JP2021116451A - Metallic member - Google Patents

Abstract

To provide a metallic member which does not need a surface treatment by SAM or the like but which has its surface with liquid repellency and anticorrosiveness.SOLUTION: A metallic member of the present invention has a porous surface which is directly coated with hydrocarbon-based oil including a zinc dialkyldithiophosphate (ZnDTP). The porous surface may be an oxidized surface, or specifically an anode oxidized surface. The metallic member may be: Al, Ti, Fe, or Mg; or an alloy of any one of them; or a stainless steel member. The concentration of the zinc dialkyldithiophosphate (ZnDTP) may be 0.1 mass% to 30.0 mass% with respect to the hydrocarbon-based oil.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to metal members.

A metal member having a liquid-repellent surface is industrially sought after.

The liquid-repellent surface is a liquid-repellent surface composed of a rough surface having a low surface free energy and a fine uneven structure and a lubricating oil film applied on the rough surface. A liquid slippery surface called is known.

A rough surface with low surface free energy improves the wetting of the lubricating oil and prevents the liquid from adhering firmly to the solid surface, so the droplets adhering to the lubricating oil film gain high mobility and are easy with a slight inclination. Sliding down.

Since SLIPS has such characteristics, it can be used not only as a liquid-repellent, antifouling, and corrosion-resistant surface, but also on a non-icing surface that prevents the adhesion of ice, and the adhesion of biological liquids such as blood. It is thought that it is possible to develop applications that are difficult with conventional superhydrophobic and superhydrophobic surfaces, such as biologically soiled surfaces that prevent water stains and water harvesting technology that utilizes the high cohesiveness of droplets on the lubricating oil film. ing.

Typical examples of substances having low surface free energy include fluororesins such as polytetrafluoroethylene (PTFE; critical interfacial tension γ _C = 18 mNm- ¹ ), but their uses are limited.

On the other hand, there is a great demand industrially for liquid repellency on various metal oxide surfaces. Although the surface free energy of metal oxides is very high compared to other substances, long-chain perfluoroalkyl groups having _{-CF 3} (γ _C = 6 mNm- ¹ _{) at the end and -CH 3} ( It is known that the surface free energy can be significantly reduced by modifying the surface with a self-assembled organic monolayer (SAM) composed of a long-chain alkyl group having γ _C = 24 mNm- ^1). Among them, the phosphonic acid derivative widely used in recent years is a very stable compound by itself, and forms a stable SAM having a higher density than the silane coupling agent known for a long time.

Further, as disclosed in Patent Document 1, regarding steel materials such as automobile engine parts, the steel materials are plasma-nitrided and then nitrogen ions are injected to make the nitrogen concentration on the surface of the steel materials 30 atomic% or more. It is known that the impact resistance, wear resistance and corrosion resistance of steel materials are enhanced by the surface treatment method of.

Japanese Unexamined Patent Publication No. 2003-073800

The chemical substance for forming the above SAM is expensive, and strict solution control is required when coating with the SAM by the liquid phase method, and expensive equipment is required when the coating is performed by the vapor phase method.

Therefore, if a metal member having a liquid-repellent surface can be manufactured without the need for surface treatment by SAM or the like, it is expected that the treatment process will be simplified and the cost will be significantly reduced in the case of large-scale industrialization.

However, in order to slide the adhering liquid down, it has been considered that surface treatment by SAM or the like for reducing the surface free energy of the metal oxide surface is indispensable.

In fact, the present disclosers cannot even prevent the adhesion of water even if a lubricating oil or silicone oil made of a fluoropolymer, which is well known as a lubricating oil for SLIPS, is used, unless the surface treatment is performed by SAM or the like. I got the finding.

An object of the present disclosure is to provide a metal member having a water-repellent and corrosion-resistant surface without requiring a surface treatment such as SAM.

The Discloser has found that the above tasks can be achieved by the following means:
<< Aspect 1 >>
A metal member having a porous surface, wherein the porous surface is directly coated with a hydrocarbon-based oil containing zinc dialkyldithiophosphate (ZnDTP).
<< Aspect 2 >>
The metal member according to aspect 1, wherein the porous surface is an oxidized surface.
<< Aspect 3 >>
The metal member according to aspect 2, wherein the porous surface is an anodized surface.
<< Aspect 4 >>
The metal member according to any one of aspects 1 to 3, wherein the metal member is a member of Al, Ti, Fe, Mg, an alloy of any of these metals, or stainless steel.
<< Aspect 5 >>
The metal member according to any one of aspects 1 to 4, wherein the concentration of the zinc dialkyldithiophosphate (ZnDTP) is 0.1% by mass to 30.0% by mass with respect to the hydrocarbon-based oil.
<< Aspect 6 >>
The metal member according to any one of aspects 1 to 5, wherein the hydrocarbon oil is an engine oil.
<< Aspect 7 >>
The metal member according to any one of aspects 1 to 6, which is a member for an automobile.
<< Aspect 8 >>
The metal member according to aspect 7, which is used for a portion to which engine oil is supplied.
<< Aspect 9 >>
The metal member according to aspect 7 or 8, which is a member for an intercooler.

