Method for evaluating deterioration of lubricating oil film, rusting monitoring device, rusting monitoring system, and lubricating oil composition used for the same

Abstract

To provide a method for evaluating deterioration of a lubricating oil film, a rusting monitoring device and a rusting monitoring system that monitor rusting on an object applied with a lubricating oil composition, and a lubricating oil composition used for them.SOLUTION: A rusting monitoring system 10 mainly comprises a rusting monitoring device 100, and an actual component 200 to which a lubricating oil composition is applied. The rusting monitoring device 100 mainly comprises an ACM-type corrosion sensor 110 that is attached to an actual component to which the lubricating oil composition is actually applied, and an ammeter 120 that measures a current flowing from the ACM-type corrosion sensor 110. The ACM-type corrosion sensor 110 mainly comprises an insulating layer 111, a conductive layer 112, and a copper foil 113 provided on the conductive layer 112. The insulating layer 111 is formed, for example, of an epoxy resin-based insulating paste, and is brought into contact with and attached to the actual component 200.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for evaluating deterioration of a lubricating oil film, a rust monitoring device and a rust monitoring system for monitoring rust on an object to which a lubricating oil composition is applied, and a lubricating oil composition used therein. [Background technology]

[0002] A method for evaluating the deterioration level of a lubricating oil composition is known, in which an atmospheric corrosion sensor, for example an ACM (Atmospheric Corrosion Monitor) type corrosion sensor, is bonded to a steel substrate and the deterioration level of the lubricating oil composition applied thereto is evaluated. When the lubricating oil composition applied to the surface of the atmospheric corrosion sensor deteriorates, a weak current flows in the atmospheric corrosion sensor, and this current is detected to estimate the deterioration level of the lubricating oil composition. In this way, the deterioration level of a lubricating oil composition applied in a thin film such as a rust-preventive oil is evaluated (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-83254 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the structure of the item on which rusting is to be observed differs from the structure of the iron substrate, the iron substrate may not rust when the actual item rusts, and therefore, even if the iron substrate is used to observe rusting of such an item, rusting cannot be accurately monitored. [Means for solving the problem]

[0005] The present invention provides a method for evaluating deterioration of a lubricating oil film, a rust monitoring device and a rust monitoring system for monitoring rust on an object to which a lubricating oil composition is applied, and a lubricating oil composition used therein. Specific aspects of the present invention are as follows [1] to

[20] . [1] Attaching a sensor to an actual part to which the lubricating oil composition is actually applied; connecting an ammeter to the sensor; applying the lubricating oil composition to the sensor; exposing the sensor attached to the real part to a predetermined environment to which the real part is to be exposed; detecting a value of a current flowing through the ammeter; A method for evaluating deterioration of a lubricating oil film comprising: [2] 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, further comprising the step of evaluating the lubricating oil film as having deteriorated when the period during which the current value is equal to or greater than a predetermined value is equal to or greater than a predetermined period. [3] 3. The method for evaluating deterioration of a lubricating oil film according to claim 1 or 2, wherein the sensor is an ACM sensor. [4] The contact area between the actual part and the sensor is 1 cm2 or more. A method for evaluating deterioration of a lubricating oil film according to any one of aspects 1 to 3. [5] The method for evaluating deterioration of a lubricating oil film according to any one of aspects 1 to 4, wherein the lubricating oil composition is an anti-rust oil containing, in a base oil, at least one additive selected from an antioxidant, a metal deactivator, and a rust inhibitor. [6] A method for evaluating deterioration of a lubricating oil film according to any one of Aspects 1 to 5, wherein the lubricating oil composition is applied to the sensor in a thickness of 0.1 μm or more and 10 μm or less. [7] The method for evaluating deterioration of a lubricating oil film according to any one of aspects 1 to 6, wherein the actual part is a part containing a metal material having pores. [8] The method for evaluating deterioration of a lubricating oil film according to any one of aspects 1 to 7, wherein the actual part is a part containing a porous metal material. [9] The method for evaluating deterioration of a lubricating oil film according to any one of aspects 1 to 8, wherein the actual part is a porous body produced by sintering.

