CN113174281A

CN113174281A - Metal member

Info

Publication number: CN113174281A
Application number: CN202110047220.XA
Authority: CN
Inventors: 稻见规夫; 小桥贤一; 幅﨑浩树; 小山辉
Original assignee: Hokkaido University NUC; Toyota Motor Corp
Current assignee: Hokkaido University NUC; Toyota Motor Corp
Priority date: 2020-01-24
Filing date: 2021-01-14
Publication date: 2021-07-27
Also published as: US20210231394A1; JP7464394B2; JP2021116451A

Abstract

The invention provides a metal member having a surface with liquid repellency and corrosion resistance without requiring surface treatment using SAM or the like. The metal member of the present disclosure has a porous surface directly covered with a hydrocarbon oil containing zinc dialkyldithiophosphate (ZnDTP). The porous surface may be an oxidised surface, in particular an anodised surface. The metal member may be a member of Al, Ti, Fe, or Mg, or an alloy of any of these metals, or a member of stainless steel. The concentration of zinc dialkyldithiophosphate (ZnDTP) may be 0.1 to 30.0 mass% with respect to the hydrocarbon oil.

Description

Metal member

Technical Field

The present disclosure relates to metal components.

Background

There is a need in the industry for metal components having liquid repellent surfaces.

As a Liquid repellent Surface, a Liquid-Slippery Surface called a Liquid-injected smooth Porous Surface (SLIPS) is known, which is a Liquid repellent Surface including a rough Surface having a fine uneven structure and a lubricating oil film coated on the rough Surface, and having a low Surface free energy.

The rough surface with low surface free energy improves wetting of the lubricating oil and prevents the liquid from firmly adhering to the solid surface, so that the liquid droplets adhering to the lubricating oil film obtain high mobility and easily slide down under a slight inclination.

Since SLIPS has such characteristics, it is considered that SLIPS can be used not only as a liquid repellent, stain resistant, and corrosion resistant surface, but also as a hardly-adhering ice surface for preventing adhesion of ice, a biofouling resistant surface for preventing adhesion of a liquid derived from living organisms such as blood, and a water collection technique utilizing high aggregation of liquid droplets on a lubricating oil film, and applications which are difficult to realize with conventional super water-repellent and super oil-repellent surfaces are also possible.

As a typical example of a substance having a low surface free energy, polytetrafluoroethylene (PTFE; critical interfacial tension. gamma.) is mentioned_C＝18mNm^-1) And the like, but their use is limited.

On the other hand, there is a great demand in industry for the repellent liquefaction on the surface of various metal oxides. It is known that the surface free energy of a metal oxide has a very high value as compared with other substances, but the surface free energy can be greatly reduced by modifying the surface with a self-assembled organic monomolecular film (SAM) comprising a polymer having-CF at the end₃(γ_C＝6mNm^-1) Is/are as followsLong chain perfluoroalkyl radical having-CH₃(γ_C＝24mNm^-1) A long-chain alkyl group of (a). Among them, phosphonic acid derivatives which have been widely used in recent years are very stable compounds themselves, have higher density than previously known silane coupling agents, and form stable SAMs.

Further, as disclosed in patent document 1, it is known that, in a ferrous material such as an automobile engine part, the impact resistance, wear resistance and corrosion resistance of the ferrous material can be improved by a surface treatment method of the ferrous material in which the ferrous material is subjected to plasma nitriding and then nitrogen ions are implanted so that the nitrogen concentration on the surface of the ferrous material becomes 30 atomic% or more.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2003-073800

Disclosure of Invention

Problems to be solved by the invention

Chemical substances for forming the SAM are expensive, and strict solution management is required when coating with the SAM is performed by a liquid phase method, and expensive equipment is required when coating is performed by a gas phase method.

Therefore, if a metal member having a liquid repellent surface can be produced without requiring surface treatment using SAM or the like, simplification of the treatment process and significant cost reduction can be expected in mass industrialization.