According to the present disclosure, it is possible to provide a metal member having a water-repellent and corrosion-resistant surface without requiring a surface treatment such as SAM.

FIG. 1A is a scanning electron microscope (SEM) image of the surface of an aluminum plate having a porous surface. FIG. 1B is a scanning electron microscope (SEM) image of the surface of an aluminum plate having a hierarchically structured porous surface. FIG. 1C is a diagram showing the contact angle of water droplets or automobile engine oil droplets with respect to the surfaces of the aluminum plates of Reference Examples 1 to 4. FIG. 2A is a graph showing the relationship between the rotation speed of the aluminum plate and the remaining amount of engine oil for automobiles (rotation time: 60 seconds) for each of the aluminum plates of Examples 1 and 2 and Comparative Example 5. FIG. 2B is a graph showing the relationship (rotation time: 60 seconds) between the rotation speed of the aluminum plate and the falling angle of 10 μL of water droplets for each of the aluminum plates of Examples 1 and 2 and Comparative Example 5. FIG. 2C shows the relationship between the remaining amount of automobile engine oil and the falling angle of 10 μL of water droplets (rotation time: 10, 60, 300 seconds) for each of the aluminum plates of Examples 1 and 2 and Comparative Example 5. It is a graph. FIG. 3 is a graph showing the relationship between the immersion time in the mixed solution and the falling angle of 10 μL of water droplets for the aluminum plates of Examples 1 and 2 and Comparative Examples 5 and 7. FIG. 4 is a graph showing the weight change of the aluminum plates of Examples 1 and 2 and Comparative Examples 1 to 6 after the corrosion resistance test. FIG. 5A is a scanning microscope (SEM) image of the surface of an anodized aluminum plate without hierarchical structuring before the corrosion resistance test. FIG. 5B is a scanning microscope (SEM) image of the surface of the aluminum plate of Comparative Example 5 after the corrosion resistance test. FIG. 5C is a scanning microscope (SEM) image of the surface of the aluminum plate of Comparative Example 3 after the corrosion resistance test. FIG. 5D is a scanning microscope (SEM) image of the surface of the aluminum plate of Example 1 after the corrosion resistance test. FIG. 5E is a scanning microscope (SEM) image of the surface of the aluminum plate of Comparative Example 1 after the corrosion resistance test. FIG. 6A is a scanning microscope (SEM) image of the surface of a hierarchically structured and anodized aluminum plate before a corrosion resistance test. FIG. 6B is a scanning microscope (SEM) image of the surface of the aluminum plate of Comparative Example 6 after the corrosion resistance test. FIG. 6C is a scanning microscope (SEM) image of the surface of the aluminum plate of Comparative Example 4 after the corrosion resistance test. FIG. 6D is a scanning microscope (SEM) image of the surface of the aluminum plate of Example 2 after the corrosion resistance test. FIG. 6E is a scanning microscope (SEM) image of the surface of the aluminum plate of Comparative Example 2 after the corrosion resistance test. FIG. 7 is a diagram showing a method of manufacturing the aluminum plate of Reference Example 5. FIG. 8A is a diagram showing the state of the surface of the aluminum plate of Reference Example 5 and the contact angle when 10 μL of water droplets are placed. FIG. 8B is a diagram showing the state of the surface of the aluminum plate of Reference Example 6 and the contact angle when 10 μL of water droplets are placed. FIG. 9A is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of the surface of the aluminum plate of Reference Example 5 after being immersed in and washed with automobile engine oil. FIG. 9B is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of the surface of the aluminum plate of Reference Example 5 after being immersed in and washed with automobile engine oil. FIG. 9C is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of the surface of the aluminum plate of Reference Example 5 after being immersed in and washed with automobile engine oil. FIG. 10 is a graph showing the electrochemical measurement results of Examples 3 to 5 and Comparative Example 8 aluminum plate. FIG. 11 is a graph showing the electrochemical measurement results of the aluminum plates of Example 3 and Comparative Examples 8 to 10.

