JPH04128376A - Highly corrosion resistant metal - Google Patents

Abstract

PURPOSE:To exhibit high corrosion resistance by forming a plasma polymerized film into multiple layers and forming particularly the inside layers into specific constitution, thereby providing such a surface layer which is improved in the adhesive property of metals and prevents the propagation of microcracks, if generated in this inside layer, up to the front layer part. CONSTITUTION:The plasma polymerized film to be formed on a metallic base material is made into the multilayered structure consisting of the inside layer, intermediate layer and surface layer. The inside layer is so formed that the ratio of the intensity of 870 to 750cm<-1> absorption peak based on the oscillation of Si-CH3 to the intensity of 1100 to 1000cm<-1> absorption peak based on the oscillation of Si-O-Si is <=0.5 and the film thickness is >=50Angstrom and <=5000Angstrom . The surface layer is formed to <=20 atomic % of oxygen concn. The intermediate layer is formed of the inclined compsn. film shifting from the compsn. of the inside layer to the compsn. of the above-mentioned surface layer and is formed to >=100Angstrom and <=15000Angstrom . The total film thickness of the above-mentioned intermediate layer and the above-mentioned surface layer is specified to >=500Angstrom and <=5mum. The highly corrosion resistant metal formed with the plasma polymerized films which obviate the generation of the microcracks in the films and exhibit an excellent adhesive property even to bending is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a highly corrosion resistant metal having a plasma polymerized coating, and more particularly to a highly corrosion resistant metal in which the plasma polymerized coating exhibits excellent adhesion. Therefore, when the present invention is applied to a metal plate, a plasma polymerized coating that exhibits excellent peeling resistance against bending can be obtained.

[Conventional technology] Conventional organic coating methods include wet processes and dry processes, and wet processes such as dip methods, roll coating methods, and spray painting methods include a drying process. Pinholes are likely to form in the resulting coating, causing rust.

-1 The plasma polymerization method, which is a dry process, does not form pinholes even in relatively thin films and does not require a drying process, so it has the advantage of requiring fewer steps than a wet process. ing.

Known techniques for imparting corrosion resistance to metals using the plasma polymerization described above include those using organic silicone monomers and Si02 as shown in (1) to (2) below.

■H, P, 5chreiber et al. (Thin 5oli
d Films 72 (1980) P487-493]
reported that when a steel plate is coated with a plasma-polymerized film of hexamethyldisiloxane and the film thickness is 2 μm or more, no corrosion is observed even after immersing it in a 4% NaCl aqueous solution for 28 days. are doing.

■, W. Bieg et al. [5olar Energy M
materials 3 (1980) P301-316]
reported that an aluminum reflector coated with a plasma-polymerized film of methyltrimethoxysilane showed excellent durability in a six-month weather test.

■Wataru Ito et al. [153rd Committee on Plasma Materials Science, 5th Research Meeting Materials (1989) P9-18]
D discloses a technique for forming a Sin2 film on a stainless steel plate to impart corrosion resistance.

[Problems to be Solved by the Invention] However, even with coated metal plates having these organic silicone-based plasma polymerized coatings or Si02 coatings, when bending is performed, the former easily peels off due to its low adhesion to the metal. On the other hand, the latter has a problem in that microcranks occur in the coating due to its low toughness, resulting in a decrease in corrosion resistance.

The present invention has been made in view of the above circumstances, and aims to provide a highly corrosion-resistant metal in which microcracks do not occur in the coating and the plasma polymerized coating exhibits excellent adhesion even during bending. It is something.

[Means for Solving the Problems] The present invention, which achieves the above object, has a multilayer structure consisting of an inner layer, an intermediate layer, and a surface layer of the plasma polymerized coating, and the inner layer has a structure of Si-0-Si in infrared spectroscopy. 11 based on vibration
Si for intensity of absorption peak from 00 to 1000 cl'
- The ratio of the absorption peak intensity of 870 to 750 cln-' based on the vibration of CH3 is 0.5 or less, and the film thickness is 50
The surface layer has an oxygen concentration of 20 atomic % or less, and the intermediate layer is formed as a composition gradient film that shifts from the composition of the inner layer to the composition of the surface layer.
00A to 15000A, and the total thickness of the intermediate layer and the surface layer is 500A to 5μm.