However, it has been considered that surface treatment using SAM or the like for reducing the surface free energy of the metal oxide surface is essential for causing the adhering liquid to slide down.

In fact, the present inventors have obtained the following findings: even when a lubricating oil or silicone oil containing a fluorine-based polymer, which is widely known as a lubricating oil for SLIPS, is used, adhesion of water cannot be prevented unless surface treatment with SAM or the like is performed.

The purpose of the present invention is to provide a metal member having a water-repellent and corrosion-resistant surface without requiring surface treatment using SAM or the like.

Means for solving the problems

The present inventors have found that the above object can be achieved by:

scheme 1

A metal component, wherein the metal component has a porous surface that is directly covered with a hydrocarbon oil containing zinc dialkyldithiophosphate (ZnDTP).

Scheme 2

The metal member of claim 1, wherein the porous surface is an oxidized surface.

Scheme 3

The metal member of claim 2, wherein the porous surface is an anodized surface.

Scheme 4

The metal member according to any one of claims 1 to 3, wherein the metal member is a member of Al, Ti, Fe or Mg or an alloy of any one of these metals or a member of stainless steel.

Scheme 5

The metal member according to any one of claims 1 to 4, wherein the concentration of the zinc dialkyldithiophosphate (ZnDTP) is 0.1 to 30.0 mass% with respect to the hydrocarbon oil.

Scheme 6

The metal member according to any one of claims 1 to 5, wherein the hydrocarbon oil is engine oil.

Scheme 7

The metal member according to any one of claims 1 to 6, wherein the metal member is an automobile member.

Scheme 8

The metal member according to claim 7, wherein the metal member is used for a portion to which oil is supplied.

Scheme 9

The metal member according to claim 7 or 8, wherein the metal member is a member for an intercooler.

Effects of the invention

According to the present disclosure, it is possible to provide a metal member having a surface with water repellency and corrosion resistance without requiring surface treatment using SAM or the like.

Drawings

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 a surface of an aluminum plate having a multi-porous surface that was hierarchically structured (sample frame).

FIG. 1C is a view showing contact angles of a water droplet or an automobile oil droplet with respect to the surfaces of the aluminum sheets of reference examples 1 to 4.

FIG. 2A is a graph showing the relationship between the number of revolutions of the aluminum plate and the remaining amount of automotive oil (revolution 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 between the rotation speed of each of the aluminum plates of examples 1 and 2 and comparative example 5 and the rolling angle of 10. mu.L of water droplets (rotation time: 60 seconds).

FIG. 2C is a graph showing the relationship (rotation time: 10, 60, 300 seconds) between the residual amount of automotive oil and the roll off angle of 10. mu.L water droplets in each of the aluminum plates of examples 1 and 2 and comparative example 5.

FIG. 3 is a graph showing the relationship between the immersion time of the aluminum plates of examples 1 and 2 and comparative examples 5 and 7 in the mixed solution and the roll off angle of 10. mu.L water droplets.

FIG. 4 is a graph showing the change in weight of the aluminum sheets 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 aluminum plate anodized without being hierarchically structured before a 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 the aluminum plate which was hierarchically structured and anodized, before the 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 view showing a method of manufacturing an aluminum plate of reference example 5.

FIG. 8A is a view showing the state of the surface of an aluminum plate of reference example 5 and the contact angle when a water droplet of 10. mu.L was placed thereon.

FIG. 8B is a view showing the state of the surface of the aluminum plate of reference example 6 and the contact angle when a water droplet of 10. mu.L was placed thereon.

FIG. 9A is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of the surface of an aluminum plate of reference example 5 after immersion in an automotive engine oil and washing.

FIG. 9B is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of the surface of an aluminum plate of reference example 5 after immersion in an automotive engine oil and washing.

FIG. 9C is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of the surface of an aluminum plate of reference example 5 after immersion in an automotive engine oil and washing.

FIG. 10 is a graph showing the results of electrochemical measurements on the aluminum plates of examples 3 to 5 and comparative example 8.

