JPH07104263B2 - Evaluation method for edge sealability of heavy anticorrosion steel sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the edge sealability of a heavy corrosion protection steel sheet.

[0002]

2. Description of the Related Art In recent years, heavy-corrosion-preventive steel sheets having a polyethylene sheet or polyurethane coated on the surface of steel sheets have been used from the viewpoints of enhancing and improving social capital of ports and river structures and urban landscape. These heavy-duty anticorrosion steel plates are characterized by a long service life and maintenance-free, but this is a problem because the heavy-duty anticorrosive coating sometimes peels off.

Regarding the cause of the peeling accident, it is considered that there is a problem in the adhesion and sealability between the steel plate and the heavy anticorrosion coating, and various studies have been conducted from the manufacturing aspect. The adhesion evaluation method between the steel plate and the heavy anticorrosion coating is generally exposed to artificial seawater at 40 ° C to 80 ° C for 1 month or more, and then peeled off between the steel plate and the heavy anticorrosion coating (hereinafter, peel strength). Called test)
The peel resistance (hereinafter referred to as peel strength) is used to evaluate the adhesion resistance.

When a heavy anticorrosion coating is applied to a steel sheet pile or the like, a coating end portion is generated in the vicinity of the fitting claw portions on both sides of the steel sheet pile, but there is no conventional evaluation method for the seal resistance of the end portion, Similar to the parts, it has been evaluated by the peel strength test.

However, even if the peel strength of the end portion is good, a peeling accident may occur at the end portion, and it is difficult to find a unique correlation between the peel strength and the seal resistance. Since the end part is close to the claw part, it is difficult to process the test piece, and it is necessary to use a special jig for the peel strength test at the bend part. Was desired.

[0006]

In order to solve the above problems, the inventors of the present invention firstly tried to thoroughly understand the cause of the peeling accident of the heavy anticorrosion coated steel sheet pile. As a result, the following was revealed. That is, (1) Peeling has occurred from the end. (2) In the edge peeling, oxygen permeated from the edge of the heavy anticorrosion coating reaches the surface of the steel sheet, forms iron oxide on the surface of the steel sheet, weakens the sealing property between the steel sheet and the heavy anticorrosion coating, and iron oxide grows further. It is generated by the mechanism of expansion and seawater (water) intrusion from the end.

From the above results, it has been found that if various factors related to the seal resistance of the heavy anticorrosion coated end portion can be clarified, measures can be taken to prevent the accidental peeling of the heavy anticorrosion steel plate. In addition, since the mechanism of edge peeling has been elucidated, in order to evaluate the edge seal resistance of heavy corrosion-resistant steel plates,
It was also found that a detector for seawater (water) may be provided at a location some distance from the end of the heavy anticorrosion coating under the corrosion acceleration test environment, and the evaluation may be performed by the time until the intrusion from the end. The present invention proposes, based on these new findings, an economical and simple method for evaluating the seal resistance of the edge of a heavy corrosion-resistant steel sheet.

[0008]

The gist of the present invention is to provide a small hole reaching the heavy anticorrosion coating on the steel plate side 10 mm or more away from the end of the heavy anticorrosion steel plate, and provide an insulating material at the center of the small hole. Insert the electrode through the other electrode and ground the other electrode to the steel plate to form a closed circuit that allows a minute current to flow.The end of the heavy-corrosion-proof steel plate is exposed to the corrosive liquid so that the corrosive liquid does not enter the closed circuit from the steel plate side. This is a method in which the edge sealability of the heavy corrosion-resistant steel sheet is evaluated by the time it takes for the corrosive liquid to infiltrate the interface between the steel sheet and the coating from the edge of the heavy corrosion-resistant steel sheet until it reaches the electrode in the small hole.

The present invention will be described in detail below with reference to the drawings. FIG. 2 shows an example of a steel sheet pile having a heavy anticorrosion coating on the valley side. In FIG. 2, 1 indicates a steel sheet pile and 2 indicates a heavy anticorrosion coating. The steel sheet pile 1 is divided into zones of a claw portion a, a flange portion b, and a web portion c. On the other hand, in the heavy anticorrosion coating 2, d is the end of the heavy anticorrosion coating.

FIG. 1 shows a method for evaluating the edge sealability of the heavy anticorrosion steel sheet of the present invention. In FIG. 1, 1 is a test piece having a flange portion and a claw portion taken from a steel sheet pile having a heavy anticorrosion coating. The heavy anticorrosion coating 2 is applied to the valley side of the steel sheet pile, and a small hole e is provided on the flange side 10 mm or more away from the heavy anticorrosion coating end d.
Is provided from the steel plate side to the heavy anticorrosion coated surface.

An electrode g is arranged in the small hole e via an insulating material f, and the other end h of the electrode is grounded to the surface of the steel sheet pile. Electrode g
A power supply i through which a minute current flows is provided between the electrode and the electrode h to form a closed circuit. The steel sheet pile having the closed circuit is dipped in the corrosion acceleration test liquid j until the heavy anticorrosion coated surface is sufficiently immersed. However, in this case, a partition plate k is provided on the cut surface in the longitudinal direction of the steel sheet pile so that the liquid j does not enter the small hole e provided on the steel sheet pile side. Also, a timer L is provided in parallel with the closed circuit.

