JPH06207283A - Method for preventing crevice corrosion during storage of chromium-containing steel pipe - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent crevice corrosion during storage of chromium-containing steel pipes. [Structure] Prior to packing the chromium-containing steel pipe 1, a paint 2 that acts as a galvanic anode is applied to a portion that comes into contact with a packing member during packing. In addition, a coating that acts as a galvanic anode is applied to the portion that comes into contact with the storage member during storage. [Effect] It is possible to prevent crevice corrosion during storage of a chromium-containing steel pipe, and it becomes possible to store it for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to a steel pipe for oil wells
The present invention relates to a method for preventing crevice corrosion when storing chromium-containing steel pipes such as% Cr and 13% Cr steel pipes.

[0002]

2. Description of the Related Art In crevice corrosion, the surface of a passive metal or alloy is shielded by a metal or a nonmetal, and when there is a crevice between them, that portion is corroded. In particular, it has a clearance of about 10 ⁻⁴ cm and occurs in the presence of anions such as chlorine ions that destroy the passive film. In a martensitic stainless steel pipe, which is a type of chromium-containing steel pipe, crevice corrosion may occur when the electrolyte has a stagnation portion, for example, chlorine ions contained in rain.
As shown in FIG. 4, this phenomenon is caused by rainwater 22 containing chlorine ions in the atmosphere containing chlorine ions when the martensitic stainless steel pipe 21 is transported by sea while being packed, or during long-term storage. It is generated by staying in the clearance with 23.

Conventionally, in steel pipes for oil wells, 9% Cr, 13%
When shipping chromium-containing steel pipes such as Cr steel pipes, as in the case of carbon steel pipes, rust-preventive oil such as linseed oil was applied to the outer surface, and they were packed in a wooden frame before shipment. 9% C in oil well steel pipe
For chromium-containing steel pipes such as r and 13% Cr steel pipes, crevice corrosion may occur at the parts where the packaging materials and storage members come into contact with the chromium-containing steel pipes during transportation and storage, especially in Southeast Asia and the Gulf Coast region. This tendency is strong in hot and humid areas.

As a method of packing the steel pipes, half-shaped sandwich frames for holding the steel pipes are arranged at several places in the longitudinal direction of the steel pipes and stacked, and the sandwich frame portions are squeezed. A method of bundling (Japanese Patent Laid-Open No. 63-191766) has been proposed.

[0005]

The method of applying a dry oil such as linseed oil to the outer surface of the above-mentioned steel pipe has a rust preventive ability of about 6 months, and when it is stored for a long period of more than 6 months, Crevice corrosion cannot be prevented. This tendency is particularly noticeable in areas where the storage location is near the coast and hot and humid areas. Further, the method disclosed in Japanese Patent Laid-Open No. 63-191766 does not consider crevice corrosion at the contact portion between the steel pipe and the packaging member.

It is an object of the present invention to prevent crevice corrosion of a portion of a chromium-containing steel pipe that comes into contact with a packaging member for long-term storage or a portion that comes into contact with a member during storage after unpacking. It is to provide a corrosion prevention method.

[0007]

[Means for Solving the Problems] The inventors of the present invention have made extensive studies to achieve the above object. As a result, by applying a paint that acts as a galvanic anode to the parts that come into contact with the packaging materials when storing the chromium-containing steel pipes for a long period of time, or the parts that come into contact with the materials that are being stored after unpacking, it is possible to ensure that chlorine ions, etc. It was clarified that the galvanic corrosion was prevented by moving the potential of the chromium-containing steel pipe to the base potential region by bringing the part exhibiting the base natural corrosion potential into contact with the paint acting as a galvanic anode, and reached the present invention.

That is, the present invention is a method for preventing crevice corrosion during storage of a chromium-containing steel pipe, characterized in that, prior to packing the chromium-containing steel pipe, a coating that acts as a galvanic anode is applied to the portion that comes into contact with the packing member during packaging. Is.

Further, prior to packing the chromium-containing steel pipe, a coating material that acts as a galvanic anode is applied to a portion that comes into contact with the packing member at the time of packing, and then the packed chromium-containing steel pipe is stored after unpacking and stored. In a method for preventing crevice corrosion during storage of a chromium-containing steel pipe, characterized in that a coating that acts as a galvanic anode is applied to a portion where the coating is not applied, or a portion where the coating is peeled or removed is there.

[0010]

In the present invention, the portion of the chromium-containing steel pipe that comes into contact with the packing member that forms the crevice is coated with a coating that acts as a galvanic anode. The portion that exhibits the potential contacts the paint that acts as a galvanic anode, the potential of the chromium-containing steel pipe moves to the base potential region, and galvanic corrosion is performed to prevent crevice corrosion in the portion that contacts the packaging member of the chromium-containing steel pipe for a long time. It can be prevented for a long time.