FIG. 11 is a graph showing the results of electrochemical measurements on the aluminum sheets of example 3 and comparative examples 8 to 10.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described in detail. The present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the disclosure.

The metal components of the present disclosure have a porous surface that is directly covered with a hydrocarbon oil containing zinc dialkyldithiophosphate (ZnDTP).

Metal component

In the present disclosure, the metal member has a porous surface.

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

The anodized surface can be obtained by anodizing the metal member, and for example, in the case where the metal member is an Al member, an oxide film (Al) can be formed by an aluminum oxide film (アルマイト) treatment, more specifically, by performing an electrolytic treatment using Al as an anode (+ electrode)₂O₃) Is obtained by the surface treatment of (1). The alumite treatment may be performed, for example, according to JIS H8601, JIS H8603, or the like, but may be performed by another method.

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

The thickness of the porous surface may 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 1nm or more and 5 μm or less. The porous surface may have a micro-scale textured structure, a nano-scale textured structure, or a mixture thereof, and may have a layered structure thereof.

For example, in the case where the porous surface has a micro-scale uneven structure, the pore diameter (diameter) of each pore of the porous surface may be 0.1 μm or more and 5 μm or less, preferably 0.1 μm or more and 0.5 μm or less.

In the case where the porous surface has a nano-scale uneven structure, the pore diameter (diameter) of each pore of the porous surface may be 1nm or more and 100nm or less, preferably 30nm or more and 100nm 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 a member of Al, Ti, Fe, or Mg, or an alloy of any of these metals (いずれか, i.e., "any"), or a member of stainless steel.

The metal member may be a member for any use, 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 oil is supplied. This is because, when the metal member of the present disclosure is applied to such a portion, even if the oil, which is the hydrocarbon oil, is separated from the surface of the metal member, the oil can be supplied to the metal member at all times.

In the case where the metal member is a member for an automobile, the metal member may be a member for an intercooler. The intercooler is a device into which high-temperature air flows, and exhaust gas also flows in depending on the configuration of the automobile, and therefore, there are also members that are easily corroded in the device provided in the automobile. Examples of such a member include a heat exchanger. Therefore, by applying the metal member of the present disclosure to such a member, the corrosion resistance of the intercooler can be improved.

Hydrocarbon oils

The hydrocarbon oil contains at least zinc dialkyldithiophosphate (ZnDTP). The hydrocarbon oil may be a paraffinic oil or a polyalphaolefin. The hydrocarbon oil may be, for example, a lubricating oil, specifically an engine oil, more specifically an automotive engine oil.

Zinc dialkyldithiophosphate (ZnDTP) imparts water repellency to the surface of a metal member in a state of being contained in a hydrocarbon oil. More specifically, it is considered that when a hydrocarbon oil containing zinc dialkyldithiophosphate (ZnDTP) is applied to a metal member, the zinc dialkyldithiophosphate (ZnDTP) is chemisorbed on the surface of the metal member or the like to form a liquid-repellent coating.

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

[ examples ]

Reference examples 1 to 4

The metal members of reference examples 1 to 4 were produced in the following manner, and the liquid repellency in each example was evaluated.

< reference example 1 >

99.5% aluminum (Al) plates were cut into a size of 20mm × 50mm, and acetone degreasing was performed for 10 minutes by ultrasonic washing. Next, the substrate was immersed in a 1.0M NaOH aqueous solution (60 ℃) for 120 seconds to remove the oxide film, and further 1.0M HNO was added to remove the contaminants generated in the previous step₃The aqueous solution (60 ℃ C.) was immersed for 180 seconds.

Next, 0.3M H was used₂SO₄The aqueous solution (15 ℃ C.) was anodized at an interplate voltage of 25V for 180 seconds to form an anodic oxide film having pores on the order of nanometers. This is done in a two-electrode system with the substrate as the working electrode and another Al plate as the counter electrode.