According to the present invention, at the same time as the start of the test (when the steel sheet pile is immersed in the corrosion acceleration test liquid j), the timer L provided in parallel with the closed circuit is activated. The timer L operates until the liquid j reaches the electrode g arranged in the small hole e, and the liquid j is discharged in the small hole e.
When reaching, the minute current flows in the closed circuit between the electrodes g and h, the electromagnet m arranged in the circuit is activated, and the timer L is stopped. Thus, the sealing resistance of the heavy anticorrosion coated surface can be evaluated by the time of immersion in the corrosion acceleration test liquid.

In the present invention, the reason why the position of the small hole is separated from the heavy anticorrosion coating end portion d by 10 mm or more is that if the small hole position is too close to the heavy anticorrosion coating end portion d, the small hole processing adversely affects the end sealability. This is because the precision of machining small holes is required and machining is wasted. The distance from the end d is not particularly specified, but is preferably about 10 mm to 30 mm (near the corner of the claw).

The size of the small hole e is not particularly limited, but it is desirable that it is as small as possible. The reason why the small hole e is provided from the steel plate side to the heavy anticorrosion coated surface is that the electrode g detects the corrosive liquid j entering the interface between the steel sheet pile and the heavy anticorrosive coated surface. In this case, care must be taken so that the small holes do not break through the heavy anticorrosion coating surface. The number of small holes is not particularly limited, and the sealing resistance in the length direction of the steel sheet pile can be evaluated by providing a plurality of small holes.

The reason why the electrode g is arranged in the small hole e via the insulating material f is to prevent the electrode g from coming into contact with the steel sheet pile and conducting with the electrode h. The power supply i is provided between the electrode g provided in the small hole e and the electrode h grounded to the steel sheet pile to form a closed circuit because the corrosive liquid j that has entered the interface between the steel sheet pile and the heavy anticorrosion coating surface is the small hole e. This is because when the electrode g is reached, a minute current flows in the closed circuit and the electromagnet m is operated to stop the timer L provided with the circuit in parallel.

Although the corrosion accelerating liquid is not specified, artificial seawater is preferable in consideration of port use. The temperature of the liquid is also not particularly specified, and a general accelerated test of 40 ° C to 80 ° C is desirable. The length in the longitudinal direction of the steel sheet pile is not particularly limited, but if the length is extremely short, the invasion of the corrosive liquid j from the cut surface may have an adverse effect, so the distance between the cut surface and the small hole is Fifty
It is desirable that it be at least mm.

[0017]

[Examples] In order to confirm whether the present invention is suitable as a method for evaluating the edge sealability of a heavy corrosion-resistant steel sheet, a heavy corrosion-resistant steel sheet pile in which a peeling accident occurred from the end in actual installation and a peeling accident did not occur. With respect to the heavy anticorrosion steel sheet pile, the end sealability was evaluated by the method of the present invention. The test pieces were taken from the subsea soil where no peeling occurred.

As shown in Table 1, the test conditions were as follows: 3% saline at 60 ° C. was used as a corrosion promoting liquid, two small holes with a diameter of 5 mm were provided at a position of 10 mm from the end of the heavy-duty anticorrosion coating, and the small holes were formed. Electrodes were inserted in the to form a parallel closed circuit, and a heavy corrosion-resistant steel sheet pile in which a peeling accident occurred (test piece A) and a heavy corrosion-resistant steel sheet pile in which a peeling accident did not occur (test piece B) were evaluated.
Table 1 shows the evaluation results. In the heavy corrosion-resistant steel sheet pile (test piece A) where the peeling accident occurred, the corrosive liquid entered from the end of the heavy corrosion-resistant coating in 7725 hours, whereas in the heavy corrosion-resistant steel sheet pile (test piece B) where the peeling accident did not occur, The seal resistance was 15380 hours or longer. This result reproduces a peeling accident from the end of a heavy-duty anticorrosion steel sheet pile that has been actually laid, and it can be seen that the present invention is a very suitable method as an evaluation method for the end sealability of the heavy-duty anticorrosion steel plate.

[0019]

[Table 1]

[0020]

INDUSTRIAL APPLICABILITY The present invention evaluates the sealing property of the edge portion of the heavy anticorrosion coating under the corrosion accelerating test environment of the heavy anticorrosion steel sheet, so that the peeling accident between the steel sheet and the heavy anticorrosion coating agent can be economically and easily prevented. can do.

[Brief description of drawings]

1A and 1B are explanatory views of an end sealability evaluation method of the present invention, where FIG. 1A is a perspective view, and FIG. 1B is A- of FIG.
The A'sectional view is shown.

FIG. 2 shows an explanatory view of a heavy corrosion-resistant steel sheet pile.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Other powers of the inventor New Year No. 1 Tobahata-cho, Tobata-ku, Kitakyushu City, Fukuoka Prefecture New Nippon Steel Co., Ltd. Yawata Works (72) Inventor, Urashima Kitakyushu City, Fukuoka Prefecture No. 1-1 Hibata-cho, Tobata-ku New Steel Works, Yawata Works (56) References JP-A-60-239665 (JP, A)

Claims (1)

[Claims] 1. A small hole reaching the heavy anticorrosion coating is provided on the steel plate side 10 mm or more away from the end of the heavy anticorrosion steel plate, and an electrode is inserted at the center of the small hole through an insulating material, and the other electrode is attached. Form a closed circuit that grounds a small current to the steel plate and fully immerses the end of the heavy-corrosion protection steel plate in the corrosive liquid so that the corrosive liquid does not enter from the steel side into the closed circuit. A method for evaluating the edge sealability of a heavy-corrosion-proof steel sheet, which comprises measuring the time it takes to penetrate the interface between the steel sheet and the coating from the edge and reach the electrode in the small hole.