JPS62157889A - Corrosion preventing method for shell constitutional member - Google Patents

Abstract

PURPOSE:To surely prevent corrosion in edge parts where the corrosion is severe, by adhesively coating the edge parts of a ship shell constitutional member with a synthetic resin sheet of U shape. CONSTITUTION:A T-shaped ship shell strength member 2 is connected on a ship bottom outer panel 1. An upper surface and outer surfaces of these ship bottom outer panel 1 and ship shell strength member 2 apply a shop primer while rust preventing paint 3 of tar epoxy system on the shop primer. And both end edge parts 4 of the shell strength member 2 applying said rust preventing paint 3 are coated with synthetic resin sheets 5 through adhesive agents. Said synthetic resin sheet 5, in which a pair of right and left sheets are previously formed into a squared shape with one end open corresponding to the edge parts 4, is adhesively attached in such a manner as to be pressed to the edge part 4 from its both sides. In this way, corrosion can be surely prevented because the both end edge parts 4, easily decreasing film thickness of the paint 3, are coated with the synthetic resin sheet of excellent corrosion resistance.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for preventing corrosion of ship hull constituent members.

(Prior Art) Fig. 6 shows an example of the structure of the ceiling part (beam below deck) of a ballast tank in a tanker or the like. As shown in the figure, hull strength members such as a deck girder 32, a deck transformer 33, and a deck lunge 34 are arranged vertically and horizontally below the deck 31 of a tanker, etc., but the parts where these are installed are located on the deck. It is directly behind 31, so in midsummer it can reach 60~ due to the heat of the sun.
The temperature will be as high as 70 degrees Celsius, and the humidity will be close to 100% due to residual seawater. In order to prevent corrosion of hull strength members in these harsh environments, shop primer and tar-epoxy anti-corrosion paint have traditionally been applied.

On the other hand, the structure of the submerged part of the ballast tank provided at the bottom of the ship is, for example, as shown in FIG.
It consists of hull strength members such as those arranged vertically and horizontally, but in this case,
Unlike the hull strength members below the deck 31, the hull strength members always come into contact with seawater, so in addition to the above-mentioned anticorrosive coating, electrolytic corrosion protection using galvanic anodes was also performed.

(Problems to be Solved by the Invention) However, the above corrosion prevention method has the following drawbacks. In other words, in the ceiling of the ballast tank, in addition to constant condensation on the hull strength members 32, 33, and 34, the corrosion resistance of the current anti-rust coating deteriorates significantly when the ambient temperature exceeds 60°C. Paint film defects may occur after a few years. Therefore, for example, if you inspect the ceiling of a ballast tank on a tanker that has been in service for five years, you will find that a rust layer up to 5 to 10 meters thick has formed.
Hull strength members whose coating film thickness tends to be thin 32.
It is clear that the particles are concentrated at the edges of 33 and 34. In addition, in the submerged part of the ballast tank,
Unlike cathodic protection of the hull outer plating 35, the hull strength members 36, 37, and 38 have various shapes, so the current density distribution becomes non-uniform, especially at the edges of the T-shaped strength members. There were many blisters caused by hydrogen molecules in the membrane.

An example of the principle by which this blistering occurs is as follows. In other words, in cathodic protection using a sacrificial anode, the following reaction occurs at the anode: ymp/+e-.

However, the electron e- generated in the above reaction (1) reacts with H'' present in water to form H'+ e--HT.--(2) hydrogen atoms and further hydrogen molecules.

Therefore, this hydrogen molecule causes a bulge to be formed.

(Means for solving the problem) Therefore, in the corrosion prevention method for hull constituent members of the present invention,
The edge portion 4 is covered with a synthetic resin sheet 5.

(Function) When the cut/nozzle portion 4 is covered with the synthetic resin sheet 5 as described above, reliable corrosion protection can be achieved regardless of the thickness of the coating film. Further, since the work of covering the synthetic resin sheet 5 is a simple work, a thick film coating can be formed quickly.

(Embodiments) Next, specific embodiments of the method for preventing corrosion of ship hull structural members according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a hull strength member according to a first embodiment of the present invention. In FIG. A ship primer is applied to the upper surface of the bottom shell plate 1 and the outer surface of the hull strength member 2, and a cool epoxy anti-rust paint 3 is applied thereon. Synthetic resin sheets 5 are bonded to both edge portions 4 of the hull strength member 2 coated with the anti-rust paint 3 via an adhesive. FIGS. 2 and 3 show how a synthetic resin sheet 5 is adhered to the both ends/notches 4 of the hull strength member 2. As shown in FIG. That is, as shown in FIG. 2, a pair of synthetic resin sheets 5 are formed in advance into a U-shape on the left and right sides corresponding to the edge portions 4, and are glued by being inserted into the edge portions 4 from both sides, or as shown in FIG. Flat synthetic resin as shown in ・'-)50
4B'lr"'1""Fiii'"ffl Next, raise the other end to make an L-shape, then bend this other end and place it along the top surface of the edge part 4. 6.2, the edge portions 4 at both ends, where the thickness of the coating 3 of the hull strength member 2 tends to be thinner, are covered with the synthetic resin sheet 5 having excellent corrosion resistance, and reliable corrosion protection is achieved. That will happen.

