JPS6191353A - Corrosion prevention of inside wall of chemical tank - Google Patents

Abstract

PURPOSE:To prevent inexpensively and efficiently the corrosion of the inside wall of a chemical tank by coating a reactive curing adhesive agent to the film coating part of a steel plate, adhering a PE film to said part, removing the film of the non-coating surface and spraying thermally plastic powder to the exposed surface. CONSTITUTION:A negative 1 which supports the coating part of the steel plate 8 is passed under a light source 2 to apply an on-off signal to an optical sensor 3. The signal is fed via an amplifier 4 and a signal transmitter 5 to a signal receiver 6 from which the signal is transmitted to an adhesive agent coating nozzle 7. The valve of the nozzle 7 is opened and closed in accordance with the signal to coat the reactive curing adhesive agent 10 to the film coating part of the plate 8. The PE film 11 is the adhered under pressure by a roller 12 to said part and thereafter the film 11 on the surface not coated with the adhesive agent is cut away by a cutter, etc. Such plate 8 is built to a tank and thereafter the plastic powder such as PE is thermally sprayed to the exposed surface from which the film 11 is removed. The powder is thus coated on the surface to a prescribed film thickness. The corrosion of the inside wall of the chemical tank is efficiently prevented by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The invention relates to a method for protecting (lining) the inner walls of chemical tanks in ships and the like used for the transportation of all kinds of chemical substances. ” ” (conventional technology)
- Conventionally, crude oil has been imported by tankers, and the anti-corrosion treatment of the inner walls of tankers is limited to crude oil and is sufficient. It was meant to be applied. However, in recent years, crude oil has been refined in its production area by helicopter, and the refined product has been imported by helicopter.

The tankers that transport these refined petroleum products are called duct carriers, and epoxy-based, polyurethane-based, and inorganic zinc-based paints are used as anticorrosion paints on the inside. These paints are used depending on the purpose, but naphtha, gasoline, and diesel oil are used.

It is said to be completely resistant to kerosene, etc.

In recent years, it has become necessary to transport a wide variety of products other than those mentioned above, such as methanol, caustic soda, fatty acids, and animal and vegetable oils, as well as chemical products that are not resistant to the paints mentioned above. Ships that transport these chemical products are called chemical tankers, and no satisfactory anticorrosion paint has been developed for them.

(Problem to be solved by the invention) Since the tank itself is made of stainless steel, the construction cost of the tanker increases because stainless steel itself is expensive, and this is not practical for large tankers. be. On the other hand, it is possible to apply high-performance plastic powder by thermal spraying, but the application efficiency is about 5 m/H, and it is impractical to apply it to the entire inner surface of a large chemical tank due to work efficiency. It is possible.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a versatile inner wall corrosion prevention method that enables efficient and inexpensive lining of chemical tanks.

(Means for Solving the Problem) A reaction-curing adhesive 10 is applied to the film-coated portion of the steel plate 8 for a chemical tank through means for selecting the film-coated portion, and a polyethylene film is applied to the copper plate using the adhesive. After that, the polyethylene film on the non-adhesive surface is removed, and the exposed steel plate surface is thermally sprayed and coated with plastic powder.

(Example) An embodiment of the present invention will be described based on FIG.

The inner wall of a chemical tank constructed by welding steel plates has reinforcing ridges (longitudinal material) protruding from the inner wall. Therefore, the steel plate as a material can be used for welding the steel plates together, fusing them together, and welding the ridges. It is necessary to select areas covered with polyethylene film and areas not coated with polyethylene film, depending on design considerations such as these.

Here, a specific example of a method for bonding polyethylene sheets using heat in a steelworks will be described.

First, the structure of the means for selecting the coating location on the steel plate 8 is that a special negative 1 that indicates the coating location on the steel plate is used, and when this negative is passed under a light source 2 at a constant speed, it is placed on the opposite side of the light source and the next The optical sensor 3 is given an ON-OFF signal for selection according to the negative, and this signal is amplified by the amplifier 4 and sent to the transmitting means 5. This transmitting means 5 directly sends a signal to a receiver 6 at the coating work site, magnifies this signal by a factor of 10, for example, and transmits it to the adhesive coating waste 5 lure. Of course, the method is not limited to directly transmitting the signal to the nozzle, and it is also possible to store the signal on a magnetic tape or use a facsimile.