[Function] As a result of extensive research, the present inventors have found that by forming a multilayer plasma polymerized film, for example, on plate materials, the adhesion of the film is good even after bending, and the corrosion resistance is equivalent to that without bending. We have developed a plasma-polymerized film-coated metal that exhibits the following properties.

In other words, the inner layer has a specific structure to improve its adhesion to metal, and even if a microcrank occurs in the inner layer, a surface layer that prevents cracks from propagating to the surface layer ensures high corrosion resistance. This is what I did.

The reasons for limiting each condition according to the present invention are as follows.

In the infrared spectroscopic analysis of the inner layer, an absorption peak of 1100 to 1000 cm due to the vibration of Si-0-Si and an absorption peak of S1-
The reason why the intensity ratio with the absorption peak of 870 to 75° cl' due to D vibration was specified to be 0.5 or less is because if it exceeds 0.5, the inner layer side will have a relatively large amount of carbon components and organic compounds This is because the adhesiveness with the metal base material decreases as the properties of the metal become stronger.

In addition, if the film thickness in the inner layer is less than 50A, there will be many pinholes, and good adhesion will not be obtained even if the surface layer of the intermediate layer 2 is stacked on top of it. It becomes easier to peel off. Therefore, the film thickness of the inner layer was set to 50 A or more and 5000 A or less.

The reason why the intermediate layer was provided was to increase the adhesion between the inner layer and the surface layer.If the thickness of the intermediate layer is less than tOOA, the adhesion during bending will not be good, and when a tape peel test is performed, the inner layer and the surface layer will be separated. Peeling off from the layer interface. On the other hand, if the thickness is too thick, the effect will be saturated and it will only take time to form the film, so 15000A was set as the upper limit.

The reason why the oxygen concentration in the surface layer is set to 20 atomic percent or less is to increase the toughness of the surface layer. Even if microcranks occur in the inner layer due to bending, the surface layer follows the bending deformation and maintains corrosion resistance. be able to.

Also, the reason why the total thickness of the surface layer and the intermediate layer is set to 500A to 5μI is that if it is less than 50μm, pinholes will be formed and the corrosion resistance will deteriorate, whereas if it is thicker than 5μm, the corrosion resistance will be lower than Wakkanai. First, it only takes time to form the film.

Organic silicone monomers that can be used in the present invention may be compounds containing St and C and have a vapor pressure under normal vapor deposition conditions, such as tetramethylsilane, vinyltrimethylsilane, hexamethyldisilane, methyltrimethoxysilane, etc. , vinyltrimethoxysilane, hexamethyldisiloxane, tetramethyldisiloxane, hexamethyldisilazane, hexamethylcyclotrisilazane, and the like.

The multilayer structure of the plasma-polymerized film according to the present invention has been explained using the expressions of an inner layer, an intermediate layer, and a surface layer for convenience. However, as long as the above conditions are satisfied, the inner layer and the surface layer do not necessarily have a uniform composition. It is not necessary that the composition be formed of a metal, and in keeping with the spirit of the present invention, the composition may change as appropriate from the adhesive surface to the metal toward the outermost surface.

[Example] FIG. 1 is a cross-sectional explanatory diagram showing a multilayer structure of a plasma polymerized film according to the present invention, in which an inner layer 2. middle layer 3
Two surface layers 4 were sequentially formed in the following manner. First, carbon steel degreased by a conventional method was used as the metal base material 1, and this was placed in a chamber of a plasma polymerization apparatus, and plasma etching treatment was performed using argon. As the plasma polymerization apparatus, an internal parallel plate electrode type was used, and 13
．． Plasma was generated using a 56 MHz high frequency power source. Note that the output was 100 W, the processing time was 10 minutes, and the substrate temperature was 35°C.