Then, the reaction was carried out with a hydrogen peroxide solution at 5 wt.% of H₃PO₄The pore diameter was expanded by immersing the plate in an aqueous solution (30 ℃ C.) for 15 minutes.

Finally, oxygen plasma treatment was performed for 4 minutes to clean the surface, thereby obtaining 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 etching pits of the order of micrometers were formed by chemical etching before anodization.

< reference example 3 >

The aluminum plate of reference example 1 was subjected to oxygen plasma treatment and then CF at 1mM₃(CF₂)₇PO(OH)₂(Perfluorooctylphosphonic acid; FOPA) was immersed in an ethanol solution for 2 days, and finally heat-treated under an atmospheric atmosphere (100 ℃ C.) for 1 hour, thereby forming a self-assembled organic monomolecular film (SAM) on the surface of the aluminum plate of reference example 1.

< reference example 4 >

A self-assembled organic monomolecular film (SAM) was formed 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.

< measurement of liquid repellency >

(measurement method)

The contact angles of water drops and automobile oil drops were measured on the aluminum sheets of reference examples 1 to 4.

The static contact angle was measured for the aluminum plates of reference examples 1 and 3 having no hierarchical structure, and the advancing contact angle and the contact angle hysteresis were measured as the dynamic contact angles for the aluminum plates of reference examples 2 and 4 having hierarchical structures.

(results)

The compositions and evaluation results of reference examples 1 to 4 are shown in table 1 and fig. 1A to C. In the table, the inside of the bracket () in the contact angle column represents the contact angle hysteresis.

TABLE 1

Fig. 1A is a scanning microscope (SEM) image of the aluminum plate of reference example 1. As shown in FIG. 1A, porous Al was formed on the surface of the aluminum plate of reference example 1 by anodic oxidation₂O₃And (5) coating a film. In addition, as shown in fig. 1B, micron-sized pits formed by etching and porous Al were formed on the surface of the aluminum plate of reference example 2₂O₃And (3) a layered structure formed by the coating.

As shown in Table 1 and FIG. 1C, the aluminum plates of reference examples 1 and 2, on which no self-assembled organic monomolecular film (SAM) was formed, had contact angles of 4.6. + -. 1.2 and 0 with respect to water droplets, respectively, and were superhydrophilic. On the other hand, the aluminum plates of reference examples 3 and 4, on which the self-assembled organic monomolecular film (SAM) was formed, had contact angles with respect to water droplets of 129.1. + -. 0.8 and 161.7. + -. 1.0, respectively, and had high water repellency.

In addition, the aluminum plate of reference example 4 having a hierarchical structure and a self-assembled organic monomolecular film (SAM) formed on the surface thereof exhibited a large contact angle of 158.2 ± 1.5 and high liquid repellency to oil droplets for automobiles, while reference examples 1 to 3 exhibited a contact angle of 90 ° or less and low liquid repellency.

This shows that the automotive engine oil can be formed into an oil film at least with respect to the aluminum sheets of reference examples 1 to 3.

Examples 1 and 2 and comparative examples 5 to 7

The aluminum sheets of examples 1 and 2 and comparative examples 5 to 7 were produced in the following manner, and their performance was evaluated.

< examples 1 and 2 and comparative examples 5 and 6 >

100. mu.L of automobile engine oil was measured, applied to the surface of each of the aluminum plates of reference examples 1 to 4, and allowed to stand for 10 minutes or more, thereby obtaining aluminum plates of examples 1 and 2 and comparative examples 5 and 6.

As shown in the evaluation of the liquid repellency of the automobile oil of reference example 4, the automobile oil was not sufficiently wet-spread on the surface of the aluminum plate of reference example 4 having a layered structure and having SAM coating applied thereto, and therefore, the automobile oil was immersed in the oil for 48 hours in advance to deteriorate the oil repellency, and then the automobile oil was applied.

< comparative example 7 >

An aluminum plate of comparative example 7 was obtained except that the automobile oil was applied to an aluminum plate which had not been subjected to the hierarchical structure by etching, the porosification by anodic oxidation, and the SAM coating in the same manner as in example 1.