By the way, heat utilization in a steelworks (mill maker) involves, for example, a continuous heating furnace connected to a continuous casting device, which has scale breaker 1 rough rolling, finish rolling, and hot straightening sequentially connected to it. Thermal energy after the straightening process, or about 200℃ after the quenching heating and tempering process
It utilizes residual thermal energy of approximately ℃. The temperature of the hot sandblasted steel plate 8 at this time is detected by a temperature sensor 9.

In the coating process, as shown in FIG. 1, a nozzle 7 is provided above the steel plate 8, and the pulp of this nozzle is
- Reaction-curing adhesive 1 that opens and closes in response to an OFF signal
0 is applied to the film coating portion of this steel plate.

This adhesive is mainly made of two-component epoxy resin,
The viscosity corresponds to the opening and closing of the pulp in the nozzle 7 and has good liquid drainage.

In this way, the adhesive 10 is applied to predetermined locations on the steel plate 8. Immediately thereafter, the process moves to an adhesion process, in which the polyethylene film 11 is pressed by a pressure roller 12 and bonded to the steel plate.

Next, the process moves on to the removal process of the polyethylene film 11 that has not been coated with adhesive on the steel plate 8, but if this film is cut and removed using a special cutter using NC control, the polyethylene film 11 for welding etc. can be removed. film 11
It is possible to obtain a laminated steel plate 8 without any cracks.

As shown in the second diagram, all ship longitudinal materials 81 used in the PC tank are made of extruded steel, and are manufactured at a steelworks with a diameter of 10 mm.
Hot blasting is performed at 0° C. to 200° C., followed by electrostatic powder coating, followed by flame-treated polyethylene powder spray coating 14 using a flame spraying machine 13 .

In addition, to repair the painted joints and damaged areas 8a where the surface of the steel plate 8 is exposed after the polyethylene film 11 has been removed, the process is moved to a thermal spraying process after being treated with a vacuum plaster. It is coated to a predetermined thickness. Preheating is required during thermal spraying, but preheating to 80°C to 150°C can also be performed using a high frequency induction heating device that can heat only the surface of the steel plate. Of course, preheating may be performed using a flame spraying machine.

By the way, polyethylene changes depending on the pressure level during polymerization.
There are three types: high pressure, medium pressure, and low pressure, but the low and medium pressure types have better crystallinity and chemical resistance than the high pressure types. However, generally the polyethylene film 11 is made of Dorol or Kijiroll.

They tend to swell slightly in gasoline, and these can penetrate the film and reach the adhesive layer. Therefore, to prevent this swelling, it is necessary to use a double layer of polyethylene film and epoxy sheet, or use a two-component epoxy resin adhesive (for example, the product name "Ecobond 45").
"Clear" manufactured by Emerson, same [Fastarbond 1
00QJ Nisshin Giken Kogyo) is preferable.

In addition, although the above-mentioned embodiment has been explained by exemplifying the use of heat from a steelworks, it is also possible to perform the construction at room temperature in a shipyard or the like. 1. It is desirable that the adhesive surface of the polyethylene used be one that has been subjected to corona discharge, electron beam irradiation, flame treatment, etc.

(Effects of the present invention) The present invention provides a chemical tank for transporting many types of chemical substances, and even if the inner wall shape is complicated, it is possible to selectively bond the coated portions of the steel plate to the polyethylene sheet. The coating can be applied efficiently and inexpensively by thermal spraying, and since a reaction-curing adhesive is used, the adhesive is strong and has a long life.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram showing a part of an embodiment of the present invention, and FIG. 2 is a partially cutaway view showing another part of an embodiment of the invention. Death ζ・Copper plate 10...Azusa 4 agent 11-・O? Liechi 1/〉Film, Narukami 1” Applicant: Chugoku Paint Co., Ltd./○~2

Claims (3)

[Claims] (1) a step of applying a reaction-curing adhesive to the film-coated portion of a steel plate for a chemical tank through means for selecting the film-coated portion; and a step of bonding a polyethylene film to the steel plate with the adhesive; A chemical tank constructed by a process of removing the polyethylene film on the non-adhesive surface, and a thermal spraying process of coating the steel plate surface exposed by this removal process with plastic powder thermal spraying after building the tank. Corrosion prevention method for internal walls. (2) A method for preventing corrosion of an inner wall of a chemical tank according to claim 1, wherein the reaction-curing adhesive is mainly composed of a two-component epoxy resin. (3) A method for preventing corrosion of an inner wall of a chemical tank according to claim 1, wherein the polyethylene sheet is produced by a low or medium pressure method.