[10] The method for evaluating deterioration of a lubricating oil film according to any one of aspects 1 to 9, wherein the actual part is a sintered part formed by sintering.

[11] 11. The method for evaluating deterioration of a lubricating oil film according to any one of aspects 1 to 10, wherein the predetermined environment is an environment in which the actual part is stored alone.

[12] A sensor that is attached to an actual part to which the lubricating oil composition is actually applied; an ammeter for measuring a current flowing from the sensor; A rust monitoring device comprising: The sensor includes an insulating layer and a conductive layer; the insulating layer is attached to the real component in contact therewith, and the conductive layer is attached to the insulating layer so as to sandwich the insulating layer between the real component and the conductive layer; The insulation resistance between the conductive layer and the actual part is 10MΩ or more. Rust monitoring device.

[13] The rust monitoring device according to claim 12, wherein the actual part is a part including a metal material having pores.

[14] 14. The rust monitoring device according to claim 12 or 13, wherein the actual part is a part including a porous metal material.

[15] 15. The rust monitoring device according to any one of aspects 12 to 14, wherein the actual part is a porous body produced by sintering.

[16] 16. The rust monitoring device according to any one of aspects 12 to 15, wherein the actual part is a sintered part formed by sintering.

[17] 17. The rust monitoring device according to any one of aspects 12 to 16, wherein a contact area between the actual part and the insulating layer is 1 cm 2 or more.

[18] A rust monitoring device as described in any of aspects 12 to 17, wherein the width of the conductive layer is 2 mm or more, the distance between adjacent conductive layers is 2 mm or more, the width of the insulating layer is 2 mm or more, or the thickness of the insulating layer is 20 μm or more.

[19] A rust monitoring device according to any one of aspects 12 to 18, Actual parts to which the lubricating oil composition is actually applied A rust monitoring system equipped with

[20] A lubricating oil composition for use in the method for evaluating deterioration of a lubricating oil film according to any one of aspects 1 to 11, the rust monitoring device according to any one of aspects 12 to 18, or the rust monitoring system according to aspect 19. Effect of the Invention

[0006] As a preferred embodiment of the present invention, there can be provided a method for evaluating deterioration of a lubricating oil film, a rust monitoring device for monitoring rust on an object to which a lubricating oil composition has been applied, a rust monitoring system, and a lubricating oil composition for use therein. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic diagram showing an example of a rust monitoring system according to the present invention. [Diagram 2] 1 is a schematic diagram showing an example of a rust monitoring system according to the present invention. [Diagram 3] 1 is a schematic diagram showing an example of a rust monitoring system according to the present invention. [Figure 4] 4 is a graph showing the relationship between humidity and current value in a conventional steel plate sensor and in a rust monitoring system according to the present invention. [Diagram 5] 4 is a graph showing current values ​​of a conventional steel plate sensor to which no rust-preventive oil is applied and a rust monitoring system according to the present invention. [Figure 6] 1 is a graph showing current values ​​of a conventional steel plate sensor to which short-term rust preventive oil is applied and a rust monitoring system according to the present invention. [Figure 7]4 is a graph showing current values ​​of a conventional steel plate sensor to which a long-term rust preventive oil is applied and a rust monitoring system according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Rust monitoring system] First, a rust monitoring system 10 according to one embodiment of the present invention will be described with reference to Fig. 1. Fig. 1(A) is a schematic plan view of the rust monitoring system 10 as viewed from the ACM type corrosion sensor 110 side, and Fig. 1(B) is a schematic cross-sectional view showing the B-B cross section of the ACM type corrosion sensor 110. Note that in this specification, claims, and drawings, rusting is also referred to as corrosion, and rust prevention is also referred to as corrosion prevention.