< evaluation of stability of SLIPS in an Environment where shear force is applied to Engine oil for automobile >

(evaluation method)

The aluminum sheets of examples 1 and 2 and comparative example 5 were evaluated for the retention property and the liquid-sliding property of the automotive oil under an environment in which a shearing force was applied to the automotive oil. The purpose is to simulate the degradation of SLIPS in an environment where lubricating oil is lost due to gravity, wind, or the like.

As an evaluation method, first, the aluminum plates of examples 1 and 2 and comparative example 5 were rotated using a spin coater at 500 to 7000rpm for 10 to 300 seconds. Then, the weight of the remaining automobile oil and the roll off angle of 10. mu.L of water droplets were measured.

(results)

The measurement results are shown in fig. 2A to C. Fig. 2A is a graph showing the relationship between the number of revolutions of the aluminum plate of each of the aluminum plates of examples 1 and 2 and comparative example 5 and the remaining amount of the automotive oil (rotation time: 60 seconds), fig. 2B is a graph showing the relationship between the number of revolutions of the aluminum plate of each of the aluminum plates of examples 1 and 2 and comparative example 5 and the roll off angle of 10 μ L of water droplets (rotation time: 60 seconds), and fig. 2C is a graph showing the relationship between the remaining amount of the automotive oil of each of the aluminum plates of examples 1 and 2 and comparative example 5 and the roll off angle of 10 μ L of water droplets (rotation time: 10, 60, 300 seconds).

As shown in fig. 2A, in any of the aluminum plates, when the rotation speed increases and the centrifugal force applied to the automotive oil increases, the remaining amount of the automotive oil decreases accordingly.

This residual amount is particularly large in the aluminum plate of example 2 having a hierarchical structure. This is considered to be because the aluminum plate having the layered structure has irregularities of micron order in which the automotive oil is retained.

In addition, when the aluminum sheets of example 1 and comparative example 5, which did not have the hierarchical structure, were compared, there was no great difference in the remaining amount of the automotive oil.

As shown in fig. 2B, it was confirmed that, with respect to the water drop roll-off angle, even in the aluminum plate of example 1 having no hierarchical structure and not subjected to SAM coating, by coating the automobile oil on the porous surface, the attached water drops slide off at a certain roll-off angle. It is considered that the surface of the aluminum plate itself of example 1 shows hydrophilicity as shown in fig. 1C, and therefore cannot be used alone as SLIPS.

When comparing the aluminum sheets of examples 1 and 2 and comparative example 5, the water droplet roll off angle increased with the increase in the number of revolutions, i.e., the water repellency gradually decreased, and the most easily decreased was the aluminum sheet of example 2 having a layered structure and not having been subjected to SAM coating, whereas the aluminum sheet of example 1 having a minimized water droplet roll off angle, i.e., having maintained water repellency was not having a layered structure and not having been subjected to SAM coating.

As the reason why the water droplet roll-off angle is particularly likely to increase in the aluminum plate of example 2, it is considered that the originally smooth lubricating oil film reflects the roughness of the rough surface with the loss of the lubricating oil, and the lubricating oil film surface is roughened to increase the contact area with the water droplets.

Even if the relationship between the remaining amount of the automotive oil and the roll off angle of 10. mu.L of water droplets was observed, the aluminum plate of example 1, which did not have a hierarchical structure and on which SAM coating was not performed, exhibited the smallest roll off angle of water droplets (good water repellency) in the case where the remaining amount of the lubricating oil was the same.

As a result, as shown in fig. 2C, the surfaces formed by directly coating the automobile oil on the aluminum plates without SAM coating as in examples 1 and 2 were able to not only allow water droplets to easily slide off, but also maintain the highest stability even in an environment where a shear force is applied to the lubricating oil, as in the case of the surfaces formed by SAM coating on the aluminum plates as in comparative example 5.