Hereinafter, embodiments of the present disclosure will be described in detail. It should be noted that the present disclosure is not limited to the following embodiments, but can be variously modified and implemented within the scope of the main purpose of the disclosure.

The metal member of the present disclosure has a porous surface, and the porous surface is directly coated with a hydrocarbon-based oil containing zinc dialkyldithiophosphate (ZnDTP).

《Metallic parts》
In the present disclosure, the metal member has a porous surface.

Here, the porous surface is a porous film formed on the surface of a metal member, and may be, for example, an oxidized surface having an oxide of a metal of the same type as the metal member. More specifically, the porous surface may be an anodized surface.

The anodized surface can be obtained by anodizing a metal member. For example, when the metal member is an Al member, anodizing treatment is performed, more specifically, Al is used as an anode (+ pole). It can be obtained by a surface treatment that produces an oxide film (Al ₂ O _{3) by electrolytic treatment.} The alumite treatment can be performed based on, for example, JIS H8601 or JIS H8603, but other methods may be used.

The thickness and pore diameter of the porous surface are not particularly limited.

The thickness of the porous surface can be appropriately adjusted according to the use of the metal member.

The shape of the porous surface is not limited as long as it is a liquid slippery surface (SLIPS). The pore diameter (diameter) of each pore on the porous surface may be 1 nm or more and 5 μm or less. The porous surface can have a microscale concavo-convex structure, a nanoscale concavo-convex structure, or a structure in which these are mixed, and may further have a hierarchical structure thereof.

For example, when the porous surface has a microscale uneven structure, the pore diameter (diameter) of each hole on the porous surface may be 0.1 μm or more and 5 μm or less, but 0.1 μm or more and 0.5 μm or less. Is desirable.

When the porous surface has a nanoscale uneven structure, the pore diameter (diameter) of each pore on the porous surface may be 1 nm or more and 100 nm or less, but is preferably 30 nm or more and 100 nm or less. ..

The material of the metal member may be any metal capable of forming a porous surface, for example, the metal member may be Al, Ti, Fe, or Mg, or an alloy of any of these metals, or stainless steel. It may be a member of.

The metal member can be a member used for any purpose, and may be, for example, a member for a vehicle, more specifically, a member for an automobile.

When the metal member is an automobile member, it is preferably used for a portion to which engine oil is supplied. This is because when the metal member of the present disclosure is applied to such a portion, the engine oil can always be supplied to the metal member even if the engine oil as the hydrocarbon oil is desorbed from the surface of the metal member.

When the metal member is an automobile member, the metal member can be an intercooler member. The intercooler is a device into which high-temperature air flows in, and exhaust gas also flows in depending on the configuration of the automobile. Therefore, the intercooler has a member that is easily corroded among the devices installed in the automobile. Examples of such a member include a heat exchanger and the like. Therefore, by applying the metal member of the present disclosure to such a member, the corrosion resistance of the intercooler can be improved.

《Hydrocarbon oil》
Hydrocarbon-based oils contain at least zinc dialkyldithiophosphate (ZnDTP). The hydrocarbon oil may be a paraffin oil or a polyalforefin. Further, the hydrocarbon-based oil may be, for example, a lubricating oil, specifically an engine oil, and more specifically, an engine oil for an automobile.

Zinc dialkyldithiophosphate (ZnDTP) imparts water repellency to the surface of the metal member when contained in a hydrocarbon-based oil. More specifically, zinc dialkyldithiophosphate (ZnDTP) forms a liquid-repellent film on the surface of a metal member by chemically adsorbing it on the surface of the metal member by applying a hydrocarbon-based oil containing the zinc dithiophosphate (ZnDTP) to the metal member. Conceivable.

The concentration of zinc dialkyldithiophosphate (ZnDTP) may be 0.1% by mass to 30.0% by mass with respect to the hydrocarbon-based oil. The concentration of zinc dialkyldithiophosphate (ZnDTP) may be 0.1% by mass or more, 1.0% by mass or more, 2.0% by mass or more, or 5.0% by mass or more, and 30.0% by mass or less. , 20.0% by mass or less, 10.0% by mass or less, or 5.0% by mass or less.

<< Reference Examples 1 to 4 >>
The metal members of Reference Examples 1 to 4 were prepared as follows, and the liquid repellency in each example was evaluated.