[0009] The rust monitoring system 10 according to the present invention mainly comprises a rust monitoring device 100 and an actual part 200 to which a lubricating oil composition is applied.

[0010] The rust monitoring device 100 mainly comprises an ACM-type corrosion sensor 110 that is attached to an actual part to which a lubricating oil composition is actually applied, and an ammeter 120 that measures the current flowing from the ACM-type corrosion sensor 110.

[0011] The ACM-type corrosion sensor 110 mainly includes an insulating layer 111, a conductive layer 112, and a copper foil 113 provided on the conductive layer 112. The insulating layer 111 is made of, for example, an epoxy resin-based insulating paste, and is attached in contact with the real component 200. To attach the insulating layer 111 to the real component 200, for example, an epoxy resin-based insulating paste is printed (applied) on the real component 200 using an IC precision screen printer, and then cured. As such an epoxy resin-based insulating paste, for example, Amicon ME-990J#BN (resin: epoxy-based, filler: BN) manufactured by Grace Japan Co., Ltd. is suitable. The conductive layer 112 is made of, for example, a conductive paste, and is attached on the insulating layer 111 so that the insulating layer 111 is sandwiched between the real component 200 and the conductive layer 112, and insulation from the real component 200 is maintained. To attach the conductive layer 112 onto the insulating layer 111, for example, a conductive paste is printed (applied) onto the insulating layer 111 using a precision screen printer for ICs, and then cured. A suitable example of such a conductive paste is Amicon C-990J#585 (resin: epoxy-based, filler: Ag) manufactured by Grace Japan. The insulation resistance between the conductive layer 112 and the actual part 200 is preferably 10 MΩ or more in a dry state.

[0012] The copper foil 113 is electrically joined to the conductive layer 112 and is electrically connected to the ammeter 120 via wiring 121. The ammeter 120 is a non-resistance ammeter, and the measurement range of the current is at least 0.1 nA to 10 mA, and the resolution is preferably at least 0.1 nA in the measurement range of 0.1 nA to 10 μA, and at least 1 μA in the measurement range of 1 μA to 1 mA. A preferred example of such an ammeter is the model "SACM-311B" manufactured by "Shrinks Corporation."

[0013] The actual part 200 is a sintered part obtained by sintering iron powder to form it, such as a gear or a bearing member, and is coated with a lubricating oil composition that is to be applied during actual storage when rust is measured using the rust monitoring device 100. The lubricating oil composition is, for example, a rust-preventive oil.

[0014] Any method can be used to apply the rust-preventive oil to the rust monitoring system 10. For example, brushing or spraying is suitable. Here, sintered parts have numerous pores on the surface and inside due to the manufacturing process, and condensation is likely to occur near the pores on the surface of the part, and moisture is likely to penetrate into the inside through the pores on the surface, which may cause rust in the sintered part. Therefore, when applying the rust-preventive oil, the rust-preventive oil is applied so as to form an appropriate oil film thickness that exhibits the rust-preventive performance required according to the part shape, material of the part, storage method, and / or storage conditions. In addition, the oil film thickness through which water can pass varies depending on the type of rust-preventive oil. Therefore, an oil film thickness that does not allow water to pass through is ensured depending on the type of rust-preventive oil. The thickness of the application of the rust-preventive oil is preferably 0.1 μm to 10 μm from the viewpoint of the measurement accuracy of the current value and the judgment accuracy of the deterioration degree of the rust-preventive oil.