Further, according to the present invention, the chromium-containing steel pipe coated with a coating that acts as a galvanic anode is contacted with a storage member which forms a gap when the chromium-containing steel pipe is stored after unpacking. Since the paint that acts as a galvanic anode is applied to the part where the paint is not applied or the part where the paint is peeled off or removed, the chlorine ion etc. that stays in the clearance that contacts the storage member of the chromium-containing steel pipe, etc. The part of the steel that exhibits a sufficiently basement natural corrosion potential contacts the paint that acts as a galvanic anode, the potential of the chromium-containing steel pipe moves to the base potential region, and the galvanic corrosion protects the chromium-containing steel pipe Crevice corrosion can be prevented for a long period of time.

As the paint which acts as a galvanic anode used in the present invention, an inorganic zinc rich paint in which the color-developing agent is an alkyl silicate and a pigment is zinc powder, or a paint using aluminum powder, magnesium or the like as a pigment is used. About 20 to 30 μm is sufficient as the film thickness of the coating material to be applied. The chromium-containing steel pipe in the present invention is a steel pipe of 9% Cr, 13% Cr, etc., and a typical example thereof is a martensitic stainless steel pipe.

[0013]

【Example】

Embodiment 1 Hereinafter, details of the present invention will be described with reference to FIGS. 1 to 3 showing an embodiment. FIG. 1 is a perspective view showing a state in which a coating that acts as a galvanic anode is applied to a portion of a chromium-containing steel pipe before packaging which comes into contact with a packaging member, FIG. 2 is a perspective view of a wood packaging frame, and FIG. It is a perspective view showing a state. In FIGS. 1 to 3, 1 is a chromium-containing steel pipe, 2 is a chromium-containing steel pipe 1, an inorganic silicate-rich paint in which a color-developing agent applied to a portion which comes into contact with a packing member before packaging is an alkyl silicate, and a pigment is zinc dust. Reference numeral 3 denotes a wood packing frame including an outer frame 4 and a partition 5. The outer frame 4 is partitioned by the partition 5 so that the chromium-containing steel pipes 1 on the upper, lower, left and right sides do not contact each other. For packing the chromium-containing steel pipe 1, four wood packing frames 3 are arranged at predetermined intervals, and the wood packing frame 3 is inserted with the coating surface of the inorganic zinc-rich paint 2 positioned on each of the partitions of the wood packing frame 3. Then, the chromium-containing steel pipes 1 between the wood packaging frames 3 are bundled by the hoops 6 and packed.

With the above construction, the portion of the packed chromium-containing steel pipe 1 in contact with the outer frame 4 and the partition 5 of the wood packaging frame 3 is coated with the inorganic zinc-rich paint 2 which acts as a galvanic anode. Therefore, even if there is a portion that exhibits a sufficiently basement natural corrosion potential such as chloride ions during transportation or storage, it will come into contact with the inorganic zinc-rich paint 2 that acts as a galvanic anode, and the chromium-containing steel pipe 1 It is possible to prevent crevice corrosion of the portion of the chromium-containing steel pipe 1 that comes into contact with the packaging member for a long period of time due to the shift of the potential to the base potential region.

Example 2 Conventionally, the outer diameter is 88.9 mm, the wall thickness is 6.45 mm, and the length is 10.
m 13% Cr martensitic stainless steel pipe was coated with linseed oil as a rust preventive agent, packed, and exported to Southeast Asia for storage.
The martensitic stainless steel pipe of No. 2 suffered from crevice corrosion and could not be used. 13 outer diameter 88.9mm, wall thickness 6.45mm, length 10m
Prior to packing the% Cr martensitic stainless steel pipe, an inorganic zinc rich paint having a zinc silicate as a color spreader and a zinc dust as a pigment is applied to a part in contact with the packing member as a galvanic anode.
Although about 60,000 tons were applied and packaged and shipped to Southeast Asia, there was no crevice corrosion during storage.

[0016]

As described above, according to the method of the present invention, it is possible to prevent crevice corrosion during storage of the chromium-containing steel pipe, and to store it for a long period of time.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state in which a coating that acts as a galvanic anode is applied to a portion of a chromium-containing steel pipe before packaging which comes into contact with a packaging member.

FIG. 2 is a perspective view of a wood packaging frame.

FIG. 3 is a perspective view showing a state in which chromium-containing steel pipes are packed.

FIG. 4 is an explanatory diagram of a portion where crevice corrosion occurs.

[Explanation of symbols]

 1 Chromium-containing steel pipe 2 Inorganic zinc rich paint 3 Wood packaging frame 4 Outer frame 5 Partition 6 Hoop 21 Martensite stainless steel pipe 22 Rainwater containing chlorine ions 23 Packaging material

Claims (2)

[Claims] 1. A method for preventing crevice corrosion during storage of a chromium-containing steel pipe, characterized in that, prior to packaging the chromium-containing steel pipe, a coating that acts as a galvanic anode is applied to the portion that comes into contact with the packaging member during packaging. 2. A paint which acts as a galvanic anode is applied to a portion of the chromium-containing steel pipe that comes into contact with the packing member, and the packed chromium-containing steel pipe is stored in a portion that comes into contact with the storage member prior to storage after unpacking. A method for preventing crevice corrosion during storage of a chromium-containing steel pipe, characterized in that a coating which acts as a galvanic anode is applied to a portion not coated with or a portion where the coating is peeled or removed.