<Reference example 1>
A 99.5% aluminum (Al) plate was cut into a size of 20 mm × 50 mm, and acetone degreasing was performed by ultrasonic cleaning for 10 minutes. Then, it was immersed in a 1.0 M NaOH aqueous solution (60 ° C.) for 120 seconds to remove the oxide film, and further immersed in a 1.0 M HNO ₃ aqueous solution (60 ° C.) for 180 seconds to remove the smut generated in the previous process. ..

Next, anodic oxidation was _{carried out in a 0.3 M aqueous solution of H 2} SO ₄ (15 ° C.) at a voltage between plates of 25 V for 180 seconds to form an anodic oxide film having nanometer-scale pores. This was performed with a two-electrode system in which the above substrate was used as the working electrode and another Al plate was used as the counter electrode.

Then, the pore diameter was expanded by immersing in a 5 wt% H ₃ PO ₄ aqueous solution (30 ° C.) for 15 minutes.

Finally, the surface was cleaned by applying oxygen plasma treatment for 4 minutes to obtain an aluminum plate having a porous anodized surface.

<Reference example 2>
An aluminum plate having a hierarchical structure was obtained in the same manner as in Reference Example 1 except that chemical etching was performed before anodic oxidation to form micrometer-scale etch pits.

<Reference example 3>
The aluminum plate of Reference Example 1 was subjected to oxygen plasma treatment, and then _{immersed in an ethanol solution of 1 mM CF 3} (CF ₂ ) ₇ PO (OH) ₂ (perfluorooctylphosphonic acid; FOPA) for 2 days. Finally, a self-assembled organic monolayer (SAM) was formed on the surface of the aluminum plate of Reference Example 1 by performing a heat treatment in an air atmosphere (100 ° C.) for 1 hour.

<Reference example 4>
Self-assembled monolayer on the surface of the aluminum plate of Reference Example 2 having a hierarchical structure in the same manner as in Reference Example 3 except that the aluminum plate of Reference Example 2 was used instead of the aluminum plate of Reference Example 1. A molecular film (SAM) was formed.

<Measurement of liquid repellency>
(Measuring method)
The contact angle of water droplets or automobile engine oil droplets was measured for each of the aluminum plates of Reference Examples 1 to 4.

For the aluminum plates of Reference Examples 1 and 3 having no hierarchical structure, the static contact angle is measured, and for the aluminum plates of Reference Examples 2 and 4 having a hierarchical structure, the forward contact is a dynamic contact angle. Angle and contact angle hysteresis were measured.

(result)
The configurations and evaluation results of Reference Examples 1 to 4 are shown in Table 1 and FIGS. 1A to 1C. In the table, the inside of the parentheses () in the contact angle column indicates the contact angle hysteresis.

FIG. 1A is a scanning microscope (SEM) image of the aluminum plate of Reference Example 1. _{As shown in FIG. 1A, a porous Al 2} O ₃ film is formed on the surface of the aluminum plate of Reference Example 1 by anodic oxidation. Further, as shown in FIG. 1B, a hierarchical structure is formed on the surface of the aluminum plate of Reference Example 2 by etching micrometer-scale pits and a porous Al ₂ O _{3 coating.}

As shown in Table 1 and FIG. 1C, the aluminum plates of Reference Examples 1 and 2 that did not form the self-assembled monolayer (SAM) had contact angles of 4.6 ± 1.2 and water droplets, respectively. It was ~ 0 and was superhydrophilic. On the other hand, the aluminum plates of Reference Examples 3 and 4 on which the self-assembled organic monolayer (SAM) was formed had contact angles of 129.1 ± 0.8 and 161.7 ± 1.0 with respect to water droplets, respectively. It had high water repellency.

Further, the aluminum plate of Reference Example 4, which has a hierarchical structure and has a self-assembled organic monolayer (SAM) formed on the surface, shows a large contact angle of 158.2 ± 1.5. In contrast, Reference Examples 1 to 3 had a contact angle of 90 ° or less and had low liquid repellency, whereas they had high liquid repellency with respect to automobile engine oil droplets.

This indicates that the engine oil for automobiles can be formed as an oil film, at least for the aluminum plates of Reference Examples 1 to 3.

<< Examples 1 and 2 and Comparative Examples 5 to 7 >>
The aluminum plates of Examples 1 and 2 and Comparative Examples 5 to 7 were prepared and their performances were evaluated as follows.