[0015] 2, the dimensions of the insulating layer 111, the conductive layer 112, and the actual part 200 will be described. The width A of the conductive layer 112, the width B of the insulating layer 111, and the thickness C of the insulating layer 111 are determined so as to conform as closely as possible to JIS Z 2384:2019, and so as to maximize the contact area between the actual part 200 and the insulating layer 111. For example, the width A of the conductive layer 112 is preferably 2 mm or more, the width B of the insulating layer 111 is preferably 2 mm or more, the thickness C of the insulating layer 111 is preferably 20 μm or more, and the contact area between the actual part 200 and the insulating layer 111 is preferably 1 cm. 2 It is preferable that the distance between adjacent conductive layers 112 is 2 mm or more. The upper limit of the contact area between the actual part 200 and the insulating layer 111 is the surface area of ​​the actual part 200. The above values ​​regarding the width A of the conductive layer 112, the width B of the insulating layer 111, and the thickness C of the insulating layer 111 are not essential requirements in the present invention, and optimal values ​​may be determined depending on the actual part.

[0016] 3 shows an example in which a gear made of a sintered part is used as the actual part 200. An ACM-type corrosion sensor 110 was applied to a surface 201 perpendicular to the rotation axis of the gear 200. An insulating layer 111, a conductive layer 112, and a copper foil 113 provided on the conductive layer 112 were applied to a part of the surface 201 by the above-mentioned method.

[0017] [Method for evaluating deterioration of lubricating oil film] After the application of the anti-rust oil, the rust monitoring system 10 is left in an appropriate environment for a predetermined time. The appropriate environment is an environment in which the anti-rust oil is actually used or an environment close to the environment, in other words, an environment in which the actual part 200 is stored by itself.

[0018] The deterioration evaluation method is performed as follows. First, in the step of attaching a sensor to a real part, the ACM-type corrosion sensor 110 is attached to the real part 200 to which anti-rust oil or the like is actually applied. Next, in the step of connecting an ammeter, the ammeter 120 is connected to the ACM-type corrosion sensor 110. Then, in the step of applying oil, the ACM-type corrosion sensor 110 is applied with anti-rust oil or the like. Next, in the step of exposing, the ACM-type corrosion sensor 110 attached to the real part 200 is exposed to a predetermined environment to which the real part 200 should be exposed, and left as it is. Then, in the step of detecting a current value, the ammeter 120 detects a current value flowing from the ACM-type corrosion sensor 110, that is, a current value flowing to the ammeter 120. Then, in the step of evaluating, when the period during which this current value is equal to or greater than a predetermined value is equal to or greater than a predetermined period, it is evaluated that the anti-rust oil film has deteriorated. In other words, when the period during which the ammeter 120 detects a current is equal to or greater than a predetermined period, it is evaluated that the lubricating oil film has deteriorated.

[0019] When the rust-preventive oil film deteriorates, the oil film becomes incomplete, and water containing corrosion factors, such as electrolytes such as chlorides and sulfides, condenses on the surface of the part, or water condenses on the surface of the part to which corrosion factors, such as electrolytes such as chlorides and sulfides, are attached, forming a water film (see "condensed water" in FIG. 2). This causes a weak galvanic current to flow between the conductive layer 112 and the real part 200 (or the steel sheet), and if this current continues to flow, corrosion will occur in the real part 200 (or the steel sheet). When this continuous current is detected, it is evaluated that the lubricating oil film has deteriorated, and it is determined that the life of the lubricating oil film has expired. This makes it possible to take anti-corrosion measures before the corrosion progresses to visible corrosion, thereby preventing the parts from rusting.

[0020] In Patent Document 1, the deterioration degree of the lubricating oil is evaluated, but even if the lubricating oil composition itself deteriorates, if the oil film on the actual part does not deteriorate, moisture does not reach the actual part 200 through the oil film, and rust does not occur on the actual part 200. In other words, deterioration and deterioration of the lubricating oil composition is not an essential condition for rusting. Therefore, the deterioration evaluation method of the present application evaluates the deterioration of the lubricating oil film, not the deterioration of the lubricating oil composition. The deterioration of the lubricating oil film is when the oil film necessary for exerting the rust prevention effect becomes unstable due to some factor. As some factor, it is considered that the oil film becomes thin and water, chlorides, etc. penetrate into the oil film.