< evaluation of stability of SLIPS in Water >

(evaluation method)

Acetic acid and a 10g/L aqueous NaCl solution (pH 3) were stirred at 1000rpm to prepare a mixed solution. The aluminum plates of examples 1 and 2 and comparative examples 3 and 7 were immersed in the mixed solution, respectively, for a predetermined period of time, and then taken out. Then, the roll-off angle of 10. mu.L water droplets on the aluminum plate of each example was measured. The amount of the automotive engine oil applied to the aluminum plate of each example was 3.75. mu.L/cm²。

(results)

FIG. 3 is a graph showing the relationship between the immersion time of the aluminum plates of examples 1 and 2 and comparative examples 5 and 7 in the mixed solution and the roll off angle of 10. mu.L of water droplets.

As shown in fig. 3, in all of the examples, the water droplet roll-off angle exceeded 20 ° which is the measurement limit within several days, but the water droplet roll-off angle remained small for the longest time (i.e., the water repellency was high), and the aluminum plate of example 1 was not subjected to SAM coating. On the other hand, in the aluminum plate of example 2 having a layered structure and not subjected to SAM coating, the water droplet roll-off angle is most likely to increase (i.e., the water repellency is decreased), and exceeds 20 ° in a short time, as compared with the case where the automobile engine oil is coated on the aluminum plate of comparative example 7, i.e., a smooth aluminum plate which is neither layered structured nor porous.

From this, it can be said that when the automotive engine oil is directly applied to an aluminum plate on which SAM coating is not performed to form SLIPS, higher stability in water can be obtained without performing the hierarchical structure.

< Corrosion resistance test >

With respect to the aluminum sheets of examples 1 and 2 and comparative examples 1 to 6, the corrosion resistance was evaluated in the following manner.

(test method)

The aluminum plates of the respective examples were immersed in the above-mentioned mixed solution for 5 days, and then the change in weight of the substrate, the change in surface morphology, and the like were observed.

(results)

The results are shown in table 1 and fig. 4, fig. 5A to E, and fig. 6A to E.

[ Table 2]

TABLE 2

In table 1, "good" means good corrosion resistance, and "poor" means no corrosion resistance.

As shown in FIG. 4, the aluminum sheets of comparative examples 1, 2, 3 and 4, which were not coated with the automotive oil, all had a reduced weightAbout 0.5mg/cm²About 1.5mg/cm². This is caused by dissolution of aluminum due to corrosion.

On the other hand, in the aluminum sheets of examples 1 and 2 and comparative examples 5 and 6 coated with the automobile oil, the weight change was 0.1mg/cm²Hereinafter, the weight reduction due to corrosion can be suppressed. In the aluminum sheets of example 2, comparative example 5, and comparative example 6, the weight slightly increased after the corrosion resistance test. This is because a small amount of white product remains even when the aluminum plates are washed with an organic solvent such as acetone after the corrosion test. 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 the corrosion resistance equivalent to that obtained by SAM coating on a porous aluminum plate can be obtained by coating an automobile engine oil on a porous aluminum plate.

The surface states of the aluminum plates of example 1, example 2, comparative example 5, and comparative example 6 after the corrosion resistance test were observed by a scanning type microscope.

Fig. 5A is a scanning microscope (SEM) image of the surface of the aluminum plate anodized without being hierarchically structured before the corrosion resistance test, and fig. 5B to 5E are scanning microscope (SEM) images of the surface of the aluminum plate of comparative example 5, comparative example 3, example 1, and comparative example 1 after the corrosion resistance test, respectively, in this order.

Referring to fig. 5A, 5B and 5D, when the aluminum plates of comparative example 5 and example 1, which were made porous and coated with the automobile engine oil on the surface, were compared, the same porous film as before the corrosion resistance test remained after the corrosion resistance test regardless of the presence or absence of the SAM coating, 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 SAM coating was performed without coating the surface with the automobile oil, the anodized surface was dissolved and the pore structure was lost. In comparative example 1, in which neither SAM coating nor automobile engine oil coating was performed, not only the anodized surface but also the aluminum plate serving as the base was greatly dissolved.