<Examples 1 and 2 and Comparative Examples 5 and 6>
Weigh 100 μL of automobile engine oil, apply it to the surface of each of the aluminum plates of Reference Examples 1 to 4, and leave it to stand for 10 minutes or more to obtain aluminum plates of Examples 1 and 2 and Comparative Examples 5 and 6. rice field.

As shown in the evaluation of the liquid repellency of the automobile engine oil according to the above reference example 4, the automobile engine is on the surface of the aluminum plate of the automobile engine oil which has a hierarchical structure and is SAM coated. Since the oil did not get wet and spread sufficiently, it was immersed in the engine oil for 48 hours in advance to deteriorate the oil repellency, and then the automobile engine oil was applied.

<Comparative Example 7>
Aluminum of Comparative Example 7 except that an automobile engine oil was applied to an aluminum plate which had not been subjected to any of layered structure by etching, porosification by anodic oxidation, and SAM coating in the same manner as in Example 1. I got a board.

<Evaluation of SLIPS stability in an environment where shearing force is applied to automobile engine oil>
(Evaluation method)
With respect to the aluminum plates of Examples 1 and 2 and Comparative Example 5, the retention and liquid sliding characteristics of the automobile engine oil in an environment where a shearing force is applied to the automobile engine oil were evaluated. This is intended to simulate the deterioration of SLIPS in an environment where lubricating oil is lost due to gravity or wind.

As an evaluation method, first, each of the aluminum plates of Examples 1 and 2 and Comparative Example 5 was rotated using a spin coater under the conditions of a rotation speed of 500 rpm to 7000 rpm and a rotation time of 10 seconds to 300 seconds. .. Then, the weight of the remaining automobile engine oil and the falling angle of 10 μL of water droplets were measured.

(result)
The measurement results are shown in FIGS. 2A to 2C. Note that FIG. 2A is a graph showing the relationship between the rotation speed of the aluminum plate and the remaining amount of engine oil for automobiles (rotation time: 60 seconds) for each of the aluminum plates of Examples 1 and 2 and Comparative Example 5. 2B is a graph showing the relationship between the rotation speed of the aluminum plate and the falling angle of 10 μL of water droplets (rotation time: 60 seconds) for each of the aluminum plates of Examples 1 and 2 and Comparative Example 5. FIG. 2C shows the relationship between the remaining amount of automobile engine oil and the falling angle of 10 μL of water droplets (rotation time: 10, 60, 300 seconds) for each of the aluminum plates of Examples 1 and 2 and Comparative Example 5. It is a graph.

As shown in FIG. 2A, in any of the aluminum plates, as the rotation speed increased and the centrifugal force applied to the automobile engine oil increased, the remaining amount of the automobile engine oil decreased accordingly.

This remaining amount was particularly large in the aluminum plate of Example 2 which had a hierarchical structure. It is considered that this is because the aluminum plate having a hierarchical structure has micrometer-scale unevenness, and the engine oil for automobiles is held therein.

Further, when comparing the aluminum plates of Example 1 and Comparative Example 5 which did not have a hierarchical structure, there was no significant difference in the remaining amount of the engine oil for automobiles.

As shown in FIG. 2B, regarding the water droplet fall angle, even in the aluminum plate of Example 1 which does not have a hierarchical structure and is not subjected to SAM coating, by applying automobile engine oil to the porous surface. It was confirmed that the attached water droplets slipped down at a certain fall angle. Since the surface of the aluminum plate itself of Example 1 exhibits hydrophilicity as shown in FIG. 1C, it is considered that SLIPS cannot be formed by itself.

Comparing the aluminum plates of Examples 1 and 2 and Comparative Example 5, the water droplet fall angle increases as the rotation speed increases, that is, the water repellency decreases, but the one that is most likely to decrease has a hierarchical structure. It is the aluminum plate of Example 2 that is not SAM coated and has the smallest water droplet fall angle, that is, it maintains water repellency because it does not have a hierarchical structure and has no SAM coating. It was an aluminum plate of Example 1 without SAM coating.

The reason why the water droplet fall angle was particularly likely to increase in the aluminum plate of Example 2 is that the originally smooth lubricating oil film reflects the roughness of the rough surface according to the loss of the lubricating oil, and the lubricating oil film becomes It is considered that the surface was roughened and the contact area with water droplets increased.

Looking at the relationship between the remaining amount of automobile engine oil and the falling angle of 10 μL of water droplets, it is the hierarchical structure that shows the smallest water droplet falling angle (good water repellency) when the remaining amount of lubricating oil is the same. It was an aluminum plate of Example 1 which did not have and did not have SAM coating.