[0021] In addition, in the lubricant deterioration evaluation method disclosed in Patent Document 1 (hereinafter also referred to as the conventional deterioration evaluation method), a commercially available steel plate shown in JIS Z 2384:2019 is used instead of the actual part 200, and the material, shape, and surface condition are different from those of the actual part that is actually applied with lubricant and stored. Since these materials, shapes, and surface conditions affect the deterioration state of the lubricant film, the deterioration tendency evaluated by the conventional deterioration evaluation method may differ from the deterioration tendency of the lubricant film in the actual part that is actually applied with lubricant and stored. In addition, the conventional deterioration evaluation method predicts the life of the lubricant film, but does not monitor the corrosion prevention state of the actual part. In particular, in parts having many pores such as sintered parts, the moisture in the air is easily condensed due to the large surface area, and it is difficult to form an anti-rust oil film because the anti-rust oil does not reach the pores, so there is a large dissociation from the evaluation using a steel plate as in the conventional deterioration evaluation method. However, according to the present invention, the ACM-type corrosion sensor 110 is attached to the actual part 200 to evaluate the deterioration of the lubricating oil film, so there is no dissociation from the deterioration tendency of the lubricating oil film in an actual part to which the ACM-type corrosion sensor 110 cannot be attached.

[0022] It is also known that the actual part 200 (or steel plate) rusts immediately after the lubricating oil film deteriorates, so the deterioration state of the rust-preventive oil film can be evaluated by evaluating the rusting of the actual part 200 (or steel plate).

[0023] In the experimental results described below, it was found that the current value measured using the actual part 200 was closer to the current value when rusting occurred than the current value measured using the above-mentioned steel plate. Therefore, it was found that the deterioration state of the rust-preventive oil film was also closer to the current value when rusting occurred than the current value measured using the above-mentioned steel plate.

[0024] Next, the results of an experiment conducted to examine the effectiveness of the present invention will be described with reference to FIG.

[0025] First, 0.2 ml of a 5% NaCl aqueous solution was dropped onto the ACM-type corrosion sensor 110 to obtain a concentration of 10 mg / m 2The wick is then attached to the sample. Next, the sample is placed in a thermo-hygrostat set at 40° C., and the relative humidity is decreased from 90% to 40% in 5% increments. After the relative humidity reaches 40%, it is confirmed that the relative humidity of 40% does not change for 10 minutes, and then the current value is measured. The reason for confirming that the relative humidity does not change for 10 minutes is because the time it takes for the relative humidity to stabilize varies depending on the type of thermo-hygrostat used. Next, the door of the thermo-hygrostat is opened, the wick in the tank is wetted with ionized water, and then the relative humidity is decreased to 90% in 5% increments, and the current value is measured after maintaining the sample at each humidity for 40 minutes. This method is applied to the steel plate used in the lubricant deterioration evaluation method disclosed in Patent Document 1 (hereinafter also referred to as the conventional deterioration evaluation method) and the actual part 200, and the obtained current value is shown in FIG. 4.

[0026] In Figure 4, points indicated using "△" (triangles) indicate the relationship between the ambient relative humidity and the current value output when rust is occurring in a rust monitoring system in which a rust monitoring device 100 is attached to a JIS G3141 SPCC-SD steel plate, and points indicated using "□" (squares) and "○" (circles) indicate the relationship between the ambient relative humidity and the current value output when rust is occurring in the actual part 200. Referring to FIG. 4, the experimental results show that the values ​​measured using the actual part 200 are closer to the values ​​when rust has developed than the values ​​measured using a steel plate.

[0027] By using the above-described rust monitoring system 10, the deterioration degree of the lubricating oil film used in a thin film state and the rust of the actual part 200 can be easily evaluated. Furthermore, if the rust monitoring system 10 is stored together with other actual parts to which the rust monitoring device 100 is not attached, rust in the other actual parts can be predicted and detected.

[0028] The atmospheric corrosion sensor is not necessarily limited to the ACM type corrosion sensor, and any atmospheric corrosion sensor capable of applying lubricating oil to the sensor portion can be applied to the deterioration evaluation method of the present invention.

