JPH01108271A - Corrosion-preventive film which prevent diffusion of water vapor - Google Patents

Abstract

PURPOSE:To obtain the title film which can prevent cracking due to blistering and expansion of the coating film caused by the diffusion of water vapor and therefore can prevent corrosion even through prolonged use, by using a base material and a specified mixture formed on its surface which comes in contact with water vapor or a water-containing substance of a temperature higher than that of the wall of the base material. CONSTITUTION:A corrosion-preventive film which prevents the diffusion of water vapor, consists of a metallic and/or nonmetallic base material and a mixture of a polymetallocarbosilane [e. g., a copolymer of a polycarbosilane having structural units of formulas I and II (wherein R1-R4 are each H, 1-4C alkyl or phenyl) with a compound having units of formulas III and IV (wherein M is Ti or Zr; R5 and R6 are each 1-4C alkyl or O)] with a ceramic powder (e. g., an SiC powder), formed on that surface of said base material which comes in contact with 1 water vapor and/or a water-containing substance of a temperature higher that that of the wall of the base material. Because of excellent resistance to diffusion of water vapor, this film as applied to a metallic and/or nonmetallic base plate of a temperature different by 5 deg.C or greater and/or in, e.g., a region wherein the temperature difference between day and night is great, can prevent the coating film from expanding and blistering due to the diffusion of water vapor so that it can produce an effect of preventing corrosion even through prolonged use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water vapor diffusion prevention anti-corrosion film that prevents swelling of a coating film due to water vapor diffusion, with the aim of preventing corrosion of general industrial equipment and equipment.

[Prior art]

Metal and/or non-metallic equipment and equipment constituting tanks, various gas absorption towers, reactors, piping, pumps, valves and other plant equipment, chemical equipment materials, semiconductors and other electrical and electronic equipment materials, etc. Many contain water vapor and/or water-containing gases, liquids, solid-liquids, or solids (
Hereinafter, it will be simply referred to as an inclusion. ), it is often corroded because it is in constant or intermittent contact with

Therefore, various coatings and linings are currently applied to improve the corrosion resistance of the metal materials of these devices, and the main ones include plastic coatings, rubber linings, and glass linings.

Glass lining has excellent properties as a corrosion-resistant coating, but since it requires baking at 600°C or higher, it cannot be used for large equipment or equipment that has already been installed.
Moreover, its construction cost is high.

Plastic coatings and rubber linings do not require high temperature baking like glass linings.
Moreover, it has many advantages such as being able to be constructed on site.

Therefore, it is currently widely used for corrosion protection of plant equipment that is used below its heat-resistant temperature.

[Problem that the invention seeks to solve]

However, the disadvantage of plastic coatings and rubber linings is their poor resistance to water vapor diffusion. For example, a coating film exposed to water vapor gradually swells, and the interior walls of metal and other equipment are also protected from corrosion.

In addition, ordinary plastic coatings cannot cope with temperatures exceeding the heat-resistant temperature range of 100 to 200° C., so stainless steel or Teflon coatings have been used, but the construction costs were high and impractical.

If the temperature of water vapor and/or water-containing substances that come into contact with metal and/or non-metal based equipment through a coating that protects these equipment is higher than the wall temperature of these equipment, water vapor and/or water vapor in water vapor-containing materials.
Alternatively, moisture diffuses within the coating film due to water vapor pressure based on the temperature difference, reaches the boundary between the coating film and the base equipment, and corrodes the wall surface.

Furthermore, the inner wall temperature of these base devices is below the freezing point of water vapor, and the temperature of the water vapor and/or water-containing material that comes into contact with these base devices through the coating film that protects these base devices is below the freezing point of water vapor. If the temperature is higher than the wall surface temperature of the coating, the water vapor that has diffused within the coating is cooled at the interface between the coating and these base devices and condenses into water.

This condensed water corrodes these base equipment, and also causes the coating film that protects these base equipment to swell, eventually causing cracks in the coating film. Corrosion and swelling phenomena of coatings, linings (hereinafter referred to as paint films) caused by water vapor diffusion are caused by thermosetting resin coatings such as unsaturated polyester resins, vinyl ester resins, epoxy resins, phenol resins, and fluororesin resins. This problem is common to coatings made of thermoplastic resins such as polypropylene resin and polyvinyl chloride resin, as well as coatings made of natural rubber and synthetic rubber.

[Purpose of the invention]

The present invention was made in order to eliminate the above-mentioned conventional drawbacks, and is a water vapor diffusion prevention corrosion protection device that can prevent the swelling of the coating film caused by water vapor diffusion, cracking due to expansion, and corrosion even during long-term use. The purpose is to provide a membrane.