From the above, as shown in FIG. 2C, the surface formed by directly applying the automobile engine oil to the aluminum plate not coated with SAM as in Examples 1 and 2 is made of aluminum as in Comparative Example 5. It has been shown that not only can water droplets slide down easily, but also maintain the highest stability in an environment where the lubricating oil is sheared, similar to the surface formed by SAM coating the plate.

<Evaluation of SLIPS stability in water>
(Evaluation method)
A mixed solution was prepared by stirring acetic acid and a 10 g / L NaCl aqueous solution (pH = 3) at 1000 rpm. The aluminum plates of Examples 1 and 2 and Comparative Examples 3 and 7, respectively, were immersed in this mixed solution and taken out after a predetermined time had elapsed. Then, the falling angle of 10 μL of water droplets on the aluminum plate of each example was measured. The amount of automobile engine oil applied on the aluminum plate of each example was 3.75 μL / cm ² .

(result)
FIG. 3 is a graph showing the relationship between the immersion time in the mixed solution and the falling angle of 10 μL of water droplets for the aluminum plates of Examples 1 and 2 and Comparative Examples 5 and 7.

As shown in FIG. 3, the water droplet fall angle exceeded the measurement limit of 20 ° within a few days in all cases, but the small water droplet fall angle was maintained for the longest time (that is, high water repellency was maintained). It was the aluminum plate of Example 1 that was not SAM coated. On the other hand, the aluminum plate of Example 2 having a hierarchical structure and not being SAM coated is most likely to have water droplet dripping (that is, decrease in water repellency), and the aluminum plate of Comparative Example 7, that is, the hierarchical structure is also porous. It exceeded 20 ° in a shorter period of time than the one in which automobile engine oil was applied to a smooth aluminum plate that had not been qualified.

From this, it can be said that when SLIPS is formed by directly applying automobile engine oil to an aluminum plate that has not been subjected to SAM coating, higher underwater stability can be obtained by not having a hierarchical structure.

<Corrosion resistance test>
The corrosion resistance of the aluminum plates of Examples 1 and 2 and Comparative Examples 1 to 6 was evaluated as follows.

(Test method)
After immersing the aluminum plate of each example in the above mixed solution for 5 days, changes in the weight of the substrate and changes in the surface morphology were observed.

(result)
The results are shown in Table 1, and FIGS. 4, 5A to 5A, and 6A to 6E.

In Table 1, "○" indicates that the corrosion resistance was good, and "x" indicates that there was no corrosion resistance.

FIG. 4 is a graph showing the weight change of the aluminum plates of Examples 1 and 2 and Comparative Examples 1 to 6 after the corrosion resistance test.

As shown in FIG. 4, the aluminum plates of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4 to which the automobile engine oil was not applied were all 0.5 mg / cm ^{2 to} 1.5 mg. / cm ² or so, weight was reduced. This is due to the melting of aluminum due to corrosion.

On the other hand, in the aluminum plates of Examples 1 and 2 and Comparative Examples 5 and 6 coated with the engine oil for automobiles, the weight change was 0.1 mg / cm ² or less, and the weight loss due to corrosion could be suppressed. rice field. The weights of the aluminum plates of Example 2, Comparative Example 5, and Comparative Example 6 are slightly increased after the corrosion resistance test. This is because even if these aluminum plates were washed with an organic solvent such as acetone after the corrosion test, a slight white product remained. The white product is considered to be a reaction product of a neutralizing agent contained as an additive for an automobile engine oil and a mixed solution.

These results show that by applying the engine oil for automobiles on the porous aluminum plate, the same corrosion resistance as when the SAM coating is applied on the porous aluminum plate can be obtained. There is.

The surface condition of the aluminum plates of Example 1, Example 2, Comparative Example 5, and Comparative Example 6 after the corrosion resistance test was observed with a scanning microscope.

FIG. 5A is a scanning electron microscope (SEM) image of the surface of an anodized aluminum plate without hierarchical structure before the corrosion resistance test, and FIGS. 5B to 5E show Comparative Example 5 and Comparison, respectively. 3 is a scanning electron microscope (SEM) image of the surface of the aluminum plate of Example 3, Example 1, and Comparative Example 1 after the corrosion resistance test.

Referring to FIGS. 5A, B, and D, comparing the aluminum plates of Comparative Example 5 and Example 1 which are porous and whose surface is coated with automobile engine oil, regardless of the presence or absence of SAM coating. After the corrosion resistance test, the same porous film as before the test remained, and it can be said that the pore structure was maintained.

