JPH0158798B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is an iron protector (hereinafter referred to as a protector) that has the function of preventing mechanical damage and chemical damage to the threaded portion of a steel pipe and improving the lubrication effect during installation and removal.
In particular, the present invention relates to a protector in which a special surface treatment is applied to an internal threaded surface or a non-threaded surface. (Prior Art) As is well known, a protector is attached to a steel pipe whose end is threaded, but this protector merely prevents mechanical damage to the threaded portion of the pipe due to external causes during transportation or storage of the steel pipe. In addition, it should be effective against corrosion damage to pipe threads that occurs when steel pipes with protectors are stored for long periods or in humid environments containing salt, etc. It must be possible to easily attach and detach the protector without causing mechanical damage to the threaded surface of the pipe due to friction between the threaded portions of both the pipe and the protector. Conventional protectors generally do not undergo any surface treatment on the internal threaded surfaces, but due to the demands for improving the various characteristics described above, it has become necessary to perform some kind of surface treatment on the inside of the protector. Examples of this include phosphate treated protectors or galvanized protectors. However, none of these methods has the disadvantage that they do not simultaneously satisfy the above-mentioned characteristics, and each surface treatment method also has the disadvantage that the processing steps are complicated. (Object of the Invention) In view of these circumstances, the present invention aims to provide a protector having a function of simultaneously solving the problems of mechanical damage and corrosion damage to the pipe thread portion. Alternatively, the zinc powder contained in a high concentration in an inorganic color vehicle is uniformly distributed in a coating film of an appropriate thickness on the inner surface of the protector, and in particular, when the protector is attached, the zinc powder The zinc powder applied to the pipe sticks closely to the pipe thread surface, so that the cathodic protection effect of the zinc powder extends to the pipe thread surface.In addition, the mobility of the zinc powder due to the low hardness of the color vehicle prevents the pipe from forming. The lubrication of both threaded portions of the protector is improved, and mechanical damage such as galling of the threaded surface of the pipe during attachment and detachment of the protector can be prevented. (Structure and operation of the invention) The present invention will be specifically described below based on embodiments shown in the drawings. First, as a paint for special surface treatment used in the present invention, one containing an organic or inorganic color vehicle and metallic zinc powder in an amount of 80% or more by weight is used. As shown in Figure 1, it was found that if the metal zinc powder content was less than 80%, corrosion damage to pipe threads could not be sufficiently suppressed, but if the content exceeded 80%, the effect was saturated. This depends on whether or not there is sufficient contact between the metallic zinc powder and the pipe thread surface. FIG. 1 shows the relationship between the content of metallic zinc powder in the paint and the corrosion resistance of pipe threads, and the corrosion resistance relative index X was determined by the following formula. X = (1 - Number of pitting marks on the pipe thread by using the protector of the present invention / Number of pitting marks on the pipe thread by using the untreated protector) × 100 In the figure, the protector with 100% metal zinc powder content is the galvanized material. It was obtained using On the other hand, the second figure shows the relationship between the metal zinc powder content in the paint and the protector attachment characteristics, and the relative index Y of attachment and detachment characteristics in the figure was determined by the following formula. Y = 100 x { Number of test materials that cannot be completely removed - Number of test materials that cannot be completely removed - Number of test materials that cannot be completely removed / Number of test materials that cannot be completely removed * *
-Number of test materials with mechanical damage on the pipe thread surface out of the number of test materials that can be completely removed / } As shown in Figure 2, even if the metal zinc dust content is 80% or less, the protector equipment described later Desorption properties are not degraded. In the present invention, a zinc powder content of 80% or more was selected as the content necessary to satisfy both functions. As organic color vehicles, for example, epoxy resins, phenoxy resins, epoxy esters, styrene, etc. are effective, and as inorganic color vehicles, sodium silicate, ethyl silicate, etc. are effective. This paint is applied mainly to the threaded portions that come into contact with the pipe threads inside the protector, which have been previously degreased. In this case, it is possible to apply the above-mentioned paint to the threaded surface of the pipe, but when inspecting the threaded surface of the pipe, there are two reasons for the process: the paint film will interfere with the inspection, and also because it is long and heavy. Coating on the pipe side has problems in terms of coating efficiency and degreasing, and as will be explained later in Tables 1 and 2, only the protector side has the same corrosion resistance and mechanical damage resistance as the pipe thread surface. It is more reasonable to apply the coating on the protector side than on the pipe side. Therefore, the amount of paint applied is as shown in Figure 3.
From the perspective of coating amount, relative index of corrosion resistance of pipe threads, and relative index of attachment/detachment characteristics, 200 to 800 g/
m ² is selected. Now, to explain Fig. 3, the corrosion resistance relative index X of the pipe thread part is as follows: ) x 100 Also, the relative index Y of attachment/detachment property is Y = 100 x { Number of attachment/detachment test materials - Number of test materials that cannot be completely attached - Number of test materials that cannot be completely detached/Number of attachment/detachment test materials * * - Completely detachable It represents the number of test materials where mechanical damage occurred on the pipe thread surface / } out of the number of test materials. FIGS. 4, 5, and 6 show L cross sections of both pipe screws 1 when the protector 5 whose interior is coated with the above-mentioned paint is attached to the pipe screw 1. The zinc powder 3 comrades or the zinc powder 3 and the iron surface (5 protector screw surfaces and 1 pipe screw surface) are in close contact, the pipe screw surface is sufficiently coated with zinc dust, and the pipe screw surface is not damaged by corrosion due to the cathodic protection effect of zinc. I will no longer receive it.
Enlarged views of parts A and B in Figure 4 are shown in Figures 5 and 6, respectively. When the protector is installed, the friction between the pipe thread surface and the protector thread surface causes minute particles to be deposited on the grease 2 previously applied to the pipe thread surface. A gap may occur, or a peeled portion 6 of the grease 2 may occur due to various subsequent causes. For example, water containing chlorine ions or the like enters or accumulates here, but it has been confirmed that even in this case, there is no corrosion damage due to the cathodic protection effect of the zinc dust 3 adhering to the iron surface. In addition, 4 in the figure represents a color vehicle. Table 1 shows the corrosion acceleration test results, and from the perspective of corrosion protection, it has the same function as a galvanized protector, and as mentioned above,
It can be seen that the same effect as when the paint was applied to the pipe thread surface was obtained.