[Structure of the invention]

The anti-corrosion film for preventing water vapor diffusion of the present invention that achieves the above object is:
It is formed on the contact surface between a metal and/or non-metallic base material and water vapor and/or a water-containing material whose temperature is higher than the wall surface temperature of the base material, and is characterized by being made of a mixture of polymetallocarbosilane and ceramic powder. That is. The anticorrosion film for preventing water vapor diffusion of the present invention has the above-mentioned advantage of being easy to apply as a plastic coating agent, and also exhibits high resistance to water vapor diffusion.

Here, the metal and/or non-metal base material in the present invention refers to tanks, various gas absorption towers, reactors, plant equipment such as piping, pumps, valves, etc., and chemical equipment on which the water vapor diffusion protection film of the present invention is formed. It refers to metal and/or non-metal base equipment that constitutes industrial materials, semiconductor electrical/electronic equipment materials, automobile/aircraft materials, etc.

The polymetallocarbosilane used in the present invention is a polycarbosilane having the following structural units (A) and (B), as described in, for example, JP-A-56-5828 and JP-A-62-48773. Silane (where R1, R2
(A) R+ (B) R3→S
i -CH2÷ -+Si -0-)-R2Ra Polymetallosiloxane having the following structural units (C) and (D) (where M is a metal atom selected from Ti and Zr, R5 and R6 are (C1 to C4 alkyl group or oxygen) (space below superimposition) (C) R1(D) 1 →O-SN -0→-1 1-(-0-M -0← Copolymerization with Rs 1 It is a combination.

And structural units (A) and (B) in polycarbosilane
) is 5:1 to 200:1, and the ratio of structural units (C) to (D) in the polymetallosiloxane is 1:30 to 30:1.

The amount of metal elements including silicon in polymetallocarbosilane influences the water vapor diffusion resistance of the coating film, and as the amount of metal elements decreases, the water vapor diffusion resistance of the coating film decreases. In the present invention, the amount of metal elements containing silicon in the polymetallocarbosilane is usually 15% by weight or more,
Preferably it is 20% by weight or more.

Such polymetallocarbosilane is prepared by mixing polycarbosilane and polymetallosiloxane in a ratio of 1:100 to 100:1, adding an aromatic solvent such as a low-molecular-weight alcohol to this mixture, and adding an aromatic solvent such as a low-molecular-weight alcohol to the mixture in an inert gas such as nitrogen. 50-150
A copolymer is obtained by carrying out condensation polymerization at a temperature of 1 to 100 hours and then removing the solvent.

The obtained polymetallocarbosilane has a molecular weight of 1000 to 5oo
Since it is a highly viscous substance with a molecular weight of 0.000, it is dissolved in an organic solvent when used as a coating film.

As the organic solvent, benzene, toluene, xylene, tetrahydrofuran, and low molecular weight alcohols such as ethanol and butanol are used, taking into account the ease of drying the polymetallocarbosilane.

In the present invention, in order for the polymetallocarbosilane coating film to maintain good water vapor diffusion performance, the type and amount of ceramic powder, ie, filler, added to reach f& are extremely important.

Ceramic powders suitably used as fillers include metal oxides such as alumina, silica, titania, and zirconia, and non-oxide ceramics such as silicon carbide, titanium carbide, and silicon nitride. Furthermore, in order to maintain the corrosion resistance of the coating film, one with excellent chemical resistance is appropriately selected depending on the usage conditions.

The smaller the particle size of such a filler, the denser the structure in the resin, which has a better effect on coating performance. Normally, 2
It is 0μ or less, preferably several μ or less. If it is larger than 20 μm, it will settle in the film after coating and cause a difference in filler density in the resin, which is not preferable.

The amount used is 20 to 250 parts by weight, preferably 50 to 250 parts by weight per 100 parts by weight of polymetallocarbosilane.

If the amount of filler added is less than 20 parts by weight, the water vapor diffusion resistance of the coating film decreases, causing swelling of the coating film. If the amount of filler added exceeds 250 parts by weight, the viscosity of the resulting coating film will increase too much, making coating defects more likely to occur and the anticorrosion performance will decrease.

The reason why the water vapor diffusion resistance of the coating film of the present invention is high is not yet clear, but as is clear from the above structural units (A) to (D), polymetallocarbosilane contains a large amount of inorganic elements such as silicon. Compared to ordinary plastic coatings such as unsaturated polyester resins, epoxy resins, and fluorine resins, it has a dense structure similar to that of ceramics, and the addition of fillers further promotes this dense structure. It is estimated that this increases the diffusion resistance of For example, as the amount of metal elements in polymetallocarbosilane decreases, the water vapor diffusion resistance decreases.