On the other hand, as shown in FIG. 5C, in Comparative Example 3 in which only the SAM coating was applied and the automobile engine oil was not applied to the surface, the anodic oxide surface was dissolved and the pore structure disappeared. Further, in Comparative Example 1 in which the SAM coating was not applied and the automobile engine oil was not applied, not only the anodic oxide surface but also the base aluminum plate was significantly dissolved.

Further, FIG. 6A is a scanning electron microscope (SEM) image of the surface of the aluminum plate which has been hierarchically structured and anodized before the corrosion resistance test, and FIGS. 6B to 6E are comparative examples 6 in order. It is a scanning electron microscope (SEM) image of the surface of the aluminum plate of Comparative Example 4, Example 2, and Comparative Example 2 after the corrosion resistance test.

Referring to FIGS. 6A, B, and D, a comparison of the aluminum plates of Comparative Example 6 and Example 2 having a hierarchical structure, being porous, and having an automobile engine oil coated on the surface is SAM. Regardless of the presence or absence of the coating, the same porous film as before the test remained after the corrosion resistance test, and it can be said that the pore structure was maintained.

On the other hand, as shown in FIG. 6C, in Comparative Example 4 in which only the SAM coating was applied and the surface was not coated with the engine oil for automobiles, the anodized surface was dissolved and the pore structure disappeared. Further, in Comparative Example 2 in which the SAM coating was not applied and the automobile engine oil was not applied, not only the anodic oxide surface but also the base aluminum plate was significantly dissolved.

From these results, it was made porous by applying the automobile engine oil directly to the surface of the porous aluminum plate in both the case where it had a hierarchical structure and the case where it did not have it. It can be said that corrosion resistance equivalent to that obtained by applying a SAM coating to the surface of an aluminum plate can be obtained.

<< Reference Examples 5 and 6 >>
Clarifying the reason why by applying automobile engine oil directly to the surface of the porous aluminum plate, the same corrosion resistance as that of the surface of the porous aluminum plate with SAM coating was obtained. After applying the engine oil for automobiles, the mixture was washed with an organic solvent, and then static contact angle measurement and surface analysis by X-ray photoelectron spectroscopy (XPS) were performed.

<Reference example 5>
As shown in FIG. 7, an automobile engine oil was applied (12.5 μL / cm ² ) on an aluminum plate having a porous surface, and the mixture was allowed to stand for 24 hours. Then, this aluminum plate was ultrasonically cleaned in heptane and dried to obtain the aluminum plate of Reference Example 5.

<Reference example 6>
An aluminum plate of Reference Example 6 was obtained in the same manner as in Reference Example 5 except that the automobile engine oil was not applied.

<Evaluation of the surface condition of the aluminum plate>
(Evaluation method, etc.)
The state of the surface of the aluminum plates of Reference Examples 5 and 6 was observed with a scanning microscope (SEM). Further, 10 μL of water droplets were placed on these aluminum plates, and the contact angle thereof was measured. Further, the surface of the aluminum plate of Reference Example 5 after being immersed in and washed with an automobile engine oil was analyzed by X-ray photoelectron spectroscopy (XPS).

(result)
8A and 8B are diagrams showing the state of the surface of the aluminum plates of Reference Examples 5 and 6, respectively, and the contact angle when 10 μL of water droplets are placed.

As shown in FIG. 8A, in Reference Example 5, the nanopores on the porous surface are clearly observed even after the immersion in the engine oil for automobiles, so that the engine oil for automobiles has been removed by cleaning. As you can see, there is no change in the pore size.

However, as shown in FIG. 8B, the water droplet contact angle in Reference Example 6 to which the engine oil was not applied was 20 ° or less and the surface was hydrophilic, whereas as shown in FIG. 8A, Reference Example 5 After the engine oil is immersed and washed, the contact angle is 110 ° or more, and it is clear that the surface has changed to a water-repellent surface.

It is presumed that this is probably because the additives in the engine oil for automobiles are chemically adsorbed on the surface and the surface is modified.

9A to 9C are graphs showing the results of X-ray photoelectron spectroscopy (XPS) analysis of the surface of the aluminum plate of Reference Example 5 after being immersed in and washed with automobile engine oil.

Zn that did not exist before the immersion of the engine oil for automobiles remained after the immersion and cleaning of the engine oil for automobiles. From the S2p spectrum shown in FIG. 9B, a peak of sulfate ion derived from anodic oxidation in sulfuric acid was observed near 171 eV, and in addition, 164 eV considered to be derived from the additive zinc dialkyldithiophosphate (ZnDTP). The peak also appeared after soaking and cleaning the engine oil.