After the plasma etching process, hexamethyldisiloxane and oxygen were introduced into the chamber of a plasma polymerization apparatus to form an inner layer by plasma polymerization. The polymerization conditions for the inner layer were: output ioow, oxygen supply amount 100 sccm, monomer flow rate 10 sccm, and chamber internal pressure 0. ITo
rr, and the substrate temperature was 200°C.

FIG. 2 shows the results of infrared spectroscopic analysis of the inner layer. Absorption spectrum of Si-0-3t (11 o ~ t
Absorption spectrum of Si-CHs (870 to 750 cl
The ratio (b/a'') to the peak height b in ') is 0.
It was 22.

Continue to gradually reduce the oxygen flow rate to form an intermediate layer.
Finally, the oxygen flow rate was set to 0 to form a surface layer. Table 1 shows the thicknesses of the inner layer, intermediate layer, and surface layer of the laminated coating film thus obtained.

A corrosion resistance evaluation test and a polymer film adhesion evaluation test were conducted on the carbon steel on which the laminated coating film was formed. In the corrosion resistance evaluation test, after extruding 6 mm with an Erichsen tester,
This was done by immersing it in a 3wt% NaCl aqueous solution and measuring the time until red rust appeared. In addition, in the adhesion evaluation test, the polymer film was scored into 1 mm x 1 mm squares with a cutter knife, extruded to 6 mm using an Erichsen tester, and then a tape was attached and peeled off. Adhesion was evaluated. The results are also listed in Table 1.

Table Nos. 1 to 4 are examples according to the present invention, and all of them satisfy the conditions of the present invention, so the red rust generation time was 30
It lasted for 0 hours or more and the grain survival rate was 100%, and it had excellent corrosion resistance and film adhesion.

Nos. 5 to 11 are comparative examples in which one or more of the conditions of the present invention are not satisfied, and the corrosion resistance and/or film adhesion are poor. No. 5.6 is a comparative example in which no inner layer is formed and the inner layer is too thin, and has poor corrosion resistance and poor film adhesion. No. 7 is a comparative example in which the film thickness of the inner layer is too thick, and both corrosion resistance and film adhesion are insufficient. Nos. 018 to 10 are comparative examples in which the intermediate layer and the surface layer are not formed or are too thin, and the corrosion resistance is poor. No. 11 is a comparative example in which the thickness of the intermediate layer is too thin, and peeling occurs between the inner layer and the surface layer, resulting in poor corrosion resistance and m-adhesion.

[Effect of the invention] Since the present invention is configured as described above, corrosion resistance and @
It has now become possible to provide a metal coated with a plasma polymerized film with excellent adhesion.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional explanatory diagram showing the plasma polymerized film according to the present invention, Figure 2 is a graph showing the results of infrared spectroscopic analysis of the inner layer according to the present invention, and Figure 3 is the total film thickness and corrosion resistance of the surface layer and intermediate layer. FIG. 4 is a graph showing the relationship between inner layer film thickness and film adhesion.

Claims (1)

[Claims] In highly corrosion-resistant metals in which an organic silicone polymer film is formed on the surface of a metal base material by plasma polymerization,
The above polymerized coating has a multilayer structure consisting of an inner layer, an intermediate layer, and a surface layer, and the inner layer has a Si- 87 based on the vibration of CH_3
The ratio of absorption peak intensities from 0 to 750 cm^-^1 is 0.
5 or less and with a film thickness of 50 Å or more and 5000 Å or less, the surface layer has an oxygen concentration of 20 atomic % or less, and the intermediate layer has a gradient composition that changes from the composition of the inner layer to the composition of the surface layer. A highly corrosion-resistant metal characterized by forming a film of 100 Å or more and 15,000 Å or less, and having a total thickness of 500 Å or more and 5 μm or less of the intermediate layer and the surface layer.