[0029] The lubricating oil composition to be measured by the deterioration evaluation method of the present invention is, for example, a rust-preventive oil containing, in a base oil, at least one additive selected from an antioxidant, a metal deactivator, and a rust inhibitor.

[0030] The base oil may be one or more selected from mineral oils and synthetic oils. Examples of mineral oils include atmospheric residual oils obtained by atmospheric distillation of crude oils such as paraffinic crude oil, intermediate base crude oil, and naphthenic crude oil; distillate oils obtained by vacuum distillation of these atmospheric residual oils; and refined oils obtained by subjecting the distillate oils to one or more refining treatments such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, and hydrorefining. Examples of synthetic oils include poly-α-olefins such as α-olefin homopolymers or α-olefin copolymers (e.g., α-olefin copolymers having 8 to 14 carbon atoms, such as ethylene-α-olefin copolymers); isoparaffins; polyalkylene glycols; ester oils such as polyol esters and dibasic acid esters; ether oils such as polyphenyl ether; alkylbenzenes; alkylnaphthalenes; and synthetic oils (GTL) obtained by isomerizing wax produced from natural gas by the Fischer-Tropsch process or the like (GTL wax (Gas To Liquids WAX)).

[0031] Examples of the antioxidant include amine-based antioxidants such as alkylated diphenylamine, phenylnaphthylamine, and alkylated phenylnaphthylamine; and phenol-based antioxidants such as 2,6-di-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate.

[0032] Examples of metal deactivators include benzotriazoles, imidazolines, pyrimidine derivatives, thiadiazoles, and the like.

[0033] Examples of the rust inhibitor include alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinate ester, polyhydric alcohol ester, and oxidized wax derivatives.

[0034] In addition to the above, the lubricating oil composition may contain additives such as a viscosity index improver, a pour point depressant, a metal detergent, a dispersant, an extreme pressure agent, and an antifoaming agent. EXAMPLES

[0035] The present invention will now be described in more detail with reference to examples, although the present invention is not limited to the contents of these examples.

[0036] [Preparation of Rust Preventive Oil] The following three types of rust preventive oil were prepared. <Short-term rust preventative oil> Daphne Oil Coat RL55 (manufactured by Idemitsu Kosan Co., Ltd.), a commercially available rust-preventive oil <Long-term rust prevention oil> Daphne Super Coat PM1 (manufactured by Idemitsu Kosan Co., Ltd.), a commercially available rust-preventive oil

[0037] [ACM type corrosion sensor] A predetermined number of rust monitoring systems 10 (hereinafter referred to as sintering sensors) in which a rust monitoring device 100 is attached to an actual part 200, which is a sintered part, and rust monitoring systems (hereinafter referred to as steel plate sensors) in which a rust monitoring device 100 is attached to a JIS G3141 SPCC-SD steel plate were manufactured.

[0038] [Evaluation method] Sintered sensor and steel plate sensor, coating amount 2g / m 2 In order to obtain the above results, short-term and long-term rust-preventive oils were applied to the sintered sensor and the steel plate sensor, which were not coated with the rust-preventive oil. Next, these sintered sensors and steel plate sensors were exposed to the open air in Okinawa Prefecture. The steel plate sensor was exposed from 0:00 on June 25, 2021 to 23:50 on April 12, 2022, and the current value was measured every hour at 00, 10, 20, 30, 40, and 50 minutes, and the sintered sensor was exposed from 0:00 on July 21, 2022 to 11:50 on September 28, 2022, and the current value was measured every hour at 00, 10, 20, 30, 40, and 50 minutes. Note that the sintered sensor is still exposed after 11:50 on September 28, 2022, as of the filing date of this application. The presence or absence of rust on the surfaces of the sintered sensor and the steel plate sensor was visually observed every day, and the current value was recorded.