Fig. 6A is a scanning microscope (SEM) image of the aluminum plate surface which has been hierarchically structured and anodized before the corrosion resistance test, and fig. 6B to 6E are scanning microscope (SEM) images of the aluminum plate surfaces of comparative example 6, comparative example 4, example 2, and comparative example 2 after the corrosion resistance test, respectively, in this order.

Referring to fig. 6A, 6B and 6D, when the aluminum plates of comparative example 6 and example 2, which had a hierarchical structure and were made porous and had the surfaces coated with the automobile oil, were compared, the same porous film as before the corrosion resistance test remained after the corrosion resistance test regardless of the presence or absence of the SAM coating, 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 SAM coating was performed without coating the surface with the automobile oil, the anodized surface was dissolved and the pore structure was lost. In comparative example 2, in which neither SAM coating nor automobile engine oil coating was performed, not only the anodized surface but also the aluminum plate serving as the base was greatly dissolved.

From these results, it can be said that corrosion resistance equivalent to that of the SAM coating applied to the surface of the aluminum plate made porous can be obtained by directly applying the automobile oil to the surface of the aluminum plate made porous, both in the case of having a hierarchical structure and in the case of not having a hierarchical structure.

Reference examples 5 and 6

In order to find out the reason why the corrosion resistance equivalent to that of the SAM coating on the surface of the aluminum plate made porous was obtained by directly coating the automobile oil on the surface of the aluminum plate made porous, the automobile oil was coated, washed with an organic solvent, and then subjected to static contact angle measurement and surface analysis by X-ray photoelectron spectroscopy (XPS).

< reference example 5 >

As shown in FIG. 7, an automobile engine oil (12.5. mu.L/cm) was coated on an aluminum plate having a porous surface²) And standing for 24 hours. Then, the aluminum plate was subjected to ultrasonic washing in heptane, and was dried, thereby obtaining an 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 oil was not applied.

< evaluation of surface State of aluminum plate >

(evaluation method, etc.)

The surface states of the aluminum plates of reference examples 5 and 6 were observed with a scanning microscope (SEM). Further, 10. mu.L of a water droplet was placed on the aluminum plate, and the contact angle was measured. Further, the surface of the aluminum plate of reference example 5 was analyzed by X-ray photoelectron spectroscopy (XPS) after dipping and washing the automobile engine oil.

(results)

Fig. 8A and 8B are graphs showing the surface condition of the aluminum plates of reference examples 5 and 6, respectively, and the contact angle when a 10 μ L water droplet was placed.

As shown in fig. 8A, in reference example 5, since the nanopores on the porous surface were clearly observed even after the automobile oil was immersed, it was found that the automobile oil was removed by washing and the pore diameter did not change.

However, as is clear from fig. 8B, reference example 6 without the oil applied thereto had a hydrophilic surface with a contact angle of water droplets of 20 ° or less, whereas reference example 5 had a water repellent surface with a contact angle of 110 ° or more after immersion in an oil and washing, as is clear from fig. 8A.

It is presumed that this may be due to the additive in the automotive engine oil being chemisorbed to the surface to cause surface modification.

Fig. 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 immersion and washing with an automotive engine oil.

After the automobile oil is immersed and washed, Zn that does not exist before the automobile oil is immersed remains. From the S2p spectrum shown in fig. 9B, a peak derived from the anodic oxidized sulfate ion in sulfuric acid was observed in the vicinity of 171eV, and a peak derived from 164eV of zinc dialkyldithiophosphate (ZnDTP) which is considered as an additive also appeared after immersion in oil and washing.

From the above results, it is understood that zinc dialkyldithiophosphate (ZnDTP) in the automotive engine oil is adsorbed to the surface of the aluminum plate of reference example 5 and surface-modified, whereby the surface free energy is reduced, and even without SAM, a stable SLIPS state is achieved, resulting in a significant improvement in corrosion resistance.