From the above results, on the surface of the aluminum plate of Reference Example 5, zinc dialkyldithiophosphate (ZnDTP) in the engine oil for automobiles is adsorbed to modify the surface, thereby reducing the surface free energy and even without SAM. It is considered that the stable SLIPS state was achieved, which led to a significant improvement in corrosion resistance.

<< Examples 3 to 5 and Comparative Examples 8 to 10 >>
Aluminum plates of Examples 3 to 5 and Comparative Examples 8 to 10 were prepared as follows, and their corrosion resistance was evaluated.

<Example 3>
An aluminum plate having a porous anodized surface was produced in the same manner as in Reference Example 1. The aluminum plate of Example 3 was prepared by applying an oil obtained by adding zinc dialkyldithiophosphate (ZnDTP) to the base oil on the aluminum plate. The amount of zinc dialkyldithiophosphate (ZnDTP) in the oil was 2% by mass with respect to the total oil.

<Examples 4 and 5>
Aluminum plates of Examples 4 and 5 were prepared in the same manner as in Example 3 except that the amounts of zinc dialkyldithiophosphate (ZnDTP) in the oil were 10% by mass and 20% by mass, respectively.

<Comparative Example 8>
An aluminum plate having a porous anodized surface was produced in the same manner as in Reference Example 1. The aluminum plate of Comparative Example 8 was produced by applying a base oil on the aluminum plate.

<Comparative Example 9>
An aluminum plate of Comparative Example 9 was prepared in the same manner as in Example 3 except that an oil in which calcium sulfonate was added to the base oil was used instead of zinc dialkyldithiophosphate (ZnDTP). The amount of calcium sulfonate in the oil was 1% by mass with respect to the total oil.

<Comparative Example 10>
An aluminum plate of Comparative Example 10 was prepared in the same manner as in Comparative Example 9 except that the amount of calcium sulfonate in the oil was 10% by mass.

<Evaluation of corrosion resistance>
(Evaluation method)
The corrosion resistance of the aluminum plates of Examples 3 to 5 and Comparative Examples 8 to 10 was evaluated by electrochemical measurement. As the corrosive solution, a mixed solution (pH = 3) prepared by stirring acetic acid and a 10 g / L NaCl aqueous solution at 1000 rpm was used.

(result)
FIG. 10 is a graph showing the electrochemical measurement results of Examples 3 to 5 and Comparative Example 8 aluminum plate.

As shown in FIG. 10, in the aluminum plate of Comparative Example 8 coated with the base oil to which zinc dialkyldithiophosphate (ZnDTP) was not added, the anode current density was large and a sufficient corrosion suppressing effect was not obtained. On the other hand, in the aluminum plates of Examples 3 to 5 in which the oil obtained by adding zinc dialkyldithiophosphate (ZnDTP) to the base oil was applied, the current density was reduced by 4 orders of magnitude or more as compared with the aluminum plate of Comparative Example 8. It showed excellent corrosion resistance.

Further, FIG. 11 is a graph showing the electrochemical measurement results of the aluminum plates of Example 3 and Comparative Examples 8 to 10.

As shown in FIG. 11, in Comparative Example 8 coated with the base oil and the aluminum plates of Comparative Examples 9 and 10 in which calcium sulfonate was added instead of zinc dialkyldithiophosphate (ZnDTP), the anode current density was large and sufficient. The corrosion suppressing effect was not obtained.

Claims (9)

A metal member having a porous surface, wherein the porous surface is directly coated with a hydrocarbon-based oil containing zinc dialkyldithiophosphate (ZnDTP). The metal member according to claim 1, wherein the porous surface is an oxidized surface. The metal member according to claim 2, wherein the porous surface is an anodized surface. The metal member according to any one of claims 1 to 3, wherein the metal member is a member of Al, Ti, Fe, Mg, an alloy of any of these metals, or stainless steel. The metal member according to any one of claims 1 to 4, wherein the concentration of the zinc dialkyldithiophosphate (ZnDTP) is 0.1% by mass to 30.0% by mass with respect to the hydrocarbon-based oil. The metal member according to any one of claims 1 to 5, wherein the hydrocarbon oil is an engine oil. The metal member according to any one of claims 1 to 6, which is a member for an automobile. The metal member according to claim 7, which is used for a portion to which engine oil is supplied. The metal member according to claim 7 or 8, which is a member for an intercooler.

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