[Table] In addition to the above-mentioned anti-corrosion effect, the second feature of the present invention is that there is extremely little mechanical damage such as galling of the pipe threads when attaching and detaching the protector, and the workability of attaching and detaching is excellent. . In other words, Table 2 shows the attachment and detachment characteristics, including the resistance to mechanical damage such as galling of the pipe thread surface when attaching and detaching the protector, and the ease of attachment and detachment due to the lubrication effect between both screws. The protector of the present invention has extremely high attachment and detachment characteristics compared to untreated materials and galvanized materials, and at the same time,
As mentioned above, it can be seen that the performance is comparable to that when the paint is applied directly to the threaded surface of the pipe. This is due to the low hardness of the color vehicle that binds the zinc dust. Here, the attachment/detachment characteristic relative index Y is as described above.

[Table] The amount of coating that optimizes the corrosion resistance of the pipe thread and the characteristics of attaching and detaching the protector is as described above. The third feature of the present invention is that, unlike conventional surface-treated protectors, it is only necessary to apply the paint to a degreased protector, and no complicated treatment steps are required.The surface treatment method itself is simple. be. Furthermore, since the paint itself dries quickly, it can be processed in a short time, and the drying time can be further shortened by promoting the polymerization reaction of the color vehicle by heating and drying, making this method advantageous in terms of production efficiency. Furthermore, the above-mentioned surface treatment method can be applied not only to protectors but also to oil country tubular joints and the like. (Effects of the Invention) As described above, according to the present invention, the effect of preventing mechanical and chemical damage to the pipe thread surface, which could not be obtained with conventional untreated protectors and surface-treated protectors, and the ease of work when attaching and detaching the protector are achieved. can be ensured.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the metal zinc dust content in the paint and the corrosion resistance properties of pipe threads, Figure 2 is a diagram showing the relationship between the metal zinc dust content in the paint and the protector installation/detaching characteristics, and Figure 3 is a diagram showing the relationship between the metal zinc dust content in the paint and the corrosion resistance properties of the pipe thread. The figure shows the relationship between the amount of paint applied, the corrosion resistance properties of the pipe thread, and the protector installation/removal characteristics. Figure 4 shows the relationship between the amount of paint applied and the corrosion resistance characteristics of the pipe thread. Figure 4 shows both threads when a protector with paint applied to the inner surface is attached to the pipe thread. The L cross-section is shown. 5 is an enlarged view of section A in FIG. 4, and FIG. 6 is an enlarged view of section B in FIG. 4. 1 is pipe screw, 2 is grease, 3 is zinc powder,
4 is a coloring agent, 5 is a protector, and 6 is a peeling part.

Claims (1)

[Claims] 1. A protector with excellent pipe thread protection performance, characterized in that a paint containing metal zinc powder contained in a high concentration in a color vehicle is applied to the pipe side thread contact part on the inner surface of the protector.