Examples 3 to 5 and comparative examples 8 to 10

The aluminum plates of examples 3 to 5 and comparative examples 8 to 10 were produced in the following manner, and the corrosion resistance thereof was evaluated.

< example 3 >

An aluminum plate having a porous anodized surface was produced in the same manner as in reference example 1. An oil obtained by adding zinc dialkyldithiophosphate (ZnDTP) to a base oil was applied to the aluminum sheet, thereby producing an aluminum sheet of example 3. The amount of zinc dialkyldithiophosphate (ZnDTP) in the oil was 2 mass% based on the whole oil.

< examples 4 and 5 >

Aluminum plates of examples 4 and 5 were produced in the same manner as in example 3, except that the amount of zinc dialkyldithiophosphate (ZnDTP) in the oil was changed to 10 mass% and 20 mass%, respectively.

< comparative example 8 >

An aluminum plate having a porous anodized surface was produced in the same manner as in reference example 1. An aluminum plate of comparative example 8 was produced by coating the aluminum plate with a base oil.

< comparative example 9 >

An aluminum plate of comparative example 9 was produced in the same manner as in example 3, except that an oil obtained by adding calcium sulfonate instead of zinc dialkyldithiophosphate (ZnDTP) to a base oil was used. The amount of calcium sulfonate in the oil was 1 mass% based on the whole oil.

< comparative example 10 >

An aluminum plate of comparative example 10 was produced in the same manner as in comparative example 9, except that the amount of calcium sulfonate in the oil was 10 mass%.

< evaluation of Corrosion resistance >

(evaluation method)

The corrosion resistance of the aluminum sheets of examples 3 to 5 and comparative examples 8 to 10 was evaluated by electrochemical measurements. As the etching solution, a mixed solution (pH 3) prepared by stirring acetic acid and a 10g/L NaCl aqueous solution at 1000rpm was used.

(results)

As shown in fig. 10, the aluminum plate of comparative example 8 coated with the base oil to which zinc dialkyldithiophosphate (ZnDTP) was not added had a large anode current density and a sufficient corrosion inhibiting effect was not obtained. On the other hand, the aluminum sheets of examples 3 to 5 coated with the oil obtained by adding zinc dialkyldithiophosphate (ZnDTP) to the base oil exhibited excellent corrosion resistance, in which the current density was reduced by 4 or more digits as compared with the aluminum sheet of comparative example 8.

Further, FIG. 11 is a graph showing the results of electrochemical measurements on the aluminum sheets of example 3 and comparative examples 8 to 10.

As shown in fig. 11, the aluminum sheets of comparative example 8 coated with the base oil and comparative examples 9 and 10 to which calcium sulfonate was added instead of zinc dialkyldithiophosphate (ZnDTP) had large anode current densities, and thus did not have a sufficient corrosion-inhibiting effect.

Claims

1. A metal component, wherein the metal component has a porous surface that is directly covered with a hydrocarbon oil containing zinc dialkyldithiophosphate (ZnDTP).

2. The metal component of claim 1, wherein the porous surface is an oxidized surface.

3. The metal component of claim 2, wherein the porous surface is an anodized surface.

4. A metal component according to any one of claims 1 to 3, wherein the metal component is a component of Al, Ti, Fe or Mg or an alloy of any of these metals or a component of stainless steel.

5. The metal member according to any one of claims 1 to 4, wherein the concentration of the zinc dialkyldithiophosphate (ZnDTP) is 0.1 to 30.0 mass% with respect to the hydrocarbon oil.

6. The metal member according to any one of claims 1 to 5, wherein the hydrocarbon oil is an engine oil.

7. The metal member according to any one of claims 1 to 6, wherein the metal member is an automobile member.

8. The metal member according to claim 7, wherein the metal member is for a portion to which oil is supplied.

9. The metal member according to claim 7 or 8, wherein the metal member is a member for an intercooler.