Furthermore, the addition of fillers not only gives hardness to the paint film, but also relieves the compressive stress that accompanies the hardening of the paint film and prevents the formation of film defects, as well as acting as a physical barrier to water vapor that has diffused through the paint film. It is estimated that this further increases the resistance to water vapor diffusion.

Next, a method for manufacturing the anticorrosion film for preventing water vapor diffusion of the present invention will be explained.

First, as a pretreatment of the metal and/or non-metallic substrates to which the anti-corrosion coating to prevent water vapor diffusion is applied, surface cleaning treatment including removal of rust and degreasing is performed on these substrates in order to improve the adhesion of the coating. . Although blasting of the base material is not essential, it is preferable to carry out blasting in order to extend the life of the coating film.

As a method for manufacturing the anticorrosion film for preventing water vapor diffusion, drying at room temperature or baking at 250° C. or lower is selected depending on the cleanliness of the polymetallocarbosilane used.

In order to thicken the coating, it is necessary to recoat the coating, and in this case, a baking method is used to harden the precoated coating in a short time.

The thickness of the coating film is usually in the range of 50 to 300μ, and if it is less than 50μ, film defects due to foreign matter entering the coating surface will directly affect the base material surface, accelerating equipment corrosion. .

Further, a coating thickness exceeding 300 μm is not preferable because it has little effect on extending the life of the device compared to the increase in cost.

The water vapor and/or water-containing substance in the present invention is
It is in any state such as gas, solid liquid, fluid including solid gas, solid, etc., and contains water vapor and/or moisture.

These moisture-containing substances are brought into contact with the substrate while being stored in the equipment, passing through the equipment, or in order to perform some treatment on the substrate.

〔Effect of the invention〕

As described above, the anticorrosion film for preventing water vapor diffusion of the present invention is
It is made of a mixture of polymetallocarbosilane and ceramic powder and has excellent water vapor diffusion resistance, so it can be used on metal and/or non-metallic substrates in areas where the temperature difference is 5°C or more and/or where there is a large temperature difference between day and night. By applying this coating, even during long-term use, it prevents the coating film from expanding and blistering due to water vapor diffusion, providing an anticorrosion effect.

Examples of the present invention will be described below.

〔Example〕

Example 1 A 50% xylene solution of polytitanocarbosilane (Tyranocoat varnish type, manufactured by Ube Industries, Ltd.) was added to fine silicon carbide powder so that the weight ratio of polytitanocarbosilane was 1:1.

After thorough mixing with a stirrer, these carbon and ceramic plates were spray coated and kept in a dryer at 250° C. for 1 hour to harden.

The thickness of the coating film was 80μ.

This painted sample was subjected to the water vapor diffusion test apparatus shown in the figure.

In this device, water is kept at 60°C in the interior 1 by a heater 2, and at 28°C in the exterior 3 by a heater 4 and a cooler 5. Sample 7 is attached facing the high temperature side).

Even after 2100 hours had passed, no abnormality was observed in the coating film of this painted sample.

Comparative Examples 1 to 3 The following three types of commercially available plastic coating agents were used at 70x
It was applied to a 20 x 5 t carbon steel plate and cured under the same conditions.

The composition, curing method, and film thickness after curing of each coating agent are shown in the table below.

Table Comparative Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Sample Name R-I R-2R-3 Coating Film Name
Epoxy fluororesin flake coating
Coating Lining composition *1 (wt%) Binder epoxy Trifluoroethylene Unsaturated poly resin (65) N resin (100) Ester resin (70
) Filler Titanium oxide None Glass Fushiku 35) -ri (30) Application method Spray method Spray method Brush, 3 coats 3 coats Paint curing Room temperature 7 days 250℃ Room temperature 7 days Conditions Leaving 1 hour Leaving film thickness *2
270 350 580 (μ) *1 Excluding the solvent part *2 Average value measured at 6 locations with an electromagnetic film thickness meter This sample R-
Samples No. 1, R-2 and R-3 were subjected to a water vapor diffusion test apparatus under the same conditions as in Example 1.

As a result, sample R-1 showed swelling in the coating film after 170 hours (reference photo 1).

In addition, sample R-2 also caused similar swelling after 170 hours, and sample R-3 did not cause swelling after 170 hours, but 39
Swelling occurred at 0 hours (reference photo 2).

[BRIEF DESCRIPTION OF THE DRAWINGS] The figure is a schematic diagram of an apparatus used for a water vapor diffusion test on a sample coated with a water vapor diffusion prevention anticorrosion film according to the present invention.

Claims (1)

[Claims] It is formed on the contact surface between a metal and/or non-metallic base material and water vapor and/or a water-containing material whose temperature is higher than the wall surface temperature of the base material, and is characterized by being made of a mixture of polymetallocarbosilane and ceramic powder. An anticorrosive film that prevents water vapor diffusion.