[0039] [Evaluation results] (Visual rust appearance on steel plate sensors and sintered sensors) For the unoiled steel sensor and the sintered sensor, rust was observed on the first day. For the steel plate sensor coated with short-term rust preventative oil, rust was observed on the 49th day, and for the sintered sensor, rust was observed on the 1st day. For the steel plate sensor coated with long-term rust-preventive oil, rust was observed on the 238th day, whereas for the sintered sensor, no rust was observed even after 90 days.

[0040] (Output current value for sintered sensor and steel plate sensor) Figures 5 to 7 show graphs showing the relationship between the number of test days and the current value for the steel plate sensor and the sintered sensor. These graphs show the moving average of the current values ​​of the 200 points before and the 200 points after each measurement point, a total of 399 points, as the current value at each measurement point. If the number of previous and subsequent measurement points is less than 200, the moving average of the maximum number of measurement points that can be secured is used as the current value at each measurement point. This eliminates the influence of spike-like data due to temporary reversible changes in the surface of each sensor, which does not indicate the change over time in the soundness (breakage state) of the anti-rust film formed by the anti-rust oil. FIG. 5 is a graph showing the relationship between the number of test days and the current value for the uncoated steel plate sensor and the sintered sensor. For the steel plate sensor, where rust was found on the first day, a medium current value continued from the first day until about the 30th day, and the current value further increased after about the 30th day. A medium current value was output due to the rust (see Figure 5(a)). For the sintered sensor, rust was observed on the first day, but a high current value was output from the first day (see Figure 5(b)). Although the steel plate sensor detected a moderate current value from the first day, this current value was lower than the current value of the sintered sensor, and it was found that the steel plate sensor cannot predict rusting of sintered parts. The sintered sensor output a high current value from the first day, and therefore it was found that it is possible to predict rusting of sintered parts.

[0041] FIG. 6 is a graph showing the relationship between the number of test days and the current value for the steel plate sensor and the sintered sensor to which short-term rust preventive oil was applied. For the steel plate sensor, rust was observed on the 49th day, and the current value increased on the 31st day (see Figure 6(a)). For the sintered sensor, rust was observed on the first day, but a high current value was output from the first day (see Figure 6(b)). With the steel plate sensor, the date on which the current value increased was earlier than the date on which rust would occur, so it was found that the steel plate sensor is capable of predicting the date on which rust would occur in steel plates. On the other hand, with the steel plate sensor, an increase in the current value was detected on the 31st day, which was much later than the date on which rust would occur in sintered parts, so it was found that the steel plate sensor is unable to predict rust in sintered parts. With the sintered sensor, a high current value was output from the first day, so it was found that it is possible to predict rust in sintered parts.

[0042] FIG. 7 is a graph showing the relationship between the number of test days and the current value for the steel plate sensor and the sintered sensor to which the long-term rust preventive oil was applied. For the steel plate sensor, rust was observed on the 238th day, and the current value increased on the 177th day (see Figure 7(a)). For the sintered sensor, no rust was observed even after 90 days, and no high current value was output even after 90 days (see Figure 7(b)). With the steel plate sensor, the date on which the current value increased was earlier than the date on which rust occurred, so it was found that the steel plate sensor can predict the date on which rust will occur in steel plates. On the other hand, with the sintered sensor, rust has not yet occurred, so experiments are ongoing to see whether the sintered sensor and the steel plate sensor can predict rusting of sintered parts.

[0043] 5 to 7, it was found that the current value measured using the sintered sensor is closer to the current value when rust actually occurs than the current value measured using the steel plate sensor. It is also known that the actual part 200 and the steel plate rust immediately after the lubricating oil film deteriorates. In view of this, it was found that the current value measured using the sintered sensor indicates the deterioration state of the rust-preventive oil film more accurately than the current value measured using the steel plate sensor.

