solid surface, wherein: Two solids are arranged so that the evaluation target surfaces of the solids are spaced apart and face each other and the lower ends of the two solids are entirely on the same plane to prepare a test material, and an immersion test is performed in which the test material is immersed in the evaluation liquid so that the lower end of the test material is entirely parallel to the surface of the evaluation liquid, The difference between the height of the liquid surface of the evaluation liquid that penetrates into the gap between the two solid bodies at an arbitrary immersion time and the height of the surface of the evaluation liquid, that is, the wetted height is measured. This measured value is used as an evaluation value of the wettability of the solid surface with respect to the evaluation liquid.

2. The method for evaluating wettability of a solid surface according to claim 1, wherein: Based on the wetting height and the gap width between the solids, the contact angle between the solid and the evaluation liquid is calculated, and the contact angle is used as an evaluation value of the wettability of the solid surface with respect to the evaluation liquid.

3. The wettability evaluation method for a solid surface according to claim 1 or 2, wherein: The width w of the gap between the solids after the immersion test was measured. 试验后 , based on the gap width w 试验后 and the gap width w between the solid before the immersion test 试验前 , the wetting height h is corrected according to the following formula (1), and the corrected wetting height h is 修正后 As an evaluation value of the wettability of the solid surface with respect to the evaluation liquid, h 修正后 =(h·w 试验后 ) / w 试验前 (1)。 4. The method for evaluating wettability of a solid surface according to claim 3, wherein: The corrected wetting height h 修正后 and the gap width w between the solids after the immersion test 试验后 The contact angle between the solid and the evaluation liquid is calculated, and the contact angle is used as an evaluation value of wettability of the solid surface with respect to the evaluation liquid.

5. The method for evaluating wettability of a solid surface according to any one of claims 1, 2, 3 or 4, wherein: The wetting extension rate of the solid-liquid interface was calculated from the change in the height of the liquid surface that penetrated into the interstices between the solids when the immersion time in the immersion test was changed.

6. The method for evaluating wettability of a solid surface according to any one of claims 1, 2, 3, 4 or 5, wherein: The atmosphere on the evaluation liquid surface during or before immersion in the immersion test is controlled.

7. The method for evaluating wettability of a solid surface according to claim 6, wherein: The evaluation liquid is molten metal.

8. The method for evaluating wettability of a solid surface according to claim 7, wherein: The evaluation liquid is molten zinc.

Images