In the above embodiment, the synthetic resin sheet 5 is bonded to the edge portion 4 of the hull strength member 2 which has been coated multiple times with anti-rust coating, but after this step, the synthetic resin sheet 5 is further bonded. Alternatively, the synthetic resin sheet 5 may be directly adhered to the edge portion 4 of the hull strength member 2 without applying any anti-rust coating, and multiple layers of anti-#a coating may be applied on top of the synthetic resin sheet 5. As the material for the synthetic resin sheet 5 that may be applied, vinyl chloride is suitable because it has excellent adhesive properties, but polyethylene, polypropylene, etc. are also suitable when considering corrosion resistance, water permeability, cost, etc. Furthermore, the synthetic resin sheet 5 does not necessarily need to be adhered to the edge portion 4 through an adhesive, and may be welded or simply covered. The appropriate thickness of the synthetic resin sheet 5 is 0.5 to 3 cm. .

This is because by forming a thick film in this way, the above-mentioned blistering can be effectively prevented from occurring based on the following principle. In other words, when a thick film coating is formed using the synthetic resin sheet 5, H
2ON is reduced at the interface between the synthetic resin sheet 5 and the base metal, and as a result, the amount of hydrogen generated is reduced. In addition, the synthetic resin sheet 5 increases the current conduction resistance,
The total amount of e- to cause reaction (2) described above is reduced, and the amount of hydrogen generated is reduced. Therefore, no blisters occur as in the conventional case.

FIG. 4 shows a hull strength member 2 in a second embodiment of the present invention.
It shows. In this embodiment, the synthetic resin sheet 5 in the first embodiment is integrated. That is, the synthetic resin sheet 5 in the first embodiment was formed separately in a U-shape or the like corresponding to the edge portions 4 at both ends of the hull strength member 2, but the synthetic resin sheet 5 in this embodiment is integrated. and covers the upper front part of the hull strength member 2. The construction procedure is the same as in the first embodiment, but in this way, corrosion protection can be applied over a wide range, and the work of gluing the synthetic resin sheet 5 can be done simply and quickly as in the first embodiment. Effective.

FIG. 5 shows a hull strength member 2 in a third embodiment of the present invention. When the hull strength member 2 is in the form of an upright plate as shown in the figure, its upper edge portion 4 is covered with the above-mentioned synthetic resin sheet 5.

The construction procedure in this case is also the same as in the first embodiment, and similar effects can be obtained.

(Effects of the Invention) In the corrosion prevention method for hull structural members of the present invention, since the edges where corrosion is likely to occur are covered with a synthetic resin sheet as described above, the thickness of the coating film of the hull strength member is Reliable corrosion protection can be achieved without any problems. In addition, a thick film coating can be formed easily and quickly, and by changing the shape of the synthetic resin sheet, it can be widely applied to various shapes of ship hull components.

[Brief explanation of drawings]

1 to 3 show a first embodiment of the present invention, in which FIG. 1 is a cross-sectional view of the hull component in a state where the coating is completed, and FIG.
Figures 3 and 3 are cross-sectional views of the hull constituent members undergoing coating work, Figure 4 is a cross-sectional view of the hull constituent members showing a second embodiment of the present invention, and Figure 5 is a cross-sectional view of the hull constituent members in the process of coating. 6 and 7 are cross-sectional views of hull constituent members showing a third embodiment of the present invention.
Each figure is a perspective view of a main part of a ballast tank showing a conventional example. 2... Hull strength member, 4... Edge portion, 5... Synthetic resin sheet. Patent applicant: Kawasaki Heavy Industries, Ltd. Figure 1 Figure 4 Figure 5 Figure 6 J/ Figure 7

Claims (1)

[Scope of Claims] 1. A method for preventing corrosion of ship hull constituent members, which comprises covering the edges with a synthetic resin sheet. 2. The method for preventing corrosion of a ship hull component according to claim 1, wherein the synthetic resin sheet has a U-shaped cross section. 3. The method for preventing corrosion of a ship hull component according to claim 1 or 2, wherein the synthetic resin sheet is adhered to the edge portion.