[0044] From the above results, it was found that the output current value by the deterioration evaluation method, rust monitoring device 100, and rust monitoring system 10 according to the present invention correlates with the degree of rust as determined by visual inspection. This shows that the deterioration degree of the lubricating oil film and rust on the actual part 200 can be easily evaluated, and rust on the actual part 200 can be detected and predicted, according to the deterioration evaluation method, rust monitoring device, rust monitoring system, and lubricating oil composition according to the present invention.

[0045] The size, shape, and quantity of each member shown in the specification and drawings are examples and are not limited to these. Also, the materials of each member are examples and are not limited to these.

[0046] Although embodiments of the present invention have been described herein with reference to the accompanying drawings, it will be apparent to those skilled in the art that modifications may be made in the structure and relationship of the parts without departing from the scope and spirit of the invention as described. [Explanation of symbols]

[0047] 10 Rust monitoring system 100 Rust monitoring device 110 ACM type corrosion sensor 111 Insulating layer 112 Conductive layer 113 Copper foil 120 ammeter 200 Actual parts

Claims

1. Attaching a sensor to an actual part to which the lubricating oil composition is actually applied; connecting an ammeter to the sensor; applying the lubricating oil composition to the sensor; exposing the sensor attached to the real part to a predetermined environment to which the real part will be exposed; detecting a value of a current flowing through the ammeter; A method for evaluating deterioration of a lubricating oil film comprising:

2. 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, further comprising the step of evaluating that the lubricating oil film has deteriorated when the period during which the current value is equal to or greater than a predetermined value is equal to or greater than a predetermined period.

3. 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, wherein the sensor is an ACM sensor.

4. The contact area between the actual part and the sensor is 1 cm ２ The method for evaluating deterioration of a lubricating oil film according to claim 1, wherein the method is as described above.

5. 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, wherein the lubricating oil composition is a rust preventive oil containing a base oil and at least one additive selected from an antioxidant, a metal deactivator, and a rust inhibitor.

6. 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, wherein the lubricating oil composition is applied to the sensor in a thickness of 0.1 μm or more and 10 μm or less.

7. 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, wherein the actual part is a part containing a metal material having pores.

8. 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, wherein the actual part is a part containing a porous metal material.

9. 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, wherein the actual part is a porous body produced by sintering.

10. 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, wherein the actual part is a sintered part formed by sintering.

11. 2. The method for evaluating deterioration of a lubricating oil film according to claim 1, wherein the predetermined environment is an environment in which the actual part is stored alone.

12. a sensor attached to an actual part to which the lubricating oil composition is actually applied; an ammeter for measuring the current flowing from the sensor; A rust monitoring device comprising: the sensor comprises an insulating layer and a conductive layer; the insulating layer is attached to the actual component in contact therewith, and the conductive layer is attached to the insulating layer so as to sandwich the insulating layer between the actual component and the conductive layer; The insulation resistance between the conductive layer and the actual component is 10 MΩ or more. Rust monitoring device.

13. The rust monitoring device according to claim 12, wherein the actual part is a part containing a metal material having pores.

14. The rust monitoring device according to claim 12, wherein the actual part is a part containing a porous metal material.

15. The rust monitoring device according to claim 12, wherein the actual part is a porous body produced by sintering.

16. The rust monitoring device according to claim 12, wherein the actual part is a sintered part formed by sintering.

17. The contact area between the actual part and the insulating layer is 1 cm ２ The rust monitoring device according to claim 12, wherein:

18. The rust monitoring device of claim 12, wherein the width of the conductive layer is 2 mm or more, the distance between adjacent conductive layers is 2 mm or more, the width of the insulating layer is 2 mm or more, or the thickness of the insulating layer is 20 μm or more.

19. The rust monitoring device according to claim 12; Actual parts to which the lubricating oil composition is actually applied A rust monitoring system equipped with

20. A lubricating oil composition for use in the method for evaluating lubricating oil film deterioration according to any one of claims 1 to 11, the rust monitoring device according to any one of claims 12 to 18, or the rust monitoring system according to claim 19.

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